5-Star Plants: Clematis Jackmanii

Clematis Jackmanii was first introduced in the mid-1800s, and it’s still recognized as one of the very best clematis for home gardens. This ever-popular variety is vigorous, adaptable and reliable. A mature plant can produce an astonishing display of color, covering itself with hundreds of velvety, deep purple flowers.

As climbing plans, clematis add a new layer of interest to any garden or landscaped area. You can train these vines to grow up a trellis, tuteur or arbor to create a new focal point. Use them to adorn an entryway or porch, or to dress up a light post or mailbox. They can also be grown along the top of a fence or wall.

What to Expect from Clematis Jackmanii

Clematis vary in height, with some growing just 2 feet tall and others climbing to 20 feet or more. Jackmanii is an easy-to-manage size, growing 7 to 10 feet tall and 3 to 6 feet wide. It blooms profusely in July and then continues to produce flowers intermittently through the fall. The blossoms are 5-7” across and usually have 4 petals, though some random flowers will have 5 or 6 petals.

As with most clematis, Jackmanii climbs by using twining leaf stems. The vines themselves will sometimes twine, but it’s the leaf stems that can coil tightly enough to establish a firm grip. Since these stems are just 1-2” long, it’s important to provide slender supports that are no thicker than a pencil.

Choose the Best Planting Site

Clematis grow best when their “heads” are in the sun and their “feet” are in the shade. If possible, choose a planting site where the top 2/3 of the plant is in sun and the bottom 1/3 is shaded by nearby plants. Mulching the soil around the roots also helps retain moisture and keep the soil cool.

For good flower production, Clematis Jackmanii should receive at least 6 hours of direct sun per day. In all but the coldest climates, clematis appreciate some protection from the hot afternoon  sun. An east-facing aspect is ideal.

As with all clematis, Jackmanii grows best in fertile, loamy, well-drained soil. They do not thrive in soggy, sandy or compacted soil and will not tolerate drought. Before planting, take time to prepare the planting area. Loosen the soil at least 12” deep and amend it with compost.

How to Plant Clematis Jackmanii

Young clematis start out looking pretty scrawny, even though they are usually 1 or even 2-year-old vines. They grow very slowly at first and it usually takes a couple of years for them to get well-established. During this time, the plant will be developing a robust root system. Though you may not see much top growth or flowers, hang in there as your patience will be rewarded.

Clematis have shallow root systems and should be planted more deeply than most other perennials. Position the crown of the plant (where stems meet roots) about 2-3” below the soil line.

How to Care for Your Clematis

Since the vines are relatively shallow-rooted, they need consistent moisture throughout the growing season. They are also relatively hungry plants and benefit from being fertilized. Place several inches of compost around the plant each spring and/or apply an all-purpose fertilizer. Supplementing with a water-soluble fertilizer during June and July will help promote strong growth and flowering.

Clematis Jackmanii flowers on “new wood,”  which means that the flower buds are produced during the same year as the flowers. This makes it very easy to prune. In late fall or early spring, you can simply cut the entire plant back to within 6” of the soil surface. If you prefer to leave some of the old vines in place, the new vines will grow up from the base of the plant and use the old vines for support. To keep the plant looking relatively neat, you will probably want to remove all the old growth every few years.

All clematis are susceptible to a fungal disease known as clematis wilt, as well as several foliar diseases including rust and powdery mildew. Keeping the plants healthy and stress-free is the best defense. Always water at ground level to keep the foliage as dry as possible.

One clematis is great, but the more clematis the better! To shop our complete assortment of varieties, click HERE.

To learn more about growing clematis, we recommend reading: All About Clematis and 6 Tips for Growing Clematis.