On Maintaining Purity of Squash Varieties

[macmex]

Folks, I removed my older post on hand pollination of squash and am replacing it with this one.
I can't finish right now (too many irons on the fire) but I will add to this thread soon, illustrating both how to identify squash species and how to hand pollinate for purity of seed.


This topic frequently surfaces when gardeners converse, and, though there is much more information available, on it, these days, still, there are many who have hardly gotten “their feet wet” in this area of seed saving. Though there are some exceptions and caveats which might be made, I want to give you the most straightforward explanation, which, for most people, will give nearly 100% success in saving pure seed. 

First of all, I would like to make the point that the terms “squash” and “pumpkin” are pretty nearly synonyms. In most parts of the United States “pumpkin” conjures up visions of a round fruited squash, which is usually orange. But the fact is, that we have the word “pumpkin” simply because we borrowed it from the French, who borrowed it from the Greeks. Sometimes we refer to “squash” because we borrowed term from Native Americans. Frankly, though many have opinions about which ones ought to be called squash and which ones ought to be called pumpkins, the terms are interchangeable. I prefer to call them all squash, simply because doing so causes the public a little less confusion than if I called them all pumpkins. So, keep in mind that any distinction between squash and pumpkins is artificial. 

If one wants to make some meaningful distinctions between types of squash, then it is good to refer to their species. In most of the gardening world we know four species of squash. There are, in fact, some other species of cucurbitae (The genus, or larger branch in taxonomic terms, is called curcurbita.). But what is commonly known and grown in the United States are four species:

cucurbita pepo: This species is by far the most well represented in gardening catalogs. It includes the well known Jack Lantern pumpkins, zucchini, yellow crookneck summer squash, acorn squash and even some small ornamental (unedible) gourds. c. pepo squash tend to grow quickly and are generally known for being able to kind of “go on hold” during a bad drought and then, with the arrival of rain, quickly recover and produce. Most summer squash (squash picked green and immature for for vegetable use, come from this species.

cucurbita maxima: This species hails from the high country in South America. Garden varieties which are from this species are Hubbard, Delicious, Cinderella Pumpkin, Turk’s Turban, Big Max, Banana squash and all of the giant pumpkins used in competitions for the largest “pumpkin.” Many of these are of the very highest eating quality. But, alas, they are the most prone to insect damage (especially vine borers) of any of the squash. Squash from this species can generally make a fast crop. They set and mature fruit rapidly. The stem connecting to the fruit is distinctive, being really fat and not as hard as the c. pepo or c. moschata varieties.

cucurbita argyrosperma: By far, the most common garden varieties from this species are what are known as the “cushaw” squash, though, there is a golden cushaw, which is a c. moschata. These are big crook necked squash. This species used to be called c. mixta.. So, if you see a seed listed this way, know that it’s the same thinig. This species is known for extreme insect resistance, though it is not known for being of the highest quality for eating. I like the ones I’ve grown. 

cucurbita moschata: Originally hails from Central America. This species is best represented in the supermarket by butternut squash. Others commonly grown by gardeners are cheese pumpkins, Dickinson pumpkin, cow pumpkins, Tahitian Melon squash and Seminole pumpkin. I grow Old Timey Cornfield Pumpkin, which is also a c. moschata. Squash from this species tend to love heat, resist insects (especially the squash vine borer) and have pretty good eating quality. Their down side is that they do require a bit more time to produce than do the c. pepo and c. maxima types. Yet, in really hot climates, this and c. argyrosperma are the preferred species to grow.
Now, here’s the first thing to note when thinking about saving squash seed. Any varieties from within the same species can freely cross. Squash are mainly pollinated by insects, especially bees. So, for instance, if you grow acorn squash and zucchini, which are both from the c. pepo species, they are going to cross unless you do something to prevent it.

The first possibility for preventing the crossing of squash varieties is to isolate varieties. I think, sometimes ¼ mile might be enough distance to effectively produce pure seed. But in hot, dry places, and during times of scarcity, bees may forage much further, in search of nectar. The stock distance, generally followed, for producing pure seed through isolation is a mile. If you have a mile between your garden and any neighbor growing squash from the same species, then, you’ve got it made. You can produce a whole lot of pure seed!

But don’t forget, this means you ought not to plant more than one squash of each of these four species, if you want pure seed and you depend on isolation to keep your varieties from crossing. As a general rule, these species can be planted side by side and they will not cross with one another. And, forget the stories of squash crossing with cucumbers or cantaloupe. They don't. People who report having seen this usually observed a cross between varieties within the same species, such as, for instance, the crossing of a ornamental c. pepo gourd with an acorn squash, which would produce an unusable product. 

The other way of producing pure squash seed is to hand pollinate. And, by “hand pollinate” I mean that one not only manually transfers pollen from stamen to the pistil, but also protects both from contamination, both before manually pollinating and afterwards. 

Hand pollination is much easier to do than it sounds. In a future post I intend to give an illustrated guide on how to hand pollinate squash.

[heavyhitterokra]

George,

Do you remember the trouble I had with my straight neck yellow squash last year?

They grew a thick, hard skin that was likened to that of an ornamental gourd. They had tiny bumps on the skin like an ornamental gourd. They dried to a hard, hollow shell like an ornamental gourd does. They had hard shelled seeds inside while very young and were never tender even as budding squash still having the blossom end intact.

They kept like no other, having an impressively long shelf life (very uncharacteristic of straight neck yellow summer squash).

Trouble was, they were nearly inedible when fried, because of the thick, tough skin and the crunchy seeds inside.

I remember you commenting at the time that you believed they had crossed with some other variety... I have saved my own seeds so long that I thought maybe I had let them cross with the gourds that I grow separate from my garden for Autumn decor.

However, recently, I found the empty seed packets that I had tucked into my garden apron pocket while planting last year. They were seeds I had bought on sale at the end of the 2015 season for 10 cents per packet. They were not seeds I had saved.

That raised a question in my mind about the origin of the seeds in the packets, but I didn't really dwell on the question for long and it soon passed from my mind...

That is, until this past Sunday afternoon, when my sweet Daughter-in-Law brought straight neck yellow summer squash all the way from her own garden in Bristow, to cook us a special dish at our house. She worked on it diligently while my Son and I were smoking chicken wings, Boston butt roast, and bologna for our lunch and supper. When she served the dish, the skins on the sliced and fried squash were thick and tough, and the seeds were crunchy. When I took the scrap stems and waste from her cutting board to feed the hogs later that afternoon, I noticed the squash she had brought with her had the very same characteristic 'bumps' on the skin as the squash I had grown last year.

The skins were thick, tough, and hard to the touch like an ornamental squash. They made a sharp,"tack, tack" sound when I tapped them on the table, rather than a very dull thud that a tender straight neck yellow summer squash should make. A squash that should have sounded like a tender zucchini sounded just like an ornamental gourd when tapped on the table top. I also noticed a green rind around the seed pocket very similar to what you would find if you cut open an unripe gourd.

This was troubling to me, as my Son and Daughter-in-Law live in Bristow, Oklahoma and buy their seeds half way across the State from where I bought mine in Tahlequah, Oklahoma. That means these seeds are widely distributed and are possibly growing in more than one State.

Has anyone out there other than we experienced similar results when planting store bought STRAIGHT NECK YELLOW SQUASH in the past two seasons?

If so, please let George and I know. It might be that we as a seed saving group need to focus and really start working on developing a true line of yellow squash seeds that have thin, tender, smooth skins, tender seed hulls, and a very short shelf life. (You know... like straight neck yellow squash used to be as recently as three short years ago).

[macmex]

Yikes! Somehow I overlooked this for years!

Ron, plant breeders have crossed certain yellow squash with ornamental gourds, in order to breed into them some borer resistance. They are fine as long as they are picked young, but when they start to get older, they often do become more like a gourd than a regular summer squash. I believe that's the reason why your daughter-in-law's squash's skin had that quality.

[john]

I have never run into that with summer squash. Perhaps if I let them get to big they will get tough. But I assume that is not what you are talking about. On a side note about crossing squash, I use an interspecific cross called Shintosa Camelforce for some of my watermelon rootstocks. It is a Cucurbita maxima x Cucurbita moschata cross. It allows me to grow really nice watermelons organically. Johnny's selected seeds sells an interspecific cross called 'Tetsukabuto' it is also used as a rootstock. Although many do raise it for eating especially in Japan. (they are sterile, so they have no viable seed in the squash)

[john]

www.johnnyseeds.com/vegetables/squash/winter-squash/tetsukabuto-f1-hubbard-squash-seed-3578.html?cgid=winter-squash

[macmex]

I've heard of a number of crosses between c. moschata and c. maxima.  That's really interesting. What problems do you have if you grow watermelon on their own roots?

[john]

Fusarium can be a big problem, especially if you aren't giving five year rotations in the soil. The squash rootstock is also better at growing in cold soil and is more vigorous. Lagenaria gourds are also a good fusarium resistant rootstock for watermelon. Most growers use a variety called 'Rampart' . I use bushel gourd.

[macmex]

Okay, I'm going to try and replace my earlier posting on hand pollination of squash (and pumpkins). As you can see from what's been posted above, there are different species of squash/pumpkin. In general terms, these species don't cross. Yet I've heard of c. mixta (a.k.a. c. argyrosperma) crossing with c. maxima and other intra species crosses which can apparently be forced to occur. I believe, as long as one has several plants flowering of a given species, one of these intra species crosses is unlikely to occur. So, if one has a mile of isolation distance from others who are growing squash of the same species, then, no hand pollination is necessary to maintain purity.



You can imagine how difficult it is, for the average gardener, these days, to meet this requirement. So, to be safe, hand pollination is a good deal.

[macmex]

To hand pollinate, one needs access to at least one plant. Squash plants, as with all cucurbits that I know of, produce both male and female flowers. These flowers are called "incomplete flowers,"  as no single flower on the plant has both male and female parts (pistil and stamen). Hence, without some form of pollination, a squash plant would never produce seed. Generally, this pollination is provided by insects. However, it can be accomplished by other means. Hand pollination is simply the task of taking pollen from the stamen (male part of a flower) and smearing it on the pistil (female part of a flower). This can be done without  assuring purity by not covering the flowers before and/or after hand pollination.

  Here's a photo of a male flower. Notice the stamen is smaller than a pistil and it's covered in pollen. (It will only have powdery pollen on it when fully mature, not the day before.)

"Squash flower" by tdlucas5000 is licensed under CC BY-NC-SA 2.0



Here's a photo of a female flower. 


"Balcony garden 2014012" by caligula1995 is licensed under CC BY 2.0


"Balcony garden 2014012" by caligula1995 is licensed under CC BY 2.0
"Squash fruit forming" by marc e marc is licensed under CC BY-NC-SA 2.0

In order to begin the process of hand pollination for pure seed, it's important to start the afternoon before the flowers to be used are due to open. Squash (and pumpkin) flowers open at dawn and are generally pollinated and wilting by noon. FORGET ABOUT TRYING TO BEAT THE BEES by getting out there at dawn. They will be flying even while you're still tempted to use a flashlight. If you go out any earlier, the pollen on the male flower won't be ready. So you need to prepare your flower buds the day before.

Don't try to prepare the flower buds before 2 pm, the day before they should open. To do so is not only extremely difficult, as they won't color up before then, making it nearly impossible to tell which ones will actually open on the following day, but also, taping a flower shut any earlier than this is likely to cause it to abort and fall off the plant.

Preparation for hand pollination of squash begins the day before the actual hand pollination will occur, between 2:00 pm and dark.

[macmex]

Preparing flowers for hand pollination of squash

Remember: This needs to be done between 2:00 pm and dark, the day before the flowers are due to open.

Varieties differ, but one can generally tell what flowers buds are going to open the next day, because they swell and take on color. Some varieties are harder to tell than others, but once you get familiar with a given variety, it's pretty easy. 

Here's a photo of two mature buds, which will flower the next day. This is an acorn squash, which "shows its colors" well.


Notice that there's a mature, male flower to the left, a mature female flower in the middle and an immature female flower to the right. That immature female flower will probably be ready in another 24 hours.

To prepare a flower for hand pollination, one simply fastens it closed, so that it cannot open in the morning. I prefer to use wide masking tape. It's easy and it's biodegradable. I've used plastic tape and duct tape, but then I have to be careful to pick up the pieces after I'm done, as it'll be in my soil for years, if I don't. I've heard of people using clothes pins and other methods to fasten a flower shut. But I'm doubtful. I first learned to hand pollinate in a location in N. Indiana, where the bees were frantic to get to the nectar and pollen. Even the tiniest crack, left open, would incite them to fight their way in, and, in the process, contaminate my seed.


Here's an image of a male flower, taped shut in preparation of hand pollination for the next morning. I am especially thorough in taping the male blossoms, as I will literally rip all the petals off of it, when I use it: no need to be careful about untaping a male flower. And, YES, it's important to tape the male blossoms. If one uses an untaped male blossom, there is likely to be foreign pollen in it, from insect visits, thus defeating the purpose of hand pollination. When I tape the female bud, I try to tape more towards the tip. That way, in the morning, I can remove the tape, and even if it tears a petal, it will still leave enough intact for me to tape it shut when finished.

In the morning, I try to get out there fairly early. It helps if bees aren't already in a "holding pattern," looking to get into my prepared blossoms as soon as I open them. I've actually had a bee dive right over my shoulder and into a blossom, as I removed the tape! With the male blossoms, I simply pick them and carry them with me to the female blossoms needing pollination. When I'm at a female blossom which needs pollination, I tear the petals off of the male blossom, turning it into a little "paint brush," for the procedure. Once the petals are removed, I find that the bees aren't very likely to be attracted to the male blossom.


I can use a squash leaf as a handle shelf, to hold my pollen "paint brush" while I open a female flower. Once the female flower is open, I quickly "paint" the pistil (female part in the center of the flower) using the "paint brush I made, using the male flower. If I have enough male flowers, I'll even use two.


Then I reseal the female flower, using masking tape.


Here's what a finished, hand pollinated squash flower looks like.


Twenty-four hours later the petals on this female flower will be showing signs of wilting. Within about three days, I'll know if this pollination will "take." Some blossoms, as pictured below, don't "take." They wither and die. This is not due to poor technique. Squash plants don't set fruit on every flower.

[macmex]

Once I've finished a hand pollination, I usually return to it about three days later. By that time the little fruit will either be growing, or it will be fading, and about aborted. If it's growing, I will use a nail or sharp object to make a mark in the skin, something which will tell me, at harvest time, that this fruit contains pure seed. I only save seed from marked fruit, never trusting my memory about whether a given fruit was hand pollinated.

Here's a photo of a squash fruit which has been marked for a couple of days.



Notice that the petals have witherd and the tape is about to fall off.

Here's a picture of a marked squash which is nearly mature and ready to pick. The mark grows with it.



Let the hand pollinated squash mature on the vine for at least as long as it takes for the skin to become so tough that a fingernail won't puncture it. Ideally, one should then leave the seed in the squash itself, for another month, as the seeds will be drawing nutrients from the fruit, during this time. This extra time produces stronger seeds which will store and maintain viability longer than seed which was harvested prematurely.


 

[heavyhitterokra]

Thanks, George,

That was very well written and well laid out.

I enjoyed the reading on this stormy night, after being shut up in the house all day because of heavy rains.

[macmex]

Bon, I don't have any documentation to prove it, but I suspect that the seed is best from about a month after the pumpkin first reaches maturity until perhaps 6 months after it reaches maturity. This is only a "gut instinct" on my part, but I suspect the seed ages, even when moist, inside the squash. With really old squash I've found the seed sometimes starts to germinate.

[rdback]

Great read; very informative.

Well done George!