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Harness the heat in a cool season

Sat., June 26, 2010

Are your tomatoes turning a funny shade of green to gray? Are your pepper leaves curling slightly and turning a yellowy green? How about basil, corn and beans?

It’s not your fault.

Mother Nature has been playing with us big time this year. She’s been generous enough to give us some good spring rain but the trade-off has been downright cold weather that has most of our warm-season vegetables sulking in the soil. Unlike a cranky kid though, the plants can’t take their marbles and go home; they are stuck.

The long-range weather forecast indicates that a La Niña event has begun and that means generally cooler weather into July with the possibility of a cooler late July into August when we normally get our warmer weather. This all boils down to the fact it may take some work to get things ripe in the garden.

So what’s a gardener to do? We can’t change the weather, but we can help the garden out by trying to capture some heat for the warm season plants.

Beans and corn are going to be tough to help. If you planted them in the last two weeks of May and they aren’t up yet, they may have rotted in the ground. If they are up, they will start growing once we get some warm weather. We will get a crop of beans albeit late, but the corn may be a challenge. The old saying that corn needs to be knee high by the Fourth of July isn’t going to happen – that’s next weekend. We are just going to have to hope for a warm August.

Basil is one of the most heat sensitive herbs in the garden. Planting starter plants in May and June has always been iffy here. Once they turn yellow in cold weather they aren’t likely to recover. The best solution is to plant seeds as soon as it warms up. With heat, you should be able to begin harvesting in mid-August.

To help tomatoes, peppers, melons, squash, eggplant and cucumber we need to capture heat close to them. Plants in raised beds or close to a warm wall or fence will have an advantage because of warmer soil and residual heat in the structure. To capture more heat, build a simple hoop structure out of PVC pipe and then cover it with floating row cover. The fabric will capture between 5 and 10 degrees of daytime heat and up to 5 degrees at night. Water and light can easily get through the fabric, and it can be left on until we start getting some 80-degree days. In late August when it starts to cool down, the plants can be covered again to capture heat and stave off possible early frosts.

Another method is to place large buckets of water or large pieces of concrete block, wood or metal around and under the plants to capture more heat. It only takes a few degrees to make a big difference.

Pat Munts is a Master Gardener who has gardened the same acre in Spokane Valley for 30 years. She can be reached by e-mail at pat@


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