Squash - The Complete Guide to Growing Squash from Seed to Seed

Growing squash is one of the easiest things to do during the summer season. Often, growers end up with far too much squash! Handing them off to neighbors and friends, who eventually stop answering the door when you pull up with your weekly wheelbarrow of squash. We’re barely exaggerating here. In order to grow squash successfully, it can be helpful to understand some basic tips and differentiations between the types of squash - particularly if you plan on saving seeds - and we recommend that you do! Now, let’s learn more about one of our favorite genus’ - Cucurbita. 

Squash, Cucurbita spp.

Whenever you see ‘spp.’ tagged to a genus (in this case, the genus, Cucurbita), you should pay attention. It means species plural, i.e. there are multiple species of squash within the genus, Cucurbita. This is critical information for the seed saver, and some fundamental botany should explain why:

Varieties of the same species can cross pollinate; varieties of different species cannot cross pollinate.  

Cross pollination produces a hybrid seed. Hybrids can be fun for seed breeders, but not for predictability within our own food systems. Let us   give you a solid example:

A gardener grows the Tahitian Butternut (Cucurbita moschata) each year. It produces an extremely productive and massive fruit, is resistant to many fungal diseases and vine borers, and stores for up to 9 months. They rely upon this squash as a large part of their family’s winter diet. They save seeds each and every year. Their neighbor grows the Tromboncino  variety (another Cucurbita moschata), beloved for its long necks and slightly sweet flavor. These two moschatas accidentally cross pollinate one year. When our grower saves seeds from their Tahitian Butternuts and replants them the following year, there is a fairly high probability that they won’t fully recognize what they’ve grown. Due to the cross pollination, the squash grown the following year will not grow ‘true to type’. It may be an obvious cross like color or shape, but maybe it’ll just lose the excellent storability of the Tahitian. They may not even know the cross has happened until they have a basement of rotting squash in February, whereas they’d usually eat those squash all the way through May. 

Types of Squash 

Predictability should be a key component to our food systems. So, knowing which of your plants can and will cross pollinate is critical, and knowing the species to differentiate your types of squash is the first step. Remember: A squash is not a squash is not a squash. A squash could be a Cucurbita pepo or a Cucurbita moschata or a Cucurbita maxima or a Cucurbita argyrosperma or Cucurbita ficifolia.      

Each of these distinct species have many variety options, but we can recognize broad traits between them. Here’s a quick breakdown to help you plan your garden:

C. pepo

This species contains almost all of the summer squash, including zucchini, patty-pans, straightnecks, and crooknecks. It also includes smaller pumpkins, hulless pumpkins (also known as naked seed pumpkins) and many small winter squash (including the Delicatas).

C. moschata

This species includes all the butternuts and cheese pumpkins (e.g. Long Island Cheese). They are known for their long storage and solid stem vines, making them a good option where vine borers are a serious pest.  

C. maxima

This species produces large winter squash that sweeten with age and have good keeping characteristics. It includes all the hubbards (and the Candy Roasters), a classic being the Blue Hubbard.

C. argyrosperma

This species (previously C. mixta) originated in southern Mexico. It enjoys the heat and can tolerate humidity and includes all Cushaw varieties.

C. ficifolia

This species is less common in North America but can be grown in temperate regions. In Central America it is commonly grown for its edible leaves (which resemble fig leaves, hence C. ficifolia) and seeds.

Growing Squash 

All squash are grown as warm season annuals in North America. The only real difference between summer and winter squash is when we harvest. Summer squash are bred to taste yummy when harvested immature; winter squash are bred to taste yummy when fully mature. All squash are heavy feeders and will need a good quality, rich soil to thrive, adding composted manure will keep them very happy. Summer squash and some winter bush varieties will grow compact, but most squash will vine and romp all over your garden. The vines can root in at their nodes and a spade full of compost at those points will give healthier, better nourished plants. 

Growing squash seedlings is easy for even the most novice gardeners. We recommend starting your seeds indoors four to six weeks before the last frost day in your growing zone. This helps you take advantage of the full season but squash seeds can easily be direct seeded into the garden as well. If transplanting, take care to not disturb the delicate root systems. Squash are notorious for undergoing transplant shock, but this can be mitigated with delicate handling and plenty of water. You’ll want to plant your squash seeds in an area with full sun and ensure they get at least one inch of water per week. 

Companion Planting with Squash

Companion planting is the art of growing different plants near each other that support each other's growth. This can be through nutrient balances, pollination needs, or pest protection. Squash is actually a core triplet of the infamous Three Sisters method of planting. Indigenous people of America would traditionally plant corn, beans, and squash all together. The corn acted as a trellis for the beans. The beans also put nitrogen back into the soil. And the wide and prickly squash leaves would shade out weeds and protect from pests like racoons or opossums.

The Three Sisters method is a beloved planting style but even if you don’t grow corn, beans, and squash together there are some other companion planting pairings that may help your squash grow. 

Nasturtium

Nasturtiums have a strong smell that deters squash beetles from staying in the area. They also attract aphids, leaving your crop free from these sucking pests.

Oregano

Growing kitchen herbs among your vegetable crops can, in general, hide or protect your crops from predators. Many pests - big and small - are deterred by the strong scents. 

Calendula

Calendula encourages pollinators as well as deters root-knot nematodes! It tends to be low-growing and can easily fit in amongst your squash plants. 

Common Squash Pests and Diseases

Like most vegetable crops, squash is not immune to its fair share of pests and diseases. In most cases, squash is resilient and prolific enough to overcome (or at least produce through) these issues. Even so, being proactive can help to avoid any potential longer term issues. 

Squash Bugs

Squash bugs tend to have explosive population growth and can quickly get out of hand. Their damage causes local necrosis of foliage and eventually plant death, though squash can often withstand their presence for a while. Due to the population explosion of this pest, early control of the eggs is critical. Look underneath the leaves of your squash for egg clusters which are golden yellow to reddish in color. Squish them as you come across them. 

Cucumber Beetles

Whether you’ve got the striped or spotted cucumber beetles in your garden, both can be found on a wide range of cucurbits including cucumbers, melons, and of course, squash. They will defoliate your plant (which is bad enough) but also carry a range of diseases including bacterial wilt and mosaic virus that can cause even bigger issues. Keep your squash covered in row cover until they start to flower - this will protect them while they’re tenderly getting established. If they’re already a problem in your garden, consider some regular applications of neem oil to reduce population growth.

Vine Borers

Vine borers are exactly what they sound like - they bore into the stems of your squash vines, typically killing the plant - unless stopped! Vine borers can sometimes be a little hard to catch because one of the first signs of their presence is just a wilted plant. You may think that your crop just needs a little extra water. Which sometimes is the case! But if that doesn’t make sense to you based on how you’ve been caring for your plants. Check at the base of the stem. You may see a chewed out hole and/or some orangey goo. This is your sign! Take a sharp knife parallel to the stem and draw it up - not all the way through - just enough so you can open the stem and look inside. That’s where you’ll find the culprit. One plant can house several grubs so make sure you locate all of them. While doing damage to your plant can hurt, if caught and removed early your crop can still recover! Simply pack the wound well with soil and keep well watered. The moisture will help to heal the wound and revive the plant. 

Butternuts (and other moschatas) are well-known for being resistant to vine borers. If this pest is a particularly large issue in your garden, consider growing those types! 

Powdery Mildew

Powdery mildew is more often than not an aesthetic problem rather than a crop problem - particularly later in the year. However it can spread rapidly and make things less than desirable. The best way to avoid powdery mildew is to be proactive. Be sure to water your plants in the mornings, plant or thin seedlings to an appropriate distance (allowing for adequate airflow), and remove affected leaves as you see them - ensuring that you aren’t removing too many so that the plant cannot produce.

Cucumber Mosaic Virus

Cucumber Mosaic Virus isn’t just for cucumbers - in fact, it affects over 1,200 species, squash included. It can look different in action depending on the plant but typically you’ll see your plants stunted, mottling on the leaves, rings of discolored tissue, and other growth distortions like curling or puckering of the leaves. It can cause total crop loss if not caught early. Catching it early means looking out for signs and removing those plants. The virus can easily be spread from one plant to another and your number one goal is to avoid that. 

Blossom End Rot

On a less jarring note, blossom end rot is a common issue that is easily avoided or fixed! While growers may be concerned about disease, blossom end rot is actually a nutrient issue and is caused by a lack of available calcium in the soil. If you see some of your fruits on indeterminate species experiencing blossom end rot, you may be able to save your future fruits by acting quickly to apply a water soluble calcium fertilizer.

Saving Squash Seeds

Squash plants have large beautiful flowers that attract many insects. This means cross pollination can happen up to a ½ mile. If you are just growing for fruit, this is not a problem. If you plan to save pure seed, the easiest option is to pick only one variety from each of the species. Since only varieties of the same species can cross, you will have eliminated any chance of cross pollination (depending on your neighbor's garden…). As you might expect, squash plants are annuals, so you can grow the fruit and save seed from it in the same year. 

However, if you want to grow a Costata Romanesco Summer Squash (C. pepo) and a Small Sugar Pumpkin (C. pepo) and you don’t have a garden big enough to plant them a ½ mile apart, then welcome to the wonderful world of hand pollination.

In brief, hand pollination means you isolate the female flower from all insects (using tape, a rubber band, or a bag) the day before it opens. The next day you grab a couple of male flowers, expose the female flower and dab pollen from the male onto the female. Then isolate the female again. This guarantees that only pollen from the same variety is doing the pollinating and the seed from the fruit that grows from that female flower will be pure seed. Hand pollination justifies further research, but know that squash flowers are a great starting point for beginners to learn about hand pollination. They are large and easy to work with.

Squash must be fully mature before being harvested for seed production. For winter squash, this is easy. As you eat your winter squash, you can simply save your seeds. For summer squash, you give up the eating opportunity for the seed saving opportunity, as overripe summer squash is not particularly tasty. Summer squash should be left on the vine until the outer shell hardens, like a winter squash would. Once it hardens, the squash should cure for three to four weeks (same as winter squash) to encourage further seed ripening. 

Once complete, cut open the fruits (this applies to any squash), scrape out the seeds and any pulp into a jar or bucket. Fill the container with an equal amount of water. Ferment the seeds for two to four days. Fermentation will occur on its own with yeasts naturally brought in from the garden. After two to four days, pour off anything floating at the top. Wash the rest of the seeds away from the wet chaff. Once clean, spread your seeds into a thin layer on a screen or sheets of newspaper. Thorough drying can take several weeks so patience is key in order to avoid any moldy seeds!

Note: squash plants are described as Monecious, meaning they have separate male and female flowers on the same plant. Even if you don’t save seeds this year, be a botanical observer and learn the difference. You’ll notice squash plants produce way more male flowers than females, so go ahead and eat some of the males! We recommend stuffing them with goat cheese, breading, and frying them - yum! 

Varieties of Squash

We’ve established that squash is fun and easy to grow. There are so many different varieties where should you even start? Luckily, we’ve got some really great suggestions for you. The squash offered by Sow True Seed fall all over the species spectrum so make sure to take note of that if you plan to save your seed.

Scallop Yellow Bush

Cucurbita pepo

The dang cutest summer squash out there! This is a very productive cheery, yellow patty pan squash that is best when picked while it’s still small enough to fit in your hand. This variety is less attractive to squash bugs than other summer squash. 

Cocozelle Zucchini

Cucurbita pepo

This stunning heirloom summer squash features slender fruits with light and dark green stripes on smooth, thin skins. This variety has an outstanding flavor with dense flesh. Flavor is best when harvested at less than ten inches long. 

Tromboncino 

Cucurbita moschata

Tromboncino squash, also known as zuccheta, grow long necks which curl in fanciful shapes. They taste best when harvested at eight to 18 inches long, and while being a summer squash, you’ll notice it’s a different species! Actually related to Butternut squash, the Tromboncino has better resistance to vine borers and powdery mildew. 

Waltham Butternut

Cucurbita moschata

Our most popular butternut, these three to six pound fruits with a rich, nutty flavor store up to nine months. They produce very vigorous vines and are a dependable producer. Like other moschatas, this butternut has good vine borer resistance. 

Cinderella

Cucurbita maxima

With only the slightest imagination does this heavily ribbed, bright orange squash turn into Cinderella’s carriage! This French heirloom was said to be very popular at Parisian markets in the 1880s. They have an excellent flavor and store very well. 

Blue Hubbard

Cucurbita maxima

The muted blue/gray warty rind holds the secret to the sweet flesh inside. The Blue Hubbard is famous for pie making, roasting, and other culinary delights. These are excellent keepers and typically weigh seven to ten pounds. 

Candy Roaster Melon 

Cucurbita maxima

This is a North Carolina original! These large, rampant vines produce 12 to 14 pound fruits. They offer delightfully warty, buttercup-shaped fruit with pinkish-orange coloring and blue-green markings. They are very sweet and excellent for baking! 

Cushaw Green Striped

Cucurbita argyrosperma

Hailing from the Caribbean, this variety of Cushaw squash also goes by the name of Tennessee Sweet Potato Squash. Cushaw squash in general is very tolerant of humid conditions and is renowned for making exceptional pumpkin pies. You can expect heavy yields of 15 pound crookneck fruits with pale green stripes over creamy white skin. This variety has a thin rind - great for cooking, not as great for storing. Try to eat or process within a month of harvesting.

Ready to get growing? Even for the most novice gardener, squash is a great place to get started learning to grow from seed as well as saving seed. Check out Sow True Seed’s curated selection of open-pollinated and heirloom squash seeds. 

	Article Written by: Hannah Gibbons
	About the Author: Hannah Gibbons, an employee at Sow True Seed since 2020, has nearly a decade of experience in the agricultural industry. Their passion for environmental education and regenerative agriculture has been the cornerstone of their work, aimed at making gardening accessible to all.