Plant Palette

Plant Palette

Late Blooming Clematis

Photo of Jennifer Schultz Nelson

Jennifer Schultz Nelson
Extension Educator, Horticulture
jaschult@illinois.edu

One of my ongoing "gardening goals" is to use more plants that begin to bloom in late summer and autumn. Like many other gardens, mine starts to look tired late in the season. Late bloomers give gardeners something to look forward to besides fall color.

It's not surprising that many of our gardens look a little ragged and worse-for-wear late in the season. Many of our plants have been in place since the early spring. Combine that with the crazy swings of weather that this year has brought, and you'd look ragged too!

Most gardeners do the bulk of their new plantings in the spring. It is human nature to gravitate towards the plants that are blooming at our local garden center after we've been cooped up inside all winter. Over time, this may lead to us having mostly spring blooming plants in our gardens.

A plant that might not immediately come to mind as a late summer/autumn blooming plant is clematis. Mine are gorgeous in the spring, totally covered in colorful blooms. I discovered quite by accident that some of mine will re-bloom in the late summer and autumn. In fact, they are blooming now, despite the touch of frost we had recently.

When I planted clematis around my patio, the intent was that we would build a pergola over the patio to provide a little shade. The clematis would climb the sides of the pergola. Well, four years later and we still haven't gotten around to building the pergola. Such is the life of a busy homeowner.

The clematis were on small trellises about three feet high. They were big enough for a year or two, but after four years some of the clematis were quite a tangled mess and were trying to climb on anything within reach of the trellis.

Late this summer I found some seven foot tall freestanding trellises that would give the clematis room to grow. Freeing the plants from the three foot trellises proved to be a huge challenge. I ended up breaking some of the vines even though I tried to be careful. They are just very brittle. Some plants lost half of their height or more. I soon saw some new buds, so I had hope for their future.

I was surprised one day to see what looked like flower buds covering one of the clematis. Soon three others followed suit. They are still flowering despite the recent chilly weather.

I figured this unusual flowering had to do with my unfortunate pruning of these plants late in the season. As it turns out, I was right. There are three groups of clematis, Groups 1, 2 and 3 (or A, B and C) and many of mine are from Group 2 (or B), which as a group is known for blooming first on "old wood" or growth from last season, and then blooming again late in the season on growth from the current season. My accidental pruning prompted lots of new growth which produced lots of blooms. The second set of blooms tends to be smaller than the first. Examples of Group 2 clematis are: rich purple 'The President', deep red 'Vino' and bi-colored pink/purple 'Nelly Moser'.

Group 3 (or C) clematis are the summer and fall blooming clematis. These clematis produce their blooms on new growth, so they benefit from a healthy pruning to a height of 18 to 24 inches each spring. If not pruned, in time they will only bloom at the very end of each vine. Blooms typically start in mid-June or later and may continue until frost.

I recently purchased Clematis jouiniana 'Mrs. Robert Brydon', which produces clusters of tiny lavender flowers with prominent white stamens. This clematis is fairly short and shrubby rather than vine-like, reaching only about five feet tall by midsummer, when it begins to flower. Flowers last into the autumn. Other examples of Group 3 clematis include: blue-purple 'Wisely', yellow C. tangutica 'Helios', and white flowered C. viticella 'Alba Luxurians'.

Sweet Autumn Clematis, Clematis ternifolia (paniculata), is a Group 3 clematis that may not behave itself in your garden. On the plus side, it is covered with tons of tiny fragrant white flowers from late summer through the autumn. But it may be a bit of a bully, as it easily grows twenty feet or more in one season and can engulf whatever is in its path when you're not looking. One description I read described its growth as "enthusiastic" rather than invasive in our Zone 5b. In warmer Southern climates, this clematis is often considered to be a noxious weed. Generally speaking it dies back enough in our central Illinois winters to keep it in check. However it may reseed itself to varying degrees.

An alternative to Sweet Autumn Clematis that is just as beautiful but may have better manners is Devil's Darning Needles or Virgin's Bower, Clematis virginiana. The flowers are very similar to Sweet Autumn Clematis, but this vine is a bit restrained in its growth, reaching a mature length 12 to 15 feet. Like Sweet Autumn Clematis, Virgin's Bower may reseed itself to varying degrees in the garden.

A late blooming clematis or two might be just what your garden needs to perk it up for the autumn season. Thinking "beyond Spring" in terms of blooms will open up a whole new selection of plants for your garden.

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