Gilding the Lily: Developments in Asiatic Hybrid Lilies
by Maureen Troesch
Gardeners have shared a centuries-long fascination
for the lily. Chiefly prized for the beauty and elegance
of their flowers, lilies have also been cultivated for
their reputed medicinal properties, as sources of perfume
and even as an edible (though not necessarily palatable)
crop.
A number of lily species are native to Europe and North
America, with our most familiar native lily being Saskatchewan's
floral emblem, the western red lily (Lilium philadelphicum).
Although lilies can be found growing wild in most temperate
regions of the northern hemisphere, more than half (about
60%) of known lily species are native to eastern Asia,
with Korea, Manchuria, and Japan having the largest
number of native lilies. It was the introduction of
these Asian species into North America and Europe in
the nineteenth and early twentieth centuries which inspired
the greatest interest in cultivated lilies, and the
great profusion of lily hybrids and cultivars which
followed. Plant breeders, both amateur and professional,
continue their efforts to gild the lily, developing
plants that are ever more robust, more disease resistant,
and more spectacular in appearance than their forebears.
At present, many of these efforts are directed towards
the creation of polyploid lily cultivars.
So, just what is a polyploid lily? The word "polyploid"
is a specific term which indicates that a plant has
more than the normal quantity of genetic information.
Almost all true lilies have 24 chromosomes on which
the genetic information for the plant is located. On
a typical plant, one set of 12 chromosomes will have
been inherited from the female parent, and the other
set of 12 chromosomes will have been inherited from
the male, or pollen parent. When sexual cells from the
female parent fuse with the sexual cells from the male
parent, the total chromosome number is restored to 24,
and a normal lily plant is formed. Such a plant, with
two sets of genetic information is referred to as a
diploid.
Alas, with lilies, as with humans, sexual reproduction
is a complex process, fraught with hazards and attended
by all manner of complications. Occasionally, something
will go awry, and instead of producing a normal sex
cell with 12 chromosomes, the egg cell or pollen grain
will contain 24 chromosomes. Should these abnormal cells
fuse to produce a viable seed, that seed will give rise
to a plant that contains more than the normal 24 chromosomes.
Such a plant would be referred to as a polyploid. Polyploids
may arise in other ways as well. Now and again, a plant
will spontaneously double its chromosome number, usually
the aftermath of a flirtation with a member of another
species. For example, wheat, which has six sets of chromosomes
(hexaploid), is the result of a cross between a diploid
and a species with four sets of chromosomes (tetraploid).
Rather than creating offspring with three sets of chromosomes
(triploid), as one might reasonably expect, their chromosome
number doubled, producing a hexaploid plant. As if things
were not complicated enough with natural alterations
occurring, plant breeders are also able to interfere
with normal seed development in plants, and deliberately
generate polyploids.
No doubt the overwhelming question at this point is:
Does anyone apart from botanists, who as everyone knows,
are a very odd group of people, obsessed by all manner
of peculiarities, really care about the sexual abnormalities
of lily plants? The answer to this question is yes,
because polyploid plants often possess a number of interesting,
and potentially valuable, characteristics. Often polyploid
plants are larger and more robust than their ordinary
counterparts. Polyploid plants are also frequently sterile.
This means that they flower, but the flowers produce
no seeds. While grain farmers would be quick to agree
that this is a bad thing in a wheat plant, those same
people would probably acknowledge that it is an excellent
quality in a banana or a grape. The tiny black specks
you see in the centre of a banana never develop into
seeds because the plant that produced the fruit is a
sterile triploid. From the point of view of a lily grower,
however, the most important aspects of polyploid plants
includes the bigger flowers, thicker petals and stronger
stems which are often found on polyploid plants. In
windswept Saskatchewan, robust flowers held on sturdy
stems are particularly valuable traits.
Numerous polyploid cultivars have been introduced in
recent years. Some good ones to try include:
When purchasing lily bulbs, you should select large,
firm bulbs reasonably free of injuries and blemishes.
Plant the bulbs in spring or early autumn in well-prepared
soil, choosing a sunny, well-drained site. Lily bulbs
are typically planted at a depth that is roughly twice
the depth of the bulb. Large bulbs are planted about
15-20 cm (6-8 inches) deep, and smaller bulbs are planted
10-15 cm (4-6 inches) deep. Approximately 30 cm (12
inches) should be left between bulbs. With reasonable
care, and a little luck, your efforts should be rewarded
with many seasons of fabulous flowers.
