There are four main types of winter squash, and some hybrid crosses. Refer back to your catalogs or websites if you are unsure which type your varieties belong to, as this helps determine when to harvest. If you haven;t grown any winter squash this year, use these photos and descriptions to help you plan for next year. Most of our photos are from Southern Exposure Seed Exchange. We tend to get caught up in the excitement of harvest, and forget to take photos!
Leave the squash on the vine until fully mature. Once the vine is dead, the squash can’t get bigger, but can ripen, change color and convert starches to sugars, (tasting better). In general, squash are fully mature and storable when the skin cannot be pierced by fingernails, but testing each one would leave ugly scars and reduce shelf life, so learn the other signs of ripeness. Yield could be 3¼ lbs per row foot (about 5 kg per meter.)
Not all the squash on one plant will be ripe at the same time, but they come to no harm sitting in the field (provided there is neither frost nor groundhogs). We harvest once a week, using pruners. We cut them with fairly long stems, which helps them store best. Those who need to pack squash in crates remove the stems so that they do not injure their neighboring squash. If you do this, you need to cure the open ends before crating. Handle squash as if they were eggs, not footballs. Bruising leads to rot in storage. Look for black rot infestations (concentric circles on butternut) and either compost those, or salvage the good parts for immediate use.
Pepo Squashes are ready soonest
The first squash ready to harvest (in early September) are the Pepo “winter” squash species (more properly called fall squash), including acorn squash, delicata, dumplings, spaghetti squash, and most orange pumpkins. If you want to start harvesting these in August next year, sow earlier than late May! Pepo squash are fast maturing, short-storing, mild flavored. They have prickly leaves and stems. They are susceptible to vine borers, and perhaps a little more susceptible to viruses than other types. Pepos have hard, five sided stems, and the fruits are often ribbed.
When they are ripe, the “ground-spot” of Pepos usually becomes the color of pumpkin pie filling after the cinnamon is stirred in, or else bright orange. The stem will still be bright green. Wait till at least 45 days after pollination. Harvesting too early will disappoint: the squash will be watery and fibrous, without sweetness. Pepos can store up to 4 months, so check them every week and eat them up before New Year.
Maxima squash plants have huge hairy leaves. Fruits have thick round stems, different from the angular stems of the other species. This group includes buttercups/kabochas, hubbards, bananas, the Big Max giant pumpkin, Jarrahdale, Candy Roaster, Galeux d’Eysines and Rouge Vif d’Etampes. They are very susceptible to wilts, borers and squash bug damage. We have found Jarrahdale to have relatively high resistance to squash bugs compared to other Maximas. The hybrid Kabocha, Cha-Cha, is reliable. Kabocha may be harvested slightly under-ripe, as they continue to mature after harvest.
Maxima squash are ripe when at least 75% of the stem looks dry and corky (tan, pocked, wrinkled). They have fine-textured good-flavored flesh They will store 3-5 months, sometimes longer.
The weakness of maxima compared to the others is susceptibility to downy mildew. There may be other fungal pathogens that maxima is more susceptible to.
In central Virginia, maximas are almost always a loss, due to squash vine borers. Ken Bezilla at Southern Exposure Seed Exchange has watched the plants live for about 70-80 days, the fruits get nice and big and then the plants die all of a sudden. The safest way to grow them is under rowcover or netting, and keep them covered for the first 60 days (briefly uncovering for weeding and pollination).
Moschata squash plants have large hairy leaves, and fruits have flared angular stems. This species is the most trouble-free, with no damage from borers and cucumber beetles. The tougher stems repel invaders. They need warm growing temperatures above 60°F (16°C). Butternuts and similar tan-colored squash, such as Seminole, Cheese, and the large Tahitian Butternut and Lunga di Napoli are in this group.
The Moschata species usually have bright orange, sweet, tasty flesh. These squash are ready when the skin is an even tan peanut-butter color, with no pale streaks or blotches. Many have green lines radiating down the squash from the edges of the stem. In some varieties, these green lines disappear when the squash is ripe, but not in all kinds. If in doubt, cook one and see. Or try a slice raw. These squash also have angular stems, but unlike the stems of pepo squashes, moschata stems flare out where they join the fruit. Moschatas can store 4-8 months or even longer. Seminole is a Moschata that will keep on the shelf for a whole year after harvest. It has a hard shell!
Mixta (Agyrosperma) Squash
The fourth species, Argyrosperma, or Mixta, includes many old-time varieties from the south. Flesh is often yellow rather than orange, and these squash are often cooked with sweeteners. Plants are rampant; leaves are large and hairy. Fruit stems are slightly flared, slightly angular, and hairy. This group has the best drought-resistance and also good resistance to borers and beetles. Cushaws are Mixta species. They are not all great storers.
Curing and Storing
Butternut and buttercup squash need to be cured at 80-85°F (27-29°C) for 7-10 days to be sweet tasting. Other varieties do not need to be cured, unless the stems have been removed, You can cure squash in a greenhouse with 80% shadecloth, or simply in a warm storage room.
Curing conditions for winter squash can be quite far from the ideals. Many people simply put the squash straight into storage Just don’t eat uncured butternut or buttercup squash, ie within two weeks of harvest, to avoid disappointment.
Store winter squash in relatively warm and dry conditions: 50-60°F (10-15°C) and 50-75% humidity. Check through stored squash once a week, removing any that are rotting. Squash have a medium demand for ventilation, similar to carrots, more than potatoes. Temperatures below 50°F (10°C) can cause chilling injury, which reduces shelf life. Do not store squash with potatoes or onions; like most ripe fruit crops, squash exhales ethylene, which increases sprouting in potatoes and onions (and other roots and bulbs).