Squash Plant Growth Stages | Life Cycle

Squash plants produce versatile, healthy fruits that are easy to grow and have an extensive array of varieties with many culinary and decorative uses. And depending on whether you grow winter or summer varieties, they can be cultivated quickly and easily for a large proportion of the year. 

The great news is you don’t always need to dedicate much effort or space since they can be grown in beds and borders, as patio plants and even vertically for optimum use of space in your garden or greenhouse.

In this article, I’ll be covering the life cycle of squash plants, what to expect when growing them, as well as top tips to get the maximum yield from your squash crops.

Conditions for Growing Squash Plants

Both summer and winter squashes are bushy, vining plants with large, lush foliage that like to spread, sending out long tendrils and can cover a large area if left unchecked. 

They are relatively robust but are happiest in well-draining soil that is fertile and packed with organic materials. According to the University of Georgia, squash plants grow in soil with an optimum pH of 5.8 to 6.8 and a soil temperature of 65 to 80ºF

Squashes are sun worshipers and known to be both hungry and thirsty plants; they prefer to be in full sun and should be well watered if you want them to produce large abundant ripe fruit.

Squashes can be grown from spring through to the first frosts and are separated into two groups – summer squashes and winter squashes. 

As the name suggests, summer squashes are grown for harvesting in the summer. Popular varieties include pattypan, zucchini, and yellow crookneck. These are best picked when they are still small and young and are known for their light and delicate flavour. 

Winter squashes such as butternut squash, kabocha, acorn and spaghetti and even pumpkins are best left to mature fully and can be picked from fall to winter depending on your climate. 

Both summer and winter squashes are best planted in USDA planting zones 3-10. Squashes can withstand relatively cold temperatures, with the idea being 65ºF. Avoid planting young plants outside until any risk of frost is over.

Water well when summer temperatures are high and in periods of drought and protect from wind damage when growing squash plants vertically. 

I find that squashes are best grown in the ground or in raised beds as this allows them to reach their optimum size. That said, most summer varieties – especially zucchini and patty pan – do well as patio container plants.

Growth Stages of Squash Plants

Both summer and winter squashes are annual plants and must be replaced yearly. Although they are both sown in the spring, summer squashes will begin to produce fruit much earlier than winter squashes but may overlap. 

It is also worth noting that winter squashes will need a larger space to spread and produce fruit.

1. Seed Germination

Both summer and winter squash seeds can be sown indoors from mid-April to May. Plant single seeds 1cm deep in compost or coir and position them in a warm spot on a sunny windowsill or a propagator at an optimum temperature of 64-70 ºF.

In warmer climates, squashes can also be sown outdoors in late spring to early summer by planting 2-3 seeds around 2-3 cm below the soil. I recommend covering with a cloche and keeping them well-watered to assist with germination. 

For germination to take place, seeds should only be planted when the soil temperature has reached a minimum of 60°. To boost chances of success, the air temperature should be between 65 and 80°F. Germination typically takes 14-21 days for both winter and summer squash.

2. Seedlings

Seedlings sown indoors should be ready to plant out 3-4 weeks after germination when they are approximately 7cm tall. As tender plants squash needs to be hardened off before planting outdoors.

For seedlings planted directly outdoors, keep a cloche in place for up to 3 weeks. Thin the seedlings out once you can identify the strongest-looking plants. For optimum growing, squash plants need to have between 3 to 5ft between each planting.

Seedlings

3. Vegetative Growth and Flowering

Once established, summer squashes will begin to vine and spread, and after 30–50 days, flowers will begin to form

Winter squashes take slightly longer to produce flowers, on average 45-60 days before flowers develop

For both types of squash, developing plants should be watered and fertilized with a fast-acting liquid feed regularly during the flowering stage. Care should be taken to avoid damaging flowers whilst watering and feeding. 

Vegetative Growth and Flowering

4. Pollination

Squash plants produce both male and female flowers, but only female flowers produce fruit. The University of Florida has a quick and easy way of telling the difference between male and female flowers. The stems underneath a male flower are straight, whereas the female is more hourglass. 

Squash plants are self-sufficient in pollination. In the main, their large and open flowers are ideal for pollinators to land on and aid pollination. If the plant has many flowers but only produces a little fruit, the plant may have produced too many males and not enough female flowers.

To assist with fruit development, remove the male flower to expose the anther and gently rub this onto the female stamen. Flower sex is dependent on the age of the plant as well as weather conditions. 

5. Fruit Development and Ripening

Squashes are formed from fertilized flowers. On average, squash fruit takes 7 days to begin forming from the time of pollination. Summer types form fruit very quickly after flowering, with summer squash fruit being ready to harvest after 21-30 days when small when they’re packed full of flavour. In contrast, winter squashes take 60-100 days to ripen and change colour before they are harvested.

Fruit Development and Ripening - Squash Plant Growth Stages

When to Harvest Squash

Summer Squash takes approximately 50-70 days from sowing before they are ready to be harvested. 

The fruits are usually produced from mid-summer through to the first frosts, but the best time to harvest them is when they are young and the skin is still glossy. 

If left too long, or if picked after the first frost, the fruit can lose its flavour, and the skin becomes tough and fibrous.

Harvesting regularly will enable the plant to retain enough energy to produce more flowers and, potentially, more fruit for a more plentiful harvest. 

Their size is a sure sign that summer squash is ready to be picked. The University of Illinois recommends harvesting elongated varieties when they are 2 inches or less in diameter and 6 to 8 inches long, whereas patty pan varieties should be harvested when they are 3 to 4 inches in diameter.

Winter Squash produces significantly larger fruit and needs to be left to grow for longer. 

On average, winter squashes need around 120 to 150 days from sowing before they are ready to be harvested.

Although planted at a similar time to summer varieties, winter squashes should be picked in the fall. As with summer squashes, they must be harvested before the first frosts, or they will spoil.

Iowa State University recommends that winter varieties should be harvested when fully matured when the skin is tough and difficult to puncture. 

It is easier to tell when to harvest winter squashes as they change colour when they ripen. For example, pumpkins will change from green to bright orange when ready to be picked. 

I recommend raising developing winter fruits off the ground to avoid pest infestations or damage that can be caused by wet soil.

Harvest both summer and winter squashes on a dry day to avoid stems getting wet and becoming vulnerable to disease.

Storing and Overwintering

Summer squashes are best eaten or used within 3-4 days of harvesting. They can be kept in the fridge for several days, but any longer, they will begin to rot or lose their delicious flavour.

Winter squashes are much easier to overwinter, but the most efficient way to store them is to leave them on the plant until you are ready to use them. 

Remove the fruit once the weather cools and frosts are imminent. Thereafter, store at temperatures of approximately 50 ºF for several months.

FAQ Squash Plant Growth Stages

For more articles about the growth stages for edibles, here’s a link to Sweet Potato Growth Stages that you may like.

Citations

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.