Thursday, August 11, 2011

Cucurbit Sex

In the summer garden, the melons, squash, cucumbers are the lookers. They've got sexy tendrils and bright, brassy, bosomy blossoms. They're such vibrant growers that they tumble all over each other and everything else, climbing trellises, walls, the ground, into the lemon tree. Unstoppable. Funny. These plants are the whole package.

If you're as entertained by cucurbits as I am, perhaps you'd like to try your hand at saving seed of your favorite varieties.

Identifying species: If you want to save seeds from your cucumbers, melons, squash, and pumpkins, you must know what species you have growing in your yard. If, among squash, you have only a butternut (a C. moschata cultivar) and a pattypan (a C. pepo cultivar), you should be able to plant seeds from the saved fruit and expect the plants to grow true. But, if you're growing a Hubbard and a Banana squash, both C. maxima cultivars, it is likely that pollen has crossed successfully between them and the seeds will not produce an exact replica of either parent. In short, like any other genus, varieties within the same species easily cross, while those of different species only very rarely do so. So, in order to keep track of what species you have, I've written a brief description of of the more common cucurbit species below.

Cucurbita pepo: All the orange carve-able pumpkins are C. pepo, but so are zucchini and pattypan. The basic identifying key is that the stem where the plant attached to the fruit tends to be very ridged with five distinct ridges. The leaves and stems tend to be very prickly.

C. maxima: The leaves of C. maxima are among the largest and are usually an even green. The fruit-to-stem attachment on C. maxima is easiest to identify: the stem is round (not ridged), it isn't enlarged against the fruit, and it is less strong. C. maxima can be just about any color, but they aren't usually bright. In other words, an orange C. maxima will be a soft, rusty pinkish orange instead of a Halloween C. pepo orange. They can be steely blue, pink, deep green, etc. In the maxima species, I am growing Uncle David's Dakota Dessert and an unidentified variety that I brought back from Argentina.

C. mixta: The fruit of mixtas (aka cushaws) usually aren't terribly tasty, but they have huge seeds with distinct, silvery rims around the seeds. These varieties are often grown for their seed alone. The fruits looks similar to washed out moschatas. I don't grow any mixtas.

C. moschata: The leaves on C. moschata plants often have silvery spots. Also, their fuzz usually is softer and less prickly than either pepo or moschata. The place where the stem meets the fruit is smooth and has five points that flare out against the fruit. The fruits are most often pinky-tan colored, a la its most famous cultivar, Butternut. However, moschata fruits can occasionally be dark green or green and ivory mottled. I grow Seminole, a historic moschata.

Pop quiz: Which two species are in this picture below? Which is which?

Cucumis cucumis: Cucumber! Easy to identify. This year, I'm growing Poona Kheera.

Cucumis melo: All melons (except watermelon) and a couple "cucumbers" (Armenian cucumber and Bari cucumber). This year, I'm growing an old favorite, Boule D'Or, two new-to-me varieties, Eden's Gem and Petit Gris de Rennes, and of course, Armenian cucumber.

Citrullus lanatus: Watermelon! Once again, easy to ID. This year, I'm growing Orangeglo.

Preventing cross pollination: The easiest way to prevent cross pollination is to grow only one of each species. While there are cases of species crossing (the mules of the cucurbit world), those are the exception rather than the rule. If you're like me, it is really hard to contain yourself to just one variety of each species. I know that I will never have a garden with just one kind of melon in it. One kind of melon! That's practically starvation.

If you choose to grow multiple varieties within a species, the most practical means of preventing cross-pollination is mechanical isolation and hand pollination. To do this, walk out to your garden and look at your flowers. Make sure you can identify male and female flowers.

This is a male squash flower. It has no immature fruit at its base, but it does have a pollen-rich anther in the center.

This is a female squash flower. It has a large, irregularly shaped stigma and an immature fruit at its base.

This is a male melon flower; melons, watermelons, and cucumbers have nearly identical flowers. The anthers are low and tucked into the base of the flower.

This is a female melon flower. It has a stigma that can easily collect pollen off the insect pollinators.

Now that you know what you're looking for, find several just-about-to-open female and male flowers of the variety you want to keep from crossing with any other variety. If you can, choose flowers from more than one plant in the same variety because that will help keep a healthy gene pool in your resulting seeds. Tape the flowers shut.

The next morning, when the flowers would open with the sun, cut the male flower off the plant, carefully remove the tape from it, and gently tear the petals off, leaving the anthers exposed. Remove the tape from the female flower, coax the petals open, and insert the male flower into the female flower, shoving the anthers up to the stigma. After you see the stain of pollen on the stigma, cover the female flower with something to protect it from any other creature that may want to crawl around in it. I use poly mesh bags, the kind that some people use for wedding favors.

Once you're sure the young fruit is growing (see below), identify it with a ribbon or stretchy tree tape to remind yourself later that this is a fruit with pure seed.

Protecting fruit: Not every fruit will "take," no matter how carefully you work to pollinate the female flowers. It's easy to determine which of the female flowers are truly pollinated, because they'll take off growing almost immediately. If you have lots of pillbugs and similar in your yard, as I do, protect the growing fruit by placing a plate, brick, or other object underneath it, keeping it off the soil.

This is a female fruit that the plant will abort. Notice that it is yellowing towards the blossom end. The stem is also anemic, telling me that this fruit won't develop further.

Saving seeds: Now that you've worked hard to protect your varieties from cross-pollinating, it is important that you save seeds from mature fruit. It is easy to tell when seeds in a melon or watermelon are mature, because they're ready when the fruits are ready to eat. However, the seeds in a zucchini that you'd eat aren't ready to save; the fruit must stay on the vine until the fruit is bloated, like an oddly shaped pumpkin, and hard, so hard that you can't pierce the skin with your fingernail.

And cucumbers that are ready to collect seed from don't even look like cucumbers anymore. Here is a Poona Kheera cucumber that still isn't ready to harvest for seed; the skin needs to toughen more, to feel like a ripe melon, before I remove it from the vine. Sometimes cucumbers will even split open and reveal their mature seeds.

When you do remove the seeds from a fruit you've saved for seed, scoop the seeds out into a colander, give them a quick rinse, then spread them on a cookie sheet (if you like, you can line it with parchment, but that really isn't necessary) to dry thoroughly. Once completely dry (and I mean completely, totally, very, very dry), store in a cool, dark place.

Cucurbit love. I've got it bad. Maybe you do too?


HelenB said...

This is all good info. It seems to me that additionally it would be helpful to mention that most cucumbers ripen to an alarming orange-yellow color when they are mature enough to collect seed.

Farm said...

great post!

Carrie said...

I kept writing and writing, telling you all about my experience with winter squash and melons this year. Then I realized that I am just trying to say, “yes! I have Cucurbit fever too!” I garden in a tiny community garden plot in DC. Normally I just don’t have the room to grow such things, but my neighbor is away all summer and loaned me her plot, so I decided to give them a try. So very glad I did. Great post here. I’ve saved it to reference if I ever have the extra room to grow cucurbits again. I hope I do…

Carrie said...

I have to add, I loved this experience enough that I am thinking about sacrificing a couple of tomato or pepper plants next year to make room for a winter squash or melon, which I will grow up a trellis as I am doing now. Do you have any opinions on what has a smaller vine, or works best on a trellis, or would fit into a little community garden plot? Thanks!

Christina said...

HelenB: Yes! The cucumbers no longer look like cucumbers, but some kind of strange, leathery party balloons.

Farm: Thanks!

Carrie: What did you grow this year? Do you have any varieties you fell in love with? And, about growing up a trellis, just about any smallish-fruiting melon will work well on a trellis. My two reigning favorites are Boule D'Or and Collective Farm Woman. Charentais has been hit or miss for me. Crane was insipid, Tigger was horrible tasting, Noir de Carmes was okay. I'm have very high hopes for what I've got this year. Another option would be a small fruited C. maxima, like Uncle David's Dakota Dessert or other buttercup type. The vines on the smaller fruited ones tend to be less vigorous viners than the larger fruited cultivars. I've grown them up single trellises with loads of success.

michelle said...

I do have curcurbit love! But I have to admit that I've not gone to the bother of saving seeds. This year it has been enough of a challenge to save enough of the crops from the rodents to meet my rather modest needs. I think my local rat populatioon rivals your slug and snail population this year.

Thanks for all the interesting and useful information about curcurbits.

Carrie said...

The melo is called ‘Green Nutmeg’ and so far I love it. It has 9 fruits and appears to be setting more, none of which I have hand-pollinated. They should be ready in a couple of weeks and I cannot wait to try them. ‘Boule D’Or’ is one I was thinking about for next year. The pepo is ‘Sugar Pie Heirloom.’ I tried to pick a smaller variety but I have not had great success, which could just be because of the extreme heat/humidity in DC this summer. Trying to hand-pollinate was like painting slip on a piece - You’re a potter, right? I am too. - as the pollen was so damaged by the weather. Still, the idea of growing a pumpkin just sings to me. Something about them speaks of bounty, and I love that feeling.

It’s exciting to be planning something new in my garden. Thanks for the advice!

Anonymous said...

I'm growing photo #3, but had no idea what it was or what to do with it. But I like it's comic shape.

I'll bet I know who gave me the seeds...

Gina said...

Thanks. That was a very informative post! I haven't tried saving seeds from the cucurbits yet - but I think that would be a fun project next summer.

If you ever have any extra seeds you would like to trade for let me know - I tend to like the more unusual varieties.

Anonymous said...

genetics 101!

Love it!

Christina said...

Michelle: I'll take my slug/pillbug attack over your rats. ARGH! It did make me laugh to think of them as little opium addicts, munching on poppy pods.

Carrie: Amy Goldman swears by "Fordhook Gem," a descendant of Green Nutmeg. Let me know how Green Nutmeg tastes when you cut one open. I'm really excited about Eden's Gem, a melon along the same lines as Green Nutmeg/Fordhook Gem: a green cantaloup. I hope it tastes as good in real life as it does in my imagination.

AH: I may have given you the seeds--I can't remember. I love these pattypans cut into chunks and steamed with butter and salt. They're also great on the grill. Do anything with them (in the kitchen!) that you'd do with zucchini. They're goofy looking fellows, for sure.

Gina: I've always got seeds. What are you looking for?

Whole Larder: Woohoo! I lurve me some science.

the good soup said...

Christina, LOVE the informative post. Question: I feel a little dumb asking, but here goes: if two pumpkins will cross pollinate, is it also possible that they produce a fruit that looks entirely other than they should? Are the two incidents entirely causal?

I planted 3 pumpkins last season: a Kent, a Chioggia something or other and a Provence something or other (sorry, not near my seed collection to remember exact names). One Chioggia plant produced an amazing pumpkin exactly as I imagined it to be: huge and ribbed with dark orange flesh. The other plant produced a pumpkin that was the same colour but completely smooth.

I actually think my question is this: even if I'm not wanting to save seed, do I have to use your method to stop cross pollinating just to keep my fruit looking/tasting right?

Christina said...

TGS: No, you don't need to isolate and hand pollinate to get the fruit that you expect from a plant. The plant will produce the fruit that its genetic coding tells it to produce; cross pollination will not affect the fruit. Cross pollination affects the genetic coding within the seed--you cannot tell by looking if your squash seed is pure or not.

Many cultivars of species have a certain amount of instability. The Marina di Chiogga plant you mention may have reverted to a previous trait or had another irregularity. If you were to save seed, you'd save seed only from plants/fruit that had the traits you wanted and expected. Also, there is another possibility that your seed source may have had some accidental cross pollination happening. That is very frequent, even from very good seed sources. I've bought seeds from the woman who literally wrote the book on seed saving and received impure seeds.

In other words, if you're not saving seeds, you don't need to do anything different than what you're already doing: growing healthy plants.

the good soup said...

Christina, that's great news. THANK YOU! My life's too messy for saving seeds presently. I'd love to in the future.

Thomas Andres said...

I am wondering if you have any seeds of Cucurbita that I could try growing in New York. I am interested in trying any non-commercial seeds, such as ones you collected in Argentina or anywhere else. I will thoroughly document them for you, including photographing them. Thank you