Flowering trees
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There’s no doubt that city gardens now
dominate that thoughts of plant breeders and nurseries and nowhere is this more
evident than in the recent trends in the development of trees. Where once trees
were though of as the major feature in a landscape, and large size was regarded
as an asset, now we find that although gardeners still like the idea of trees,
most find their bulk offputting. Today’s popular trees are those that are both
‘manageable’ and attractive; trees like the various forms of Gleditsia
triacanthos, small rowans (Sorbus spp.) and Japanese maple (Acer
palmatum) cultivars.
Country gardeners, however, with their
generally larger gardens, still need trees that make an impact and fill space.
Large trees also help to reduce the force of the wind and can be used a
boundary. Many country gardens are therefore both sheltered and defined by
boundaries of large trees. But as effective as such plantings are at protecting
the garden, filling space and hiding unsightly out-buildings or waste areas,
they tend to be rather monotonous — often just one or two tones of green. A
garden surrounded by a large shelter belt of conifers can, as the trees become
larger, become very cold and darkly shaded.
The answer is to inject some colour, and
adding flowering trees to your shelter is one of the easiest ways of doing it.
Flowering trees can also be used to brighten up dark corners anywhere in the
garden and they are of course beautiful in their own right, irrespective of
where or how they are used in the garden.
Planting styles
There are hundreds of trees that combine
bright or interesting flowers with excellent growth characteristics. Some of
them, such as the flowering gums (Eucalyptus
spp.) and lace bark (Hoheria populnea),
are suitable for breaking up a monotonous shelter belt, others are better used
where their growth form has room to develop and be better appreciated.
Specimen planting is one way to emphasise
the characteristics of a particular type of tree. The silk tree (Albizia julibrissin), for example,
generally looks best when grown as an individual specimen where the full beauty
of its branch structure and spreading growth habit may be appreciated.
Other trees are better grown in groups.
Eucalypts and acacias are particularly suited to group planting and can be used
in paddocks to create small shelter blocks or woodlots. Although acacias are
prone to wind damage, they are very good for shelter as they are palatable to
stock. Also, they are leguminous and therefore nitrogen fixing, though this is
of little consequence except in the immediate vicinity of the trees.
Most leguminous trees, for example
acacias and carob, can be used for supplementary fodder; either through
allowing the stock to browse low branches or by trimming some of the foliage as
required. Carob, of course, also offers the benefit of its highly nutritious
pods.
However, stock rotation is important.
Don’t leave the stock among the trees for more than a week or so, especially if
feed is short supply, or the trees may suffer from stock grazing on or
stripping the bark through rubbing. Dividing up your paddocks so that each
contains a small shelter wood should avoid any problems developing.
Some flowering trees, particularly the
eucalypts, are suitable for use as timber trees or for coppicing. You will lose
much of the benefit of the flowers with timber trees as they will eventually
grow too high for the flowers to be very visible. On the other hand the regular
trimming of coppiced promotes rapid new low-level growth that will develop into
flowering wood at relatively. It is worth considering the flowering potential
of your coppice trees when selecting plants and planning your trimming.
The ultimate use of flowering trees is in
a natural sustainable woodland. If you have the room
this can be the most satisfying form of gardening, allowing all manner of
perennials and other plant to be grown under the trees. Also, there’s nothing
to stop a woodland being used for stock shelter,
coppicing or even selective felling.
Such small woods serve a variety of
purposes: timber production, shelter recreational or aesthetic value and for
its value as a wildlife habitat. Managing woodlots to best achieve these
multiple objectives requires careful planning and a thorough understanding of
the methods available. It is usually wise to consult forestry professionals.
Planning
Integrating flowering trees in your
existing garden, shelter belts, woodlots can be viewed
as landscaping on a grand scale. Getting the right combination of beauty,
diversity and utility requires that the same considerations be borne in mind:
size, colour, arrangement, texture, and form.
Trees are, of course, large plants and
seldom moved once established. This demands that you plan ahead to avoid any
embarrassment as they grow. Just because you may have a large garden it doesn’t
mean that you can’t run into problems with trees outgrowing their allotted
space. Remember to consider the spread as well as the height: some trees, like
the silk tree (Albizia julibrissin),
may be wider than they are high, which is great if you need a shade tree for a
lawn but is less appealing where fences and hedges set limits for the spread of
the tree. Consider the roots too: it’s no fun having to dig up your sewers or
clean out drains blocked or crushed by tree roots.
Equally important, any plant you choose
must be able to survive in your climate and soil. Frost and wind tolerance and
rainfall are the main climatic concerns, while drainage, depth, humus content,
and pH are the most important soil considerations. The climate will also
determine the rate of growth. Some trees are naturally fast growers, and the
more suitable the climate the quicker the tree will grow.
The aspect and the angle of the sun,
which varies with the seasons, determine how much shade a tree will cast. Any
large tree will provide shade throughout the year, but when the sun is at its
lowest in winter, a wide-spreading tree can shade a considerable area. Dense,
heavily foliaged evergreen trees provide the best privacy but have little else in
their favour; they cast too much shade and it’s very difficult to grow other
plants under them.
A good selection of trees will provide
year-round colour and interest. It may be difficult to find many trees that
bloom in winter in inland or southern areas with cold winters and regular heavy
frosts, but in most parts of the country it is possible to have at least one or
two trees in bloom at any time. Cherries, crab-apples, dogwoods and the like
are the traditional spring-flowering trees; they are followed in summer by the
brighter-flowered eucalypts, pohutukawa (Metrosideros
excelsa) and sub-tropicals such as Jacaranda;
Autumn sees the cassias (Cassia and Senna spp.), Hoheria, kamahi (Weinmannia racemosa) and more eucalypts; while winter is the time
for the witch hazel family, and, as the season turns to spring, the acacias
begin to bloom.
If your winter climate is too cold for
much in the way of bloom, consider the beauty of coloured bark. The vivid red twigs of the dogwood (Cornus stolonifera); the stark white stems of the ghost gum (Eucalyptus pauciflora) and the silver
birch (Betula pendula); or the rich
reddish-brown, peeling bark of the paperbark maple (Acer griseum) or the Arbutus species.
Foliage is important too. Given the
choice, most gardeners will opt for evergreens over deciduous plants — the
advantage of year round foliage is nearly always decisive. However, deciduous
trees have plenty to offer, not just in terms of their superiority as shade and
compost providers, but as ornamental plants too. Think of deciduous trees and
the first thing that comes to mind is autumn foliage, those vivid tones of
yellow, orange and red, but the bright green of the new spring growth should
not be underestimated. There is also a wide range of summer foliage colour among
the deciduous trees, the bright yellow of Robinia
‘Frisia’, the deep blackish red of the copper beeches (Fagus) and the silvery grey of the weeping silver pear (Pyrus salicifolia).
So, what are the best flowering trees?
Well, that really depends on your climate and personal preferences, but the
following selection covers most of the proven performers.
Acacia
The over 500 species of wattle, most of
which are native to Australia, are predominantly evergreen, quick-growing,
heavy-flowering, generally hardy and range in size from small bushes to large
trees. Most have golden-yellow flowers, are relatively short-lived and tend to
have rather brittle branches that are easily damaged by wind. This brittleness
makes most wattles unsuitable for shelter plantings, although the sallow wattle
(A. floribunda) is often used as a
quick screen. A light, sandy or gravelly soil will slow the growth rate and
lead to stronger branches.
Despite the enormous choice, relatively
few are commonly grown. By far the most common is the Cootamundra wattle (A. baileyana), which has fine, feathery
foliage, grows to about 8 m high × 10 m wide, and produces massed
clusters of flowers in late winter and spring. The alpine wattle (A. pravissima) is smaller (around
5 m × 6 m) and has bright yellow flowers. It has triangular, pointed
phyllodes (leaflets) and is hardy over most of the country. Acacia cardiophylla has ferny foliage,
strongly cinnamon-scented pale yellow flowers in winter and spring, and grows
to about 12 m × 8 m.
In common with other legumes, wattles
have the ability to store atmospheric nitrogen in nodules on their roots. They
also have edible foliage and flowers. Their sap is used as a gelling and
thickening agent in foods, particularly ice-cream.
Albizia
Because of its flat-topped, spreading
habit, the common deciduous silk tree (A.
julibrissin) is usually grown as a shade or lawn tree. It has large
fern-like (bipinnate) leaves composed of many tiny leaflets. In summer it
produces fluffy, ball-shaped, filamentous, pale yellow and pink flowers. The
form ‘Rosea’ has deep pink flowers. The silk tree grows to about 6 m ×
8 m and thrives in light well-drained soil. It is inclined to be shallow
rooted and benefits from staking when young.
A.
lophantha is a somewhat frost-tender evergreen
species that closely resembles an acacia. It has bright, slightly glaucous,
green pinnate leaves and 100 mm-long fluffy yellow bottle brush flowers. It
grows rapidly to 7m × 4m and can become invasive as it self-sows freely.
Ash
Ash (Fraxinus
spp.) is a Northern Hemisphere genus. The common F. excelsior is a 15 m high × 9 m wide, broad-headed,
deciduous tree that is frequently used as a street tree. It has
200 mm-long pinnate leaves usually made up of seven leaflets and bears
panicles of tiny, fragrant, white flowers in spring. Although this species does
not flower as well as some of the others, several forms, the most common of
which is the claret ash, ‘Raywoodii’, have been selected for their autumn
foliage colour.
The desert ash (F. oxycarpa) is similar but has slightly smaller leaves. It is flower very heavily in spring and is
tolerant of drought and a wide range of soil conditions.
The third common species is the manna ash
(F. ornus). This species has a dense foliage cover and large flower heads. It
colours well in the autumn. F. mariesii
is similar to F. ornus in shape and
leaf, and is probably the best flowering species.
Ashes are among the last trees to come
into leaf in spring, which makes them effective paddock trees as the spring
grass growth can get underway without excessive shading. They can be used as
fodder trees but do always regenerate quickly.
Cabbage tree
The native cabbage tree (C. australis) is extremely well known for its distinctive foliage and growth
habit, but less well known for its beautiful, large panicles of fragrant,
creamy-white flowers. These appear in spring and are followed by small white
berries. Several selected foliage forms, including the beautiful variegated
‘Albertii’, are available.
The mountain cabbage tree (C. indivisa) has much wider, somewhat
glaucous, leaves with prominent ribbing. It is an attractive plant but demands
moist soil and high humidity to be at its best. Cabbage trees prefer moist soil
and are quite tolerant of poor drainage. They can be used as living pumps to
aid drainage in wet areas.
Carob
The carob tree (Ceratonia siliqua) is evergreen and has 300 mm-long, leathery,
pinnate leaves. It grows to about 15 m high and is strongly built, with a
particularly stout trunk. Carob has very strong roots that can lift paving, so
take care not to plant it near paths and driveways. It is very drought tolerant
once established.
The mid to late spring panicles of red
flowers are followed by 150–300 mm-long seed pods that are filled with
seeds surrounded by a sweet edible pulp. The pods make a very nutritious stock
feed, but the tree requires a hot, dry climate to grow well and set seed.
Cassia
Many of the species in this large genus
have been reclassified as Senna, but
they are likely to be known as Cassia
for many years. The most common species is C.
corymbosa, particularly the form ‘John Ball’. It grows to about 4 m ×
4 m and has bright green pinnate leaves that are up to 150mm-long and
composed of leaflets with prominent midribs. It produces yellow, buttercup-like
flowers in large clusters appear from about the middle of March. Grow in light
well-drained soil in full sun and protect from frost when young. Most other
species have a similar appearance but vary slightly in size, leaf shape and
flowering season. C. tomentosa is a
shrubby winter-flowering species that may self-sow and become invasive.
Cassias are legumes and can fix
atmospheric nitrogen, which enables the plants to grow on relatively poor
soils. The seeds often have a laxative effect (one species is the source of
senna), though how this affects stock is not clear.
Catalpa
The Indian bean (C. bignonioides) is a large (20 m × 15 m), deciduous
North American tree. It had large, light green oval leaves and in summer
produces upright clusters of cream to very pale pink, tubular flowers. It is
often said that this is one of the few very hardy trees with flowers that can
rival the flamboyance of the tropical trees. This may be stretching things a
bit, but there’s no denying that a mature catalpa in full bloom is an
impressive sight. The Indian bean is easily grown and the only real
complications are those that may result from its large size.
I was unable to confirm that the large,
succulent foliage is edible, but as the plant belongs to the bignonia family it
is unlikely to be poisonous.
Cercis style='font-family:"Times New Roman";
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Judas tree (C. siliquastrum) and
Chinese redbud (C. chinensis) both
grow to about 8 m × 5 m, have distinctive light bronze-green,
heart-shaped leaves and springtime flower clusters in an unusual shade of
purplish pink. The flowers are followed by bean-like seed pods. White flowered
forms are available. The foliage often colours well in the autumn. These trees
are nitrogen-fixing, drought-tolerant once established and easily grown in any
reasonably well-drained soil.
Crab-apple and hawthorns
Crab-apples (Malus spp.) used to be among the most widely planted flowering
trees before they were tainted with a reputation for spreading the fungal
disease fireblight. Although this discrimination has been shown to be somewhat
unfair, the damage has been done.
Hawthorns (Crataegus spp.), which are closely related to crab-apples, have
suffered from the same problem. They too are superb flowering trees and really
do merit a revival in popularity.
Both crab-apples and hawthorns are very
hardy. Most species are deciduous, though a few, notable the Mexican hawthorn (C. pubescens), are evergreen. They
produce apple-blossom-like flowers in spring, which may, depending on the
cultivar, be single or double, in various shades of white, pink and red. The
flowers are followed by conspicuous fruit that is usually red or golden yellow.
The fruit is edible but very tart, it can be used for
making jams or jellies.
Popular cultivars include the heavy
flowering M. floribunda; M. ‘Oporto’, which has very deep plum-coloured
flowers; M. ‘Jack Humm’, which is
primarily grown for its bright red fruit; and C. laevigata (syn. oxyacantha),
particularly the white-centred, red-flowered ‘Puniceus’ and the double forms.
Crepe myrtle
The crepe myrtle (Lagerstroemia indica) is a beautiful heavy-flowering small
(6 m × 4 m) tree that needs consistent summer heat to flower well.
Although deciduous it is not particularly hardy, being damaged at about -6°C.
The simple glossy deep green oval leaves are about 60 mm long and are usually
carried in groups of three. In summer the tree produces clusters of 30 mm
diameter frilly flowers. There are many colour forms in shades of white, cream,
pink, mauve and red; there are also dwarf forms suitable for tub cultivation.
Grow in well-drained soil in full sun and water well in summer.
Dogwood
Dogwoods (Cornus spp.) are among the most beautiful small deciduous flowering trees, but they do tend to prefer the clearly defined seasons of a continental climate.
Dogwoods have simple but bold spring
flowers, good autumn foliage colour, and some have brightly coloured winter
stems. C. controversa, C. florida and C. kousa usually have
the best flowers, while C. nuttalii
provides brilliant autumn colour. C.
alternifolia has a graceful tiered growth habit, but insignificant flowers.
C. stolonifera has bright red winter
twigs and C. capitata is evergreen with unusual fruit.
Most species have pointed oval leaves
about 125mm-long and there are some attractive variegated forms. The flowers
have four leathery petals and are usually white when first open but develop
pink tints as they age. The flowers are often followed by large round fruits
that are seen at their best on C. kousa
and the evergreen C. capitata.
Most dogwoods are very hardy but C. capitata is often damaged at -6°C
when young. They do best when planted in moist, humus enriched, well-drained soil in sun or light shade. Dogwoods are great
for use around the edges of a woodland; providing interest through most of the
year and adding a graceful light touch in spring.
Eucalyptus, Agonis and Melaleuca
These three genera from the myrtle family
are almost exclusively Australian plants. They thrive in any well-drained soils
but vary in their frost-hardiness.
We all know the typical eucalypt or gum
tree with its peeling bark and sickle shaped glaucous green leathery leaves.
All produce filamentous flowers in shades of white, cream, pink, yellow, orange
or red, varying in size and season. Some, such as scarlet-flowering gum (E. ficifolia), put on a truly
magnificent floral display while others, such as E. nicholi, have insignificant flowers.
Eucalypts range in size from the snow
gum, E. pauciflora var. niphophila, at around 6 m high to
giants, such as E. globulus, which
may exceed 60 m. Gums vary in their hardiness: some are almost totally
intolerant of frost while others can withstand -15°C.
Many gardeners reject eucalypts because
of their rapid growth, leaf and bark litter, and potentially large size.
However, they are among the most attractive and easy care evergreen trees
available. And of course they really shine as quick-growing farm trees; a range
of species can provide plants suitable for timber, coppicing and flowers, which
are particularly popular with bees. Some, such as E. sideroxylon, are multi-purpose trees.
Although Agonis flexuosa could easily be mistaken for a eucalypt when not in
flower, its clusters of star-shaped creamy-white flowers, which appear in
summer, give it away. This 8–10 m high tree is usually upright and quite
narrow with weeping branches. It is easily grown but will not tolerate heavy
frosts.
Melaleuca
or paperbark is a genus of about 140 species of
evergreen shrubs and trees. Most have tiny needle-like or elliptical leaves.
The flowers are similar to those of the closely related bottlebrush (Callistemon sp.) but are usually smaller. There are species in almost every
colour of flower, though cream, yellow, pinkish mauve and red predominate.
Paperbarks will grow in a wide range of soils but few are hardy below -6°C.
Eucryphia
While not widely grown, this genus
includes several attractive large shrubs or small trees native to Chile and
Australia. The most common species is E.
cordifolia, a Chilean native. The other Chilean species, E. glutinosa, is rarely seen in gardens
but has been crossed with E. cordifolia
to produce the hybrid E. × nymansensis.
The three Australian species, E.
milliganii, E. moorei and E. lucida are
rarely seen. All have similar anemone-like white flowers that appear in spring.
Golden-rain tree style='font-family:
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The golden-rain tree (Koelreuteria paniculata) grows to about
10 m × 7 m and has pinnate leaves that may be as much as 50 cm
long. The foliage tend to be among the last to fall in
autumn and often turns a bright yellow before dropping. In summer it produces
large terminal heads of yellow flowers that are followed by clusters of papery
seed capsules. It will grow in most soils and can withstand high alkalinity, as
well as being very heat and drought tolerant once established.
Grevillea
There are at least two species of this
proteaceous genus that develop into trees. Both G. banksii and the silky oak (G.
robusta) have bronze green pinnate foliage and develop into round-headed
trees. Though similar in appearance, G.
robusta is considerably taller than G.
banksii: 15 m high as opposed to 6 m. Both flower in late spring
to mid summer. G. banksii has red
flowers while those of G. robusta are
golden orange. These trees prefer a well drained, somewhat acid soil and are
frost tender when young. When mature they will tolerate at least -5°C.
Several other protea family genera, most
notably Banksia, Embothrium, Macadamia and Telopea, include tree-sized species. The New Zealand honeysuckle or rewarewa (Knightia
excelsa) is also in the protea family. Its brownish-red flowers, while
interesting and unusual, are scarcely spectacular. Bellbirds and other
nectar-feeders find all of these flowers attractive.
Hoheria style='font-family:"Times New Roman";
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Trees of this New Zealand genus are commonly known as ribbonwoods or lacebarks because of the
fine filigree of bark that underlies the surface bark. The most common species
is the evergreen H. populnea. When
young it is a very upright tree, but as it ages it becomes more round-headed
and grows to about 12 m high. Various foliage forms are available,
though all produce massed small clusters of 2 cm diameter white flowers in
late summer and early autumn. Other evergreen species grown include H. sexstylosa, which is very similar to H. populnea, and H. angustifolia.
The two deciduous
species, H. lyalli and H. glabrata, are similar to one another. H. lyalli grows to about
7 m while H. glabrata is a
little taller at 9 m. The leaves are similar to H. populnea but covered in fine hairs. H. glabrata has somewhat bluish leaves. Both species flower in
summer and are hardy to at least -15°C. Grow in moist, humus enriched, well-drained soil in sun or light shade.
Jacaranda style='font-family:"Times New Roman";
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Jacaranda
mimosifolia is common in milder areas and is
sometimes used as a street tree. It is a semi-evergreen or deciduous 12 m
× 8 m tree that is almost totally frost-tender when young, but tolerates
-5°C once well established. Although the very finely divided fern-like leaves
are attractive, jacaranda is mainly grown for its spectacular clusters of bright
purplish-blue trumpet flowers. These may appear in spring in very mild areas,
with summer the main flowering season. White and pink flowered forms are
occasionally available. This tree needs warm temperatures to flower well and
does best in moist well-drained soil in full sun.
Kamahi
Kamahi (Weinmannia racemosa) is a very attractive native evergreen. Up to
15 m high when mature, though shrubby for many years, it has elliptical,
deep bronze-green, serrated-edged leaves up to 100 mm-long. In summer, the
tree produces masses of 150 mm-long, narrow creamy-white bottlebrush-like
flower heads. The massed flowers often swarm with bees as they are heavy with
nectar and pollen. The flowers are followed by 20 mm diameter red
berry-like fruits. There is also a purple-leafed form. Kamahi prefers a moist,
slightly acid soil and is easily grown in most parts of New Zealand. The towai (W. silvicola)
is a similar species that occurs in the north of the North Island,
although it appears to be hardy well outside its natural range.
Kowhai
So well known as to scarcely need
describing, the two common tree-sized kowhai species (Sophora tetraptera and S.
microphylla) are hardy,
heavy-flowering and easily grown. These species are evergreen for most of the
year but often drop most of their leaves as flowering begins in late winter or
early spring. S. tetraptera has large
olive-green leaflets that can be quite stiff and leathery, which tends to make
the leaves curl slightly. It has pendulous clusters of large bright yellow
flowers. S. microphylla has very
small deep green leaflets and flowers that are smaller than those of S. tetraptera, but there are more blooms
per cluster and they tend to be a golden, rather than bright, yellow. The
flowers of both species are followed by brown, bean-like seed pods. Kowhai is
best grown in moist well-drained soil in full sun.
Several exotic species are also grown. Of
these, S. japonica is the most
common. It has deciduous, 200 mm-long, light green, pinnate leaves and
cream, or occasionally pale pink, flowers in 200–300 mm-long terminal
panicles. It may grow to 15 m × 12 m but is often grafted onto
2 m standards to produce a small weeping tree. It is hardy to at least
-25°C.
Lagunaria style='font-family:"Times New Roman";
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The Queensland
hibiscus (L. patersonii) is a small
evergreen tree. Quick-growing when young, it slows considerably after reaching
4 m. It has mid green leathery oval leaves about 75 mm-long with
silvery grey undersides. The 40–50 mm diameter mid pink
mallow-like flowers are followed by seed pods that contain irritant hairs.
Remove the pods before they ripen unless you want to collect the seed. Queensland
hibiscus is frost tender but otherwise easily grown in most well-drained soils
and is a good coastal tree.
Laurel style='font-family:"Times New Roman";
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The bay laurel (Laurus nobilis) while doing double duty as a classic culinary herb
and a first rate garden specimen is seldom grown for its flowers. The Canary
Island laurel (L. azorica), however,
offers equally attractive evergreen, deep green, oval foliage with the added
bonus of large clusters of cream flowers in late spring. It is a hardy and
easily grown tree that can mature to 15 m high or more.
Lily-of-the-valley tree
The lily of the valley tree (C. arborea) is an evergreen large shrub
or small tree — advanced specimens may reach 6 m × 3 m. It has large, deep
green, laurel-like foliage and from mid summer bears masses of mildly fragrant,
white, lily-of-the-valley flowers in large panicles. It is not entirely hardy
but will withstand occasional frosts of -6°C. Clethra does best in cool, moist, humus enriched soil in sun or
light shade.
Magnolia style='font-family:"Times New Roman";
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Most species of magnolia can eventually
reach tree-like size, but those most commonly grown as trees are the deciduous M. campbellii and the evergreen M. grandiflora.
M.
campbellii, which may grow to 20 m × 12 m, has long, mid green, oval leaves, very like those of the
common M. soulangiana. It is also one
of the earliest to flower: usually starting to produce its vase-shaped cream to
deep pink blooms in mid August. M.
grandiflora grows to a similar size and has leaves that are a glossy mid
olive green on top with rust coloured felting below. Some forms, such as
‘Ferruginea’, have very heavy felting. The flowers, which are fragrant, are
creamy-white and cup-shaped. In some forms they can be up to 250 mm in diameter.
Plant magnolias in moist, humus enriched
well-drained soil in sun or very light shade.
Paulownia
This is a Chinese genus of about half a
dozen very quick-growing deciduous trees, some of which have recently been
promoted as timber trees. P. tomentosa
is the species generally grown as a garden specimen. It is a hardy, strongly
branched tree with large (up to 300 mm-long), heart-shaped leaves, deep
green on the upper surfaces and light green underneath with some felting. It
grows to about 15 m high × 8 m wide. The spectacular purplish-blue
trumpet flowers are carried in foxglove-like heads and open in spring from the
terminal heads of furry brown buds that are carried right through winter. They
are followed by rounded seed capsules that hang on well into winter. Trees
often carry the current year’s seed capsules and the following season’s buds at
the same time. Paulownia grows satisfactorily in most well-drained soils.
Prunus
The showy flowering Prunus — cherries, apricots, plums, peaches and almonds — are among
the most common ornamental deciduous trees. Several species and many hybrids
are grown and they range in size from the very dwarf almonds, such as the P. glandulosa forms, which are suitable
for small gardens and containers, through to large spreading trees, such as P. sargentii, which may grow to
18 m × 12 m.
Always heavy flowering, they vary in
colour, size, style and season and growth habit. Among the most popular are the
weeping and horizontal standards. These are naturally low, spreading plants
that have been grafted onto upright standards from 1–2.5 m high. The
standard trunk doesn’t grow any higher than the point at which it is grafted
but the branches arch up and spread out to make a substantial plant.
Flower colours are mainly white and
various shades of pink. There are also a few very deep pink, bordering on red,
cultivars and some with orange tints. Flowers may be single, semi-double or
fully double. Often a double-flowered form will also carry some single flowers.
Many of the ornamental forms are sterile and do not bear fruit, but some
develop small, usually inedible, fruit after flowering. The trees are generally
very frost hardy, although some of the very early flowering forms, such as P. subhirtella ‘Autumnalis’ or ‘Geisha’,
may suffer flower or bud damage from hard frosts. Plant in
moist well-drained soil.
Pohutukawa and rata
From mid November the pohutukawa (Metrosideros excelsa) becomes a very
conspicuous feature of our coastal gardens as its clusters of intense deep red
filamentous flowers begin to open. The simple rounded leaves are a bright
glossy mid green on young plants but mature trees have deep green leathery
leaves with white indumentum. Old trees often develop aerial roots on the trunk
and branches. Various flower colours and leaf forms are available. Except for
being frost tender, especially when young, this is an easily grown tree. It
tolerates most soils and is particularly well suited to coastal conditions.
The southern rata (M. umbellata) and the
northern rata (M. robusta) are far
tougher plants but they seldom do well in gardens. Their flowers are similar to
those of the pohutukawa, but while spectacular in the wild, they are less showy
in a garden. Both species are hardy to at least -10°C so they are worth trying
in areas too cold to grow M. excelsa.
They grow very slowly and may take many years to flower from seed.
All Metrosideros
flowers are nectar-rich and very popular with bees, birds and geckos.
Puriri
The puriri (Vitex lucens) is one of the few native trees with pink flowers.
Most often seen in late winter, the panicles of bloom may occur at any time.
They are followed by bright red 20 mm-long berries. The foliage of the puriri
is very handsome: the leaves are a lustrous, glossy green; and composed of 3–5
broad leathery leaflets that are up to 125 mm long. Puriri grows to
15 m × 10 m and is a very impressive tree in all respects. Fittingly,
it is host to one of our most impressive insects: the puriri moth. The
caterpillars of this large moth can often be found on trees in the wild, but
they usually do little damage. Puriri does best in a humus-enriched, moist
well-drained soil and should be shaded and protected from wind and frost when
young.
Puriri wood is one of the most durable
native timbers. It has been used for piles, fencing, bridges and other
construction, while also being suitable for fine furniture. However, its slow
growth rules it out as a commercial proposition.
Robinia
The golden-leaved R. pseudoacacia ‘Frisia’ is the most commonly planted member of
this genus and has become enormously popular over the last ten years. However,
it seldom, if ever, flowers. The true species, R. pseudoacacia, on the other hand, produces attractive, fragrant,
white flower clusters in late spring and early summer. It can grow up to 25 m
high and may be used as a fodder tree for stock capable of dealing with the
vicious thorns on the stems.
A selected form of another species, R. hispida, has recently been promoted
as the pink wisteria tree. It has long racemes of pink flowers and grows to
about 4 m. Robinias are easily grown in well-drained soil but have brittle
branches that are easily wind damaged, so stake them well when young.
Rowan
The bright orange berries of the 8 m
tall mountain ash or rowan (Sorbus
aucuparia) are a common sight in autumn. Though usually grown for its
berries, the cream spring flowers, while often rather unpleasantly scented, are
nevertheless conspicuous. The colour of the berries varies with the species.
Mountain ash has orange berries, S. americana has white berries, while those of S. hupehensis are white tinted pink. The smaller growing (up to
4 m × 1.8 m) S. vilmorinii
is available in pink, yellow or red berried forms. Birds are attracted to the
yellow, red or orange berries, but tend to leave the white berries. Some
species, most notably S. discolor,
have attractive autumn foliage but most show little autumn colouration. Rowans
are easily grow in any well-drained soil and are most
at home in areas with distinct winters.
Strawberry tree
The strawberry tree (Arbutus unedo) is so called because of its prominent warty red
fruit (attractive to birds) that follow the spring and summer clusters of
lily-of-the-valley-like flowers. It is a hardy evergreen with rounded, dark
green red-stemmed leaves, about 60 mm-long and finely serrated. The
reddish-brown bark is attractive too, especially when wet. It is tolerant of
coastal conditions and alkaline soil, which is unusual for an
a member of the erica family. Grow in moist, well drained, humus
enriched soil in sun or light shade. Although A. unedo is by far the most common species, I prefer A. canariensis as a flowering specimen.
Styrax
These small deciduous trees have a neat
growth habit and an attractive spring flower display. The most common species, S. japonica, grows to about 7 m and
has deep green pointed heart shaped leaves and slightly drooping racemes of
small bell-shaped white flowers. S.
obassia is a slightly taller species that has fragrant flowers. Both prefer
cool, moist, well-drained soil and cool, moist summer conditions. They blend
well with rhododendrons, camellias and fuchsias.
Tamarix
Tamarisks can be untidy rangy growers,
but are among the best flowering trees for coastal conditions. They have tiny
adpressed leaves that are reminiscent of heather (Calluna). T. parviflora is
usually regarded as the best flowering species and produces masses of minute,
bright pink flowers in spring and summer. It grows to about 6 m ×
3 m. Tamarisks prefer light well-drained soil in full sun. They are able
to tolerate the full blast of coastal salt winds but are neater and heavier
flowering if cared for with regular water and occasional trimming.
Vanilla tree
The vanilla tree (A. microphylla) is a rather open growing tree (around 8 m ×
5 m) with tiny rounded deep bronze green leaves and springtime clusters of
small fluffy yellow flowers that are strongly vanilla scented. It is easily
grown in most well-drained soils. A very attractive golden-cream variegated
form exists but is only rarely available. A.
lanceolata is a similarly sized species with larger leaves and larger but
less scented flower clusters.
Virgilia
Although they provide a good flower
display, care should be taken when planting these evergreen South African
natives. In many areas they self sow freely and may become weeds. Some
authorities consider the two species, V.
capensis and V. divaricata, to be
variations of the same species. Both have deep green, somewhat leathery,
pinnate leaves composed of many small leaflets. The underside of the leaves is
light green to slightly silvery. From spring to early summer, pendulous
clusters of pink to mauve sweet pea-like flowers appear. A tree in full flower
is quite spectacular but the display doesn’t last long. Virgilias are easily
grown in any light well-drained soil. They are best used as quick-growing
temporary plants, as trees over fifteen years old often become very untidy and
open.
Witch hazel
The witch hazels (Hamamelis spp.) are hardy deciduous shrubs and small trees valued
for the fragrant winter flowers, which have narrow, strap like petals and are
best described as spidery. The most popular species, H. mollis, has spicily scented bright yellow flowers from mid
winter. It may grow to 5 m × 3 m but is usually much smaller. H × intermedia, which is believed to be
a H. mollis × H. japonica cross,
includes several excellent forms, such as the brownish-orange-flowered ‘Jelena’
and the large-flowered ‘Arnold Promise’. All of the species and hybrids are
hardy to at least -20°C although the flowers may be damaged by very severe
frosts. Grow in moist, humus-enriched, well-drained soil in sun or light shade.
The Persian ironwood (Parrotia persica) is a closely related
plant that has reddish-orange flowers in late winter. Its rounded leaves can
become very colourful in autumn.
Sycopsis
sinensis is another related plant. Its winter-borne
flowers are golden-yellow to orange and the plant is evergreen.
Planting
As with just about every aspect of
cultivation, the more time you put into preparation before planting your trees,
the better the results. When you’ve taken great care to choose the right tree
and the right place, why rush to plant it?
The roots of a tree
spread far more widely and deeply that those of a shrub. Dig over the soil to about 300 mm below the depth of the new
tree’s root ball and to at least 500 mm greater diameter that its current
root spread. This will allow the tree to establish new roots quickly, which
will help to boost its growth and help to stabilise it. Dig in plenty of fine
compost to improve the soil texture and increase its moisture retention. If you
live in an area with a hard clay sub-soil use a crowbar or a pick to break up
the clay or you may find that your trees start to suffer from poor drainage and
impeded root development once their roots strike the clay.
Remove the tree from its container and
plant to the same depth as it was in the container. If the tree is bare-rooted
rather than container-grown, look for marks on the trunk that indicate the soil
level at which the tree was growing in the field. If the surface roots are
showing, plant a little deeper, but take care that you don’t bury the union
point of grafted or budded trees. Hammer in a stout stake, taking care not to
damage the roots. The ground around the tree will need to be trodden down somewhat
to firm up the tree, but don’t overdo it; you don’t want to compact down all
that laboriously loosened soil.
In very dry areas or where the tree must
fend for itself it’s often a good idea to make a small ridge of soil around the
drip-line of the tree. This ensures that any moisture dripping from the foliage
is channelled back to the roots.
Allow the tree to establish before adding
fertiliser. If you apply fertiliser before the tree begins to grow, it may
develop a too compact root system because there is no need for new roots to
seek out soil nutrients. Making the tree stable should be your first
consideration, staking helps but encouraging a quick root spread is the best
way. When you apply fertiliser put it just outside the drip-line and water it
in well to encourage the roots to spread downwards and outwards.
Maintenance
Maintenance is most important during the
first two years after planting. Trimming to shape, loosening
ties and restaking, fertilising and watering are all necessary to ensure that
your trees get the best start.
Unless you intend to train a tree to a
specific shape or style of growth, the pruning of young trees is generally just
a matter of removing any damaged branches and those that are likely to head off
at strange angles. Garden trees often look better if they’re allowed to develop
naturally, just aim to maintain a clean trunk with good canopy development,
there’s no need to prune to a perfectly straight trunked forestry specimen.
A young, newly planted tree with a large
head of foliage is very likely to be damaged by the wind, either directly
damaging through broken branches or by wind rocking damaging the roots. Young
trees must be firmly staked, but staking can cause problems too. Young trees
have soft bark that is easily damaged if it continually rubs against a stake or
against the ties that hold the tree to the stake. As the tree grows the stake
and ties may cut into the bark. Use ties made of a soft material that breaks
down with time and regularly check that the ties are still slightly loose and
the stake is not rubbing on the trunk. The new foam rubber tree ties are
excellent and can be adjusted as the tree grows, but strips of old cloth are
really just as good and they are biodegradable. Usually the stake can be
removed after two years, often sooner, but don’t underestimate the strength of
the wind.
Young trees will establish more quickly
if fed and watered, but as mentioned earlier this is better kept at a
subsistence level in order to encourage good root development. Established
trees will also benefit from feeding, especially if their roots are at all
confined. Use a general garden fertiliser and water it in well.
Young trees are usually vigorous growers
that are not greatly troubled by pests and diseases. If problems do occur they
can be treated just as you would a large shrub. However, large established
trees are difficult to treat; they are often too tall safely get to the top of
and effective coverage with sprays is all but impossible with domestic
gardening equipment. Controlling pests and diseases in large trees is usually
an area for professionals.
Taking the time to give your trees a good
start and looking after them in their early years will not only lessen the work
required later on, it will ensure that they will repay you with healthy growth
and brilliant colour.
Copyright Geoff Bryant
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