Grow veg

Grow blight resistant tomatoes

If you lost your entire tomato crop to blight during 2021, don’t let it happen again. Read on ……….

Where tomato growing is concerned, 2020 lulled many people into a false sense of security. The sun shone, the rain stayed away and the tomato plants grew strong and healthy. It was an unusual year. 2021 on the other hand was much more typical. Damp, mild, damp again. Tomato blight was in its element, it had free rein to spread and infect and the plants were decimated. Down at my allotment site in north London, a lot of people had lost all their plants to late blight by August, before any of the fruit had had a chance to ripen. It’s so disappointing when that happens and the trouble is, if you’re growing plants outside in a bad year there’s really not a lot you can do about it.

Unless you grow blight resistant varieties.

What is tomato blight?

The blight that affects tomatoes is the same one that will kill off your potato plants. It is caused by a fungal-like pathogen called Phytophthora infestans, or late blight. It infects plants through spores carried on the wind, usually from potatoes, especially ‘volunteer’ potatoes that were infected the previous year and left in the ground to regrow the following year. These spores land on the leaves and stems of tomatoes where they sporulate (love that word!) when conditions are mild and the leaves are damp – specifically the temperature needs to be above 10 degrees C for two consecutive days combined with relative humidity of 90% for at least six hours. So the mild, rainy weather that typifies a British summer is perfect for it’s spread and it hits just as the first tomatoes are starting to ripen and you’re looking forward to eating them.

If you’re not sure what blight looks like, keep watch for black patches on the plant stems and black blotches on leaves. Once you’ve seen them they usually spread quickly and infect the whole plant, including the fruit.

This is a potato in the early stages of blight. I didn’t have a good photo of a tomato with blight but it looks very similar.

So blight resistant varieties don’t get blight?

In fact they do get blight, and you might even see signs of it on your plants just as you do on the plants that aren’t resistant, but they wont succumb to it in the same way. It won’t spread through the plant – or at least nothing like as quickly, and it won’t usually kill your plant so your tomatoes will have time to ripen and you can eat them.

Blight resistant varieties

Firstly, there are old and new blight resistant varieties. Ferline, Losetto and Lizzano were some of the first to be introduced. Ferline isn’t very resistant in my experience, although Losetto and Lizzano are better. More recently there have been very successful programmes of breeding carried out and it seem that breeders have had amateur growers in mind in these, so there’s been an emphasis on getting fruit with good flavour as well as getting plants that stay healthy. The healthiness is acheived through more complex modern breeding methods that have allowed them to introduce more than one set of blight resistant genes. So whereas some of the early varieties lost their resistance as blight mutated (in much the same way that dieseases like rose black spot and, indeed. coronavirus mutate), these new varieties have greater resistance and remain more resistant even when blight changes.

Bringing hope to outdoor tomato growers all over the UK, Mountain Magic and Crimson Crush were among the first of this new breeding to be introduced. Since then there’s been an avalanche. We’ve had Crimson Blush, Crimson Cherry, Crimson Cocktail and last year, Crimson Plum. I think Crimson Plum is the first blight resistant plum tomato which was something I was really looking forward to. I like cherry tomatoes to eat whole but plum ones are much better for cooking with.

Consuelo and Cocktail Crush, both cherries were introduced recently and two or three years ago Oh Happy Day (one of my favourites) appeared. This is an excellent blight resistant beefsteak variety. On my allotment last year both Oh Happy Day and Crimson Plum came through the difficult season with flying colours. There were a few dark patches that showed they’d been exposed to blight, but they lived on, in fact they thrived and I was still picking fruit in October. They both taste good, too. In fact I like the flavour of most of the new varieties I’ve tried, but tastes vary to it’s woth trying as many as possible for yourself and seeing which ones suit you.

Breeding continues and this year I’m going to try two more newbies – Crokini and Goldwin Golden Cocktail. I’ll let you know how they get on.

Fruit of Oh Happy Day and Crimson Plum picked in late September 2021

You can buy seeds (or plants, including grafted plants) of the most recent blight resistant varieties from seed companies such as Pentland Plants, Plants of Distinction, Simply Seed, Marshalls and Mr Fothergill’s seeds.

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