Introduction
Winter squash presents a unique challenge for growers. Although it requires substantial space and can yield inconsistent results, its value during the winter months makes it a worthwhile crop when fresh produce is scarce.
- Sow: Late April - June
- Time to maturity: 5 months
- Module sow: 1 seedling or sow directly
- Spacing: 1 plant per square metre, or more for larger varieties
- Frost tolerance: None; wait until well after the last frost date and have fleece ready
- Watering: Mulch thickly, water infrequently but deeply
- Plant: In full sun or very light shade
Why Grow Winter Squash
Winter squash may not score highly on the value scale, as it occupies a considerable amount of space during peak summer growing season, often resulting in a low-value harvest compared to other crops. It requires significant nutrients and water, leading to unpredictable yields that can vary widely from small to abundant.
Despite this, Wellies and Waxjackets continues to cultivate winter squash for its culinary versatility. It provides fresh calories during a challenging time in winter and adds aesthetic appeal to the garden, making the growing process enjoyable.
Winter squash thrives in full sun but can tolerate a bit of shade during the day.
How Many to Plant?
Though winter squash is not the most productive crop, it provides substantial stored calories for winter. Yield can vary by variety, but a single Crown Prince plant typically produces about two fruits. One fruit can sustain two people with roasted squash and soup for two weeks. Assuming an eight-month storage period, two people would require 16 fruits, translating to at least eight plants, each occupying 1m² of space (4m² per person). For individual growers, selecting smaller varieties can be advantageous, although vertical growing methods can optimise space.
Suitability for Different Growing Environments
A wide variety of squashes (cucurbits) is available to accommodate different growing environments. Smaller varieties can thrive in 35-50 litre containers, while larger varieties require ample space and nutrient-rich soil. Some squashes are climbers, provided they have proper support for their fruits.
Vertical growing offers several benefits, such as optimising space and creating a natural shade for summer leafy greens, enhancing the overall garden aesthetic.
Lifecycle
Winter squash plants require careful nurturing when young, particularly during cold nights and fierce winds in late spring and early summer. Once established, they grow rapidly. When fruits reach a reasonable size, they can either be consumed fresh or left to mature until mid-autumn. As the skins toughen, they create a protective seal, allowing for long-term storage from late autumn through to the following summer—given that there’s enough yield to last.
It’s important to note that squash differs from pumpkins; the latter are larger, have thinner skins, and a more watery texture, limiting their storage life to around December.
Harvesting usually occurs in late September or early October to allow time for planting alliums and field beans in the same area. When grown vertically, harvesting by October still allows time for winter lettuce and spinach to thrive once the squash are removed.
Sowing and Harvesting Periods
Winter squash doesn't benefit significantly from early sowing, as cool conditions hinder growth, potentially impacting overall yield.
First Earlies (Sow late March to plant under cover in late April)
This option suits those looking to harvest young fruits in a greenhouse or tunnel. The best varieties for this approach are climbers. However, it’s essential to weigh the benefits of winter squash against the more reliable courgette.
Early Main Crop (Sow early April to plant out in mid-May)
This category is sown 3-4 weeks earlier than the main crop, planted in sheltered areas and protected with fleece. This strategy accelerates growth, although it's advisable to sow extra main crop plants as backups.
Main Crop (Sow late April to plant out in early June)
Most growers will find the main crop sowing sufficient. It’s best to grow summer squash for an earlier harvest without attempting a late crop. Planted at the right time, winter squash often grows faster and yields more than early-planted varieties.
Late Crop
Wellies and Waxjackets does not find late crops worthwhile.
Recommended Varieties
Several varieties suit different growing environments and preferences.
How to Sow
Starting squash in a six-cell tray is effective, as it minimizes root disturbance.
Sow seeds 2 inches deep on their sides to reduce the risk of rot. Germination thrives at temperatures between 20-24°C, so using a propagator or placing them on a sunny windowsill is beneficial.
How to Prick Out/Pot On
For those opting to pot on, creating a depression in the compost and gently placing the root ball into it with minimal disturbance yields excellent results.
Where to Plant
Winter squash thrives in full sun, in rich soil with ample compost. A sheltered spot away from wind is beneficial, as squash has extensive root systems and requires significant water.
How Many to Plant (Spacing)
Sprawling squash can create a tangled mess if planted too closely. For small bush types, 1 per m² is sufficient, while larger varieties should be spaced at 1 per 2 m².
How to Plant
Before planting, check the long-range weather forecast to ensure conditions are suitable, typically starting around mid-May.
- Mulch the intended planting area with a thick layer of wood chip.
- Water plants thoroughly.
- Pull back the mulch.
- Dig a hole twice the size of the plant pot and partially fill with compost and well-rotted manure.
- Water the hole before planting.
- Remove the pot and gently lower the plant into the hole, ensuring it’s set lower than the mulch.
- Water the edge to settle the soil without overwatering.
- Replace mulch around the plant stem.
Protecting and Supporting Plants
Fleece should be used to protect young plants from frost or high winds, but must be removed on sunny days to prevent scorching. If growing vertically, tie plants to supports as needed.
How to Feed and Water
While squash has deep roots and doesn’t require frequent watering, when needed, water deeply to penetrate the mulch. In sandy soil, watering every two weeks may suffice, while silty or clay soils might require less.
Fertility varies by soil; rich soils may not require feeding, while Wellies and Waxjackets recommends using tomato fertiliser every two weeks in sandy soils.
How to Prune/Manage While Growing
Though squash can manage their own growth, pruning is often necessary to control spread. In vertical growth, train and tie stems to a structured frame to maximise space and ensure optimal fruiting.
How to Hand Pollinate a Courgette/Squash Plant
While insects typically handle pollination, hand pollination can enhance yields, especially in greenhouses.
Identify Male and Female Flowers
Male flowers are taller with long stems and contain pollen, while female flowers have shorter stems with a swollen ovary.
Collect the Pollen
Select a male flower early in the morning, remove petals, and expose the pollen-laden stamen.
Transfer the Pollen
Gently dab the stamen onto the female flower’s stigma or use a small brush to collect and transfer pollen.
Repeat the Process
Continue this process with new female flowers as they bloom to maximise pollination and yield.
How and When to Harvest
Recognising harvest time becomes easier with experience. Generally, fruits should be picked before the first autumn frost, but waiting until late September for most leaves to die back and the stem to dry is ideal.
By October, it’s often necessary to harvest regardless of readiness due to reduced light and warmth.
When harvesting, leave a T-shaped stem about 2-3 inches long to minimize mould risk.
How to Store
Squash requires curing before storage. Store in a warm, sunny place for 2-3 weeks to enhance sweetness and dry the skin.
To preserve squash into spring, keep in a cool, dry location above freezing.
How to Deal with Pests and Disease
Pests and diseases are minimal in the UK, though mildew may appear as plants age. This does not significantly affect yield.
When and How to Remove the Plants
Cut plants off at the root, and if tied with string, compost everything post-harvest to accelerate decomposition.
What to Plant Before
When growing vertically, there’s no opportunity to plant anything before or after. If sprawling, consider planting winter brassicas, lettuce, Asian greens, spinach, or radish.
What to Plant After
After harvesting sprawling plants, field beans, garlic, broad beans, salad onions, over-wintering onions, spinach, and lettuce are suitable options, ideally under fleece.
What to Interplant With
Vertical growers won't have space for interplanting, but sprawling squash can be paired with sweetcorn.
While the ‘three sisters’ method is popular, it often leads to tangling and difficulties during harvest.
Interplanting should focus on plants that benefit each other, considering nutrient access, pest protection, water levels, growth rates, and shading needs.
