Indoor plants benefit from fresh compost occasionally, but some resent the root disturbance that comes with complete repotting. Others perform best when their roots are confined and some are simply too large to be easily repotted. These plants will all benefit from a layer of top dressing.
Scrape off 2.5-5cm (1-2 inches) of soil and replace with fresh compost, then water.
Pots: Choosing containers
There is a great range of pots available from garden centres that are suitable for indoor plants. The main choice you will need to make is between terracotta and plastic pots. Each has its benefits and drawbacks. Plastic pots are cheap and easy to get hold of, they are light and easy to move, contain moisture well and will not break if dropped. However, many people prefer the natural appearance of terracotta and their added weight can be helpful with large, top-heavy plants. Whichever type you choose, it is important to keep the same type throughout the life of the plant. Each creates quite different environments for the plant roots and growth may be checked if you change from one to the other.
When buying a container, always check that there are drainage holes. There are lots of decorative pots available which do not have any. These are only useful as an ornamental container for another pot with drainage holes.
To avoid checking growth, indoor plants should always be potted on into a slightly larger pot each year. This gives them some fresh compost to grow into, preventing the roots from getting congested. Pot your houseplants on at the beginning of spring when the plants are just starting into growth.
Carefully tip the plant out of its existing pot. If it does not come out easily, hold upside-down and tap the edge of the pot against the edge of a bench or table. You can also push the plant out through the drainage holes.
If the roots of your plant are tangled and congested, tease them out carefully as this will encourage them to grow into the new compost, rather than circling the existing root ball. Pull away some of the compost from the surface of the root ball.
If using a terracotta pot, place some pieces of broken pot or crocks over the holes in the base as this will help drainage even further. Fill the bottom 2.5cm/inch or so of the pot with compost and place the plant onto it.
Carefully feed compost down the sides of the root ball. Use your fingers to make sure there are no pockets of air and to firm down the compost. Then add more compost to the surface until it reaches the level of the old compost. Make sure the soil level is at least an inch below the rim of the pot. This makes watering easier. Finally, water the plant in. You will not need to feed the plant for about a month.
When re-potting cacti you need to protect yourself from the spines. Wear sturdy gardening gloves. Take a piece of newspaper and fold it into a strip before joining the two sides together to form a loop. This loop can then be wrapped around the top of the plant to help pull it out of its pot. Pot on as for other plants but always make sure there is plenty of drainage at the bottom of the pot. To make sure, add a layer of grit at the bottom and another layer on the surface of the soil to prevent rotting around the stem.