Jackman's Clematis Plant Profile

Jackman clematis flower closeup.

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Jackman's clematis is one of the most popular of all flowering vines—so commonly grown that some gardeners despise it for its very popularity. But popular plants generally gain their popularity for good reasons. Jackman's clematis is a vigorous yet compact vine with fabulous flowers. The fact that a great many people grow it does not detract from these superior qualities; on the contrary, it confirms them.

Jackman's clematis is a hybrid plant, which is why the botanical name of this buttercup-family member is sometimes given as C. x Jackmanii, the parents being C. lanuginosa and C. viticella. Its large 5 -inch blooms are a delicious dark purple, making it on of the prettiest flowering vines. This vine is big enough to capture your attention when in bloom without being too overpowering for a small space.

Clematis vines are often used to camouflage eyesores in the landscape, or for landscaping around mailboxes, where the vine is trained up a mailbox post as a decoration. It can be trained up almost any vertical structure, from garden walls to small trees.

Botanical Name Clematis 'Jackmanii'
Common Name Jackman's clematis, Jackman clematis, Jackman virgin's bower
Plant Type Deciduous flowering vine
Mature Size 7 to 10 feet (occasionally more)
Sun Exposure Full sun to part shade (prefers shaded roots)
Soil Type Fertile, well-drained, evenly moist soil
Soil pH Neutral
Bloom Time July
Flower Color Blue-purple
Hardiness Zones 4 to 8
Native Area Nursery-created hybrid (parent species are native to China)

How to Grow Jackman's Clematis

This vine is fussier than most plants about how you plant it. It is best planted so that the top of the root ball is a full 3- to 4- inches below the level it was in the nursery pot. Planting at this depth promotes the development of "latent" buds below ground level. Their presence is your insurance policy against the clematis wilt disease that sometimes infects above-ground vegetation.

The practice of deep planting also helps keep the roots cool. It is critical to shelter clematis roots from the blazing sun. Another way to keep your vine's roots cool is to spread about 2 inches of mulch over the root zone. Other gardeners shade the base of the vine with ground covers—but avoid any plantswith deep root systems, as these can interfere with the root system of the clematis). Still others place flagstones or other objects at the base of the clematis to cast shade. However, the latter practice can provide an open invitation to slugs.

This perennial is a true climber. It will twine its way around any support (trellis, etc.) that you provide for it. A wide variety of structures can serve as support for the vine's vertical growth, whether they are existing features in your landscape or features that you create specifically to showcase the plant. Many growers train their clematis vines to climb upon other plants (shrubs and vines, mainly). Two famous garden writers, Allen Armitage and Michael Dirr, make mention of this practice in their gardens. Just remember to clean up in fall by cutting back this growth, which will allow you to "hit the reset button" for next year.​

Light

Treat this flowering vine as a perennial vine for sun in the North. But it can take a bit more shade than can many other types of clematis; in the South, it is a good idea to give it partial shade.

Soil

Jackman's clematis prefers fertile, well-drained soil. A major soil consideration in growing Jackman's clematis is to keep the soil relatively cool. If the soil gets too hot, it is bad for the vine's roots. Cooling the soil is normally done by shading the base of the clematis with other plants or with stones.

Water

Do not let the soil dry out completely at any point during the period of active growth for the plant. It very much prefers consistent moisture.

Fertilizer

If you are an organic gardener, fertilize the clematis with compost. Otherwise, apply a complete fertilizer each spring, then monthly through the growing season. When using commercial fertilizers, err on the side of too little rather than too much.

Pruning Jackman's Clematis

For pruning purposes, Jackman's clematis is considered a "class 3" clematis that blooms on "new wood"—producing flowers on stems that have grown in the current growing season, not last year's growth. This means that the best time to prune the vine is from late fall to early spring, after flowering is complete but before new growth has begun.

It is best not to prune a new vine very much, giving it time to put on some growth (unless it is to remove dead branches, which can be done at any time) But once it matures, a clematis may begin to lose vigor or become overgrown, and this is the time to begin an early spring pruning regimen. While some perform a drastic pruning, most growers prune clematis in a more targeted fashion, cutting the vines down to a preferred height where there are good leaf buds present.

Related Varieties

Jackman's clematis is not the only kind with bluish or purple flowers. Others include:

  • C. Etoile 'Violette' has smaller blooms than 'Jackmanii', and blooms through the end of the summer.
  • C. x Durandii is a non-twining clematis that will sprawl over the ground unless manually tied to a vertical support. It blooms for a remarkably long time, through the entire summer and into fall.
  • C. 'The President' has huge flowers that bloom twice—in late spring and early summer, then again in late summer and early fall. Vines grow as much as 10 feet tall.
  • C. macropetala 'Maidwell Hall' has smaller, nodding flowers with white centers. This easy-to-grow vine has a maximum height of 6 to 8 feet.
  • C. 'Venosa Violacea' has large 6-inch flowers with petals that are white with purple margins. It grows 9 to 12 feet tall.

Common Pests/Diseases

Slugs like to eat clematis almost as much as they do Hosta. If you use stones to shade the base of the plant, lift them often to check for slugs napping beneath. Dispatch any slugs that you do find. Pest damage can also come from earwigs and spider mites.

Clematis wilt, a fungal disease that attacks the base stems of the plant, can be fatal to clematis. Its symptoms are a sudden progressive shriveling of the entire plant, usually in early summer. Black spots on the leaves may be evident. There is no cure for clematis wilt, but you may be able to prevent it by keeping the soil evenly moist, making sure the soil is neutral or slightly alkaline, and watering at the base of the plant rather than on the leaves.

If clematis wilt appears, remove all damaged portions of the vine. If the root system is strong, the plant may recover by the next season.