CLIMBING HYDRANGEA
Hydrangea anomala petiolaris
Hydrangeas [hy-DRAIN-gee-ahs] are highly valued for their abundant handsome foliage and their showy flower clusters. While the most familiar hydrangeas are shrubs, Climbing Hydrangea (Hydrangea anomala petiolaris) is a woody vine. It clings to surfaces by small rootlets all along its stem. One of the most satisfactory of all woody vines, it ranks among the top 10 climbing vines in the world for ornamental value. Once established, it climbs with gusto up trunks of tall trees or various kinds of walls.
IDENTIFYING CLIMBING HYDRANGEA
Height and Spread
Unrestrained, climbing hydrangea will grow up to 75 feet. Vine branches may extend laterally as much as 3 feet from the main stem on which it is climbing. It clings to its support by means of holdfasts resembling rootlets. It does not require tying or fastening. While it takes several years to begin vigorous growth, once it takes hold, climbing hydrangea rapidly forms a dense mat of flowers and foliage.
Foliage
Climbing hydrangea leaves are 4 to 5 inches long. Broadly egg-shaped with pointed tips and toothed edges, the leaves are a lustrous, bright green. They turn brownish gold in the fall. Because this vine is deciduous, they (drop)in the late fall. The exposed woody stem with its peeling cinnamon colored bark makes an attractive winter sight.
Flowers
Climbing hydrangea blossoms are usually about 6 to 8 inches across. They blanket the vine in mid-June in creamy white flat clusters composed of tiny bud-like florets ringed by open florets. They have a nice fragrance. As the season wanes the blossoms become pinkish, and then brown. They often cling to the vine well into winter.
Better Varieties
There is only the one form of climbing hydrangea available. However, a plant in a related species offers many of its virtues. Japanese hydrangea vine (<MI>Schizophragma hydrangeoides<D>) grows to only half the size of climbing hydrangea, making it more suitable for residential yards. Its flowers are similar, as are its leaves which are more obviously toothed at the edges. It does not have the attractive peeling bark of the climbing hydrangea.
Where Hydrangea Grows Best
Hardiness
Climbing hydrangea is hardy as far north as the Great Lakes and northern New York. It survives winters in these regions and along the Atlantic Coast into Maine (zone 4), tolerating temperatures as low as -25<198>F.
Locating and Planting
Climbing hydrangeas are extremely flexible, handling full sun to medium shade comfortably. Furthermore, these vines do well on many kinds of soil, insisting only that it be well-drained. They do best if the soil is slightly acid to somewhat alkaline (pH 5.5 to 7.0.).
Climbing hydrangeas are readily available in most nurseries, often found tied to a supporting stake in their container. Choose containerized plants that are from 8 inches to 2 feet tall. They do not look very attractive at this stage, but it is best to plant young plants, since older ones do not like to be transplanted. Choose a spot in an east or north exposure, near a brick or stone wall that it can fasten to. Plant climbing hydrangea in the spring or the fall.
Remove the vine from its container and gently loosen and spread any matted roots. Dig a saucer-shaped hole that is wide enough to accommodate the spread roots, and as deep as the container. Set the plant in the hole, taking care that the top of the rootball is at, not below, ground level. Fill the hole with soil, firming it around the rootball periodically until it is at the level of the surrounding ground. Water generously to provide good root to soil contact. Do not fertilize at this time. Climbing hydrangeas are notorious for their slowness in establishing themselves. Newly transplanted plants take a year or two to start major growth, 3 to 5 years for first flowering.
Design Considerations
Climbing hydrangea can be utilized as a low growing ground cover, a low, dense shrub, or a vine. Encouraged to climb a wall or fence, it provides a wall of flowers early in the season and a cool foliage back(drop)in the summer. Do not locate it against a wall that requires periodic maintenance. Avoid clapboard walls because this vine will insinuate itself underneath the boards and pull them loose. Choose any mature hardwood tree, except maple, or even an open softwood tree such as white pine, as a support for climbing hydrangea. Allow it to cover a prominent rockpile, ledge, or utility area. Encourage it to cover an arbor or pergola in the shade, or a trellis. It is ideal for softening harsh architectural lines.
Plant Care
Fertilizing
Hydrangeas are fairly heavy feeders. Sprinkle a handful of an all-purpose granular fertilizer on the soil over the vine roots in the early spring for the rain to soak in. A fertilizer featuring a slow release or timed release form of nitrogen will supply steady nutrition over the growing season.
Mulching and Weed Control
Spread a layer of organic mulch 2 or 3 inches thick on the soil under each hydrangea vine. Either alone or over landscape fabric laid on the soil first, a mulch of chopped leaves, wood chips, pine needles, peat moss or the like, will deter serious weed problems and keep the soil moist longer. It will also protect vine roots in winter from heaving of the soil caused by its alternate freezing and thawing.
Watering
While climbing hydrangeas cannot tolerate wet, soggy soil, they also are not comfortable in very dry soil either. It is important to water generously when they are first planted and just before the ground freezes in the winter. Check them when rainfall is irregular and supplement their water when their soil is dry more than a few days. During prolonged droughts in the summer, they will need periodic watering. Run the sprinkler or a drip system for about one half hour weekly.
Pruning and Grooming
Climbing hydrangea vines do not require routine pruning. However, they do respond to clipping to control their size and spread. Do this in the early summer, immediately after blooming. Thin dense growth by cutting back branches to the main vine trunk. Cut back the growing tips of branches to reduce top heaviness that may cause the vine to pull away from its support. Because they are brittle and easily damaged, it is important to prune damaged or broken stems promptly to forestall disease.
Occasional Cultural Problems
Leaves Turn Yellow: Chlorosis
Hydrangeas can not handle very alkaline soil. It causes their leaves to turn yellowish. In the absence of evidence of insect attack or disease, this may be the cause of leaf yellowing. Scratch some ammonium sulfate into the soil to acidify it. Avoid excessive use of lime, which renders the iron in the soil unavailable to plants. A new way to cure chlorosis is to use iron chelates either as foliage sprays or soil drenches. These compounds are sold under such trade names as Sequestrene of Iron, Versenol and Perma Green Iron 135. If the problem persists, consider doing a soil test.
Occasional Insect Pests
The following pest control recommendations stress products that selectively kill target pests without harming other insects in the yard. Use all pesticide products with care. Read and follow the instructions on their labels for use, storage and disposal.
Leaves Skeletonized, Flowers Damaged: Rose Chafers
Rose chafers are grayish or fawn-colored and 1/2 inch long. These slow-moving beetles chew holes in leaves and damage flowers, especially white ones, by feeding on the petals and soiling them with excrement. Control them by hand-picking. For major infestations, spray beetles with a pyrethrum spray. Use it late in the afternoon to avoid harming beneficial insects and honeybees. If rose chafers are a chronic problem, cover plants with cheesecloth or fleece a week or so before their estimated appearance time. For long-term control, scratch milky spore powder (<MI>Bacillus popilliae<D>) into the soil. This disease will attack their larvae over 2 or 3 years, reducing the problem substantially.
Leaves Curled And Distorted: Aphids
Aphids are soft-bodied, pear-shaped sucking insects, about the size of the head of a pin. They cluster on tender new shoots and leaves, sucking plant sap. They retard and distort plant growth. Under their attack hydrangea leaves may turn yellow or brown, wilt under bright sunlight, or sometimes curl and pucker. Check leaf undersides for small groups of the pests. Hit them with a forceful spray of water 3 times, once every other day, in the early morning. If that does not work, spray them with insecticidal soap every 2 to 3 days until they are gone. A neem insecticide sprayed on shrub foliage 2 or 3 times at 7 to 10 day intervals will also control aphids.
Leaves Webbed Together: Leaftiers
Hydrangea leaftier larvae are green caterpillars, 1/2 inch long, with dark brown heads. These caterpillars protect themselves while feeding by binding adjacent leaves together. Hydrangea foliage becomes ragged and unsightly, turns brown and dies. For minor infestations, crush the larvae in their rolled hideouts. To counter major attacks, spray the foliage of vulnerable shrubs with Bt (<MI>Bacillus thuringiensis<D>) just as the caterpillars begin feeding. Repeat every week or 10 days while the caterpillars are feeding. They will ingest the bacteria as they feed and die in a day or two.
Leaf Margins Burned: Mites
Mites are about 1/50 inch long, barely visible to the unaided eye. They may be yellow, green, red or brown. Two-spotted spider mites cause damage on hydrangeas resembling sunscald. The leaves look burned, especially along their edges. Start control measures as soon as you notice evidence of burning on the leaves or delicate webbing near leaf stems. Spray the shrubs in the early morning with a forceful water spray to knock the mites from the leaf undersides. Repeat the water spray daily for 3 days. If that does not do the job, spray the mites with insecticidal soap every 3 to 5 days for two weeks. Spraying the bare canes with dormant (heavy) oil spray in early spring before leaves emerge destroys many overwintering mites.
Small, Round Bumps On Twigs: Scale Insects
Oystershell scale sometimes attack hydrangeas. They usually appear on the upper ends of the stems. Scale insects are covered by rounded waxy shells, which protect them while they feed. The shells may be white, yellow, or brown to black, and are about 1/10 inch in diameter. Spray infested shrubs with light, or "superior" horticultural oil which will coat the scale and smother them.
Knotted Growths On Stems, Roots: Nematodes
Nematodes are not insects, but slender, unsegmented roundworms. Most are soil-dwellers, less than 1/ inch long, and are invisible to the unaided eye. They have piercing-sucking mouthparts. Stem nematodes cause hydrangea stems to become swollen and split. As a result their leaves (drop)off. Infested plants look sickly, wilted, stunted, and have yellowed or bronzed foliage. They decline slowly and die. The root systems of affected plants are poorly developed, even partially decayed. To control these pests, add lots of compost or leaf mold, if it is available, to the soil around the hydrangea plants to encourage beneficial fungi that attack nematodes. Pour liquid fish emulsion into the soil as a drench to fertilize affected shrubs and to repel nematodes.
Occasional Diseases
Buds And Flowers Spotted, Deteriorate: Botrytis Blight
This blight disease is caused by a fungus which attacks dense hydrangea flower clusters during wet weather. The flowers become spotted, and the spots coalesce into blotches. Promptly remove all diseased parts, and spray shrubs with a copper fungicide when symptoms first appear. Repeat the spray every 10 days in wet seasons. Increase air circulation around the hydrangeas and avoid overhead watering which dampens their leaves and blossoms.
Leaf Undersides Covered With White Powder: Powdery Mildew
Powdery mildew is caused by a fungus which covers leaf undersides with white mold. The upper surfaces of the infected leaves may stay green or turn purplish brown in color. Buds and new growth may also be attacked. Spray affected shrubs thoroughly with a wettable sulfur fungicide once or twice at weekly intervals starting as soon as the whitish coating appears. Collect and discard all aboveground refuse in the fall to prevent the fungus from overwintering on yard debris. Mulch shrubs to prevent rain from splashing fungal spores up onto leaves. Recent research suggests that spraying foliage vulnerable to mildews with anti-transpirant spray helps it resist infection, as the spores have difficulty adhering to the coated leaves.
Leaves Spotted With Powdery Brown Pustules: Rust
A rust disease caused by a fungus attacks certain hydrangea varieties. The leaves become brittle and spotted with many yellowish to rusty brown pustules, especially on the undersides. The disease overwinters on old plant parts. Prune out and destroy any affected branches and spray with wettable sulfur at weekly intervals until the symptoms disappear.
Circular Rings Form On Leaves: Ring Spot Virus
This virus causes circular areas consisting of concentric bands of alternating dark and light green to develop on the hydrangea leaves. These areas then become small spots of dead tissue. There is no cure for viruses, so dig up the infected plant promptly and destroy it to prevent the spread of the virus to nearby healthy plants.
Resources
Books
Ball and Ball. <MI>Yardening: The Nongardener's Guide to Creating a Beautiful Landscape<D>, Macmillan 1991.
Buscher and McClure. <MI>All About Pruning<D>, Ortho Books, 1989.
Cresson, Charles. <MI> Charles Cresson On the American Garden<D>, Burpee Expert Gardener Series, Prentice-Hall, 1993.
Liability Statement
New Response, Inc. and the authors have researched this information as thoroughly and carefully as possible. They take no responsibility for any personal harm or plant damage that might occur from using the information contained herein.
<189>Liz and Jeff Ball, New Response, Inc. 1993. Box 338, Springfield, PA 19064 215-544-5308.
