The Root System of a Climbing Hydrangea

A striking semi-woody climbing vine that can grow to 60 to 80 feet tall, the climbing hydrangea has one root system below ground and another above ground. Underground roots provide stability for the plant and also gather moisture and nutrition for the plant's seasonal growth. Aboveground, aerial or adventitious roots help the vine cling to the sides of houses, barns or whatever structures it climbs.

They tolerate full sun, but climbing hydrangeas usually do better with some shade and can tolerate intense shade. The plant's lacy clusters of tiny, fragrant white flowers open early in summer and bloom until midsummer. Tiny fruits attract birds. Like other hydrangeas, climbing hydrangeas are woodland plants and require moist, well-drained soil. Too much sun or too little water will stress plants and cause leaves to droop. Older stems develop an unusual cinnamon-coloured peeling woody bark, adding visual interest even when the vine is dormant in winter.

The climbing hydrangea prefers rich, evenly moist but well-drained soil. Under ideal soil conditions it seems slow to establish itself, even compared to other hydrangeas--producing little new vine growth and few flowers--because in the first few years most of the plant's energy goes into establishing a strong root system. Protect and support the development of plant roots by watering regularly and thoroughly during prolonged heat or dry periods. Add thick layers of compost or other organic mulch to enrich the soil and conserve moisture.

It's important to plant these hydrangeas in well-drained soil because, despite their preference for moist soils, climbing hydrangeas can fall prey to two types of root rot--mushroom root rot, also known as Armillaria root rot, and Phytophthora root rot. The fungi that cause mushroom root rot, ever-present in many soils, are more likely to attack drought-stressed plants, so proper plant care is preventive. Phytophthora root rot often gets established in container-grown plants.

The aerial roots of the climbing hydrangea excrete a concrete-like substance that attaches the plant firmly to whatever it climbs--making it very difficult to remove--which is why it's not necessarily a good idea to climb this plant up the side of your home. You can train climbing hydrangeas up tree trunks, alternatively, allow them to sprawl across unsightly areas such as rock piles or even use them as a tall groundcover.

Start with healthy rooted cuttings to grow your own climbing hydrangeas. Cut small five- or six-inch non-woody branches, remove the two lowest leaves, and dip the cut ends in rooting hormones. Poke cuttings into moist--not soggy-wet--vermiculite in deep pots, and cover the pots with cling film, being careful not to let the plastic touch the cuttings. Place the cutting pots in bright shade, out of direct sun, and wait two or three weeks for the cuttings to root. Add water only if soil surface dries out, to prevent rot.