Helen Yemm: how to make lazy geraniums sit up, a tip for lily of the valley, follow your nose for good manure

Helen Yemm
Lily of the valley makes clumps that can be split when the plant is dormant - Getty Images Contributor

LILY OF THE VALLEY

When is the best time to split lily of the valley? I have some in a large tub outside my back door so I can enjoy the perfume, but they are now very overcrowded. Should I do it now while they are still in leaf, or wait until they die down?

C. Mordecai – via email

Lily of the valley (Convallaria majalis) belongs to the same plant family as asparagus and has a similar, spreading rhizomatous root system, sending up dark little pointed fast-growing shoots in late spring. These leaf up and produce their tiny intensely perfumed flowers little more than a month later, the leaves gradually dying back thereafter. By late autumn there is no trace of them left above ground. 

This is a plant that dislikes full sun and is actually far happier where it can “wander”. In fact, it particularly likes damp, leafy soil and is admirably un-fussy about soil pH. In my garden lily of the valley is happily spreading along the edge of a shady brick path where its roots can stay cool and damp, and are striking out further afield, boldly showing up between nearby hellebores. Grown in a container, your plants have nowhere to go, and you would do well to divide them every few years.

Dig up your plants at any time between September and November, gently separating the tangle so you have bundles of three or four shoots, replanting them straight away, about 4in apart, in fresh, loam-based compost (John Innes no. 3) that is ideally enriched with leafmould and a little bonemeal. 

Plant them at the same depth as they were in their previous abode, with their “noses” just under the soil surface. Any spares can be given away to friends – with the proviso that they should be planted immediately and not allowed to dry out.

TIP OF THE WEEK

GERANIUM SUPPORT

Elise Furnival complains that her Geranium ‘Johnson’s Blue’ is always a mess. Some of its noble relations, she says, she expects to straggle. She welcomes ‘Nimbus’, ‘Anne Folkard’, most recently ‘Rozanne’ and other untidies into her garden, so they can scramble around for weeks and distract the eye from a multitude of messes. But of ‘JB’ she expects more. Apparently, after a wonderful, early, relatively compact flush of silvery-blue flowers, it collapses. If she cuts it back hard, will it flower again, Elise asks. She does that to a furry-leafed very early-flowering blue geranium that she inherited (name unknown – could it be G. magnificum?), and it doesn’t repeat-flower.

‘Johnson’s Blue’ is one of those geraniums that is immeasurably improved by good support. I use the grid-on-legs type, installed in early May so the plant grows up through it. It makes no end of a difference to the way the flowers hold themselves up above the foliage, and when they dwindle, I grasp all the lanky stems that have flowered and give them a short, sharp tug, which detaches them at the base, leaving newer foliage intact. From within this, with a bit of luck a (smaller) flush of flowers will appear a few weeks later. With this geranium, cutting back everything, in my experience, shocks the plant too much. It produces new leaves eventually, but hardly any more flowers.

 

FREE MANURE

We have been offered some free horse manure by a local farmer – we can just roll up, bag it and take it away, he says. All we know about it is that it is “pretty old”, but I know there are some pitfalls with manure. Can you tell us how to recognise them?

Colin and Anne B – via email

First, do the smell test: really well rotted manure should be more or less pong-free. If this isn’t, you should bag it up and take it (never look a gift horse…), but leave it in the bags for a while longer – six months at least. It will go on rotting in there quite happily, as long as the bags are pretty well sealed up. Another option is to mix it in with the contents of your existing compost heap, which will help to speed up the rotting of both manure and heap considerably. 

Free horse manure that is fresh and smelly potentially carries loads of grass seed within it, as well as being too “strong” for safe contact with plant roots and shoots. Another possible pitfall: if the pile has been sitting uncovered in a field for a long time, it might well be nicely “mature”, but could have been gathering nettle seeds and who knows what else on the surface. So my advice is the same, whatever condition the manure appears to be in: dig deep. Rather you than me, though.

 

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