Preparing Perennial Herbs for Winter

23 September 2011, written by Helen Gazeley

Some of the most popular herbs are both perennial and evergreen, which makes it tempting to let them do their own thing. Oregano, thyme, sage and lavender are all very easy to neglect when there are so many other things clamouring for attention but this is exactly why at one moment they can be compact mounds of aromatic delight and then, seemingly a moment later, an unwieldy sprawl of woody stems.

I inadvertently left an English lavender untrimmed for several years early in its life, and it now has a forest of bare stems at its base. (Yes, I know all the textbooks would have me grub it up and start again, but it’s so matronly that I keep it. It’s also a constant guilt-trip that makes me pay attention to all the herbs that might go the same way.)

Preparing Sage, Oregano and Thyme for Winter

This time of year is a good time to sort through the sage, oregano and thyme, cutting out any dead wood and extracting weeds that have grown around their base. Most importantly, trim off the dead flower heads to help keep the plants bushy. Don’t trim too low down the stems (a light trim of the top leaves is enough) as the plants need time to recover before the cold weather arrives and small tender shoots engendered by fierce pruning won’t take kindly to being bathed in frost.

Trimmed sage bush — A sage bush after seed heads have been removed for its winter trim

Trimming the plants also gives you a chance to dry the pruned-off leaves, removing the need to trek down the garden in the depths of December to gather a bouquet garni. One of the easiest ways to dry herbs is to peg individual sprigs to a line strung up somewhere warm and dry, until the leaves are ready to crumble. Then store in air-tight containers.

Although sage, oregano and thyme will provide leaves over winter without protection, you should check their growing guides in case your winter temperatures are so low that small plants should be potted up and taken indoors. Fleece can help protect larger plants and, even in more temperate climes, you might think it worth throwing some fleece over them in winter to obtain a greater supply of larger, more tender leaves.

Rosemary can be trimmed in winter or you can wait until spring. For details, see our article on The Worst Enemies of Rosemary.

Overwintering Bay Laurel

One herb that must be protected in all but the most sheltered positions is the bay tree. Bay trees really don’t like being frozen and, caught out by the sudden arrival of snow, I kicked myself last year for not rushing out to protect my treasured lollipop-trained specimen. Mulch bay trees with compost to protect the roots from frost and, when the cold weather threatens, wrap the plant itself in fleece. If the worst happens and a ground-planted bay seems to have been killed off, it’s nevertheless almost certainly going to shoot up again from the base when spring arrives, as the roots will have been protected in the ground. The same cannot be said of pot-grown bays, however, as the freezing temperatures will have penetrated the roots. To avoid this, pots should ideally be moved indoors or, if too heavy to move, swathed in bubble-wrap, while the top growth is again protected with fleece.

A bay tree resprouting after being killed by frost

Preserving Mint

Mint is a perennial that will begin to die off soon and it’s often recommended that you pot up mint to take indoors for winter use. I’ve tried this a couple of times and, to be honest, it didn’t really work; the mint got all straggly and miserable and died off anyway. Further research revealed that mint seems to need to fall dormant for a period, so that explains why. If you do want to preserve mint for cooking over the winter months, it’s better to harvest clean, fresh leaves now, chop finely, pack into ice-cube containers, immerse thoroughly in water and freeze.

Fennel Seeds

Another favourite perennial, fennel, also dies off for the winter. By the end of summer it will be carrying seed heads on stately stalks up to around five feet high. If, like me, you have a relaxed view of weeds, you might like to let fennel stand over winter as the skeletal seed heads make an attractive winter feature. However, fennel self-seeds with aplomb and, if you don’t spot the tiny shoots early, they can put up a bit of fight when you try to pull them up. To avoid this, cut down the stalks before they get the chance to chuck the seeds around. Alternatively, place a bag over a seed head or two in order to catch the ripe seed when it falls, and gain a supply for curries and stews or to sow next spring.

By Helen Gazeley