Lilacs
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Lilac time already? No, winter is definitely not lilac time. But if you want to be sure
of being first in the queue for what is always a limited supply of these choice
shrubs you need to order your plants soon. For while lilacs are currently
rather unfashionable, there are still enough gardeners with good taste that the
small numbers produced by nurseries are likely to have been sold by the time
the first one blooms.
Some idea of the lilac’s fall from grace
can be gained from the age of many of the cultivars currently available. Most
are over 50 years old. That’s simply because nothing better has come along to
replace them. Indeed, although up to 1500 cultivars have been raised, no
completely new cultivars were introduced between ‘Maud Notcutt in 1956 and ‘Monore’ (syn ‘Blue Skies’) in 1994, just a few sports and
releases of seedlings raised years earlier.
Yet a lilac in full flower is captivating.
Not just for the beauty of its flower heads, but also for that unmistakable and
often overwhelming spicy fragrance. And therein lies
the surprise: we’re exposed to its scent in so many products that we all know
what lilac smells like, but few of us grow it. Strange too, now that
old-fashioned and fragrant plants are so popular, that lilac is still out of favour.
While there are over 20 species, the most
common garden lilacs by far are Syringa
vulgaris and the cultivars derived from it. A native of south-eastern
Europe, the common lilac reached western Europe around
1550 when it was introduced from Turkey by
the same man who gave European gardeners the tulip: Ogier de Busbecq, the Holy
Roman Emperor Ferdinand I of Austria’s
envoy to the court of Suleiman the Magnificent. By the end of the 17th
century several cultivated varieties were known but it wasn’t until the 19th
century, when it became very popular in France,
that lilac breeding took off. ‘Charles X’, introduced in 1831 by Audibert
Frères is recognised as the first named cultivar.
Liège, now Belgian but then in France,
was the first centre of French lilac breeding, but when Victor Lemoine in 1850
bought plants of the first double-flowered cultivar, ‘Azurea Plena’ (1843), the
scene was set for a shift to his home town of Nancy in
north-western France.
This, however, didn’t happen for another 20
years, when in 1870 Nancy was occupied during the Franco-Prussian War. Needing to keep
themselves busy while trade was at a standstill, Lemoine and his wife started
hand-pollinating lilacs. From the introduction of ‘Jacques Callot’ in 1876 that
little pastime obsessed several generations of the family and led to a further
224 named cultivars. Although few of the original Victor Lemoine cultivars are
currently available, the white double, ‘Madame Lemoine’ (1890) is still common.
Later Lemoine cultivars, such as the strongly scented ‘Katherine Havemeyer’
(1922), are the mainstay of local lilac growers.
Not content to work with just S. vulgaris, the Lemoines made crosses
with an early-flowering Chinese species, S.
oblata, leading to the S. ×
hyacinthiflora hybrids, which flower slightly earlier than cultivars with a
purely S. vulgaris background.
‘Esther Staley’ is probably the most widely available S. × hyacinthiflora hybrid in New Zealand.
Even before Lemoine’s nursery finally
closed in 1955 the centre of European lilac breeding had shifted to Holland, where
there was a connection with lilacs dating back to Huguenot times. Unhappily,
little of note has come to New Zealand from the Dutch breeding other than the bicolour ‘Sensation’ (1939),
which has white-edged purple flowers, and the very pale yellow ‘Primrose’
(1949). And few, if any, of the over 100 cultivars raised by the Russian Leonid
Kolesnikov (1893–1973) are found here.
If they’re not French or Dutch or possibly
German, most lilacs seen in New Zealand gardens have American origins. American have
a long association with lilacs, the first being planted around 1650. George
Washington grew lilacs and Thomas Jefferson planted some in his garden at Monticello. Early
French and Dutch settlers, often Huguenots, brought lilac seeds to America.
The Dutch originally settled in New England, but many families later moved to Ohio, where
several fine cultivars were raised. Many of the modern American cultivars were
developed at Highland Park, Rochester, New York. Their fist, ‘President Lincoln’, was raised in 1916.
Lilacs other than S. vulgaris cultivars and S.
hyacinthiflora hybrids are grown in New Zealand but they’re not easy to find in nurseries and garden centres. The
Korean lilac (Syringa patula) is
probably the one most often seen. Native to Korea and
northern China, it is a 3 m high × 2 m wide bush with loose sprays of
lightly scented lavender flowers.
Persian lilac (Syringa × persica) is a
2 m high twiggy shrub that is thought to be a hybrid between S. × laciniata (itself a S. protolaciniata × S. vulgaris hybrid) and S.
vulgaris. Often slow to bloom, it is well worth waiting for because the
flowers are strongly scented.
Syringa japonica, S.
wilsonii and Syringa reflexa are
similar shrubs and well worth seeking out.
Syringa microphylla is a smaller bush. Left untrimmed it
eventually reaches 1.5 m high, but can be kept trimmed to under a metre
and may be grown among small shrubs or even in large rockeries. It flowers
heavily in shades of light to deep purple and is strongly scented, though you
have to get close to the plant to appreciate the fragrance.
Cultivation
Lilacs prefer moist, well-drained,
humus-rich soil with a near neutral pH. A hard compacted soil lessens their
ability to make good root development, which, as described later, is vital for
healthy growth. If the soil is inclined to be heavy or wet in winter, plant on
a mound of gritty soil. Sunlight is essential for flower bud production, though
dappled shade allows the flowers to last longer. Half-day sun usually gives the
best results.
Lilacs are not difficult to grow. In fact
they often grow only too well, producing suckers some distance from the main
stems. For this reason lilacs are sometimes grafted onto privet rootstocks.
However, I think its better to grow them on their own
roots. There are two reasons for this. First, the distant suckers form roots at
their base and are therefore an easy way to propagate the plant. Second, and
more important, the suckers are the plant’s natural method of rejuvenating itself.
Old stems, say those over 15 years old, lose their vigour and produce few
flowers. If these are cut out at the base, strong young stems will grow to
replace them.
That’s really the trick to pruning S. vulgaris lilacs. Remove and weak or
distant suckers, cut out the old unproductive wood at ground level and allow
the strong basal suckers to grow. Aim to keep about 7–12 stems of varying ages
that form a vase-shaped bush in which the stems do not overlap or rub on each
other.
After blooming the old flowers will die
away and fall. There is a brief period when they’re a little unsightly, but
don’t be tempted to dead-head them or you may remove the dormant buds that will
be next year’s flowers. For this reason avoid topping the main stems. Just
remove any weak side shoots or dead wood. The bush may eventually reach
5 m tall, but if you have some strong basal shoots coming on the very tall
stems can always be cut out when they get too tall.
If a bush is really overgrown it should be
reshaped over several seasons. Cut it back by a about a third in the first
winter, let strong new wood develop in the summer, then
remove most of the old wood in the next winter. After the third winter the bush
should be almost entirely made up of new growth that is then thinned as normal.
This usually works, though very old or poorly grown bushes sometimes simply
fail to regrow.
If your lilacs are grafted, keep them
trimmed to one main trunk and make sure the rootstock, which should be California privet
(Ligustrum ovalifolium), doesn’t send
up suckers of its own. Because you are relying on one main stem and its side
branches the plant will gradually lose vigour after about ten years. There’s no
easy way to rejuvenate it. It’s sometimes possible to produce suckers from the
lilac scion by burying the graft union, but that also encourages the privet
suckers to grow. Avoid lilacs grafted on Syringa
vulgaris stock as it’s far too vigorous and its suckers will eventually
take over.
The shrubby lilac species are easier to
prune. Just give them a light trim after flowering and cut out any old, damaged
or dead wood.
Copyright Geoff Bryant
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