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Saturday, September 21, 2019  Spokane, Washington  Est. May 19, 1883
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Get ready to plant squash, pumpkins

Average last day of frost is fast approaching

Last year’s winter squash and pumpkins were cured in a sunny greenhouse before going into storage. (Photo by Susan Mulvihill)
Last year’s winter squash and pumpkins were cured in a sunny greenhouse before going into storage. (Photo by Susan Mulvihill)

It’s just about time to start planting warm-season crops in the vegetable garden. This includes beans, corn, tomatoes, peppers, eggplants and summer and winter squash.

In this region, our average last day of frost is May 15. I plant beans and corn in the garden at that time and then wait another week or two before planting the rest of the warm-season crops, depending on the weather.

Winter squash and pumpkins are a lot of fun to grow. Since our frost-free growing season is about 120 days long, it’s important to choose varieties that will mature in less than 100 days. That’s because the days to maturity listed on seed packets begins once a plant has been set out in the garden.

The types of winter squash I’ll be growing this year are acorn, sweet dumpling, delicata, spaghetti and red kuri. The pumpkin varieties I’ve had the best luck with are New England Pie and Rouge Vif d’Etampes.

Large blue Hubbard squash can be risky to grow since they need a longer growing season. Some smaller varieties like Blue Ballet and Baby Blue mature in 95 days and are worth experimenting with.

Another slow-growing winter squash is Sweet Meat, which takes 105 days to reach maturity. Ordinarily, I’d be hesitant to plant something that needs so much time to mature but after eating some last year, I’ve fallen in love with their delicately sweet taste and want to try growing them.

Here’s my game plan for growing winter squash and pumpkins this year:

I will plant the seeds indoors on May 10. The plants will need about two weeks to develop a good root system and a few leaves.

At that point, I’ll transplant the seedlings into garden beds that have been covered with red plastic. Since the beds are watered by soaker hoses, the plastic is placed on top of the hoses and secured to the soil with metal pins. The red plastic increases the soil temperature by a few degrees, which is ideal for warm-season crops.

Each seedling is planted through a small “X” cut into the plastic and then watered in with a diluted fish fertilizer.

The most important step is the last one: I will cover the beds with floating row covers to give the plants an even warmer environment. This should get them off to a great start.

If you are unfamiliar with row covers, they are made of lightweight fabric that lets in air, light and moisture while giving plants a few degrees of frost protection. Organic farmers frequently use them as barriers to damaging insects as well. Because squash flowers need to be pollinated, I’ll remove the covers once the plants start blooming. Fortunately, squash plants are relatively pest-free.

Once each plant has a couple of squash developing on its vines, I’ll trim back the vine tips to force the plant to focus its energy on growing and maturing the existing squash.

Later in the season, the easiest way to determine if a squash is ripe is to do the thumbnail test: press your thumbnail into the skin of the squash. If it easily cuts into it, the squash isn’t mature yet. If you can’t pierce the squash, it’s ripe.

Winter squash and pumpkins should be harvested before a hard frost. Leave a couple of inches of stem attached and place them in a sunny, warm and dry area for two weeks. This will cure the squash so it can be stored for a long time in a cool, dark place.

Susan Mulvihill can be reached via email at her blog at for more gardening information, tips and events.

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