University of Vermont Extension
Department of Plant and Soil Science
Anytime News
Article
CARY AWARD
WINNERS FOR 2012
Dr. Leonard Perry, Extension Professor
University of Vermont
In New England, distinctive trees and shrubs are given
the Cary Award. Named for a
Massachusetts nurseryman, and administered by the Tower Hill Botanic
Garden,
this award is given to several winners each year as judged by a
panel of
professionals. These are either new
plant introductions, or others that aren't new but deserve wider use
in
landscapes. The two winners for this year include a rose and a
yucca—shrubs,
but which are often grouped under perennials even though their tops
generally
don’t die back to the ground in winter.
Adam’s needle or yucca (Yucca filamentosa) has a quite
interesting and different habit,
consisting of long sword-shaped leaves with sharp tips (use eye
protection when
working around them, and keep children away).
Flowers in June and July are on stalks to 7 feet high above the
basal
leaves, which are only up to 2 feet high.
The large and creamy white bell-shaped flowers are held in large
open
clusters of several dozen flowers, making quite the show. The sweet
scent of
flowers attracts a pollinator in native areas— the very small yucca
moth.
Although evergreen in winter, in colder climates such
as much of Vermont, the leaves may get quite a bit of browning from
winter
injury. This damaged growth dies back
the next season in these climates as new growth emerges. It will
grow to USDA zone 6 in the north (0
to -10 degrees F minimum in winter), and in protected sites in the
colder zone
5.
Adam’s needle has been used medicinally and the
leaves, with their white curly threads or filaments along the edges,
have given
rise to the species name. Native peoples
used the strong leaf filaments to weave into fabrics.
This species of
yucca, with its dark green leaves, is native to southeastern states
while other
species are seen in Mexico and the Southwest.
It has gained popularity with the introduction of several cultivars
(cultivated varieties) with variegated leaves.
‘Color Guard’ has bright yellow centers in leaves, ‘Gold Heart’ has
creamy yellow centers, while ‘Bright Edge’ has wide yellow edges to
the shorter
leaves. ‘Golden Sword’ also has bright
leaf edges, only with larger leaves. ‘Variegata’
has white leaf edges.
With such striking habit, it lends itself to a
specimen in borders. It is a perfect
choice for Mediterranean, Spanish, or contemporary style gardens.
It is a good choice for urban gardens as well,
tolerating poor soils, soil compaction, pollution, and winter salt
spray from
roads. Give well-drained soil and full
sun, although it will tolerate a few hours (3 or 4) per day of
shade. Once
established, the long tap root makes it quite drought tolerant.
This means too, that you should place it
where it will stay as it resents moving.
It is difficult to get all the roots, and those left will resprout
to
form new plants. In fact, root cuttings
are a main method to propagate this plant.
The other Cary winner for 2012 is the now well-known
Knock Out roses. These have become the
top selling roses nationwide as they are relatively hardy, disease
resistant,
and long blooming. Knock Out is actually
a group of 7 different named selections with flower variations of
pink or
yellow. The original introduction, from
the year 2000 and the Wisconsin botanist William Radler, has reddish
pink and single
flowers. They are reliably hardy to USDA
zone 5 (-10 to -20 degrees F minimum in winter).
Although when left unchecked they’ll reach 3 to 4 feet
tall and wide, they can be kept shorter with spring pruning.
Pruning to about 12 to 18 inches above the
ground in spring may result in more vigor and blooms in warmer
areas. At the minimum, remove dead growth in Spring, crowded stems
to allow more air circulation,
and about every 3 years remove one third of the older branches.
There is no need to prune off spent flowers
(termed “deadheading”) as plants are “self-cleaning”.
As with all roses, give well-drained soil and full
sun. Fertilize with a rose fertilizer after each bloom cycle during
the
season. Once established, these roses
are quite drought tolerant.
Use Knock Out roses in masses, in borders, or in a row
to form a hedge. They combine well with
pinks (Dianthus), daylilies,
perennial salvia, ornamental blue fescue grass, and lamb’s ear (Stachys)
among other perennials. For annuals, consider combining them with
petunias,
sun-loving coleus cultivars, licorice plant (Helichrysum),
the silver plectranthus, and spider flower (Cleome) among
others.
Other great trees and shrubs for New England can be
found on the Cary Award website (www.caryaward.org).
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