Roehampton Garden Society

Urgent: action needed to counter tomato blight

Growing tomatoes this year? It’s that time of year, when rain and warmth together mean tomato blight can flourish. Many allotmenteers may be affected – particularly on outdoor grown plants.

There is no recommended remedy available at present, unfortunately, but in the early stages, removing affected leaves and fruit may slow things down. Once the stems are affected you must harvest any fruit you can and pull up and destroy the plant.

What to Do

  • Please check tomatoes now – early signs can be brown spots on leaves and fruit.
  • If blight is established, pull up the plant and bag it. Clean your hands and tools – not in the water tanks, please! You can keep any green tomatoes and eat any unaffected ripe ones.
  • Don’t put affected fruit and plants in your compost bin – the temperature is unlikely to be high enough to kill the spores and blight will come back next year. You can put them in green waste collection for the council as their facility runs at higher temperatures.
  • To avoid spreading blight, be careful when watering tomatoes. Don’t splash water up the stems or on to lower leaves as the soil may contain blight spores.

Watch Monty deal with his tomato blight problem here:

Here’s advice from the RHS also: .

Let’s see if we can stop it spreading now ……….

If anyone has treatment recommendations to share, please do contact us by email.

August jobs on your allotment

Maintaining soil structures and planning ahead

  • Green manures such as Mustard and Phacelia and Grazing Rye can be sown now.
  • Continue regular weeding to avoid build-up of work later.

Sowing and Growing

  • Sow oriental vegetables such as mizuna, pak choi and mustard greens for salad leaves- they bolt less at this time of year.
  • Sow parsley to last through till spring on a sunny windowsill.
  • Sow Swiss chard and perpetual spinach at the beginning of the month.
  • Make a last sowing of beetroot at the beginning of the month.
  • Sow fast-growing ‘catch crops’ for autumn use, such as radish, lettuce, rocket and turnips.
  • Plant out winter brassicas, broccoli, kale and cabbbages in soil which has been limed at least 6 weeks before, to reduce club root infestations.
  • Plant new strawberries now, either as detached runners or new plants.
  • In dry weather keep runner beans well-watered twice a week to aid setting.
  • To reduce risk of tomato blight, water directly onto the roots not the leaves.
  • Feed courgette plants weekly with a high potash liquid feed to continue fruiting.
  • Summer prune trained fruit trees such as fans, espaliers and cordons.
  • Prune plum and damson trees after fruiting. On grape vines shorten fruit bearing branches to two leaves beyond the fruit bunch.
  • Prune out fruited canes of summer raspberries.
  • Tie in new canes on raspberries and blackberries.
  • On grape vines shorten fruit bearing branches to two leaves beyond the fruit bunch.
  • Cut back chives if showing signs of rust and new shoots will quickly appear. Remove mint plants showing signs of rust. The disease will persist over winter and re-infect new plants next year.
  • Pick off and destroy rosemary leaf beetle which are active at this time of year.
  • In the greenhouse avoid splashing water onto leaves. Moisture triggers spore germination of fungal diseases.


  • Harvest sweet corn when a grain exudes milky juice when tested with a fingernail and the whiskers are brown.
  • Harvest onions and shallots when the stems are dry and papery.
  • Start harvesting runner beans, parsnips and cucumbers when ready.
  • Complete harvesting of second early potatoes and begin to harvest main crop potatoes as they begin to flower.
  • Harvest early ripening apples and pears.
  • Harvest carrots, but leave protective insect mesh on carrots until autumn.

Gardening for wildlife

  • Leave some flower seed heads on plants as source of food for wildlife.
  • Cut and shake ripe seed heads of annuals over suitable patches of bare soil for flowers next year.