More than 200 species of clematis plants exist. The "autumn" clematis is any number of late-flowering clematis plants, but usually people associate autumn-blooming clematis plants with the "terniflora" variety, commonly called the "sweet autumn" clematis. Regardless of the exact clematis variety, proper care is relatively standard for most late-flowering clematis plants. Only healthy and well-pruned autumn clematises will produce blossoms.
Difficulty: Moderately Easy
Prune the clematis plant in early spring, cutting the stalks to a height of about 18 inches. Autumn clematis plants begin their life cycle in early spring. "Hard cutting" gives the plant room to expand and grow new buds, whereas an unpruned clematis will be stunted and produce few flower buds.
Cut back nearby trees to provide full sun or partial shade. Clematis plants cannot bloom in full shade, but a little bit of shadow is acceptable.
Mix hydrated lime pellets into your soil. Clematis plants prefer soil with lime. If your garden features regular loam or peat soil, adding lime can perk up your clematis plants for brighter, fuller autumn flowering.
Water frequently during the summer months, making sure the soil is moist and soft. Your finger should feel wet and cool when you stick it into the soil around a clematis. Though they bloom in autumn, late-flowering clematises undergo most of the season’s growth during summer; generous watering during this period promotes flower bud growth.
Cut off blackened leaves immediately. "Phoma clematidina" fungus, commonly called "clematis wilt," is a major problem for late-flowering clematis plants. A plant infected with clematis wilt rarely produces healthy blossoms in autumn. When you snip off the black, wilted leaves at the stalk, healthy plant tissue can regrow at the pruning juncture. Spray the entire plant with fungicide to prevent future outbreaks.