By Sharleen Pratt, Master Gardener
Clematis is a genus of about 300 species within the buttercup family, Ranunculaceae. They are a very popular perennial climber and produce many beautiful flowers in the summer months.
When purchasing a clematis, remove the plant from the pot and check for a tiny white bud on the very bottom roots. This will ensure a healthy plant. For best results, purchase a clematis that is at least two years old as they are tender when very young and take several years to mature.
Clematis absolutely demand good drainage. Either add sand to the soil, or line the bottom of the hole with a layer of gravel. When planting, it’s important to bury the crown of the plant at least two inches (6 cm) below the surface of the ground to encourage more stems to grow from the base. Water deeply at least once a week until the plant is well established.
To encourage good flowering, sprinkle superphosphate fertilizer onto the surface of the soil at planting time to promote good root growth and winter hardiness. For mature plants, add fertilizer once in the spring and again in June.
Clematis need at least six hours of sun per day, but their roots like to be kept cool. One suggestion would be to plant a large hosta at the base of the Clematis. Their roots are shallow so they won’t compete for nutrients. You could also use large rocks or flagstones.
If the stems of very young plants seem thin, pinch them back to just above a set of buds. This will help the stem to thicken, making them tougher and more resistant to damage.
You need to understand the kind of clematis you have before attempting to prune. Some clematis grow on last year’s vines, so you want to avoid cutting them to the ground in spring. Others flower on current-year vines, so they don’t mind being cut to the ground each year.
A very tough clematis is the Clematis x jackmanii, which is an old reliable climber, easily growing to three metres with large, deep purple flowers. It is the oldest large flowered cultivar, bred in 1858. Another easy to grow clematis is Clematis ‘Abundance’, which has a deep red flower with greenish-yellow stamens, which flowers in mid June.
You might consider checking The International Clematis Society website. It is full of valuable information for people new to growing clematis, with several links to catalogues, nurseries and education publications.