With so much to do in the garden now, it's easy to forget our indoor plants. Most of these will appreciate a yearly repotting or rejuvenation. Pot-bound plants (those with a solid mass of roots crammed into the pots, or running round and round the inside) should be repotted into a larger pot, just an inch or two greater in diameter. Use a John Innes compost (a formula, rather than a brand name), which is more nourishing and water-retentive than the cheaper, more common peat-based composts.
Plants already in huge pots can be reinvigorated by gently removing some of the old, tired compost from around the roots and replacing it with fresh stuff. The same regime should be followed for perennial outdoor containerised plants.