University of Vermont Extension
Department of Plant and Soil Science
Spring News
Article
LOVELY
LILACS
Dr. Leonard Perry, Extension
Professor
University of Vermont
Lilacs are ubiquitous in New England
in the spring, great in landscapes as well as cut in vases. They
are an historic plant, found around many
old homes and even surviving around old foundations after the home is
fallen
down. They are easy to grow, require
little care, have a famous fragrance, and come in variations of red,
pink,
white, and purple. Even though blooms
only last a couple weeks, with a diversity of different plants from the
various
species you can have blooms over a 6-week period.
The two main requirements for lilacs
to succeed are a well-drained soil and full sun. They will
tolerate some shade, just won't be
a dense nor bloom as well. Once
established, they will even tolerate dry soils and drought.
After planting you may want to water
with some liquid fertilizer, or use fertilizer stakes you can buy as
such. Once established, fertilize lightly each year
if at all. In good loamy soils, or with
some compost placed around plants, they may need no fertilizer.
If
fertilizing, do so right after bloom. Too early and flowers may
abort
with just
leaves coming out. Too late and plants
may not harden properly for fall. Around
the fourth of July is about as late as you should fertilize, or for
that matter
prune.
You should plant lilacs where you
can appreciate their informal upright natural shape. If you want
neatly rounded shrubs, look for
other plants with this habit. A couple
of dense and rounded exceptions are the single purple Paliban Korean
lilac (Syringa
meyeri) that gets 4 to 5 feet tall and
a bit wider, and the single violet 'Miss Kim' (S. patula) that is
similar. If you need to prune branches
that are obstacles, or crossing and rubbing on each other, right after
bloom is
best.
When it comes to pruning, experts
have a couple of opinions you can choose from.
Some (such as myself) only prune branches as needed, eventually
removing
about a third of old branches each year.
This allows the plant energy to go into the new branches.
Eventually most lilacs will get tall (maybe 8
to 15 feet), with most the flowers at the top.
This makes them hard to see close up, but fine from home windows, the
street, or a distance. Plus, with some
pruning of lower branches you can appreciate the attractive stem
architecture.
Others like to prune about a third
of new growth off each year, but do so pruning back to sideshoots, not
shearing
as a hedge. This keeps plants and their
flowers lower, but sacrifices the natural shape and effect of the
stems.
Make sure when planting you allow
plenty of room for the mature height (and width) of a lilac, otherwise
you may
need to "basal prune" all stems back near the ground, and then wait a
couple years for new shoots to come up and start getting a few feet
tall.
Lilacs are often seen near building
foundations, especially good near corners.
They make great specimens in lawns and borders, and planted in a line
make a good seasonal hedge.
The main problem you may see with
lilacs if your site has late morning dew and little air circulation, is
the
white powdery mildew disease on leaves.
It is more an aesthetic issue, not causing enough harm to plants to
really warrant treating with sprays. In
some really wet springs some branches may all of a sudden wilt, with
black
tips. This is a blight which should only
come once, with new buds emerging from stems in a few weeks.
Occasionally a
lilac may get small rounded brown bumps, or scales, which can be
treated with a
spray or infected branches cut off.
Most lilacs gardeners are familiar
with are the common lilacs (S.
vulgaris) and their cultivars
(cultivated varieties) that bloom in mid to late May in the
north. Some that bloom just a bit earlier are the
hyacinthiflora hybrids, first bred by the famous Lemoine nursery in
France in
1876. Examples of these are the single
purple 'Pocahontas', the single white 'Mount Baker', the single blue
'Blanche
Sweet', or the single magenta 'Asessippi'.
As you see, lilacs come in more than
the color "lilac" and white.
Lilac specialists have grouped the over two dozen species and hundreds
of cultivars into 7 flower colors: white, violet, blue, lilac, pink,
magenta,
purple. For each of these there are
singles and doubles. In addition there
is the single yellow 'Primrose', and the bicolor 'Sensation'. The
latter arose as a mutant in a Dutch
greenhouse (from the lavender 'Hugo de Vries' that was being forced to
flower
at Christmas) in 1938, and has purple petals each in white.
The other large group are the late lilacs, mainly the Preston hybrids
originally bred by a Canadian breeder by that name. These may not
have the wonderful fragrance of
the common lilacs, but bloom a week or 10 days later and tend to be
larger in
all respects-- leaves, flowers, and wider plants. A few of my
Preston favorites are the deep
pink 'Miss Canada' and 'Donald Wyman', and the white 'Agnes
Smith'.
I often get asked what is my
favorite lilac. It is hard to answer as
so many, in fact most including the common species, are
beautiful. The one that stands out for me and many
though is 'Krasavitsa Moskvy', or as many know it Beauty of
Moscow. It was selected by a famous Russian breeder
in 1947 from an offshoot of 'Belle de Nancy'-- one of the French
Lemoine hybrids.
The pink buds open into creamy white flowers tinged with pink, a
silvery opal
color.
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