What ails my potted conifer?

QI love rescuing other people’s neglected plants and have just taken on a poorly conifer. It is in a small pot and stunted, so how can I make it beautiful again, and keep it in a container?

Claire Birchill, Cannock, Staffordshire

AAs a child, most of my plant collection consisted of rescued plants and restoring them to health was really satisfying. Plants in containers generally need more care than those in the ground, starting with an appropriate potting compost, correct positioning, and then regular watering and feeding.

After a few years, they will fill their pots with roots and need potting on to a larger container, or perhaps have their roots pruned and potted back into the same one. Weeding, topdressing with fresh compost, and watching out for pests and diseases are ongoing tasks.

Step by step is the way to go. Begin by removing the plant from its pot. With help, try upending and rapping the rim against a solid wooden fence post. If the pot is too large, lay it on the ground and tap the rim with a thick wooden stick. If rootballs stick in a pot-bellied container, cut around the outside using an old knife. This seems brutal, but is similar to root-pruning and saves breaking the pot.

A large goat willow had seeded among the roots of my demonstration plant. Removing weeds is sometimes helpful, as it loosens the congested roots of the potted tree. If root-cutting and weed removal have not done enough, take time to tease some roots out. Look out for vine weevil larvae, as they enjoy living in containers, although I rarely find them on conifer roots.

Choose a new pot carefully. While more depth and width is needed, too much empty compost will mean roots are starved of air and might rot off. A well-drained potting compost will help, so opt for something like three parts soilless compost, two parts John Innes No2 and 10% potting grit.

When positioning the plant, make sure that the top of the old rootball lies a good 1in (2½cm) below the rim, to allow for watering. 2

Remove the plant from its pot, then pull away the weeds and loosen roots from the tight mass. 3

Place crocks over the drainage hole, add moss over the crocks, and then some compost. Spend time siting the plant at the correct height and at the best angle. 4

Fill in around the roots with compost, firming gently as you go. Place in a sunny position and water in well, using a rose on the can.

In a slightly larger container, the conifer already looks happier, and with access to fresh, nutritious compost should put down new roots ready to make fresh growth next year Pick a new pot carefully, as with this Chamaecyparis obtusa ‘Tempelhof’, to balance depth and airflow Given a few years, you can easily grow large, happy specimens such as these Cryptomeria japonica

Add a slow-release fertiliser in spring