In order to grow clematis in pots, or other containers, you need to make sure that you choose planters that are deep enough. Clematis typically needs about 20 inches (50 cm) of soil to grow properly, though it is possible to start out with a smaller pot and transplant into larger ones as the need arises. The other main concerns when growing clematis in pots are related to the temperature of the soil, and drainage. Clematis pots should be wooden or stone, though plastic can be used if the planter is in full shade. Good drainage can be achieved by using a planter that has holes in the bottom, and by placing large rocks, or broken pieces of old pots, inside.
Clematis is a genus of over 300 different plants that are characterized by attractive flowers that grow on climbing vines. One of the first types of clematis to become popular with gardeners was hybridized in the 1860s, and new hybrids are still being created each year. These plants tend to be somewhat hardy, though there are cultivars suited to a range of climates. Clematis can be planted directly in the ground, though with the proper preparation and care, it is also possible to grow it in pots.
The first factor to consider if you want to grow clematis in pots is that these plants require a certain amount of soil to grow. If you start off with a very small plant, you can transplant it into larger pots as necessary. Each time you do so, however, you should plant the clematis several inches deeper than it was in the old pot. This is also true when transplanting from a pot into the ground. About 20 inches (50 cm) is typically enough soil to successfully grow clematis, though it is also very important to make sure the dirt does not become compacted.
Drainage is the other main concern that you need to address when growing clematis in pots. Waterlogged soil will cause the roots of these plants to rot and die, so it is important to choose a container with adequate drain holes. You can also help the water drain better by filling the bottom of the planter with broken up pieces of an old pot, rocks, or whatever other similar materials you can find.
The type of planter you choose can also help determine how successful you are at growing clematis in pots. These plants prefer soil that is cool, so plastic containers are typically a poor choice. Wood and stone planters will tend to remain cooler during the warm summer months, which can help keep your clematis healthier. If the planters are in full shade, then the issue of heat buildup in plastic containers may be less of an issue.