Lottah Nursery Tasmania, Australia
Frequently asked questions and answers about lilacs and their cultivation are listed on this page. More will be added when we know what the questions are.
Why aren't my lilacs
flowering?
(back to top)
Assuming that the climate is suitable and the plants are healthy and
getting sufficient winter-chilling check the following:
a) the flowering buds have not been pruned away in winter
b) flower buds had not been frost damaged
c) plants are getting sufficient sunlight
d) nitrogen/potassium ratio is adjusted for flowering - reduce
nitrogen if growth is excessive
e) pH is around 6.5
f) clone is not in juvenile stage making a lot of vegetative growth
g) clone is not floriferous - we have found some clones to have poor
flowering, e.g. our S. x hyacinthiflora 'Clarke's Giant'.
Would deep planting of
grafted lilacs establish scion roots? (back to top)
Our limited experience using constriction ties on nurse-grafts over
a range of rootstocks suggest that while it is possible with
juvenile material, the likelihood decreases with increasing age,
i.e. more than a few months old. However any suckers emerging from
the scion underground are likely to initiate their own roots.
Should grafted lilacs be
planted with the graft underground? (back to top)
Probably; at worst that will hide the unsightly union. However any
rootstock suckers developing will emerge from underground and be more
difficult to remove completely.
The belief held in certain gardening circles that grafted lilacs do
not flower unless they form their own roots is a fallacy. Some of our
newly introduced Russian cultivars grafted in December 2004 were
flowering 10 months later when plants were standing around 300 mm
high.
Why are self rooted
lilacs superior to grafted plants?(back to top)
a) no long term incompatibility
b) no rootstock suckering problem
c) generation of multiple stems for renewal pruning
d) easy multiplication with clonal suckers
e) no loss of plant if top is lost to blight or animals - more
shoots will emerge from the root system
f) dwarf varieties require their own roots to preserve size
How long do I have
to wait for the first flowers?(back to top)
Most varieties are precocious and flower the second season, if not
the first, in the greenhouse; provided plants make normal growth,
flowers may be expected the year after planting.
I live in
(somewhere) - would lilacs grow here? (back to top)
Best advice is to check neighboring gardens for presence of
lilacs. Given the popularity of the genus their absence would
probably indicate their unsuitability. Presence of apple trees is
likewise another good indicator that the area experiences
sufficient winter chilling for growing lilacs. For
marginally suitable areas with lower winter chilling we
would suggest trying S. protolaciniata or its hybrids
x chinensis. Please check our page on warm
climate lilacs.
What fertilizers should I use
for lilacs? (back to
top)
Check soil acidity and add lime/dolomite in late Autumn or early
Winter to bring pH up to around 6.5 - at the rate of no more than
250 g/m2. If phosphorous is required add
some a few weeks after liming. Nitrogen and potassium
are best applied in split applications through the growing season.
Alternatively add your favorite mix approximating 5-10-10
(relatively low nitrogen and high potassium to encourage flowering)
a few weeks after growth begins. On no account should concentrated
fertilizer other than the slow release types be applied into the
planting holes as excess salts would damage emerging roots.
Another method used by growers elsewhere is to apply fertilizers in
Autumn but we have no first-hand experience in this.
We link to an article for treating clay soils with gypsum.
How long do lilacs
live? (back to top)
In the U.S. vulgaris selections growing at the Governor
Wentworth estate in Portsmouth, N.H. are reported to be 250 years
old. Trunk diameters approaching 600 mm are not unknown.
S. pekinensis trees in their natural habitat have been
reported to have trunk diameters over 600 mm and standing at 12 m
high, which would make them fairly ancient trees.
Would suckers
emerging from self rooted lilacs cause a problem in later
years? (back to
top)
We suspect this is likely - a sharp spade to remove undesirable
suckering in the early stages should prove temporary respite.
Can lilacs be
multiplied using suckers? (back to top)
Certainly, if they are on their own roots and not grafted. Simply
dig up the sucker with sufficient roots after leaf fall and
transplant them to another site.
For a better root system girdle the sucker or use electrical cable
ties for constriction underground to encourage more profuse rooting
during the second season.
Do you export lilacs
outside Australia?
(back to top)
Generally we encourage northern hemisphere customers to purchase from
north America or Europe because the seasons are synchronised. Tasmania
has a relatively mild climate and plants do not get sufficient winter
chilling until late August. This is rather late in the season to be
planting lilacs in the north.
Although we have successfully exported lilacs to Japan, our
preference is for dealing with southern hemisphere customers.
How do
I learn more about lilacs? (back to top)
A great deal of information together with a good selection of images
is available in Fiala's book, Lilacs: The Genus Syringa.
Beyond that, join the International Lilac
Society to keep up with the latest in lilac happenings:
ILS Secretary
c/o The Holden Arboretum
9500 Sperry Road
Kirtland, OHIO 44094-5172
USA.
How do I prune
lilacs? (back to
top)
Go to our Pruning page.
How large are the plants
offered for sale?
(back to top)
There would be a fair amount of variation amongst the different
cultivars. Dwarf varieties may be expected to be offered as smaller
plants. Size of tissue cultured lilacs bear some relation to the time
when they were deflasked as well as on cultivar charcteristics. In
general we are more interested in providing an adequate foundation
in the form of a good root system than in stem height.
To be more specific 'Maiden's Blush' offered in 2004 range from 500
mm to 1 m height, often with multiple stems.
External Links: Another Lilac FAQ
2006 (6, 14, 120, 1321)