In the wild, a plant’s roots can grow unrestricted into new soil in their search for food and water. In a container, however, the limited room for expansion means that instead of stretch­ing out freely, the roots are forced to circle around inside the pot. Unless more space is provided, in terms of a larger pot, this results in a “pot bound” plant, with slow growth and a poor show of flowers. Most plants need to be moved into a new. slightly larger pot with fresh potting soil once a year, normally in spring as the new growth for the season starts.

Planting Up and Potting On

‘PIanting” indicates that a dry bulb or corm is being put into a new soil mix. “Potting on” refers to the moving of a plant from a smaller pot into a larger one.

Houseplants are usually bought in containers and so the terms “planting” and “planting-up” only apply to young plants grown from seed and bulbs, corms, and tubers. Young, actively growing plants should be moved into large’ pots on a regular basis to make sure that they have enough room to grow, without suffering a check as a result of their roots becoming cramped. This process is known as “potting on.” How often this is done will depend on the plant itself, with quick-growing specimens in ideal conditions requiring potting on more often than slow­er growing ones.

The newly bought plant

When a plant is first purchased, the chances are that it is already becoming pot-bound, because most plants — especially foliage ones — are sold in the smallest practicable pot in order to make the plant look larger and, therefore, better value. The easiest way to tell if this is the case is to examine the base of the pot for protruding roots — the more there are, the more pot-bound the plant is likely to be. If there are lots of protruding roots, it should be potted on into a larger pot immediate ly to keep it actively growing. Teasing out a few o. the main roots when planting will help the plant establish in its new pot and start to grow. Carefully trimming off a few of the main roots at this stage will slow down the growth of the plant if it is like­ly to grow too quickly for its surroundings.

How to pot on

Check that the new container has drainage holes in the base to prevent waterlogging, and that it is a; least 2 in. (5 cm) larger in diameter than the old one. If the plant dislikes excess moisture around the roots, first cover the base of the pot with pieces of broken crockery, then add a layer of potting soil. Remove the plant from its existing pot and place it inside to gauge the level, adding more potting soil underneath if necessary, then fill up around the sides, firming it gently with your fingertips. Fill the pot to 1 in. (2.5 cm) below the brim, then water it to settle the soil. If the soil level sinks back, add more potting soil.