Happy, healthy houseplants just need the right growing medium
Houseplants vary in their requirements for survival so when it comes to potting compost there is no method which fits all; some need a free draining sandy compost and some need humus rich which holds on to the moisture. The best time to re-pot is in early spring just before the plant starts its summer growth spurt. Use a pot which is just one size larger than the pot it is in already; if the plant sits in too much wet compost the roots can rot.
Terracotta pots are attractive and give that rustic feel, but they do tend to dry out quickly; as they are porous they suck the water out of the compost which then evaporates through the sides. Plastic or glazed are better for conserving moisture. Make sure the pot has a drainage hole in the bottom; just stand it in a saucer or place it in a decorative pot cover. If you are re-using a pot scrub thoroughly with a weak bleach solution, rinse well and allow to dry.
Symptoms of a plant needing re-potting are the roots emerging from the bottom of the pot and slow new growth which is very small, they also dry out really quickly. Check for the plant being pot-bound by gently easing it out of the pot; if the pot is full of root or the roots are coiling around the bottom of the pot then it needs re-potting.
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Place some new good quality houseplant compost in the bottom of the pot, gently tease the roots apart, place the plant in the pot so that the surface is the same as it was in the old pot and firmly fill around the sides with compost. Gently tap the pot on the work surface to settle the compost and get rid of any air pockets. Water thoroughly and allow to drain before placing on a saucer.
A large established slow growing plant may only need re-potting every couple of years, but a vigorous plant will need doing every year. Once your plant has reached the largest size of pot you can cope with, take it out of the pot every year and remove as much of the old compost as possible and replace with fresh. If the pot is full of roots cut them back by about a third.
Houseplant compost performs several functions: it enables the plant to stand upright, it provides food and water, it prevents the roots from drying out and it holds onto pockets of oxygen which is needed by the roots. It is recommended that you use a specific compost for your plant, such as: general houseplant, orchid, citrus, cacti and succulent, African violet or streptocarpus. Don’t use an ordinary garden multi-purpose as they are not usually suitable. Peat based compost holds onto a lot of moisture so is generally used for plants which need to be kept evenly damp, such as: African violets, streptocarpus, begonias and ferns.
Bark compost is used for the epiphytic plants which don’t like to sit in wet compost, such as some orchids and bromiliads. Cacti and succulents and some palms which are used to growing in dry conditions will need some sand and/or grit adding to increase the rate at which the water flows through the compost. Perlite is small grains of expanded volcanic rock which is added to the mix to improve drainage and water holding capacity. Vermiculite holds onto water and minerals then releases them gradually. It also opens up the texture of the compost, improving drainage and aeration.
