How to begin a begonia and curb a clematis, by garden expert Helen Yemm

Every week, our Telegraph gardening expert gives tips and advice on all your problems whether at home or on the allotment

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Blackmore & Langdon's begonias at Hampton Court Flower Show
Blackmore & Langdon's begonias at Hampton Court Flower Show Credit: Paul Grover for the Telegraph

If you have a gardening question for Helen Yemm, see below for how to contact her.

Begonia beginnings

Phil Watmough, from Preston in Lancashire, asks when he should start tempting his begonias into action. Last year he set them off in April, he says, and they seemed to take an age to get going.

This is a hard one to answer with confidence, because it depends not just on his geographical whereabouts (readers, it is often essential to know…) but on his greenhouse set-up – so I have to presume an unheated one – and on the kind of spring we have. As I recall, we had a particularly tricky stop-start one last year, which may be the simple explanation as to why Phil’s begonias took so long to “get going”.

It is important not to get them shooting too early lest they get singed by unexpectedly cold nights, either in the greenhouse or after they have been turfed outside in late April without being properly hardened off (i.e. out during the day, back in at night). Sticking my neck out… I should say that Phil might want to start them off in March this year and keep a beady eye on the weather forecast. I know: not very helpful.

A reader who just calls him/herself “Clueless”, asked almost apologetically for guidance about some “funny shaped” begonia tubers he/she has been given. Which way up should they be planted? Rounded, smooth but very possibly slightly hairy side down, knobbly shaped slightly concave side up, is the answer. They should be pressed gently into the surface of free-draining compost and barely watered until they shoot.

And finally, it may reassure Wendy Campbell, who was surprised not to find any corms she could grow again when she de-potted the remains of her fabulous but unlabelled specimen, to know that not all begonias grow from corms; some have fibrous roots and are best treated as annuals.

Liverwort spread

I have identified the problem on some of my soil as liverwort. In the past I have managed it by scraping away from time to time, but I would like to do better. Would ground cover plants prevent its growth? I have read that improving soil drainage would help, but how? Can you suggest any organic solutions?

Amanda Nicholl, via email

Hepaticae (Liverwort), by Ernst Haeckel, 1904 Credit:  FineArt / Alamy

Liverwort is a rootless, primitive ground-hugger that forms a green mat of platelike “leaflets” over the soil surface. Like related moss and algae, liverwort spreads particularly efficiently in areas that are damp and shady, most rapidly on soil that is slightly acid, impoverished and compacted. This mild, wet winter is perfect for it.

For long-lasting dismissal of your liverwort, you will have to scrape away as much as you can. Don’t add the scrapings to your compost bin, as, like moss, liverwort does not rot down satisfactorily. Then, as you suggest, you will have to de-compact the soil where the liverwort took hold by loosening it with a fork, reducing its basic acidity by applying garden lime and digging in as much coarse organic matter (compost, rotted manure or bark, even coarse sand) to enrich and open up the soil texture.

In the improved soil, plants could thrive and definitely make life easier for you in the future, but beware of ground cover thugs, the control of which would be, as the expression goes, a “whole nother story”.

Your pond reflections

Clearing duckweed out of a pond using a small fishing net Credit: gapphotos.com

My request for your tips on duckweed control (January 25) brought forth differing responses: some people put in considerable effort. Tony Billington and his wife drag duckweed to one end of their sizeable pond (via a heavy rope slung between them on the water surface) before netting it out. Tom and Rosie Laurie now quarantine every scrap of pond life they put in their cleansed and renovated pond since, they say, duckweed is often imported on aquatic plants.

Others give a pragmatic sigh. “You just have to keep on top of it,” was Michael Lancey’s contribution, along with some advice about acquiring a large fine-meshed skimming net with, crucially, a lightweight telescopic handle (buy online), and also a reminder about leaving weed for 24 hours on the pond’s edge so that creepies and crawlies can slink back in.

Graham White is even more laid back: “Don’t bother to try to get rid of it,” he says; his duckweed “mops up some of the nitrogen” which, along with his water lily, seems to slow down the growth of algae. On the subject of algae (both green water and blanket weed), for those who struggle with it: Ecopond (ecopond.co.uk) tells me it has developed a new natural product, Barley-bio Algae Control, which uses microorganisms that are grown on barley straw.

 

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