I want to grow a clematis from seed next year. Will it grow much in the first year? It will be situated in full sun. I have clay soil
Thanks for contacting the Toronto Master Gardeners with your question about propagating clematis through seed.
Clematis are beautiful plants and ideal for small spaces, as their growth is mostly vertical. There are some shrubby types, however, as well as non-clinging ones that can be grown as groundcovers and sprawlers.
Clematis perform well in clay soil, especially one that is alkaline and has been amended so that it does not hold moisture for too long. The ideal soil will be enriched with compost to make a clay loam that is moist but well-drained and not too heavy. Also, while most like full sun (6-8 hours daily), they do appreciate some shade at their base, so can be grown with groundcovers.
There are a few “species clematis” (non-hybridized) such as Clematis integrifolia or the native Clematis virginiana L. which can be grown from seed. These are the small-flowered type. Most cultivars and varieties with bigger blooms are propagated by home gardeners by taking stem cuttings and rooting them in containers. This is a cost-effective way of making new plants. Dividing a plant is another method.
Another inexpensive option is to take a young and flexible stem, wound it slightly by making a small cut horizontally through the stem at the point of a leaf node, and then pin the stem with a small twig or toothpick to hold it down on top of the soil (or in a container with potting soil). Or use a small stone to weigh it down. Make sure to water regularly to keep the soil from drying out. When the stem has rooted at the wounded point, you can cut it off from the mother plant and root it in a pot. This process is called air layering and can lead to a larger plant faster, because the stem is still attached to the main plant. If you are interested in further information about clematis in general or the air layering process, you may find the below links helpful.
I would not recommend trying to grow clematis from seed unless you want the species kind. Even if the seed is viable, it can take a long time (sometimes months) to germinate. Clematis are also similar to ornamental grasses, in that they usually follow the old adage of “first they sleep; then they creep; then they leap”), so they can sometimes take three or so years to put on significant growth even if you purchase a well-rooted potted plant (although Clematis terniflora/paniculata (Sweet Autumn Clematis) and the native Clematis virginiana L. (Virgin’s Bower) can be exceptions.
I hope you find success with propagating clematis.