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Gardeners generally associate any abnormal plant development with a plant disease. Some diseases are a result of an infectious organism, such as a fungus, invading the plant. But many plant problems are simply due to poor cultural or environmental conditions. In fact, you may find that certain problems can be prevented by simply ensuring the right growing conditions before planting.

When it comes to this summer’s crop of tomatoes, whether you grow them in a container, in the ground, or even in a greenhouse, your plants may be subject to two common problems: blossom-end rot and leaf roll.

Blossom-end rot appears mainly on immature tomato fruit, usually on the bottom end. The symptoms start as a sunken depression that eventually turns brown or black, covering one-third to half of the fruit, which may also take on a leathery feel. The dead tissue may also succumb to infection by secondary organisms, resulting in the fruit rotting. The first set of fruits is usually affected more than later ones. Some gardeners mistake these symptoms for late blight, but the late blight fungus attacks the entire plant while blossom-end rot only affects the fruit.

Leaf roll affects the tomato plant’s older lower leaves, which will curl upward in a tubular fashion. The leaves remain green but will feel leathery, while the rest of the plant shows no symptoms in terms of either growth or fruit production.

The best way to control both tomato problems is to prevent them from occurring in the first place. The following tips should help you to reap a healthy tomato harvest this year:

• Maintain soil health. Test your soil pH level, and maintain adequate calcium levels using lime or calcium chloride. Reduce your use of fertilizer if applying plenty of compost or other organic matter.

• Provide sufficient space between tomato plants. If growing tomatoes in a container, select a container of ample size.

• Maintain uniform soil moisture at all times, without over-watering or over-drying. Keep soil well drained. Mulch soil surface whenever possible.

• Avoid applying a high-nitrogen fertilizer or large quantities of fresh manure.

• Do not cultivate too deeply within 30 centimetres of plants.

• Refrain from severe pruning.

• Choose cultivars with care. While resistance to blossom-end rot and leaf roll is not documented, some cultivars, such as Beefsteak tomatoes, tend to be more prone to leaf roll.

Conway Lum is a Certified Horticultural Technician at Mandeville Garden Centre in Burnaby. Questions can be emailed to him at clum@canadawide.com