Pumpkins Are Not the Easiest Crop To Grow

In last week’s column we took a quick look at pumpkins and pumpkin lore. One of the things I mentioned more than once was that pumpkins aren’t necessarily easy to grow.

What’s interesting is that the first time you grow them it’s easy, but then each successive year it can get harder and harder. As the diseases and insects that affect pumpkins and many other of the vine crops in the cucurbit family take hold, they tend to return year after year.

All of the cucurbits — squash, pumpkins, cucumbers, melons — are warm-season crops. They grow best during hot weather and cannot tolerate frost, and the cultural requirements are virtually the same. Seeds will germinate at 60 degrees Fahrenheit but germinate best at 75 degrees and over. Pumpkins and squashes grow best at temperatures of 75F to 85F day and 60F to 70F at night. Growth virtually stops at temperatures below 50F, and the plants may be severely injured and maturity delayed by temperatures below 40F for several days. For this reason, those of you who try to get a jump on the season next year, beware.

Plants are usually killed by one hour or more of frost. Therefore, plant pumpkins in the patch when soil temperatures are high enough for good germination and all chance of frost has passed. For earlier pumpkin production, black plastic mulch and/or row covers will raise soil temperatures and provide some protection against frost. If starting seeds indoors, use 3-inch or larger peat pots then plant the pot with the plant.

Cucurbits are called monoecious plants — that is, each plant produces both male and female flowers. Normally, several male flowers form before female flowers develop. During periods of cool temperatures (below 70F) most pumpkin and squash cultivars respond by producing primarily male flowers. Male flowers do not form fruit. By contrast some cultivars of summer squash appear to form mostly female flowers in response to cool temperatures. Without male flowers to provide pollen, however, the female flowers do not form fruit. Hot temperatures (over 85F) combined with dry conditions will cause the plants to drop (abort) blossoms and small fruit.

Pumpkins and squashes are relatively deeply rooted and can tolerate dry conditions fairly well. However, extended dry periods will result in poor fruit set and/or poor fruit development and size. The plants can tolerate wet conditions as well, but foliar diseases and fruit rots will increase under these conditions, and in wet summers it’s not uncommon for entire crops to be lost. With this in mind, if you do need to water the plants do your best to keep the foliage dry.

Pumpkins and squashes are usually grown without irrigation, but it’s a great benefit if available. If irrigation is available, apply 1 to 1 ½ inches of water per week during flowering and fruit development only. Summer squashes will usually benefit from regular irrigation throughout the production season. Remember, the only place you need to water is the spot where the plant is rooted — where you planted it.

Luckily for us, both pumpkins and squashes grow very well in our sandy loam soils. Avoid low-lying areas as these areas, especially inland (think Pine Barrens) and upstate tend to get early frosts some years. Remember also that crop rotation is critical for soil health and to reduce insect and disease problems. And since these plants like the hot weather, they work well where you may want to grow an early crop such as lettuce or spinach. If you are planning your patch now it’s also great to seed it now with a cover crop then turn it in when the soil is workable in the spring.

Seeding is usually done by hand for the home garden, but in larger plots you can plant the seed with a mechanical seeder that is set for the same size seed as corn. The smaller varieties can be planted just about anywhere. They can be grown in the vegetable garden or even in the perennial border simply letting the vines wander about leaving their little orange surprises about the beds in the fall as other garden flowers and foliage begin to fade. For medium sized varieties, row planting may be preferred with the rows 6 to 8 feet apart with the plants spaced 18 to 24 inches apart in rows. Some growers use a planting block method using 6-foot-by-6-foot blocks, which allow for better cross pollination.

For larger varieties with fruit sizes of 20 pounds or more, plants will require a minimum of 35 to 40 square feet each. Smaller spacing can lead to overcompetition and may result in smaller fruits. About 100 square feet per plant may seem excessive, but there is evidence that this type of space actually yields the largest plants. Another problem with the plants crowding is that this forces the plants to become “airborne” — meaning the vine that would normally root on the soil at the nodes will not be able to and the vine grown then becomes tangled and stunted.

If you happen to have a spare hill or a sloped area on your property the crown of the slope is a great place to plant your vines then encourage them to “run” down the slope. This encourages great drainage, and if the slope faces south to southwest your drainage and exposure may be perfect.

If you are not growing your pumpkins on plastic mulch, then you need to consider weed control. This is critical since the weeds not only compete for light, water and nutrients but they also attract insects that you don’t want around your plants. Frequent shallow cultivation of the soil early on will solve most of the problems, and then as the vines begin to fill in they will keep the light from reaching the soil and most weeds won’t be able to survive.

Bees (and other insects) are an essential part of the production of not just pumpkins but all vine crops. Wild bees are usually all that are needed, but remember that any insecticides used in your garden, even pyrethrins, will kill bees. The blossoms of pumpkins are not very dense (very few per square foot) and don’t tend to attract bees so the more that hang around the better your fruit set will be. Pollinator-attractive flowers nearby can also be a helpful lure. A cucumber flower needs to be visited about 15 times for complete pollination to take place.

Expect about one or two pumpkins to develop per vine, but this is also dependent on the variety. Bush or semi-bush types tend to be more productive than the vine types, but the fruits tend to be smaller. Miniature pumpkins such as Munchkin and Jack-Be-Little may set as many as 15 fruits per vine. Pumpkins as large as 350 pounds can be grown, and these are the ones you see in competitions. But then you need a tractor to move them. For those with limited space who still want larger pumpkins, a strong trellis may be the trick.

This can be a great plant for kids to grow, and I enjoyed putting a few seeds in my boss’s formal gardens every year for the shock effect come fall when the fruits are “discovered.” Remember also that pumpkins vary as much in shape as they do in color so they can be big or small as well as orange, yellow and even white. Mix and match for added fun and surprises as cross-pollination can yield very interesting results.

Before we get back to next year’s pumpkin patch, a bit about the pumpkin growing in my front lawn that I never planted. I hear lots of stories about pumpkins showing up where they were never planted. Most of these are the results of pumpkin seeds overwintering in compost piles. Not mine.

Out of the blue, my wife, not at all a gardener, decided our front porch needed a pumpkin last year. It sat on the front step well into the fall until at last it imploded and “melted.” I asked her to get rid of it, and she took one of my shovels, scooped it up and dumped it over the porch railing. The chipmunks discovered the seeds and apparently one got planted under a timber that edges the planted border in front of the house.

Late last spring some strange foliage emerged from near the timber, and I was perplexed so I let the leaves along. Then there was a vine. It got longer and longer and stretched 10 feet into my lawn. Then it flowered. Huge and beautiful 10-inch-diameter bright yellow flowers that screamed to the pollinators “HAVE SEX WITH ME,” and they did.

The result was one early orb that rotted followed by three more that didn’t, and since they pollinated at different times each one is a different size and are now from 10 inches in diameter down to 3. As of the end of September the large one is desperately trying to turn orange, but as the days are shorter and cooler it’s debatable if this will be our 2024 pumpkin or not. Lots of fun to watch though. Will it mature and result in a 2025 surprise? Keep growing.