"The first year it sleeps, the next year it creeps and then it leaps." I may not have quoted this saying accurately, but it is exactly what ivy does when planted in the garden. You wonder if it will ever fill in and cover ground and then you wonder how on earth you will ever keep it under control. For my new garden, I will probably use one of my small variegated leaf ivies in a section where I can keep a sharp eye on it.
Of the five or nine species of Hedera, (depending on your source) the most common in temperate climate gardens is Hedera helix (English Ivy), rated hardy to USDA zone 5.
Among other species are:
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H. canariensis (Algerian Ivy), native to the Canary Islands and northern Africa, is hardy only to USDA zone 7, and, according to Dirr, is most successfully grown in zones 9 and 10. It is closely related to H. helix, but differs in having red twigs and petioles and very glossy leaves that can be up to six inches long. It is supposed to be a rampant grower.
H. colchica (Colchis Ivy), native to Asia Minor, hardy to USDA zone 5 or 6, has leaves four to ten inches wide, leathery and rarely lobed. It is said to be very fast growing, but has a somewhat coarser appearance than H. helix.
H. nepalensis comes from the Himalayas, Afghanistan to western China and northern Burma.
H. rhombea (Japanese Ivy), rated hardy to USDA zone 8, comes from Japan and the Ryukyu Islands.
All are woody vines climbing by means of aerial roots that adhere to wood or masonry. All of them have both juvenile and adult foliage that differ quite markedly in appearance. Juvenile foliage, usually palmately lobed, appears on flexible stems, while the adult foliage is generally not lobed and appears on stiff, nonclimbing stems.
Adult foliage looks nothing like the ivy we are used to seeing. Once ivy has climbed to the maximum height it can reach and has gotten old enough, the adult foliage appears and the plants flower. Flowers are in umbrels, arranged in panicles. They are generally small and greenish, but on some cultivars they can be quite amazing as this photograph shows.
The first time I saw ivy in flower, I had no idea what it was and had to ask someone. Some of my species H. helix has begun to form adult foliage and flower, but so high up in the trees that you can't see it. The only reason I know that it's doing this is that some was blown down with a dead branch by high winds last winter. I can testify that the fruit is a black berry.
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