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Gardening: Don’t let the heat fool you; hold off on planting

Lena Walker carries petunias for planting at her home in Coeur d'Alene in April 2012. Give new plants time to adapt to the outdoors before planting, Pat Munts writes. (FILE)
Lena Walker carries petunias for planting at her home in Coeur d'Alene in April 2012. Give new plants time to adapt to the outdoors before planting, Pat Munts writes. (FILE)

Hang on a minute folks. By the way the tomato plants were flying out of the WSU Spokane County Master Gardener Garden Fair last Saturday you’d think the vegetable gardening season was in full swing. It’s not. It’s too early to plant tomatoes, peppers, eggplant, squash, melons, cucumber and especially basil.

Yes I know the snow is off Mica Peak, but that bit of local garden lore doesn’t hold this year. In reality, all the warm-season crops need much warmer air but especially warmer soil before they can take off growing. Late May is a better time to plant. Placing them in cold soil shocks the plant into a state of dormancy that can stunt their growth to such an extent that they don’t readily recover enough energy to grow properly. As a result when the midsummer temperatures are warm enough to set fruit, the stunted plants aren’t ready to flower. Normally we have a very short window of nights between mid-July and mid-August that the temperatures stay about 55 degrees allowing fruit set.

Another point is that the plants you bought probably just came out of the greenhouse and haven’t adjusted to the outside temperatures. Exposing them to our current temperatures will also set them back and will actually kill the more fragile ones.

So you have a box – or several – of baby plants that you can’t plant, what can you do? First harden off your new acquisitions by setting them outdoors for a couple of hours a day for a week and then bring them back indoors in front of a sunny window. Once they have adapted, they can go outdoors in their containers. Keep them watered and a frost cover handy, as frosts are still possible.

If you are bound and determined to plant, there are some things you can do to speed things up a week or two. Cover the area in your garden where you intend to plant with black plastic laid flat on the ground. The plastic will capture the sun’s heat and slowly raise the temperature a few degrees. It will take at least a couple of weeks to make a difference and you can’t rush it. At the same time you can create a temporary greenhouse over your bed by inserting lengths of PVC pipe in the ground and then covering them with floating row cover. This fabric allows in water air and light while raising the air temperature around the plants. Again set this up for about two weeks before your plant so the soil and air have a chance to warm the space.

Now, to that basil you bought. If you thought tomatoes were cold sensitive, they don’t hold a candle to basil. Planted in cold weather and cold soil basil goes into a major sulk it usually doesn’t recover from. Plant what you bought in a big pot and keep it indoors until the end of May. Then put it in the deck. Plant basil seed directly in the garden in late June for an August harvest.

Contact Pat Munts at pat@ inlandnwgardening.com.

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