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Cold Weather Affects Vegetable Plants

Rosie Lerner, Consumer Horticulture Extension Specialist

It's been quite a year for Indiana gardeners already and its only just begun! We've had just about the whole range of possible weather from drought to flood, from late frosts to blazing heat.

Recent cold weather has frustrated many vegetable gardeners. Plants such as tomatoes, peppers, beans, squash, cucumbers, and melons must be successfully pollinated in order to produce their fruit. Extreme temperatures, below 55 or above 90 degrees F, will dramatically decrease pollination. Fruits that do form may appear distorted as they mature later on. Southern crops such as okra, lima beans, and sweet potatoes are even more sensitive to cold. Not only will the okra and limas not set fruit, but their roots will likely not grow much during cold weather.

Seed germination and development of all warm-season crops will be slower in cold weather so for late sowings of vegetables, they may be delayed, or may even rot in relatively cold, wet soil. This may also lead to perfect conditions for "damping-off", a fungal disease that attacks germinating seedlings.

The good news is that many of our cool-season vegetables that more typically give up by this time of year are still thriving. If they made it through the earlier spring hot drought, crops such as lettuce, spinach, peas, and radishes do best in cool weather.

Thunderstorms have been scattered so some areas may still be on the dry side, while others may be under water. Excess water along with cool temperatures can cause the appearance of blisters or bumps on leaves and stems. This condition called oedema, is caused by too much water in the individual cells. Eventually, the cells in these bumps burst and often become corky and brown in appearance as they dry out. Oedema is not an infectious disease, nor is it a serious problem. Plants will outgrow the minor damage.

Whatever the cause of plant stress, gardeners should be ready to water if dry weather returns. In areas of heavy rains, side-dressing with nitrogen fertilizer will help replace that which was washed away during the downpours. And be prepared for more "weather" this summer!

The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by the Purdue University Cooperative Extension Service is implied. Any person using products listed assumes full responsibility for their use in accordance with current direction of the manufacturer. Purdue University is an equal opportunity/equal access institution.

Information listed is valid only for the state of Indiana.

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Last updated: 17 June 2001/tlm.

The Plant & Pest Diagnostic Laboratory at Purdue University.