Learn the best way to plant your squash seeds outside, how to successfully germinate them indoors to produce seedlings, and when to plant them outside.
As a general rule, squash seeds are planted 1” (2.5cm) deep or slightly deeper if the soil has low water retention. Place 2-3 seeds and thin them out to one plant in rows, or 5-6 seeds and thin them out to 3 plants on hills. Soil temperature should be at least 65°F (18.3°C).
Squash plants (Cucurbita spp.) thrive under warm weather conditions and are one of the most productive plants in the garden.
Summer squash will start producing tender fruits within a short period, while winter squash will take more time but the harvest stores for longer.
They are not the easiest plant to grow, which is why you need to start with the most vigorous and healthy plants possible.
We share all you need to know from starting to germinate seeds indoors to producing seedlings, and how to successfully plant your seeds directly into the soil.
How to Plant Squash Seeds
Squash is normally used as a vegetable, botanically, however, it is categorized as a fruit. There are hundreds of squash varieties, but they are normally divided into summer and winter varieties.
Summer squash is harvested and eaten before it is fully mature when the skin and seeds are still soft. Most of the varieties are bush-type plants with a more compact growing habit. Some of the most common types are Pattypan, Zephyr, Tromboncino, Crookneck, Tatum, Causa, Straightneck, Zucchini varieties, Luffa, Yellow varieties, and others.
Winter squash is eaten when the fruit is mature, and the seeds and skin are harder. These types can be stored for a longer period. They are normally vining types that spread and need more space to develop. The most common types are Acorn, Buttercup, Sugar Pumpkin, Carnival, Kabocha, Hubbard, Delicata, Butternut, Spaghetti, Red Kuri, and others.
Squashes are annual plants that need to be planted again each year. They are frost-sensitive plants that prefer warmer growing conditions. Summer types will start producing 45-60 days after planting them, while winter types will require 80-110 days from seed to harvest.
The two main ways to produce squash plants are in rows and hills (mounds). Rows can be used in soils with a good balance between drainage and water retention. Raised hills will have warmer soil and better drainage, while inverted hills are better for soils with poor water retention.
The best way to plant squash seeds is to place them horizontally instead of vertically. It could be confusing to decide which way up to put your seeds, and doing this will also help you plant them at the right depth. Put your squash seeds in a furrow or hole of about 1” (2.5cm).
When deciding how many squash seeds to plant together in a hole, use the following rule of thumb. For row planting, place 2-3 seeds and thin them out to one plant, if growing in hills plant 5-6 seeds and thin them out to 3 plants. Cut excess seedlings out with scissors when they are 3” (7.5cm) tall.
When spacing your summer squash plants 24-30” (60-76cm) between plants in rows or 3-4 feet (0.9-1.2m) apart in hills, they grow more compact and could be tutored to grow vertically. For winter types leave 36-48” (91-122cm) between plants in rows or space the hills 4-5 feet (1.2-1.5m) apart.
Start your squash seeds indoors 3-4 weeks before you are planning to take them outside. Put 1-2 seeds at ½-1“ (1.2-2.5cm) depth in a 4” (10cm) diameter pot, and keep the substrate moist until the seeds germinate. Place them on a sunny windowsill so they don’t grow leggy.
Squash plants can grow in containers, but the container needs to be at least 12” (30cm) wide and high for bush-type plants and bigger for vining varieties. Place 2-3 seeds, 1“ (1.2-2.5cm) deep into the soil and thin them out to one individual plant. Smaller containers will need constant watering.
You can plant your squash seeds directly into the bed when the risk of frost is low, and soil temperatures have reached at least 65°F (18.3°C). Place the seeds 1“ (1.2-2.5cm) deep in garden beds and raised beds, keeping the soil moist until the seeds germinate.
How to Germinate Squash Seeds
Squash seeds will remain viable for 4-6 years if they are kept inside an airtight container and stored in a cool and dry place. As time passes the seeds will lose their germinating potential, and fewer will germinate each year.
Seeds are only viable after the fruit has fully matured. You can plant the fresh seeds right out of the fruit from a store-bought squash, but it is better to clean and dry them before using them. This will prevent them from rotting afterward and increase their viability.
To prepare your seeds before planting them you can soak or scarify them. Squash seeds have a thick coat and these techniques will make them soak up water easily, and speed up the germination process.
Scarification means slightly weakening the seed coat (without damaging the embryo). The easiest way to do this is by gently scratching either side of the seed on sandpaper. The aim is not to perforate the coat but to make it more permeable.
Soaking squash seeds is normally not necessary, but it helps to speed up germination. Place your seeds in a bowl with warm water for 8-12 hours and plant them right after. We do not recommend leaving them for longer than 24 hours as they could start rotting.
As a general rule, squash seeds will take between 7-10 days to germinate under favorable conditions. Depending on the temperature, this might vary. Germination will be normal if soil temperatures have reached 70°F (21°C), and it will be faster at 95°F (35°C).
One of the best ways to germinate your squash seeds faster is to first slightly scarify them, and then soak them in warm water for 8 hours. You can also pre-germinate them using the paper towel method, which also presents a good way to determine if your seeds are still viable.
We have a detailed article with a step-by-step video explaining the paper towel method here.
One of the most common reasons for squash seeds not germinating is lower temperatures. If soil temperatures drop to 60°F (15.5°C) or below seeds will not sprout normally. The second common reason is that the soil is too dry and seeds lack the necessary moisture to start sprouting.
Once your squash seeds have germinated plant them directly into the garden bed where they will grow, or in a 4” (10cm) diameter pot to grow it as a seedling. Place the seed with the root facing down to a depth of 1” (2.5cm) and keep it moist until it sprouts.
It’s better to start squash seeds indoors if the soil is too cold or if you prefer taking the seedlings outside once they’re a little bigger. It takes 3-4 weeks from seed to a developing seedling. If temperatures are cold or a late frost is expected, replant your seedlings into a bigger pot first.
How to Grow Squash Seedlings
Squash plants will transplant well if the seedling is not too old and temperatures are warm enough. They will resent transplanting or relocating once they are older and more developed. In case relocation is absolutely necessary, prune them afterward to promote root growth and avoid dehydration.
Sometimes squash seedlings might experience a transplant shock, meaning that they could wilt, stop growing, or sometimes die. To avoid this you can start hardening off your seedlings, one week before transplanting them, by gradually exposing them to sunlight and outdoor conditions.
You should transplant your squash seedlings as soon as they have 1-2 true leaves. At this point, the plant will already have a strong root system, so it is better not to wait much longer as the roots can get damaged during transplanting.
You can separate squash seedlings but be careful not to damage the fragile roots. Try doing this when they are still small and the roots are not intertwined. If the seedlings are bigger, use water to wash off the soil and separate the roots. Transplant right away so they don’t dry out.
Be sure not to plant squash seedlings too deep when transplanting. Try to place the root crown (the junction between stem and root) just below the soil surface. The easiest way to do this is to just dig a hole as deep as your pot and place your seedling carefully without damaging the roots.
You can still transplant and save your seedlings if they grew elongated (leggy). In this case, it is important to bury the plant deeper leaving the soil level 1” (2.5cm) below the cotyledons. The stem will develop new roots but avoid pressing too hard on it or it could get damaged.
Make sure to transplant your squash seedlings after the last spring frost or when the risk of a late frost is low. For better results, we recommend waiting until the soil has warmed up to 70°F (21°C). Squash plants will thrive in a place with full sun and warm temperatures.
You now have all you need to start successfully germinating and planting your squash seeds for the growing season. We recommend growing 2-3 different varieties side by side to determine which ones work best for you. Transplanting new plants outside after 4-6 weeks will ensure a longer harvest season.
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