Back to seed saving!
I was going to do a post about saving squash seed in October but I just got a customer question about it yesterday so I'll move it up in the queue!
The method you use to save squash seed sort of depends on what you plan to use it for. Ask yourself: Are these seeds just for me to replant next season? Am I planning to give these to a seed library or distribute to friends and family? Am I saving seed on contract for a seed company?
For homescale seed saving then you can decide how clean you need the seed to be but for contract seed saving you will definitely need to clean it well.
Winter squash seed is ready for harvest when the squash are ready to eat. These are squashes like butternut, acorn, sweetmeat, hubbard, spaghetti etc. Summer squash seed like zucchini and patty pan are ready for harvest long after they are nice for eating. They become huge and the rind should be hard enough to pass the fingernail test.
The fingernail test: Press your fingernail into the skin of the squash. It should have a hard time making a dent. If it is soft the squash needs to sit on the vine longer. Both types of squash, when saved for seed, can sit on the vine for quite a while. In fact, even after harvest it is beneficial for the seed to store the squash somewhere cool for several weeks to even months before opening for seed harvest. The seed will continue to gather vigor from the squash during this time.
When you determine that a squash is ready, the process is quite simple. Cut it open and scoop the seeds and pulp into a bowl or bucket. If you are only doing one squash in the kitchen then it can be pretty easy to just wash off the seed in a colander and then dry the seed on a ceramic plate indoors or on a screen in the shade.
If you plan to do several or several hundred at once then you may need to scale up your operation and hold a Squash Smash. On our farm we often clean 100-200 squash in a day and invite friends to help and then take home any edible flesh left over from the cleaning. Pigs and cows also love the leftovers!
For a mass cleaning the process is similar.
1. Cut open and scoop the seeds into buckets. Then we add an additional step.
2. Fermentation. Add water to the buckets of seeds to make a seed soup. Leave this for about 2 days somewhere warm and shady and be sure to stir a bit.
3. The seed pulp will break down and now you can easily spray the seed through a screen or try water winnowing. Unfortunately squash seed doesn't always sink- sometime all the good seed floats. This makes the separation process harder.
If the seed sinks you can simply pour off all the pulpy water several times until you end up with clean seeds. If the good seed is floating then scoop it off onto a screen that is a bit smaller than the seed. Then spray it with a strong jet of water to give it a final clean.
4. Dry your cleaned seed on a screen in a warm shady place with good air circulation. After a few days transfer to a paper bag and bring indoors to keep drying. When the seed snaps in half when bent it is ready for your final storage: cool, dry, dark and airtight.
When saving squash seed remember that squash can cross pollinate easily in your garden. There are three main species and you can grow one variety of each at the same time while maintaining pure seed stock.
Cucurbita pepo- most summer squash, acorn, spaghetti, many pumpkins, delicata
Cucurbita maxima- sweetmeat, hubbard types, some pumpkins
Cucurbita moschata- butternut types
This means if you grew a zucchini and a spaghetti squash in the same garden the seeds will likely be crossed and if you plant those seeds next year you may or may not get zucchini. The solution is to choose ONE variety from each species to plant in your garden if you also plan to save seeds.
Squash you buy at the farmer's market are usually NOT suitable for seed saving either. They are often hybrids and will not produce true to type seeds. The farmer has also likely grown other squash of the same species nearby and the seed is likely crossed.
Lastly- Remember to select the best squashes for saving seed. If you have off-types or mold then don't save seed from those. When saving seed it is important to always select for the traits you want to see in future generations!
I hope this information helps and that you give squash seed saving a go this fall. Let me know if you have any questions!