One clump, three plants: divide your herbs now
Mint, comfrey and chives practically multiply themselves in September – all you have to do is split them. Five minutes per plant, and you save yourself a trip to the garden centre next spring.
A herb clump that has sat in the same spot for years eventually goes bald in the middle and only pushes fresh growth around the edges. That is not a sign of disease, it is an invitation: the plant wants to be divided. And September is one of the best moments in the whole year for it.
Why now is a good moment
The soil is still warm from summer while the air has already cooled down noticeably. Roots love that combination: they keep growing while there is hardly any leaf mass left to support. Freshly divided pieces therefore establish faster than in spring, when the plant is trying to push new growth at the same time.
Count on four to six weeks before the first serious frost. In most parts of Austria, Germany and Switzerland, a date up to early October is comfortable. At higher altitudes, mid-September keeps you on the safe side.
Three you can split right away
Mint is the easiest place to start. It spreads through underground runners, and almost every piece with a shoot will take root again. The plant encyclopedia lists September and October as planting months.
Comfrey divides well in autumn and bulks up again quickly afterwards. One thing to be clear about: comfrey is not a culinary herb but purely a mulch and fertiliser plant – it contains compounds that do not belong in your salad. Its potassium-rich leaves do make excellent mulch for tomatoes and potatoes, though – one more reason to turn one plant into two.
Chives are the classic case. After three or four years the clump thins out in the middle and grows ridged at the edges. Dig it up, break it into fist-sized chunks, replant – done. The encyclopedia lists April to June as the planting window: if autumn feels too tight where you are, simply move the division to spring, it works just as well.
These are better left alone
Sage, thyme, rosemary and lavender are subshrubs. They do not form a clump you can pull apart – they turn woody from the base upwards. Tear one in half and you end up with two half-dead plants. Propagate them from cuttings or layering instead, ideally in early summer.
Oregano sits somewhere in between: it also turns woody, but it creeps outwards with shallow runners. Older mats can therefore be cut away and divided quite happily – take the young outer sections rather than the woody centre.
Tarragon is better divided in spring; freshly split, it goes into winter reluctantly. And rhubarb waits until October, once the leaves have died back and the plant is genuinely dormant.
How to divide a clump
Lift the plant generously with a spade, a good hand’s width outside the foliage, so you catch most of the roots. Shake off the loose soil – now you can see where the root ball naturally wants to come apart.
Split it with your hands, an old bread knife or the spade. Each division needs roots and at least two or three shoots. Smaller pieces work too, they just take a year longer before there is anything to harvest. The worn-out centre of the old clump can go on the compost; it only sprouts half-heartedly now.
Replant each piece at exactly the depth it grew before, firm the soil and water it in generously. Too deep and the shoot rots, too shallow and the roots dry out.
The first week decides it
Keep the new divisions evenly moist for two weeks, even when it is cool and it does not feel necessary. Roots without proper soil contact dry out faster than you would expect. A thin mulch of grass clippings or leaves holds moisture and later softens the first frost.
Skip the fertiliser for now. It would trigger soft growth that the first frost takes straight back. And in this first autumn, harvest a few leaves to taste at most – the plant is putting its energy into roots, not foliage.
Where the new plants should go
With chives it pays to look at the neighbours: they sit happily next to carrots, strawberries and tomatoes, but they hold back peas and beans. A divided clump is the perfect excuse to extend the chive row along the carrots instead of leaving everything in one spot.
Mint and comfrey call for the opposite of generosity. Mint belongs in a pot or behind a root barrier, otherwise in three years you will have a mint bed where the herb bed used to be. Comfrey regrows from even small root fragments, so think the spot through properly before you put the spade in.
In Rootivo you can draw the new divisions straight into your bed, and the companion-planting lines instantly show you in green or red whether the new neighbour is a good match.
Im Lexikon: Schnittlauch