Squash for Winter

In warm climates, you can sow outside very easily, just as long as the soil temperature is 20 °C/68 °F or higher.

This section is more about sowing under cover, in regions where summer is not quite long enough to include the propagation phase as part of outdoor growing.

• Seeds germinate in four to seven days, depending on warmth.

Sowing time

Sow approximately one month before your last frost date. This allows sufficient time to raise a large plant, which effectively gains you a month of growing time. At Homeacres we sow around the middle of April, and definitely before the end of April, to transplant in mid-May.

Sowing method

Smaller modules are better than large pots for two reasons:

1. They need less space if you want to keep them warm during the germination phase.
2. There is less chance of overwatering and seeds rotting. A 5 cm/2 in cell diameter works well, and a similar depth, no more.

There are many suggestions about which way to place seeds when sowing – up, down or across. We find that simply flat on their side works really well. Roots come out of the slightly flatter end and easily find their way down into the compost.

Use any multipurpose, potting or container compost – there is no need for sowing or seed compost.

• Water trays to capacity either just before or after sowing, then water little for the first week.
• It is worth germinating them in your house if your climate has cold nights at sowing time.

Pot on?

This is a necessary phase of raising these fast-growing plants, when there are more than two weeks between sowing and transplanting. Once seedlings are at the stage in modules where leaves touch each other and stems are elongating, you will also notice that the roots have filled all available module compost.

Pop rootballs up from the cells with a gentle push, and place them at the bottom of a 10 cm/4 in pot. Fill that pot with more of the same potting compost and keep reasonably warm, as before, always with frost protection if nights are very cold. Should frost be forecast, this can be a layer or two of fleece or row cover over the top of all leaves in the evening, until soon after dawn. You don’t need to cover the plants every night.

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Transplant size and time

These plants are very tender to frost, so you must be absolutely sure that no more frost is possible after you have transplanted them. Plants can be quite large, preferably not yet flowering, and the pots may be brimful of bright white roots.

Should a very cold night be forecast when plants are in the ground, lay fleece over them on the evening before, to be on the safe side. One late frost is enough to lose a whole harvest.

Transplant method

Make a hole slightly larger and 5 cm/2 in deeper than the pot size, then push the rootball in firmly. You want to bury the stems, or some of them, for two reasons:

1. So that plants do not blow too much in the wind.
2. To make it easier to maintain a high moisture level around the new rootball, for at least its first two weeks in the ground.

I find that that the 10–20 days after transplanting are critical, for both of these factors.

• In 2017, we lost six squash plants to a high wind, 50 mph gusts, on 6th June, three weeks after planting. Somehow it rotated plants around until the stems snapped off.
• Then, in 2018, it was the opposite, with fine weather and extremely hot sun. This meant that although we laid fleece over new transplants, within three days we needed to remove it because they wilted so fast in the afternoon, even though fully watered in the morning.

The long and the short of it is that these plants grow, and need to grow, extremely fast. Until the roots are well established, keep an eye on them water-wise during dry weather.

Interplant

Despite their leaf size and vigour, squash plants lend themselves to interplanting as they actually don’t need a long time to grow. The season of full growth for winter squash is shorter than that of summer squash, which continue to grow right into autumn and until first frost. Plus the wide spacing allows other plants to establish and get underway in the empty areas between, before squash have used every bit of the ground.

The native Americans had a way to use this space with an interplant called ‘Three Sisters’. Between each squash plant were some corn plants and next to each corn was a climbing bean plant. The desired harvest was dry corn, or maze, and dry beans. However, if you try to pick sweetcorn from a Three Sisters planting, it can be difficult and damaging because the bean stems are twined around the corncobs.

This does not matter in mid-autumn, when a dry harvest is taken of everything.

• Unless your summer is hot enough to allow easy maturity of dry beans, Two Sisters with a sweetcorn option is more viable than Three Sisters.
• In temperate climates, an option would be to transplant two sweetcorn in the gaps between each squash plant.
• Or make a small teepee for beans to harvest dry, again in the space between squash transplants.

Both of these interplantings may require extra watering. They are an efficient use of space.

Spacing

1 m/39 in is a good all-round figure. Kuri varieties can be closer, at 75 cm/30 inches, while Butternuts and Crown Prince can use a little more space.

When days are warm and there is enough moisture, any extra space between plants is not wasted, because of how they put roots down from the trailing stems. They feed into path soil as well.

• This is one part of growing enormous pumpkins – allowing loads of space for one plant and thinning fruits to one per plant.
• With winter squash plants you do not need to thin at all, they sort that for you!

Support

In theory, one can grow these plants up trellises and many kinds of support. I find in practice that they are not too happy growing in that way, and certainly not where it may be windy.

• In sheltered gardens, and where you have time to tie stems to a structure, it’s a fun thing to try.

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Once your plants are watered in and starting to grow strongly, it may be that you don’t need to water for quite a long time. Winter squash mostly start their life with the benefit of soil moisture from a previous winter.

• More than half of their lifetime’s needs should already be present in the soil.
• In the second half of summer, they need water for developing several fruits.

Or, if it’s dry and you do not water, plants survive but will fruit less. For more harvest, water once you see many small fruits, if the soil is dry – give a decent soak, twice a week.

Extra mulch to retain moisture and kill weeds?

Plastic mulches, for smothering summer weeds, combine well with growing widely spaced squash plants. You need a few holes in the plastic and it can then be easily used again for a similar purpose, to kill weeds through light exclusion.

You can plant through plastic by first cutting a cross with a sharp knife, giving four diagonal flaps. It’s not too difficult to then make a hole through these with a trowel and pop in the rootball of your squash plant.

How does this plant receive water, when its roots are below impermeable plastic?

• The answer is that rainfall drifts around on top and a lot of it goes in the plant holes.
• Plus the plastic cover also retains moisture in the first half of summer.

It’s a neat option if you have bindweed, for example, because for both squash and bindweed, the season of growth is summer. The plastic mulch deprives new bindweed of shoots of light, while squash leaves use the light above and roots take the moisture from below.

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How to judge readiness

For winter squash to store (in comparison to summer squash mentioned below), they need to be fully developed, with a hard skin and sweet flesh. If they are picked before this stage you still have food to eat, but it is less sweet and does not store for so long. It is more like a ripe summer squash, with firm skin, seedy flesh and decent flavour.

A sign of ripe squash is the stalk going dry. In fact, when the fruit are ripe, you can’t actually cut the stalk anymore because it is so wiry and tough. That is a good sign!

How to pick

Best wait until all fruits are ready to harvest. Do not pick the few immature ones; they can go to your compost heap because, by autumn, they will not grow or ripen anymore.

Handle fruits carefully and do not damage their skin, for long storage.

• Cut the plant stems either side of each stalk, rather than trying to cut the stalk itself.

This avoids damage to the fruits. Sometimes, when trying to cut a squash stalk, it snaps off, making an open wound in the fruit itself. This squash will then not store for more than about six weeks.

When to pick

Watch the weather forecast for any warnings of a first frost, around mid-autumn and just before your normal first frost date. Squash fruits tolerate a light freezing, more than the leaves, but it’s safest to harvest them all before this occurs.

Storing

Bring your squash to the house’s warmest room, ideally for a week, in temperatures above 20 °C/68° F. This hardens the skin and ensures that they are fully dry. After that, keep them anywhere dry and not too cold.

I store squash all winter and often through spring, on windowsills in my conservatory where they are in any sunlight. This does not dry them because they are such a sealed unit. If anything, the flavour sweetens over time.

I find it amazing that some of the Crown Prince, in particular, are still excellent to eat as late as early summer, as you see in the photo below. The flavour was still very good!

Saving seed

Easy to do, too easy sometimes! Seeds are all there to remove, wash and dry when preparing a squash to eat.

The question is, did the fruit’s female flowers receive pollen from a male flower of the same variety? If not you will have an unknown cross between different varieties. The photo above gives some idea, and it was from exactly one Kabocha fruit that I grew such an interesting selection of winter squash!

• Cross-pollination does not affect the appearance or flavour of fruits. It does affect the genetic information inside seeds.

One way to be sure of having seed that grows the same as its parent plant is to grow only one squash variety in your garden. Also, there must be no neighbours growing a different variety within maybe 30 m/close to 100 ft, or less if a tall fence is in the flight path between.

To be sure of growing seeds true to variety, you need to hand-pollinate the female flower before any insect does.

1. Place a paper bag held with a rubber band over a female fruit flower you want to pollinate.
2. Do this before the flower opens.
3. Within two to three days, open the bag and rub a male flower of the same variety against the now open female flower.
4. Re-cover the female flower for two days or so, until it has died. Keep a marker on the fruit, to make sure of harvesting the right one for seed.

See Real Seeds for more information.

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Slugs damage weak and struggling plants. However, when you are correct with timings of sowing and transplanting, slugs should not be a problem, except in unseasonal weather. It’s hard to foresee this, so it’s wise to keep a few transplants in reserve.

• A good rule of propagation is to raise more plants than you need. It’s better to put a few on the compost heap than not to have enough.
• Above all, you do not want gaps in the garden during the growing season, such a waste of prime space.

Disease

As I have written above, mildew appears from midsummer and is not a problem for healthy plants. It could be a problem if your plants are not comfortable with your climate. The problem then is the weather, not the mildew! Perhaps your summers are too cold; if so, maybe next year squash need to grow under cover.

Viruses sound bad, but I have yet to see an issue of virus preventing eventual growth. Sometimes the young leaves can be yellow with a viral appearance, yet I find that plants grow out of it to give almost a normal harvest.

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