Although gardening season is over, it’s prime time to collect seeds from your favourite squash.  Most varieties are long keepers and will survive without spoilage until the end of the year.  

Do you have a favourite squash variety? Maybe it’s Butternut, or perhaps it’s Hubbard? 

Whatever the variety, if done correctly, squash is one of the easiest vegetables to save seeds from. There are just a few steps that need to be followed and you will be well on your way to saving seeds from your favourite squash varieties.

In this post of my Seed Saving Series, I will be discussing the steps involved in saving squash seeds.  I will also cover isolation distances to ensure seed purity, to prevent cross-contamination.

When we think of squash (Cucurbita), we often think of acorn and butternut squash, possibly hubbard and spaghetti, delicata, pumpkins, gourds or zucchini.  However, there is an endless list of squash types. In order to better understand our favourites, we need to look at the five squash species and where our favourite types are categorized. 

Cucurbita pepo

Cucurbita pepo is the species of squash that we are most familiar with.  It includes spaghetti and delicata squash, zucchini, acorn, scallop, marrow, many species of pumpkins and numerous ornamental gourds.

The different varieties in this species typically have a thinner skin than varieties within the other species, making them poor long-term keepers.

Varieties within this species will crossbreed easily, so if planning on saving seed from any of the squash included in this species, be sure to only grow one variety within this species, at a time.

Cucurbita maxima

The Cucurbita maxima species produces the largest-sized squash of all the species.  Some of its well known varieties include hubbard, candy roaster, kabocha, kuri and banana.  Many of the prize pumpkins that reach up to 1000 lbs. in competitions, come from squash within this species.

This species produces squash that are high in beta carotene, giving them that beautiful deep orange and yellow coloured flesh. Although the original wild species originated in the northern Andean mountains of South America over 4000 years ago, the maxima species has adapted to be a good choice for the northern gardener.

Cucurbita moschata

Cucurbita moschata is a species that is typically better suited to a hot, humid climate, due to its origin in Central America and northern South America.  However, with breeding and selection, many varieties in this species may grow comfortably in the north.

Typically varieties in this species include butternut squash, crookneck squash, long island cheese pumpkin and golden cushaw. 

Flesh is typically yellow to pale orange and exterior skin ranges from tan to dark green.

Cucurbita argyrosperma

Cucurbita argyrosperma (formerly known as Cucurbita mixta) is a less common species of squash.  Originally cultivated in Mexico, it is known for producing the silver seeded gourd, grown for its nutritious seeds.  Other common varieties in this species are the green and white cushaw gourd.  Fruit shape may be an oblate sphere or an elongated long neck, either straight or bent.

Cucurbita ficifolia

This is the least well-known of the five squash species.  Fruits typically resemble a watermelon in shape and colour and flesh is typically white.  Seeds are flat and black in colour, similar to a watermelon.  This variety is hardier than others for a northern garden.  Flowers are self-fertile.

Common varieties include the fig leaf gourd, malabar gourd and the black seed squash.

Isolation Distance

When growing different squash varieties within a species, a separation distance of 1.5 to 2 miles (2.4 to 3.2 km) needs to be maintained, in order to prevent cross-pollination and seed contamination. 

For example, if planting C. pepo ‘Delicata’ and C. pepo ‘Cinderella’ pumpkin, an isolation distance of 1.5 to 2 miles needs to be maintained, as the two varieties will cross.  If there are landscape barriers in place, this distance may be shortened a bit. 

A distance of 1/2 a mile (0.8 km) needs to be maintained when growing a single variety of a species near a variety of a different species. 

If growing C. maxima ‘Hubbard’ squash and C. moschata ‘Butternut’ squash, a minimum isolation distance of 0.5 mile (0.8 km) needs to be maintained.

C. pepo and C. maxima will not cross allowing the two species to grow side by side, without risk of cross-pollination.  However, C. pepo will cross with C. moschata and C. argyrosperma, therefore a minimum isolation distance of 1.5 miles (2.4 km) should be maintained to prevent the risk of cross-pollination between these two species.

Hand Pollination

If the intent is not to save seed, then it makes no difference how many squash varieties you would like to grow in one garden. However, if space is problem, and it typically would be for the home gardener, consider hand-pollination when the intention is to save seed.  

For specific details on hand pollinating your squash and zucchini plants, please refer to my upcoming post.

Here’s What to Do:

Tools Needed For Seed Saving:

• Knife
• Large bowl or bucket
• Spoon
• Colander
• Cutting board
• Plate or flat screen
• Masking tape or sticky label
• Pen or permanent marker

Directions:

1. Squash seeds are ready for harvest after the fruit has matured for at least 4 weeks after picking and the stem is completely dry.
2. Make a shallow cut into your squash lengthwise, and gently pull the two squash halves apart. This process will prevent damaging the seeds inside.
3. Using your knife, slice the edges of the inner seed cavity, to help remove all the seeds, pulp and strings.
4. Scoop out the seed cavity with pulp into a bowl.
5. If you are only cleaning one squash fruit, hand pick the seeds out of the pulp and strings and rinse them clean through a colander.


Rinse your seeds through a colander.

6. If you are collecting seed from several fruit, put all the pulp, strings and seeds into a large bowl or bucket and fill with water. Stir the seeds around. The seeds that float can be disposed of, along with any floating pulp. Then tip the bowl over to allow the loose pulp to wash away. Strain the seeds through a colander and use your hands to help wash away any bits of pulp or strings attached to the seeds.


Seeds have been rinsed clean.

7. Once all the seeds are clean of pulp, lay them out on a plate or screen to dry.


Clean seeds drying on a screen.

8. Label your seeds with masking tape or a sticky label.
9. Once the seeds are fully dry (approximately 2 to 4 weeks, depending on the humidity level in your home), brush away any flaky seed coating that will appear.
10. Discard any seeds that feel hollow in the centre. These seeds do not have an endosperm on the inside of the seed coat and are not viable.
11. Seeds are ready for storage when they are completely dry and hard. If they feel soft or pliable, leave them to dry for an additional week or two.
12. Once seeds are fully dry, store them in a glass jar or paper envelope.


’Marina di Chiogga’ squash seeds ready for storage.

13. Be sure to label your envelope with seed type and variety, along with storage date. Feel free to add any additional details to help identify the colour, shape, size and maturity date of the saved squash seeds.

A Planting Idea

If space is limited and you would like to plant squash, with the intention of saving seeds, consider planting one variety of Cucurbita pepo, one variety of Cucurbita maxima and one variety of Cucurbita ficifolia in one garden. 

An example of this would be delicata squash, Georgia candy roaster squash and malabar gourd in one garden. 

The three species will not cross and will allow you to grow three different squash varieties in one garden space.  

Alternatively, plant a zucchini variety, kuri squash and figleaf gourd in one garden, with no risk of cross-pollination.

Last year, I planted Georgia candy roaster (C. maxima) and Delicata squash (C. pepo) in one raised bed. It provided us with an abundance of delicious squash, and the ability to save seed to replant again in future.

It’s a very satisfying process to save seeds from your favourite squash plants.  Before composting your unused squash seeds, consider saving a bunch to plant again in the future.  It couldn’t be easier. By doing so, it will supply you with an abundance of seed for future planting.

Happy Gardening!