The Pumpkin Project Continues

In last week’s column I suggested that now is the time to plan your pumpkin project. For beginners it’s virtually a sure thing and I can nearly guarantee a great crop. This can be a wonderful project to do with kids and I have to admit to popping a pumpkin seed into my garden here and there only to see what surprises show up next fall.My last pumpkin plot was done with my son when he was seven. We used seed from three different types of pumpkins and that fall we had over 20 pumpkins ranging in size from tennis balls to beach balls. We used a timed-release fertilizer at planting and for the rest of the summer we did nothing other than oooh and ahhh. No spraying, no weeding, no feeding. We were very, very lucky. Not a bug or disease and not a vine lost. I know better than to push my luck again. For those of you wanting to try your luck this year, and I hope you will, here are the basics:

All of the cucurbits—of which pumpkins and the squashes are all members—are warm-season crops. They grow best during hot weather, cannot tolerate frost and the cultural requirements are virtually the same. Seeds will germinate at 60° Fahrenheit, but germinate best at 75 degrees and over. Pumpkins and squashes grow best at temperatures of 75 to 85 degrees in the day and 60 to 70 degrees at night. Growth virtually stops at temperatures below 50, and the plants may be severely injured and maturity delayed by temperatures that are below 40 for several days. For this reason, those of you who try to get a jump on the season or those of you gardening upstate, beware. Plants are usually killed by one hour or more of frost, therefore plant pumpkins in the field when soil temperatures are high enough for good germination and all chance of frost has passed. For early summer squash production, plastic mulch and/or row covers will raise soil temperatures and provide some frost protection. Low temperatures also have an adverse effect on flowering and fruit set.

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 70), 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 85 degrees) combined with dry conditions will cause the plants to drop, that is, abort, blossoms and small fruit.

Pumpkins and squashes are relatively deeply rooted (as in feet, not inches) 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 fairly 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.

Summer squashes are especially susceptible to drought because the fruit develop and are harvested within a few days after pollination. Lack of sufficient moisture often results in poor or irregular fruit development.

Pumpkins and squashes are usually grown without irrigation, but it is a great benefit if available, especially if you want the big kahuna. If irrigation is available, apply one to one and a half inches of water per week during flowering and fruit development only—and drip is much preferred to overhead watering.

Luckily for us, both pumpkins and squashes grow very well in our sandy loam soils, but you need to avoid low–lying areas, as these fields, especially inland 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. Growing pumpkins in the same spot year after year is a recipe for disaster. And since these plants like the hot weather, they work in well where you may want cool crops like early-season greens.

Seeding is usually done by hand and the seeds are large enough for children to handle easily. The smaller varieties can be planted just about anywhere, while larger types need to ramble. 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 six to eight feet apart and the plants spaced 18 to 24 inches apart in rows. Some growers use a planting block method using six-by-six-foot blocks, which allow for better cross-pollination.

One of the newer developments in pumkinland are the semi-bush type pumpkins. Look for these if you’re limited on space, but also keep in mind that most of the bush types mature earlier than their vined cousins. Both Bushkin and Neon fall into this category.

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 over-competition 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 them 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 are not growing your pumpkins on plastic mulch, then you need to consider weed control. This is critical since weeds not only compete for light, water and nutrients, but 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 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 they don’t tend to attract bees, so the more that hang around the better your fruit set will be. A pumpkin flower needs to be visited 10 to 15 times for complete pollination to take place.

Only 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. But then you need a tractor to move them. For those with limited space who still want larger pumpkins, a trellis may be the trick.

This can be a great plant for kids to grow, and I enjoy putting a few seeds in the 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. If you need more information, by all means let me know or just search the web. In the meantime, it’s time to hit the seed racks and pick your Jacks and of course … keep growing.