Q: I have a lovely fig tree that was planted four years ago. It has grown vigorously and could do with a trim. When is the best time of year to trim a fig tree? How heavy should I go? WM, Co Dublin
A: Lucky you, if there’s such a thing as fig envy, then I think I have it. This handsome, heat-loving, exceptionally long-lived tree (Ficus carica) grows best against a sunny, south-facing wall in a mild, sheltered garden where its sweet, sticky, delicate fruits can slowly ripen over summer. Expensive to buy and difficult to transport, growing your own is a decadent joy. But in a cool, wet year, it can be a hit-and-miss crop, so it’s not really suitable for colder gardens unless grown under cover of a glasshouse or polytunnel.
Your young tree’s exuberant growth suggests that its root systems have free rein to roam, which is a problem. Ideally, these should be restricted by growing it in a large pot/tub, or in a ‘planting pit’ measuring roughly 60cm square and deep with the edges retained with old roof slates or paving slabs and the base of the planting hole lined with stones/broken bricks. These two time-honoured methods will keep it compact , force it to fruit early and well, and discourage it from producing too much leafy top growth.
The good news is that you can still do this retrospectively by carefully digging a narrow, square-shaped trench around the base of the tree and then placing some slates or paving slabs on their edge into it to box the roots in and restrict their spread before backfilling with soil. Just be careful not to dig too close to the trunk of the tree.
You don’t say whether your tree is intended to be (a) a freestanding bushy tree; or (b) grown against a wall as a fan-trained specimen, where the branches are spread out flat like splayed fingers. Either way, any substantial pruning of a fig tree should be carried out in March/April towards the end of its winter dormancy, and after the threat of severe frost has passed.
If you’re growing it as a freestanding tree, then start by using a sharp, clean secateurs to cut a quarter to a third of the oldest branches back to the desired height, ideally to young healthy growth. Nipping out the growing tip of the main stem will also stop it getting taller and encourage it to fatten up.
If it’s a fan-trained tree, then gently spread out and tie the main branches flat against the wall. Use a sharp, clean secateurs to remove any dead, damaged, diseased or crossing branches, as well as any unwanted branches that can’t be trained into this fan-shape – including any stems sticking straight out from the main branches or side stems that are cluttered too closely together.
Whether freestanding or fan-trained, in late May/June, nip the tips/ends of young shoots back to four-five leaves to encourage the production of fresh, healthy, fruit-bearing growth. Confusingly, fig trees are technically capable of producing two crops a year, but not in cool, damp Ireland. For this reason, in late autumn, it’s best to remove any unripe fruits larger than a pea still left on the plant in order to encourage the development of new fruit for the following summer. In late autumn the latter are already present as tiny embryo figs hidden near the tips of the young shoots but can be damaged by harsh winter weather. You can protect them with horticultural fleece or by growing your fig tree in a large container under cover of a glasshouse or polytunnel.