We start harvesting winter squash at the end of August. They are called “winter squash” because some of them (although not all and not in all regions and not in all years) store into the winter (or at least December). There are four species of squash: pepo, maxima, moschata, and argyrosperma. Each species has certain growing requirements and taste and texture characteristics, as well as typical storage capability. Historically, only moschata and argyrosperma winter squash have been grown in this region, except in the mountains where they can also successfully grow some maxima squash. Those species continue to be the only types of winter squash with which we have success, although even that is changing as our summers continue to become warmer overall. Since we receive a lot of questions about squash this time of year, I thought I would share some generally recognized, accepted, and understood information about the different types of squash, as well as our own farming observations.
The pepo species of squash includes: summer squash like yellow crookneck and zucchini and winter squash such as typical jack-o-lantern pumpkins, acorn, spaghetti, and delicata squash. The pepo species is by far the most diverse species group and is sometimes divided into two based on place of origin. Although summer squash can be grown here successfully throughout the summer by succession planting (or using chemicals), it is much more difficult to successfully mature pepo winter squash varieties here. High heat and high humidity or high heat and drought produce the same effects in all varieties: under stress, they mature quickly producing small specimens with mild flavor that do not store nearly as long as they should. Jack-o-lantern pumpkins (especially newer hybrids) can be produced here. Conventional farmers seem to have more luck with the latter, which suggests that there is also a disease component. By contrast, in New York (ten years ago…and that is important), we produced large quantities of sizable, healthy, sweet pepo squash for mid- to long-term storage without much effort. They are most commonly grown in the Upper Midwest.
Maxima squash includes several other non-jack-o-lantern pumpkins, hubbards, banana squash, buttercup squash, and candy roaster squash. These squash as a class do not do well under high heat and are also more susceptible to insect pressure. When Ken and Irena, from Southern Exposure Seed, were visiting, they told me they had never successfully matured a maximasquash. We have had a little more luck in cooler years with candy roaster squash (which were original bred by Cherokee Indians in the S. Appalachians…a very different climate than the valley today). Most maxima squash are grown primarily in the Northeast and the Northwest. They do well in areas with cool summers and consistent rainfall and little insect pressure. They typically store very well and are considered by many the best tasting squash.
Moschata squash includes butternut squash and most other buff-colored squash and pumpkins, regardless of shape, as well as most Central American and Caribbean squash often referred to collectively as calabaza or ayote. As a species, they are much more tolerant of heat, humidity, and disease and insect pressure. They also store fairly well (although this is dependent on growing conditions) and have good flavor and good texture. Although maxima squash are great for baking and eating as is, many people prefer moschata squash for soups, pies, and breads. Season after season, moschata squash are our best producing squash. However, some of the varieties that we have always grown are having more and more difficulty producing well in our climate. Both Waltham Butternut (originally from Massachusetts) and Long Island Cheese pumpkin (originally from New York) show increasing intolerance of heat.
I have been thinking a lot lately about decreasing seed quality as a result of high summer heat (especially in winter squash/pumpkins, corn, and beans). When plants are stressed (particularly by heat), they respond in two ways: they speed up the maturation of fruits already on the plant and stop producing new fruit. This can produce inferior quality seed. If we continue to have hot summers, will our seed quality continue to decrease in some vegetables? I think this is what is happening with Waltham Butternut and Long Island Cheese pumpkin. We have seen variable germination, decreasing seedling vigor, and decreasing plant vigor over the past several seasons. A sign that seed quality is diminishing. I hope to find several sources of butternut next season to trial. We also will continue to trial moschata squash from the Deep South, Southeast Asia, and Central America like Tahitian Butternut, San Jose Club Squash, Ayote, Magdalena, and Upper Ground Sweet Potato. All of these varieties have done well for us over the past two seasons (and much better than butternuts or cheese pumpkins).
The last species group is argyrosperma. Argyrosperma are originally from Mexico but are also common in the Southwest and Southeast because of their high heat tolerance and resistance to vine borers. Argyrosperma are much more mild that other winter squash (some say bland) and do not store as long. They are commonly used in savory dishes or sweetened for pies or desserts. Their seeds are also used in many traditional cuisines. Some have “naked” seeds. There are many heirloom varieties of these squash, and I would love to grow more of them. However, they are a hard-sell amongst most Americans who are used to sweet squash.