Q: My neighbor told me I need to prune my jackmanii clematis now. Is he right? How much do I cut back? This is a new plant for me and I don’t want to lose all those gorgeous flowers.
A: Clematis ‘Jackmanii’ belongs to the group of clematis cultivars that bloom on new wood (stems that start growing on the plant each spring). If left alone, the plant will become thin at the base, and over time it will be riddled with dead stems instead of the lush flowers we associate with healthy clematis.
Here’s a little basic clematis growing information. Clematis grows best in full sun or partial shade. It’s hardy in USDA zones 4 to 8 and likes moist, well-drained soil. You may have heard that clematis like their head in the sun and roots in the shade. This is best achieved with a 3-inch layer of mulch around the base. Mulch also keeps the soil moist, but to prevent stem rot keep the mulch about 6 inches from the stems.
The best time to prune jackmanii clematis is late winter or very early spring before the plant comes out of dormancy. Cut the stems back to about a foot off the ground, just above two strong buds. (See illustration) Leave two to four sets of buds per stem. You don’t have to make angled cuts; a straight cut will do just fine.
As the weather gets warmer and buds appear, train the new vines onto your trellis. This is your opportunity to space them so the flowers will show better.
You may have noticed clematis branches do not twine around the trellis. Clematis climb by twisting thin corkscrew shaped leaf stems, called petioles, around a support.
As soon as you see new growth, feed the plant with an all-purpose granulated fertilizer such as a 10-10-10. Following these simple steps you can expect to enjoy your jackmanii clematis for years.
Contributed by Eileen Tully, Certified Colorado Gardener. Photo and illustration courtesy of Park Seeds.