Blight October

When astronaut Mark Watney got left behind on Mars in The Martian, his only hope of survival was to grow some of his own food, by planting a few handfuls of potatoes sent along with the crew for a special Thanksgiving dinner. Combined with NASA rations and a plentiful supply of tomato ketchup, it was just about enough to keep him going until he could be rescued.

He was lucky he had potatoes to plant, as they offer up a good yield and make a surprisingly good contribution to a healthy diet. But whilst Watney faced a number of different challenges, farming on Mars, his plants were safe from the one thing that makes relying on potatoes a risky prospect here on Earth.

This year was the first time I have had an issue with late blight – a disease that can devastate both potato and tomato plants – in my garden. I wasn’t growing potatoes, but it cut down my tomatoes quite late in the season, right when they were starting to become productive. Spread by spores that are ever-present in the environment, blight attacks when the weather conditions are right, waiting for warm and moist conditions. Usually, once a plant is infected it is quickly reduced to a pile of dead stems. Potato tubers may survive for a time under the soil, but are inevitably at risk of rotting.

There are three options to protect a tomato crop. The first is to grow early varieties, which mature and can be harvested before late blight is likely to be an issue. The second is to grow your tomatoes in the greenhouse, where they are somewhat protected from blight spores. It’s not 100% guaranteed that they will be safe – this year I heard from a friend whose outdoor tomatoes were fine whilst his indoor tomatoes succumbed (it’s a matter of temperature, the conditions just happened to be right in the greenhouse).

The third option is to choose blight-resistant varieties. Suttons made a splash this year with their new Crimson Crush tomato plants, which seem (by all accounts) to have stood up to infection. You can now buy Crimson Crush seeds if you want to grow your own plants, and the variety will be available as plants again next year. It’s not the only blight-resistant variety on the market – Victoriana Nursery Gardens have a selection of blight-resistant tomatoes – so keep an eye out in the catalogues for ones which meet your requirements.

For potatoes you really only have two options, since they’re not a greenhouse crop. So you either confine yourself to growing early varieties that should have produced their harvest before blight hits, or you grow blight-resistant varieties. Otherwise there’s a real risk that you’ll be watching your potato plants topple like dominoes before the end of the summer. Although I had blight-free potato crops in my old garden, when I transferred to an allotment I chose to grow blight-resistant Sárpo varieties, which meant that I could harvest a good crop even when my neighbours lost theirs.

The organism responsible for late blight is constantly evolving, and so blight-resistant varieties don’t stay that way forever. If we’re going to enjoy potato and tomato harvests in the future then we need people to keep breeding new resistant varieties – and they will only do that if customers buy them. So rather than just ordering your favourites for next year, why not trial a blight-resistant variety and see whether you like it?

Of course, if you really want to avoid problems with late blight then you can look to other crops to take the place of tomatoes and potatoes. Tomatillos are just as easy to grow as tomatoes, and are the traditional fruit used in salsa. Cape gooseberries are another possibility, easy and fruitful although a little more on the ‘fruit’ side of the spectrum than tomatoes. And potatoes could be ‘replaced’ with sweet potatoes (which are slowly getting easier to grow in the UK climate) or other tuber crops such as Jerusalem artichokes, Andean oca or the new edible dahlia varieties.

What are you strategies for dealing with blight? Do you just cross your fingers and hope it won’t come your way?