Understanding Flavor & Yield in Winter Squash

Winter Squash and edible pumpkins ought to taste sweet and cook up smooth and pleasantly dry. So why does store-bought squash so often disappoint, with bland, watery flavor and stringy flesh? The late Dr. Brent Loy, a cucurbit breeder and professor emeritus at the University of New Hampshire, called this the "grower's paradox."

Markets reward growers for high-yielding varieties and for harvesting fruit when it looks its best. The paradox has two sides. First, the best-eating varieties contain more dry matter and so yield less by fresh weight. Second, squash often looks ripe well before it is fully mature, and full maturity is needed for the best flavor.

Growing great squash and edible pumpkins takes patience and careful variety choice, so it pays to know what makes the best varieties stand out and how to grow them to bring out those traits.

Two traits largely decide how good a squash tastes: its sugar content and its starch content.

Here are three points to keep in mind about each.

Sugar: 3 Key Points

• As Dr. Loy explained, plenty of sugar does more than make squash taste sweet; it also covers up off-flavors that some varieties carry.
• To estimate sugar, take a small piece of flesh, freeze and thaw it, then squeeze out some juice. A refractometer measures the juice's percent soluble solids, which approximates sugar content and is usually reported as degrees Brix (see definitions).
• A reading of 10 is acceptable, but 11 or higher gives the best flavor.

Starch: 3 Key Points

• A smooth texture comes from starch, which tracks with dry matter (see the definitions box).
• Dr. Loy reported that sugars and starch make up roughly 50–70% of a squash's dry matter as it nears maturity. Starch turns into sugar as the fruit matures and after harvest, in storage. So squash with more dry matter at maturity end up with better texture and flavor.
• His research found that varieties reaching about 18–25% dry matter at maturity have the greatest potential for good eating quality.

Low-dry-matter varieties may taste fine for a little while, but their starch runs out in storage as it becomes sugar, leaving the flesh watery and stringy. Because they hold more water, they also weigh more and yield more by weight. In other words, a higher-yielding variety can eat worse than a similar variety that yields less: the first side of the grower's paradox.

Specially bred squash varieties have been selected for excellent eating quality. Brix and dry matter data are collected over the many years that it takes to develop a new variety. Sometimes the best-tasting squash fails to meet our standards in other areas, such as powdery mildew resistance or storage — so it doesn't make the final cut. We aim to offer varieties that have a good blend of desirable characteristics and excellent eating quality.

Beyond picking a good variety and growing it well, harvesting at the right moment is key to flavor.

Small types like acorn can reach full size and color around 20 days after pollination or fruit set, but Dr. Loy's research showed fruit picked then is essentially inedible. Butternuts likewise may turn their typical tan color about 35 days after pollination and look mature while still lacking flavor. That's the second side of the grower's paradox: good-looking fruit doesn't always taste good.

Why are looks so misleading? At full size and color, which can come as early as 20 days after pollination, fruit is still low in starch and dry matter. Those peak later, around 30–35 days, and seeds aren't fully developed until about 50–55 days after pollination. Seed maturity matters because seeds in fruit picked too soon keep developing off the vine, drawing on the fruit's dry matter and starch and lowering eating quality.

For every type of squash, a good rule is to harvest 50–55 days after pollination or fruit set. A few types also give visual clues that they're mature (see below). Record when your plants begin setting fruit, and keep plants healthy until the fruit matures.

Harvesting & Storage Recommendations for Best Eating Quality — ALL TYPES

• Harvest 50–55 days after pollination or fruit set.
• Cut ripe fruit from the vine and handle it gently.
• Cure fruit in the field in the sun for 5–7 days, or, if a hard frost threatens, cure indoors for 5–7 days at 80–85°F/27–29°C with good airflow. (Acorn types are the exception; they generally store better without curing.) Curing hardens the skin for better storage and can shorten the post-harvest rest some types need for best quality.
• After curing, store fruit at about 50–55°F/10–13°C with 50–70% relative humidity and good airflow. Repeated exposure to temperatures below 50°F/10°C can cause chilling injury.
• Check stored fruit often and pull out any that are rotting.

TYPE-SPECIFIC Harvest & Storage Recommendations for Best Eating Quality

Cucurbita pepo : Delicata, Sweet Dumpling, Acorn & (most) Pie Pumpkins

• Pie pumpkins should be fully orange.
• Acorn, delicata and sweet dumpling squash should show a deep orange "ground spot" where the fruit sat on the soil.
• These can be eaten right after harvest, are at their best within 2–3 months, and keep about that long.

Cucurbita maxima : Kabocha, Hubbard & Buttercup

• A dry, corky stem is another sign these types are mature.
• Kabocha, hubbard and buttercup sunburn more easily, so if the vines decline and leave fruit exposed, they can be picked early, around 40 days after pollination. They'll then need curing followed by 10–20 days at room temperature (70–75°F/21–24°C) to eat well.
• C. maxima squash usually have the highest dry matter of any type and are often too dry to eat right at harvest. A period of storage lets starch turn into sugar for a better-balanced eating experience.
• Mini kabocha of any color and red-skinned types (such as 'Sunshine' and 'Red Kuri') are the exception. They can be eaten right after harvest and keep for 2–3 months.
• Buttercups, full-size green or gray kabocha and hubbards eat best after 1–2 months in storage and keep 4–6 months.

C. moschata : Butternuts & (some) Edible Pumpkins

• Mini butternuts such as 'Butterscotch PMR,' can be eaten at harvest and keep about 3 months.
• Full-size butternuts and other C. moschata varieties, including 'Long Island Cheese,' an heirloom edible pumpkin, should be stored 1–2 months before eating and keep for 4–6 months. Storage also raises their carotenoid levels, adding to their nutritional value.

For winter squash and edible pumpkins that taste their best…

1. Choose varieties bred for flavor. Some high-yield varieties hold more water and less dry matter, which often means poorer eating quality.
2. Don't pick fruit before it's mature, about 50–55 days after pollination.
3. Cure and store fruit under the right conditions.
4. Sell or eat fruit at the right time, starting with small types like acorn and delicata, then moving on to larger ones like kabocha and butternut.
5. If you sell squash and pumpkins, think about your market. Winter markets and CSAs, for instance, are a good fit for kabocha and butternuts at their peak.

To dig deeper into winter squash and pumpkin eating quality, see these publications by the late Dr. Brent Loy:

• Maximizing Yield and Eating Quality in Winter Squash — A Grower's Paradox
• Managing Winter Squash for Fruit Quality and Storage