When to Fertilize Clematis

These woody perennial vines produce many massive, showy blossoms in a range of colors. As a vine, clematis can climb to cover a mailbox, trellis, fence or woodpile. Clematis does not require much special care in terms of fertilizer. Once established, you may be able to stop fertilizing them altogether. When starting new plants, a correct fertilizer routine ensures healthy growth.

Starting New Plants

• When you obtain a new clematis plant, the Ohio State University Extension recommends starting the plant in a gallon-sized flowerpot during its first season allowing the plant to grow larger moving into the garden. If you start your plants in this way, encourage growth by fertilizing the plants throughout the spring and summer with a 3-1-2 or 4-1-2 fertilizer. Transplant the plants into your garden in the fall.

Spring Plant Care

• Once established, fertilize clematis in the spring. Choose between two different periods when fertilizing your plants. In the first method, once you see the first signs of buds, gently work a 3-1-2 or 4-1-2 fertilizer into the soil’s surface, applying a 1/2 lb. of fertilizer per 50 square feet of garden. Fertilizing at the first sign of buds has both advantages and disadvantages. It causes all of the blossoms to open at once, creating a vibrant display, but the blossoms won’t last as long. The second method waits to fertilize until after the flowers appear, lightly prune the plant and then apply fertilizer. This encourages a second round of blooms.

Frequency

• Fertilize your plants only once per year and avoid fertilizing while there are open blossoms on the clematis. Once the plants are established, stop providing fertilizer altogether but keep them properly mulched.

Mulch

• Mulch plays an important role in your clematis’ health. Like fertilizer, it restores nutrients to the soil, as well as boosting levels of organic matter and improving drainage and soil structure. Apply mulch twice per year. In the spring, once the soil begins to warm, provide 2 inches of mulch to keep the root zone cool as temperatures rise. In the fall, a layer of compost or aged manure blankets the root zone over the winter while simultaneously adding nutrients and organic matter to the soil.