How to divide herb roots

BBC Gardeners' World Magazine

Published: Tuesday, 24 September 2019 at 10:08 am

Find out how to divide the roots of herbs that produce creeping rhizomes, such as tarragon, horseradish, mint and sweet woodruff.

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As the weather turns colder in autumn, it's sensible to be prepared and insure your precious herbs against damage. Herbs that are worth spending time on in the late autumn and early winter are tender herbs needing protection from frost, such as French tarragon.

Autumn is the ideal time for taking root cuttings from herbs that produce creeping rhizomes – shoots or suckers – from the roots. Plants such as French tarragon have thick and fleshy roots that store food, enabling the root to survive and grow once detached.

The following steps are a beneficial and rewarding way to produce lots of new plants.

The steps can also be used for horseradish, mint and sweet woodruff.

You Will Need

Large modules or small pots
Compost
A large pot-grown plant
A saw or bread knife
Vermiculite or fine grit
Shredded bark

Total time: 30 minutes

Step 1

Adding compost and vermiculite to the seed tray

Choose large modules, or small pots. Half fill each with compost consisting of one-third finely shredded bark, one-third vermiculite and one-third potting compost. Water well.

Step 2

Sawing the rootball in half

Choose a large pot-grown plant, remove the pot, then saw the rootball in half. Repot one half, using fresh compost. The remaining half can then be divided to give masses of root cuttings.

Step 3

Pruning the top growth from the cuttings

Cut off the top growth from your cuttings and prune the hairy roots so that each cutting fits in a module, taking care not to damage the creeping rhizome – the engine of next year's crop.

Step 4

Firming compost over the cuttings

Firm into the module, cover with more compost to just below the rim, water lightly, label, then place in a cold greenhouse or cold frame. Only water again to prevent the compost from drying out completely.

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