Pruning and Trimming Herbs

Cutting Back After Flowering

Pruning out of finished or fading blooms can help promote the development of further bursts of flower buds, but not all herbs are capable of flowering continuously. Some, such as Lavandula angustifolia, will only flower once, but others, such as cultivars of L. stoechas and L. pinnata, can flower almost continuously throughout summer if the flowering stem is cut back to a node or to lower developing buds.

Herbs such as lemon balm (Melissa officinalis) and fennel (Foeniculum) will seed themselves prodigiously if not deadheaded or cut back. Deadheading will also prevent seed development, so always leave a few to set if you wish to harvest the seed for sowing or culinary purposes.

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Trimming Back

Maintaining a neat and productive set of culinary herbs is dependent on regular usage or harvest. New growth is the most colorful and flavorsome and to keep this coming, regular rejuvenation is vital. Trimming off flowerheads will often prevent annuals and biennials from dying while perennials may go on to produce a second flush of foliage.

As the flowers fade, cut back with sharp scissors, aiming to reduce the stems by about half on the first occasion. (image 1)

The foliage will grow back by 1/2-3/4 inches within a few weeks and this new growth can be trimmed off for immediate use. (image 2)

Hard Pruning

Many herbs are shrubs and some, such as santolinas and Helichrysum italicum, can become woody and sparse at their bases. Renovate in late spring or early summer when there is little chance of the tender new growth being damaged by frosts. Some of the prunings could even be used as cutting material.

Using sharp pruners, cut out all dead and diseased wood to just above ground level; cut back all other stems to around 4 inches. (image 1)

Thin out the remaining branches to leave 6–12 stems with a number of new shoots on each—aim for an open goblet shape. (image 2)