Fool Proof Guide To Autumn Pruning

There’s a lot more to autumn gardening than simply chopping everything in sight. Here’s how to be prudent with your pruning for the best results, says Graham Rice

Graham Rice

Never mind spring cleaning, in the garden there’s nothing like a good autumn tidy up. The urge to rake up leaves, chop back shrubs, prune perennials and shove it all in the compost or garden waste collection bin can be irresistible at this time of year. But before you sharpen the secateurs be aware that not all plants will benefit from being given the chop.

Exhausted and frosted annuals can certainly go on the compost – there’s no sense leaving their bedraggled foliage to detract from the chrysanthemums, perennial anemones and autumn bulbs at their peak. With perennials, however, it varies: some can be cut back now; others are better left alone until spring.

To chop or not to chop may be the question, but there simply is no definitive answer. It all depends on the plant. Some perennials – the likes of campanulas, phlox, astrantias and alstroemerias – are best cut off at soil level; the same applies to fennel, which will otherwise repay you with a forest of irritating seedlings.

With others, there are definite benefits to holding fire. By not cutting back the statuesque Phlomis russeliana, achilleas, eryngiums, perennial astilbes, sedums, alliums and many ornamental grasses, we can enjoy their structure against a winter sky – the sight of their stems silvered with frost adds a whole new level of interest to the garden.

The third way

There’s also another option: cutting back, but only by half or a third. This is the ideal approach for the likes of penstemons and agastaches. If left alone they will rock in winter winds, the roots will be loosened and their chances of survival greatly reduced.

Some summer-flowering shrubs, such as Hydrangea paniculata, have an impressive winter structure and can be left until spring in sheltered places, although thinning the stems is advisable in windy gardens. By all means enjoy clematis seedheads into winter, but cut back buddlejas, caryopteris, perovskias and hybrid tea and floribunda roses by half to reduce wind rock. You can then finish the job in spring.

When cutting back, also bear in mind that certain seedheads are lovely for drying. Cardoons, nigellas, poppies and grasses are all particularly effective when dried – just don’t leave it too long as they’re less easy to dry after being soaked by autumn rains.

Leave some for wildlife

And don’t forget that, for many forms of wildlife, the very plants we might be tempted to cut back offer valuable sources of food and shelter in the colder months. Beneficial insects hibernate in stems and in dried seed heads in winter, and in spring the twiggier pieces will be used for birds’ nests.

Finches, in particular, will appreciate seedheads – especially those of teasels, sunflowers, scabious and Michaelmas daisies. Leave a few in situ for them now and feathered visitors will return the favour by eating your aphids in spring.

Plants to cut back...

Hard

Delphiniums