How to Choose Fall Cucurbits

Yield vs. Eating Quality

Good eating quality is determined mainly by the percentage of sugars and starch in the edible portion of the squash.

Dr. Loy explains the two:

"High sugars not only contribute to a desirable sweet taste, but also mask undesirable flavor components associated with certain varieties. Sugar levels can be estimated easily by pressing juice from a small sample of flesh and measuring soluble solids in the juice with a hand-held refractometer. Relative sugar content is given in units of percent soluble solids (or degrees Brix). Soluble solids levels of 10% are passable, but generally levels of 11% or greater are considered necessary for good eating quality in squash.

"The pasty texture of squash is attributable to starch. At harvest, starch comprises about two-thirds of the dry matter of squash, so squash with high dry matter also have high starch content. Starch provides substrate for conversion to sugars during the latter stages of squash maturation and during subsequent storage. Squash with low dry matter, generally less than 16%, lack sufficient starch levels to produce the combination of pasty texture and degree of sweetness desired for acceptable eating quality. In varieties with low dry matter, starch is rapidly depleted during storage by conversion to sugars, and the texture of the squash becomes watery and fibrous."

Obviously, squash with higher dry matter content is better for flavor, and dry matter content is largely determined by variety. The "grower's paradox" that Dr. Loy refers to is the fact that a higher percentage of dry matter means a lower fresh weight; a variety with an excellent level of dry matter, say 20%, will weigh only half as much as a variety with 10% dry matter. In the wholesale market where growers are usually paid by weight, so heavier is better for income even if not for flavor.

Harvest and Storage

Another critical factor in eating quality is maturity of the squash when it is harvested. Most small varieties reach full size by 20 days after fruit set. Accumulation of dry matter and starch content peaks at 30 to 35 days after pollination. However, the fruit is not mature until the seeds are fully developed, which occurs about 55 days after fruit set.

Dr. Loy stresses the importance of maintaining healthy plants until at least 50 days after fruit set because photosynthesis is essential to the development of sugars and dry matter. A squash that is picked too early will continue to develop seeds, but it does so by depleting the dry matter, thereby reducing eating quality.

Although fruit and seed maturity are similar across the three main species of edible winter squashes and pumpkins, harvest and storage recommendations vary by type.

Cucurbita maxima | Kabocha, Hubbard, and Buttercup Squashes

Kabocha, hubbard, and buttercup (C. maxima) varieties should be harvested before complete seed maturation, at about 40 to 45 days after fruit set, when the fruit is still bright green. That's when the rind is hardest, so less likely to be damaged in storage. They also are susceptible to sunburn as the vines die down, so it's best to get them harvested and out of direct sun before then to prevent the rind from turning brown or, with extreme sunburn, white. Kabocha squash have a high dry matter content and small seed cavity, so seed maturation off the vine is not a problem. However, once harvested, they should be stored at room temperature for 10 to 20 days to allow sugars to reach acceptable levels.

C. pepo | Acorn Squash, most Pie Pumpkins

Acorn squash (C. pepo) are misleading because they reach full size and develop a dark green-to-black mature color about two weeks after fruit set — 40 to 50 days before they should be harvested. Dr. Loy says that a better way to judge maturity is to look at the rind where it touches the ground. Immature squash have a light green or light yellow ground color, whereas mature squash have a dark orange ground color. Immature acorn squash have low sugar levels and although they will develop sweetness after harvest, they do so by depleting the dry starchy matter to convert it to sugars. This means storage life is shortened and eating quality declines.

C. moschata | Butternut Squash, some Pie Pumpkins

Butternut squash (C. moschata) are easier to judge by sight because they don't acquire their characteristic tan color until late in development, 35 days or more after fruit set. If the weather stays frost-free, they should be allowed to remain on the plants until 55 days after fruit set. In short-season areas, they often are harvested soon after turning tan because of the risk of frost damage. At that point, however, the sugars have not elevated to the 11% required for good flavor, so butternut squash harvested at 55 days after fruit set should be stored for 60 days at 56-60°F/10-16°C, with relative humidity between 50 and 70%. Carotenoid content also increases in storage, making the butternut squash more nutritious after it's been stored for a couple of months. To accelerate maturity and increase sweetness, Dr. Loy has found that butternuts held at warm temperatures (up to 85°F/29°C) for two weeks develop acceptable levels of sugars.

Achieve Peak Flavor

To grow the best-tasting winter squash, look first for varieties renowned for flavor rather than weight. Don't harvest them too early, and keep them in storage long enough for the sugars to reach acceptable levels, but not so long that they begin to deteriorate.

Calculate the scheduling of each type of squash before you decide which to grow, matching peak flavor to the duration of your markets in fall and winter. It would be pointless to have bins full of butternut squash reaching the best eating quality after your markets close. You would be better off growing larger quantities of varieties that reach maximum flavor during your busy selling season.