JUNE
2003

 

 

By
B. Rosie Lerner
 
Purdue Extension
Consumer
Horticulturist

 

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6-5-03

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The Good and Bad about Cool, Rainy Weather


Depending on your plants' perspective, our relatively cool, rainy weather can be a good or a bad thing.  

Cool-season plants, such as peas, lettuce, spinach, radishes and pansies, should be jumping for joy! It's been nearly perfect weather for plants that get stressed out in hot, dry weather. These plants produce their best growth and, in the case of the veggie crops, best flavor during such cool weather. And, of course, if you happen to have a bluegrass lawn, you and your mower have been spending a lot of time together between downpours! Unfortunately, many weeds also thrive under these growing conditions.

However, warm-season plants, such as tomatoes, vine crops, sweet potatoes and petunias, are not finding any cause for celebration. They need warmer temperatures to establish roots and shoots as the foundation for a good crop later, be it for roots, foliage, flowers or fruit.

In addition to making poor vegetative growth, many of our warm-season vegetables 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, 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.

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.

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 called oedema. This condition 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!

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox