Ask a Master Gardener

Growing Squash


Fresh squash is one of my summer favorites, but I hear growing squash successfully can be tricky. What do I need to know before planting some squash in my garden? DB

Squash can be a versatile vegetable for your menu and a robust producer; however a couple of vegetable gardener’s least favorite insects can ruin your day concerning squash pretty quickly. However, there are some strategies to help you be more successful in your efforts to grow squash.

When the Tulsa Master Gardeners started our Seed to Supper Farm last year, we had a small debate as to whether to grow squash or not. The reasons to grow squash are numerous. The reasons not to grow squash basically boil down to two insects: squash vine borers and squash bugs. We decided to forge ahead and were able to harvest many pounds of squash before we looked away for a moment and then found the rows of squash infested with squash bugs. It was good while it lasted.

That growing experience did leave a bit of a bad taste in our mouths, but undeterred, we just planted over 200 feet of squash last week as we promised ourselves to be more vigilant in our efforts to keep these plants squash bug free.

You can plant squash as transplants or seeds. For seeds to germinate successfully, soil temperatures need to be above 70 degrees, so now is a great time to plant. We have a link on our website where you can access soil temperatures in our area ( in the Lawn and Garden Help section/vegetables.

Squash plants are sometimes considered “heavy drinkers” meaning they need a fair amount of water, about an inch of water each week. If your soil is on the sandy side you may need more and if you soil has a high concentration of clay, you may need less. Squash plants will tell you if they need water. Those big leaves tend to go limp pretty quick when they need a drink.

One question we get quite often each year involves squash plants that are flowering but aren’t producing any fruit. In most cases this is not a problem. It just stems from the fact that squash plants are monoecious, meaning that each plant has both male and female flowers. For pollination to happen, the pollen from the male flowers needs to make its way to the female flowers for fertilization to happen. This transfer of pollen is accomplished by insects visiting your garden.

The male flowers are typically the first ones to bloom, which causes people concern when they don’t see any fruit beginning to develop. But is isn’t long before the female flowers arrive on the scene. Female flowers look like they have a very tiny fruit where the flower attaches to the stem. So, once you start seeing these, you’ll know that production is not far behind.

Squash plants don’t have a lot of disease issues, but they can fall victim to powdery mildew. At the first sign of powdery mildew, you can begin a fungicide treatment with an organic fungicide such as copper fungicide. You’ll need to repeat application of this fungicide following the directions. Now, what about those two insects.

Squash bugs overwinter as unmated adults in plant debris. Before planting squash, consider tilling up the soil. This exposes overwintering adults to the elements. However, this should have already been done since squash bugs tend to emerge in late April of early May. After emerging and mating, squash bugs lay their eggs over a several week period. Your first line of defense against squash bugs begins with monitoring the underside of your squash plant’s leaves for eggs. These eggs are small, brown, and usually in clusters. If you find them you can simply crush them, or if you’re not about that life, you can just cut off the leaf where the eggs are located and throw it away. Just fyi, crushed squash bug eggs can emit a strong odor.

Another strategy is to lay a piece of wood like a 2x6 in your garden next to your squash plants. Squash bugs tend to congregate under the board overnight. Then, go out to your garden first thing in the morning, flip over the board, and see if you have any squash bugs. If you do, destroy them in an appropriate manner. Spinosad is an organic pesticide is a good choice to dispatch your squash bugs.

It’s important to be diligent in eliminating this insect from your garden early in the season because squash bugs can produce 3 to 4 generations per year. Knocking back that first generation will be key to keeping them controlled during the growing season.

The other bane of a squash grower’s existence are squash vine borers. Squash vine borer moths emerge during the spring and lay their eggs at the base of the squash plant’s primary stalk making them hard to see. When the eggs hatch, these larvae enter the stem and begin to eat. This feeding eventually destroys the plants’ ability to transfer water a nutrients from the soil up to the leaves and so the plant dies rather quickly. If left unattended, these larvae will eventually re-enter the soil to begin preparing for next year’s growing season. This is another reason to till your garden soil each spring before planting. My apologies to the “no till” people.

While there are several ways to counter the effects of the squash vine borer on your plant, once again early detection is the key. If you notice squash vine borer damage on the stem of your plant, you can slice open the stem, pick out the larvae, and bury the damaged part of the plant under some soil. The hope is that the plant will re-root so it can once again thrive. I have not been successful using this method.

Another option would be to inject some bacillus thuringiensis (bT) into the stem of the plant. The squash vine borer larvae will eat the bT which kills them. But again, the key to this working is early detection.

Because of the reduced pest load, many gardeners plant their squash in their fall gardens. Or, if all this is too much, I hear the farmer’s markets have beautiful squash available. See you in the garden!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at Photo: OSU Ag. Communications