Hartley Magazine

All the latest news, hints, tips and advice from our experts

Matthew Biggs

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Gardening Diary

A regular panellist on BBC Radio 4’s ‘Gardeners’ Question Time and author of several gardening books. He writes regularly for several magazines, including ‘BBC Gardeners’ World’ magazine, ‘Gardens Illustrated’ and the Royal Horticultural Society’s Magazine, ‘The Garden’.

All views expressed are that of the author and not necessarily that of Hartley-Botanic.co.uk

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Rainfall Levels and Tuber Infection

Looking at the rainfall levels it seems that the prediction that this summer would be hotter than the last, might have been a little optimistic. All of that wonderful rainwater is free and it’s too good to waste so I’ve been buying water butts to put around the house, garage and greenhouse. There’s a range of designs from subterranean giants to slim-line wall mounted designs; but whichever you choose for your garden remember that the outlet should be high enough for the watering can to fit under the tap. Most manufacturers provide purpose built stands, though timber or a stack of slabs are useful alternatives; stock bricks should be avoided as they eventually crumble. If you are placing them directly onto the soil remember that the weight of water can cause them to sink over time. I’m convinced that plants prefer rainwater ‘straight’ as nature intended, it doesn’t contain chlorine or other additives and is better for acid loving container plants like rhododendrons and camellias, even if you live in a ‘soft water’ area. Greenhouse plants prefer their drinks tepid, so a rotation of several watering cans allows the water to warm under glass for at least 24 hours before use.

The downside is that moist, humid weather in July is prime time for potato blight. Spores are spread by wind and rain these conditions when temperatures are 10oC (50oF) or above. Brown or black patches appear on the tips and margins of leaflets, that curl and wither, it then spreads rapidly to the leaves and stems before the plant finally collapses. The spores are then washed down to the tubers, the skin becomes discoloured and a reddish-brown rot appears, this, alongside secondary infection reduces the tuber to a foetid, liquefied mass and it rapidly devastates crops that are growing or stored.

Tuber infection can be reduced by ‘earthing up‘ or mulching with a thick layer of organic material like hay or straw. Remove infected foliage immediately can slow its spread and stop spores from spreading to the tubers then don‘t harvest the crop for at least 3 weeks, after this the tubers will have thicker skins and spores on the surface will have died. Lift even the tiniest infected tubers and dispose of them away from the garden and always plant ‘seed’ from reliable sources. Early maincrop varieties are more prone to blight, plant early so that they mature before it appears. Planting alternate rows of different resistant varieties can improve cropping. Check tubers in store regularly; remove any that are rotting.

Another option is to apply Bordeaux mixture, copper oxychloride or mancozeb before plants become affected. Listen for ‘Blight Infections Periods‘ are mentioned on Farming Programmes or weather forecasts and hope that the weather becomes dry and sunny, halting the spread of ‘blight‘. There are several ‘resistant’ varieties like Colleen, Premiere, Cosmos, Lady Balfour, Pomeroy, Orla, Remarka, Cara, Milva, Valor, Verity, Arran Victory. Sarpo Mira, the first to score 100% in commercial evaluations against blight is ushering in a new era of blight and virus resistance, more varieties, including ‘Sarpo Axona‘ following; roll on the bight resistant revolution!