Clematis

Best for Iowa
Park Seed
Suggested clematis species for Iowa
1 Parkton Ave., Greenwood, SC 29647
include (flowering occurs on the
http://www.parkseed.com
wood type as indicated):
Thompson and Morgan Inc. (seed)
• Clematis alpina—blue flowers (old)
P.O. Box 1308, Jackson, NJ 08527-0308
• Clematis integrifolia—indigo blue flowers (new)
http://www.thompson-morgan.com
• Clematis macropetala—lavender blue flowers (old)
• Clematis orientalis—yellow flowers (new)
Wayside Gardens (plants)
• Clematis recta—white flowers (new)
1 Garden Lane, Hodges, SC 29695-0001
• Clematis terniflora—white flowers (new)
http://www.waysidegardens.com
Clematis
• Clematis texensis—scarlet flowers (new)
• Clematis viticella—purple flowers (new)
For more information
Suggested varieties according to
For more information on selection, planting,
color include (flowering occurs on
cultural practices, and environmental quality,
the wood type as indicated):
contact your Iowa State University Extension
county office, or visit one of these ISU Web sites:
Purple—‘Gipsy Queen’ (new), jackmanii ‘Superba’
(new), ‘The President’ (old, new)
ISU Extension publications—
Blue—‘Mrs. Cholmondeley’ (old, new), ‘Ramona’
http://www.extension.iastate.edu/pubs
(old, new), ‘Lord Nevill’ (old, new), ‘Ascotiensis’
ISU Horticulture—
(new), ‘Betty Corning’ (new)
http://www.yardandgarden.extension.iastate.edu
Red—‘Madame Edouard André’ (new) ‘Lincoln
Reiman Gardens—
Star’ (old, new), ‘Ernest Markham’ (new), ‘Niobe’
http://www.reimangardens.iastate.edu
(new), ‘Ville de Lyon’ (new), ‘Rouge Cardinal’
(old, new)
White—jackmanii ‘Alba’ (new), ‘Henryi’ (old,
File: Horticulture 2-1
new), ‘Marie Boisselot’ (old, new)
Written by Sherry Rindels, former extension horticul-
Pink—‘Comtesse de Bouchaud’ (new), ‘Hagley
turist; revised by Richard Jauron, extension horticul-
Hybrid’ (new), ‘Bees Jubilee’ (old, new), ‘Duchess
turist; and edited by Diane Nelson, extension
of Albany’ (new)
communication specialist. Illustrated by Jane Lenahan,
extension graphic designer.
Bicolor—‘King Edward VII’, (old, new)
‘Nelly Moser’ (old), ‘Star of India’ (new)
Issued in furtherance of Cooperative Extension work, Acts of May 8
and June 30, 1914, in cooperation with the U.S. Department of
Agriculture. Stanley R. Johnson, director, Cooperative Extension
Sources
Service, Iowa State University of Science and Technology, Ames,
Busse Gardens (plants)
Iowa.
17160 - 245th Ave. NW,
. . . and justice for all
The U.S. Department of Agriculture (USDA) prohibits discrimination in
Big Lake, MN 55309
all its programs and activities on the basis of race, color, national
http://www.bussegardens.com ($3 for catalog)
origin, gender, religion, age, disability, political beliefs, sexual
orientation, and marital or family status. (Not all prohibited bases
apply to all programs.) Many materials can be made available in
alternative formats for ADA clients. To file a complaint of discrimina-
Greer Gardens
tion, write USDA, Office of Civil Rights, Room 326-W, Whitten
1280 Goodpasture Island Road
Building, 14th and Independence Avenue, SW, Washington, DC
20250-9410 or call 202-720-5964.
Eugene, OR 97401
http://www.greergardens.com
RG 307 Revised December 2004

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lematis ar
C
e often referred to
Group 2: Flowers on both old and new growth
A mulch provides winter protection for the crown
as the queen of the flowering
Examples: ‘The President’, ‘Henryi’, and ‘Ramona’
and keeps the root system cool during summer
vines. Plants in this versatile
heat.
The second group of clematis blooms twice. Large
genus produce single or double
flowers are produced from May to July on the
After planting, trim to 12 inches or to a pair of
flowers from May to October in a
previous season’s growth. In late summer, plants
low buds to encourage multiple branching and
variety of colors. Sepals—not petals
will bloom on the current year’s growth.
additional shoots. Fertilize established plants with
—make up the colorful portion of
a balanced all-purpose garden fertilizer (such as
the flower. These may be thin, wide,
In early spring, prune out the dead wood. Spring
10-10-10) in spring.
pointed, rounded, crinkled, twisted, or even
blooms will be sparse if plants suffer extensive
crimped. They may be marked with center bars,
winter dieback. Plants will bloom more heavily
Support
stripes, or vivid shadings. The flower form varies
in late summer.
Clematis climb by twisting their petioles or leaf
from nodding, pitcher-shaped, bell-shaped,
Group 3: Flowers on new growth
stalks around a support. They can be grown on
or star-shaped, to the familiar large, flat, erectly
Examples: Clematis viticella, Clematis terniflora
trellises, fences, lampposts, deck rails, and other
held blossoms. Flowers may have contrasting
(paniculata), and large flowered hybrids such as
structures. Clematis also can be allowed to climb
colored stamens or no stamens at all. Small
Clematis × jackmanii, ‘Ernest Markham’, and
over shrubs, small trees, tree stumps, and rock piles.
flowered varieties offer a range of fragrances
‘Hagley Hybrid’
When planting near a non-living support, allow at
lacking in the large flowered varieties.
least a foot between the support and the plant. Near
The third group of clematis flowers on the current
shrubs, trees, and other living supports, locate plants
Some species can grow 8 to 12 feet in a single
year’s growth (new wood). Vines produce one
at least 2 feet away from the support. New growth
season, others reach a height of only 2 to 4 feet.
main flush of bloom (sometime from late May to
will wind through the support towards the light.
More than 250 species and at least 5,000 cultivars
September). Because they bloom on current year’s
Clematis do not possess tendrils or aerial rootlets;
exist in the world. Not all of these are hardy in
growth, Group 3 clematis are the most reliable
you may need to help young plants start to vine
Iowa, but we can select from numerous hardy
performers in Iowa.
where you want them.
species and cultivars.
Pruning is relatively easy. Vines can be cut back
Types of Clematis
to within 6 to 12 inches of the ground in late
Pests
Vining clematis can be divided into three groups.
winter/early spring. An alternative method is to
Clematis don’t have serious insect pests. However,
wait until bud break in spring and prune back to
clematis wilt is an occasional problem. Affected
Group 1: Blooms on the previous season’s
the uppermost new growth.
vines wilt suddenly and then die. Dead vines should
growth (old wood)
be cut at ground level, removed, and destroyed.
Examples: Clematis alpina and Clematis
Growing tips
Clematis wilt rarely kills the entire plant. Affected
macropetala
Clematis thrive in rich, well drained soils with at
plants usually send up new shoots.
least 6 hours of sunlight each day and 1 inch
The earliest clematis bloom between April and
of water per week.
June. Flowers develop from buds located on the
Clematis in vases
previous season’s growth.
When planting, dig a generous-
Clematis are excellent fresh cut flowers and can last
sized hole and fill with a mixture
four days or longer. Look for flowers that have just
This group is the most difficult to grow in
of soil and compost or moistened
opened or are only three-fourths
Iowa as the vines may need to be protected
peat. Do not add lime unless your
open on thick, strong
over winter to insure their survival. To provide
soil is highly acidic. Clematis
stems. Three choices
adequate protection, the vines and their support
prefer soils with slightly acidic to
include ‘Beauty of
may need to be taken down in the fall, laid on the
neutral pH levels. Plant the crown
Worcester’, ‘The Presi-
ground, and then covered with several inches
1 to 2 inches below the soil
dent’, and ‘Nelly Moser’.
of mulch. If not protected, vines may suffer
surface. Water well and mulch
Many clematis also form
extensive dieback and produce few, if any,
with 2 to 3 inches of organic
attractive seed heads.
flowers. Wait until bud break before pruning
material such as wood chips or
Group 1 clematis. Prune back to live wood.
compost.

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