Tulips
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Ask a group of gardeners to list the top ten
spring-flowering bulbs and the chances are that they’ll all put tulips near the
top of their lists, probably just below daffodils. So I don’t really need to
describe tulips, do I? Everyone knows them and most of us love them, but though
beautiful and spectacular, they’re not always the easiest bulbs to grow well.
Gardeners in mild areas often find that their tulips’
flowering is limited because their winters lack the cold needed to adequately
chill the bulbs, while aphids, viral and fungal diseases are problems
everywhere. However, with a little care and attention, tulips can be very
rewarding and productive.
History
Tulips have been in cultivation for a long time. Exactly how
long is not known. We know for sure that they first reached temperate European
gardens in 1554, but the earliest mention of them in a gardening context is in
a Persian poem of 1258, so we can assume they had been cultivated in their
native lands for some time before then.
Even the name tulip has dubious origins. The Persian and
Turkish name for the bulbs was ‘lale’, and it seems
likely that the Belgian diplomat, Ogier de Busbecq’ who sent the first bulbs
and seeds to Vienna simply
corrupted the Turkish word for turban (tülbent) to tulipam as a description of the shape of the flowers.
What is certain is that within 75 years of their arrival in Europe
they were so widespread and intensively cultivated that John Parkinson in his
1629 book Paradisus was able to list
140 cultivars. And it was only five years later that the Dutch craze for
tulips, known as ‘Tulipomania’, began.
Tulipomania was a speculators’ promotion based on getting
rich quick by selling desirable tulip varieties to those who would breed them
and then sell the progeny. Think ‘1987 crash’, phone cards or ostriches and
you’ve got a pretty a good idea of what it was all about. Needless to say the
bubble burst and many people lost their fortunes. But for the brief period
between 1634 and 1637 tulip speculation was all the rage and, like all boom and
bust cycles, those who knew when to get out did well. Records discovered in a
demolished Brussels house revealed
that it had been built with proceeds from the sale of just three tulip bulbs.
Even though their height of financial fame didn’t last,
tulips remained popular and continue to be grown in large numbers, particularly
in Holland. However, instead of
being cultivated for the production of bulbs, the vast majority are now grown
to satisfy the demands of florists. Tulips, whether
forced into bloom under lights or grown outdoors, last remarkably well when cut
and have always been popular cut flowers.
Tulips are also extensively cultivated by botanic and show
gardens, which often plant out massed beds for spring displays. Here in New
Zealand the Wellington Botanic Gardens tulip beds are a highlight of spring in
the capital and attract thousands of visitors.
Tulip divisions
However they’re cultivated, tulips are beautiful plants, but
with so many that are so similar to one another they’re difficult to classify.
So, in common with other genera, such as lilies and daffodils, that have been
extensively hybridised and developed, tulips are divided into several groups or
divisions based on parentage, flower type and flowering season.
Types
Apart from the obviously very distinct types, such as the
frilly Parrot tulips and the distinctly different species, differentiating
between these groups is something of a minefield for the everyday gardener.
Unless you’re a real tulip buff, in which case you probably know all the
details, it’s probably best just to stick to broadly defined flowering times
(early, mid and late) and buy your tulips on the basis of the photographs in
the nurseries and garden centres. But for those who need to know a little more,
here are the main types.
Early
The single-flowered early tulips are 15–40cm tall and occur
in a wide range of colours, including bicolours, striped and otherwise marked.
They include some of the oldest tulips still cultivated, with some dating back
to the 1700s. The doubles tend to be self-coloured or more simply marked and
are at the taller end of the size range, around 30–40cm tall. They tend be
rather open, frilly-petalled doubles rather than rosebud or peony-form in
style.
Mid-season
Similar to the Early Tulips, the Mid-season group includes
two types: the 40–50cm tall Triumph hybrids and the 50–70cm tall Darwin
hybrids. Triumphs, which now include many of the earlier Mendel tulips, were
developed in the years between the two world wars. They occur in a huge range
of colours and new hybrids are still being developed. Darwin
hybrids date from the early 1940s and are generally robust plants. They don’t
cover quite the colour range of the Triumphs but make up for that with vigour
and clarity of colour. Darwin
hybrid tulips are everyone’s idea of what a tulip should look like. They’re the
style most often used for mass bedding.
Late
In addition to the typical single and double forms
(peony-flowered), this group includes five fancy styles: lily-flowered, with
long pointed petals; Fringed, with finely cut or fimbriated petal edges;
Viridiflora, with flowers in pastel tones marked and flared with green;
Rembrandt, in which the flower patterns are caused by the tulip breaking virus;
and Parrot, a selection of sports in which the petal edges are deeply cut and
sometimes recurved.
All of these flower types occur in a wide range of colours.
The very darkest-flowered or “black” tulips are to be found in the
late-flowering group. Many of these fancier blooms appeal for their novelty
value and are grown as single specimens, either in the garden in mixed
plantings or in containers.
Botanicals and Species
This catch-all category encompasses all the wild species,
their cultivars and a few stray garden forms that may or may not be hybrids.
The wild species, of which there are around 100, are of
course an enormously variable group. They include the tiny flowers of T. biflora, the beautiful yellow and
creamy white T. tarda, the strangely
shaped, narrow, yellow and red petals of T.
acuminata and even a few stoloniferous species. Some of the species,
particularly T. eichleri
and T. batalinii, occur in several
cultivars.
Three selections of species hybrids are large enough to be
recognised as distinct groups. They are: Kaufmanniana, usually less than 30cm
tall with flowers in yellow, orange, red or combinations of theses colours;
Fosteriana, 25–50cm tall with cream, yellow, orange or red flowers often with a
contrasting throat colour; and Greigii, usually less than 25cm tall with
purple-mottled foliage and flowers in much the same colour range as the Fosterianas.
Climatic requirements
As with virtually all plants, success with tulips is largely
a matter of replicating as close as possible their natural growing conditions.
Tulips are native to southern Europe, western and
central Asia and North Africa,
and most come from areas with a cool, wet winter and a distinct spring season
that is followed by a dry summer.
Although some of the species, notably those from the Mediterranean
region, will thrive in mild climates, most tulips need a prolonged period of
winter cold. This doesn’t have to be severe, but unless the soil temperature
falls below 8–10°C during their slow winter development, tulips may flower on
very short stems at near ground level or the buds may be aborted entirely. The
soil temperature at planting time is also important because if it remains at
over 14°C for a prolonged period, the bulbs may start into leaf growth but
abort their flower buds.
If you live in an a mild area where the warm autumn weather
lasts well into May or where the soil temperature tends to stay above 10°C year
round, you may have to chill your tulip bulbs in a refrigerator or buy new
stocks each year. Keeping the bulbs in the vegetable compartment of your
refrigerator at 2–5°C for around 8 weeks prior to planting should be adequate.
If you have to chill the bulbs make sure they’re planted at the coldest time of
the year, usually around late June to mid July. That means putting them in the refrigerator
from late April onwards.
Planting
Tulips should be planted from late autumn to early winter in
a sunny position with well-drained soil that is preferably very slightly
alkaline (pH 7.0–7.5). Most soil types can support tulips, but it’s important
that the soil should deeply cultivated and
well-drained in order to keep the bulbs rot-free and too allow the roots to
spread as much as possible.
They generally do best when planted fairly deeply, say
around 12–15cm. If you intend for the bulbs to remain in the ground and
naturalise, plant even deeper, down to 30cm. Shallow planting will often cause
the foliage to appear too early, making it prone to winter damage, and the
flower stems will not be as strong and droop-resistant as those of more deeply planted
bulbs. Planted at such depths, it’s not uncommon for the roots to reach as far
down as 60cm, at which level they can obtain a steady supply of minerals from
the subsoil, in turn further improving the vigour of the bulbs.
Deep planting also ensures a more stable soil temperature,
which means that the bulbs are not much affected by any unusually hot or cold
conditions that might prevail for a day or so during winter or early spring.
Flowering
Tulips are very sensitive to being damaged as they emerge
from the soil and as their flower buds develop and expand. Take great care when
cultivating around the bulbs because any small nick or scrape on the developing
foliage will enlarge as the leaves expand and may form a hole or leave an
unsightly scar. The flower buds are sensitive to sudden changes in temperature
and soil moisture, and if stressed too much will simply cease developing and
abort.
Provided they are fed well and receive plenty of sunlight,
tulips should be largely self-supporting. However, it often occurs that the
flower stems are rather floppy and inclined to droop. Planting the bulbs
en-masse so that they help support one another is one solution, but sometimes
you may need to use small bamboo canes to support the longest flower stems.
This is best done early, before the flowers open, droop and become mud
spattered, and of course take care not to spear any bulbs with a bamboo cane.
Watch the flowers for signs of aphids. Inside the flower
heads is one of the first places these pests are found.
Once the flowers are spent, remove their heads to prevent
any pests from sheltering within. Any flowers that have shown signs of viruses
should be burnt.
Pests
Because they often completely smother the
flowers and buds, aphids are the pest that are most easily noticed, but more
insidious are bulb mites, which attack the bulbs and multiply within them,
causing the bulbs to become soft and eventually rotten.
Dipping the bulbs in insecticide before planting will ensure
they start life clean and healthy. A dusting of soil insecticide about the time
the foliage starts to really make a growth spurt will keep them that way.
Aphids often occur in such heavy infestations that they can
be very debilitating. They not only suck the sap of the tulips and drain their energy,
but dust and debris will stick to the aphids’ honeydew secretions making the
foliage unsightly. Fortunately, aphids are not very vigorous creatures and are
easily controlled even with very mild insecticides and soap- or detergent-based
sprays. However, they certainly have the weight of numbers and breeding
potential on their side, so constant vigilance is essential.
Both bulb mites and aphids spread diseases and should be
controlled as much for that reason as for the direct damage they may cause.
Diseases
Tulip fire (Botrytis
tulipae) is a fungal disease that can attack any part of the plant, but
which is most readily observable when the foliage develops a greyish-white
‘ashen’ look. It usually occurs when the bulbs are stressed, such as when hit by
late frosts or during periods of unusually warm humid weather.
The fungal spores spread rapidly and are a major threat
where tulips are grown en masse, such as in commercial flower or bulb beds. The
disease is not always well controlled by fungicides and the only sure method of
control is the rapid removal and burning of infected stocks. It’s also
advisable to avoid planting tulips in an infected area for at least two years
after an outbreak.
The best known and most significant viral disease of tulips
is tulip breaking virus or TBV. It may in fact be a combination of several
diseases that cause splashed, spotted or striped markings known as ‘broken’
colours. These brilliantly marked tulips, known as Rembrandts, are certainly
spectacular but the virus eventually weakens them and they gradually lose
vigour and die.
Once offered for sale, such plants are no longer
deliberately bred. Although their striking colouration may tempt you to keep
any infected tulips, remember that plant viruses are virtually incurable and
that the disease could spread.
The bulbs are also prone to a soft rot that causes them to
decay in the ground. Although it’s discouraging to find that your bulbs have
rotted before they’ve even emerged, this isn’t really that serious a problem. It
isn’t spread easily and usually only develops if the drainage is poor. Dipping
the bulbs in a fungicide before planting and providing good drainage will
largely prevent rot developing.
Lifting
Once the bulbs have sprouted, flowered and died back, you need
to consider their summer requirements. Tulips generally prefer warm, dry summer
conditions and many of the same areas that are too mild in the winter are often
too damp in the summer to ensure the bulbs’ continuing good health. Even in
dry-summer areas it’s usually best to lift the bulbs so that they aren’t
damaged by being cultivated around or through competition with other plants.
The bulbs planted in the winter are spent during the
flowering process and are replaced by a new flowering sized bulb and one or more smaller ‘daughter’ bulbs. So when you come to lift the
bulbs you should notice an increase in their number.
The lifted bulbs should be cleaned of soil and other debris,
dusted with flowers of sulphur to keep them fungus-free and stored dry at around
15–21°C. Heavy brown paper bags are best for storage as they allow the bulbs to
breathe and because they will quickly reveal if any moisture is present.
The bulbs will start to show foliage in the late autumn and
in suitable areas may be planted as soon as the soil is cool enough.
In areas with an appropriate climate, such as most of the
east of the South Island, tulip bulbs can be left in the
ground all year. In warmer and wetter areas take care to select species tulips
from mild climates if you want to leave the bulbs untouched. Good choices for
mild gardens include T. bakeri, T. clusiana, T. kaufmanniana, T. cretica,
T. sylvestris and T. saxatilis. Tulipa sylvestris and T.
sprengeri are particularly tolerant of damp summer conditions.
Copyright Geoff Bryant
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