Choosing and Growing Echinacea and Purple Coneflower
CHOOSING & GROWING ECHINACEA - PURPLE CONEFLOWER
INTRODUCTION
Cone crazy? Our guest writer this week, William Cullina, explains the coneflower
species, Echinacea. Learn, in non-technical language, how
the coneflower grows, why some flourish in wet to normal soil, and some are
difficult to grow or to transplant.
The natives with slender leaves also have a
taproot and are suited to dry areas. They can be difficult to transplant. Many hybrids that share the narrow leaf fall into this
category. They do not want fertile
or moist soil. These coneflowers need
to be transplanted when young into a difficult, sunny, dry space.
Look for hybrids with wide leaves in beautiful new
colors of red, white, yellow, and orange along with the signature pink and
purple. The wide leaves denote a strong
purple coneflower parentage in their background. The plants will be easier to transplant (no taproot) and
will stand up to most garden conditions if they share this background.
Bill writes that raising coneflowers from seed is
very easy, and he tells how. He
also suggests that if you have a Tennessee yellow coneflower in your garden
along with purple coneflower, you might find your own hybrids coming up from
seed.
Find out how to grow coneflowers successfully,
especially the purple coneflower and its hybrids, which have evolved into true
garden plants. GardenSMART
visited the Coastal Maine Botanical Gardens and visited with Bill Cullina, the
Plant and Garden Curator.
There are very few native plants with wider appeal
than the coneflower (Echinacea spp.) This uniquely North American genus of
ten species epitomizes the meadow or prairie wildflower. In general, coneflowers are easy to
grow in sunny, well-drained soil and the large daisy-shaped blooms remain
colorful for at least a month.
The plants grow from a woody crown, sending up
first a tuft of basal leaves followed by leafy flower stems that rise up in
mid-summer. Each stem is topped by
one large bloom that can be as much as 4 inches across and once the first bloom
begins to fade others grow from small side branches to take its place.
Like other members of the aster family, Echinacea
flowers are technically inflorescences made up of many small flowers serving
one of two functions. Each petal
or ray is really a single flower with five petals fused into one. The ray flowers form a ring around the
central cone, which is also composed of many individual flowers that have no
petals.
The division of labor has particular consequences
for pollination and seed set. The
rays are sterile, functioning merely as advertisement for the less noticeable
fertile flowers that make up the cone. These later produce nectar and pollen as well as seeds. A bee or butterfly cannot help but
notice the ring of large, colorful ray flowers as it passes, and the cone
provides a perfect landing pad for the insect as it comes in to investigate.
What the bug finds is a host of little, nectar
rich blooms packed in together - a sort of one stop shopping that is very
appealing. Rather than wasting
energy flitting here and there, the bee or butterfly can settle in and drink
from a bunch of flowers at once. When you plant coneflowers, the butterflies and bees are sure to follow.
This combination of colorful advertising and
concentrated, easily accessible flowers has made the aster family one of the
most successful and diverse in the world. However, the coneflowers appear to be a new member of this large family
as most of the species are nearly similar in leaf and flower shape and color.
Coneflowers likely evolved fairly recently during
the drying of the North American climate during the Pleistocene that allowed
the development of prairie grassland habitat from the Southeastern U.S. to the
western mountains. The typical
color of the bloom is light lavender with a deep red or black cone bristling
with yellow or red knobs. These
knobs or bristles likely aid pollination by providing scaffolding for the pollinator
to crawl on and then discourage predation of seeds by birds.
There are
two basic leaf types in the genus - one characterized by a 2-3 inch wide, ovate
blade with a rounded or heart-shaped base and the other by a narrow (<1 inch
wide) linear leaf. The
narrow-leaved species tend to grow in drier habitats than the two wide-leaved
ones (Echinacea purpurea - purple
coneflower, which is found in the prairies west of the Appalachians and Echinacea laevigata, smooth purple
coneflower, which is a rare species from the eastern side of those same
mountains).
The most
widespread of the narrow-leaved species is E.
pallida, pale coneflower from the prairies east of the Rocky Mountains. It is closely related to the smaller E. angustifolia, narrow-leaved purple coneflower,
which grows on both sides of the Rockies. There are several other related species, notably Tennessee coneflower (E. tennesseensis), which is very similar
to E. angustifolia but restricted to
dry, rocky prairie remnants on the
Cumberland Plateau of Tennessee. Like
most coneflowers, it is adapted to rather parched, fire-prone grasslands.
From a
horticultural point of view, this is important as most of the species resent
wet soils and poor air circulation around the leaves and crown of the plant. They have large, fleshy taproots that
burrow deep in search of moisture and act as a food pantry to help the plant
recover after drought or the frequent fires that sweep through their habitat.
CULTURE
Taproots
resent disturbance, rot easily if drainage is poor, and generally make plants
more difficult to transplant and cultivate. The exception in this genus is Echinacea purpurea, which prefers damp or even wet prairies and consequently has evolved a more
forgiving fibrous root system that functions much better in this type of soil.
From a
functional point of view, purple coneflower is a much easier and forgiving
plant to cultivate and it is no wonder that it has become the unquestionable
favorite among gardeners. It has a
further advantage in that its ray petals are wide and flat unlike the narrow or
curled rays of the other species.
The rays
of wild plants point downward much like the feathers of a badminton
shuttlecock, though breeders have selected forms that hold their rays parallel to the ground for flatter
appearance. Tennessee coneflower
is the only species with rays that naturally orient lightly upwards, and
breeders have crossed this one with purple coneflower to yield hybrids with
even flatter heads.
THE HYBRIDS
One
coneflower stands apart from the others in a more noticeable way. The variety of Echinacea paradoxa from Arkansas and Missouri has yellow ray petals. Like a red-haired child among a family
of brunettes, yellow purple coneflower is a bit of a mystery. As a garden plant, it is interesting
but not outstanding as there are plethoras of yellow daisies available that
grow more easily and have larger, flatter flowers.
However,
several breeders realized that if you cross this plant with purple coneflower,
all manner of white, orange, red, purple, and pink progeny result. Some crosses also bring in Tennessee
coneflower to flatten out the rays.
In recent
years, a number of yellow, orange, and red coneflower hybrids have hit the
perennial market and most are quite beautiful. However, many have suffered from the same problems that the tap
rooted species face under cultivation - namely root rot and transplanting
difficulty. The best hybrids have
a double dose of the fibrous-rooted purple coneflower in their background and
you can distinguish these by their wider leaves.
Color is not the only option as regards coneflowers. When I worked at Niche Gardens in the early 1990's, we
selected and introduced a compact coneflower I named Kim's Knee-high after the
owner of the nursery, Kim Hawks. It
grows to only 16-18 inches, a half to two-thirds the height of a typical purple
coneflower, yet it flowers prolifically.
This was
one of the first coneflower cultivars to be tissue cultured and it has proven
itself in gardens over the last 15 years. Tissue culture and the natural variability of the plants have both
yielded other forms including types where some or all of the cone or disk
flowers develop double or semi-double ray petals. As Itsaul Plants, one of the primary coneflower breeders
operating today puts it, we have "gone cone crazy!"
HOW TO RAISE CONEFLOWERS FROM SEED
Though
some of the hybrids are sterile, you can raise the species easily from seed,
and if you grow yellow purple coneflower together with the purples, you might
even find some hybrids among its seedlings. The seed is ripe when the cone dries out. At this time, the bristles turn dark
brown and rather sharp and spiny.
The
silvery gray seeds are packed in among the bristles and both fall out when you
shatter the cone. I don't bother
separating the seed from the bristles. The seed germinates after 6-12 weeks of cold, moist
temperatures.
Sow seeds
outdoors or in pots in late fall (cover them lightly). Alternatively, you can soak the seeds in
a cup of water for a few hours, and then towel them lightly dry before putting
them in a sealed baggie in the refrigerator for the requisite number of weeks. After their chilling, sow the seeds
indoors or outside after the danger of frost is passed. They should sprout in 2 weeks.
In the
nursery, coneflowers mature rapidly and often flower the first summer from seed
germination in the spring. Transplant
your plants into well-drained but moist topsoil where they will receive at
least 5 hours of summer sun.
HOW TO GROW
Many
coneflower species are restricted to high pH soils, so add lime if your soil is
naturally acidic (below a pH of 6.0). The narrow-leaved species do better in slightly nutrient-poor soils, but
purple coneflower and its hybrids need higher fertility to do their best. I have found that most of the hybrids
and fancy cultivars are less vigorous than the wild type purple coneflower, so
you will need to give them more attention. Unlike their wild cousins that grow just as well in the
meadow or prairie, the fancy cultivars are really strictly garden plants.
