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Growing Things: Take precautions to prevent tomato blight

Tomato blight is a fungal problem and requires a variety of steps to prevent.
Tomato blight is a fungal problem and requires a variety of steps to prevent.

Q: One of the four tomato plants growing in tubs on my balcony has small pear-shaped tomatoes that are turning black from the bottom as they ripen. Some of the leaves are shrivelled and curled. This happened to some plants last year as well.

Is this tomato blight? What causes it? How can I prevent it happening again? Is it safe to reuse the soil?

A: It sounds like you have a two-fold issue going on with that one tomato plant. The problem with the tomatoes turning black on the bottom is called blossom end rot and we have discussed this in the past. As for the blight, this is caused by a fungus. There are a few cultural things you can do to prevent this from taking hold next season:

– Select plants that are resistant to blight. Doing your research ahead of time can save a lot of grief and work.

– Allow space between plants to allow for good air circulation. Blight likes wet conditions, so maintain the space and use tomato cages to keep the fruit and branches off the soil.

– Water from below. The key is to keep the foliage as dry as possible. This will help to prevent the spread of the blight.

– Check your plants frequently. If you can catch blight early enough you can help contain its spread. If you see leaves being affected remove and dispose of the leaves.

– Do not reuse the soil in containers of plants that have been infected with blight, and in the garden rotate crops on a regular basis. Keep tomatoes away from potatoes that may overwinter late blight.

Q: The planting along the side of my cottage used to be all variegated. Over the last few years the variegated plant is losing ground and turning solid green.

It seems like the variegated plant is just losing its unique colouring and changing to solid green. I can’t notice any signs of one dying off and another starting. It seems like a slow movement of solid colour that’s moving more each year. Any idea of what’s going on? Your explanation would be very much appreciated.

A: The plants you refer to in your photo are silver-leafed dogwood. Reversion of colour in variegated leaves does occur in many plants. This loss of colour could be due to several factors including lighting, seasonality, or other factors. Some experts think it might be a survival tactic while others think it might actually be cell mutation in the leaves.

If the variegated plants are growing in the shade they are already at a disadvantage because they have lower levels of chlorophyll than plants that are completely green. The shade then compounds the problem with lower light levels on top of lower chlorophyll. This means they are less vigorous than the green plants. This situation usually results in the reversion you have described. It could also be due to the plant being waterlogged, or if the weather has been unfavourable for the variegated plant.

I have seen this happen several times before and I’m afraid there is little that can be done to stop the progression.

Q: During one of our bad storms about 10 days ago a lot of my onions got pounded flat. I seem to remember that if you want them to ripen, you should bend the stalks. Does this mean that I should therefore harvest them now? They are a good size but some are getting soft and I’m worried they’re going to rot. The other problem is my cold room isn’t very cold yet.

A: If the stalks have not shown signs of standing back up then yes, you should be harvesting the onions as soon as possible. One of the secondary problems that can arise from this situation is soft rot can set in, and that might be happening already.

If you have a garage lay the onions on newspaper in the garage and let them dry out. I’m afraid there is little else that can be done until your cold room temperature drops. Good luck and happy gardening!

Gerald Filipski is the author of Just Ask Jerry. E-mail your questions to . To read previous columns, go to and search for Gerald Filipski

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