Oilseed Pumpkins

Winter 2012-2013
‘Gleisdorfer’ oilseed pumpkin
‘Gleisdorfer’, one of the oilseed pumpkins Bonsall trialed last summer. Photo by Will Bonsall.

By Will Bonsall

We usually class pumpkins along with other succulent vegetables; however a particular type of pumpkin is much more nutrient-dense, in that it is an oilseed, like sunflowers, sesame and peanuts.

For centuries, Eastern European farmers have raise pumpkins for the seed from which quality oil was pressed. This served as a vegetable oil where olives could not be grown. Around 1870 an exceptionally useful trait arose: a cluster of related genes causing a highly reduced testa, or seed coat: no hulls! This made pressing oil easier (naked seeds contain 40 to 50 percent oil) and created a nut-like treat suitable for eating out of hand, raw or toasted.

As kids we always scooped the seeds out of our Jack-o’-lanterns, salted and toasted them for a fun snack (certainly no worse than the green apples and raw rhubarb we used to sprinkle salt on and then gnosh). But we were kids and paid no mind to those white bits of pumpkin seed hull that caught in our teeth – although we might have tired of them quickly if anyone had tried to make us eat them. Now I incorporate pumpkin seeds into main meals and no one complains, because the hulls are gone. Most important, we can grow our own.

Today many varieties of hulless pumpkins exist, all Cucurbita pepo (along with other pumpkins, various summer squashes, spaghetti squash, delicata and acorn squashes), most of which I consider inferior for winter fare, compared with Cucurbita maxima (buttercup, hubbard, kuri …). Some folks have asked, as have I, wouldn’t it be great if there were a hulless maxima, with dry sweet flesh and the naked seed trait? No such luck. I believe the two species are too remote to make any such cross by any “moral” (non-genetically engineered) means. So I grow both, each for its own specific use, with the assurance that seed purity will not be an issue.

Bonsall cucurbits
Some of the many varieties in Will Bonsall’s Cucurbita pepita trials. Photo by Will Bonsall.

Growing Pumpkins and Squash

Much of what I suggest about growing pepitas could apply to any kind of pumpkin or squash; my method for growing all of these is a bit unorthodox.

Pumpkins cannot be planted outdoors before the last frost, but that leaves my ground bare and unproductive from snow-go to Memorial Day, which always struck me as intolerably wasteful. Couldn’t I plant some cold-hardy crop before the pepitas, something that could at least build the soil, or better, be left as a mulch for the pumpkins?

I settled on oats, sometimes mixed with field peas, as the best early cover crop for this situation. I sow them as soon as the ground is bare, not always waiting until it is dry enough to be cultivated, but just raking or tramping the seed in so that birds can’t find it. The oats are several inches tall when I start to chop them in, a week or so before I plant the pumpkins. Even then I don’t chop them all in – only those where I’m actually going to plant pumpkin hills (2-foot circles about 6 to 8 feet apart); the rest of the oats keep growing.

Moreover, pumpkins are very heavy feeders, but I don’t fertilize the whole plot, only the hills where the plants will grow. I use a spadeful of night soil compost and a double fistful of wood ash (lime doesn’t grow on my farm) per hill. (Night soil compost – humanure – is not permitted on certified organic farms; see my article on the subject in the summer 2012 issue of The Maine Organic Farmer & Gardener.)

I never direct seed, but start these plants in 4-inch peat pots two to three weeks before transplanting outdoors. This is especially helpful with some Eastern European varieties that like a long, warm season. It also ensures better germination, as the hulless seeds are especially vulnerable to rotting in colder soils. But the greatest advantage is in a trick I learned years ago from a voracious vole. Pumpkin seeds in a furrow are like a smorgasbord for a burrowing critter, whereas widely spaced plants with cotyledons already present do not interest fat-seeking rodents.

With the pumpkin transplants in place and growing, the oats can keep growing alongside them, until the pumpkin plants are ready to sprawl – for me around the 4th of July. By then the oats are at least 20 inches tall and near flowering. At that point I used to mow them and turn them under, but that left ground bare and sprouting a new crop of weeds. Now I flatten the oats to make a heavy mulch by holding a 4-by-4-foot sheet of plywood on edge in the oats and flopping it down parallel to the pumpkin row. I tread all over this before flipping the panel down the row and treading it again, and so on. Then I flatten the areas between the hills so that a thick thatch of succulent green oats covers the entire plot.

The only problem is that the oats will not stay down; they are not dead, and soon try to straighten up in response to sun. To prevent this I cover the oat mulch with a thin layer of any kind of tree leaves; last year’s old pile of matted leftovers will be perfect. The layer needn’t be heavy, just enough to block sunlight so that the oats can die and rot in peace. A sheet of black plastic would work, if that grows better on your farm; I have lots of leaves.

Because leaves will dry out and tend to blow away, I cover them in turn with a thin layer of trashy old hay – milkweed, goldenrod, etc., all welcome – just to keep the leaves in place, like a hairnet. This compound mulch is a formidable barrier to weeds, and the rotting oats create a congenial environment for the rapidly spreading pumpkin roots.

A remarkable side-benefit (this is big) that I never anticipated is that the growing oats seem to completely deter the striped cucumber beetle, which otherwise is a serious pest for me. I don’t know what it is about the oats, but one year I had a cover crop of red clover instead and it didn’t have the same effect.

If at the end of the season the mulch is still sufficiently intact to repress weeds, I may not turn it under even then, but simply reinforce it with more mulch for the following season’s crop. This doesn’t work well with everything, but certain plants – especially tomatoes and cabbage family with wide spacings – can simply be planted through the mulch, which incidentally has now become an excellent source of fertility as well as an herbicide. I know this looks like the beginnings of the lasagna method (layering organic materials to make a thick, permanent mulch), but I’ve never worked it for more than two consecutive seasons and it doesn’t always work then; the whole thing can be ruined by witchgrass.

Soon after the first killing frost levels the pumpkin foliage, I gather the mature fruits under cover. The seed can stand repeated frosts, but the fruits will not store as well, and I want to store them for two reasons: to let me focus on other chores and deal with the pumpkins at my later convenience; and because the seeds improve post-harvest as they continue to draw energy from the placenta.


Pumpkin flesh may provide some sweetness and vitamin A to the diet, but its nutrient load pales compared with that of the seeds. Aside from the fat content, seeds have abundant protein (particularly tryptophan) and lots of trace minerals that are often lacking in other foods, most notably zinc, but also manganese, magnesium, copper and iron. (I try to eat food without over-analyzing it, but I know some readers are really into this stuff.)

Even the oil is exceptionally wholesome, containing a group of fatty acids that includes omega-3. That’s all hearsay – I wouldn’t know a fatty acid if I tripped over one, but they’re supposed to make for healthy prostates; there’s even a pepita variety named ‘Prostate.’ (What’s next? A phytoestrogen-rich soybean variety named ‘Uterus’?) But people of both genders find the nutty kernels delicious, and they’re also heart-friendly – we all have hearts, right?

You may also read elsewhere that the people of ancient Troy fed pumpkin seed to their young men to ensure sexual virility – don’t believe it. I suspect the whole Trojan thing is a subliminal link; in fact, the Old World didn’t know about pumpkins before 1492! (Jack-o’-lanterns were originally carved from turnips.)


A few supposedly multipurpose pepita varieties are offered. I call these SAK (Swiss Army Knife) varieties – e.g., the screwdriver snaps off, the scissors won’t cut toilet paper, the spoon spills everything. The only part that really does what it’s supposed to is the corkscrew. (Trust the Swiss to know their military priorities.) In my experience, the SAK pepitas tend to be rather small for spook carving, mediocre as pie filling and not completely hulless. That last I consider their greatest defect, as that is my main objective.

Plant breeder Brent Loy of the University of New Hampshire identifies four degrees of hullessness, given that the hull is genetically reduced to a flimsy membrane that is easily sloughed off and blown away. For toasting and eating out of hand, the intermediate types might be acceptable, but pepitas have far more potential than just as a snack food, and those uses require fully hulless varieties.

In the past I have mostly grown ‘Lady Godiva’ (naked seed, get it?), which Loy rightly criticizes for its irregular, sprawling habit, hogging much space relative to seed yield. His breeding work has focused on developing a more compact bush habit in order to increase planting density, and for smaller, more numerous fruits so that the plant diverts fewer photosynthates to producing flesh. This is a very useful project for amateur plant breeders – and if you wish to jump into pepita breeding, know that the naked seed trait is maternal and recessive, so crosses must be made on the hulless parent (assuming only one is hl) and then backcrossed to recover the hulless gene.

Roy Curtis at the University of Connecticut developed a number of promising lines which, sad to say, are preserved at the USDA collection at Ames, Iowa, where they were grown out in block-plantings for pollination control, which is to say, no control at all, so they might as well have been thrown away.

The original or Styrian types have found some popularity here, but I have some issues with their flavor. The dark green seed is large, brittle and packed with fat, but that dark color, probably from tannin, seems to impart a rankish taste that I find slightly off-putting. I’ve learned that the taste is not a problem for the consumers of those varieties, because they’re strictly for oil pressing, which I suppose leaves the coarse taste behind. Indeed, one of those strains that I trialed last summer (‘Gleisdorfer’) was quite acceptable. The pumpkins from ‘Steiermark’ are generally quite large and late – I’ve never seen them turn yellow.

Among my pepita trials from Eastern Europe and Turkey, I found a couple of accessions that seemed to have a trait I was not expecting: tasty flesh! I was “gutting” for seed and noticed a couple of fruits had denser yellow flesh than the others, so I tried steaming and eating some. Knowing what a pepo-bigot I am, you will perhaps take me seriously when I say that some were more than edible – I mean downright palatable, to the point of freezing 10 pounds of mashed flesh, which the family enjoyed during the winter.

I also discovered that those large tasty fruits may have a further use. The shells were so tough I had to open them with an axe, and while scraping out the steamed flesh, I found that the outer layer, the very thick “skin,” was hard and woody. Thinking of spaghetti squash, whose gourd-like shells can be dried and used as serving bowls (perhaps for toasted pepitas?), I wondered about these hefty pumpkin shells, which reminded me more of monkey pod wood. If Peter Pumpkin-Eater had put his wife in one of those, he might indeed have “kept her very well”! By the time I had discovered these traits among the busted shell fragments, it was too late to identify which varieties had the combined traits; however I have about three prime suspects and I hope to explore them further and introduce one or more to the American seed trade.

Fedco’s Heron Breen has been trialing pepitas with an eye for fruit storability, as he prefers to remove seeds from the shells as he uses them (especially useful if you also intend to use the flesh). At some point, the seeds may sprout in the fruit cavity; barring that, as I mentioned, seed quality may benefit during the post-harvest period.

Eating Pepitas

Much as I love pepitas as an out-of-hand nibble (they puff up nicely when lightly toasted, but be sure to stir them constantly during toasting), I use them mostly as an oily meal, much as I use sunflower seeds. Sprinkled on steamed veggies, the meal imparts a taste and texture reminiscent of both butter and cheese (at least to one who hasn’t tasted either in 40-plus years). To “dry-fry” veggie-burgers or home-fried potatoes without extracted oil, I preheat a cast-iron pan and sprinkle pepita meal on the surface, just before adding the burger mix or whatever (hurrying, lest the meal scorch; nothing refined here).

To make an exquisite salad dressing (sans extracted oil), I heat a vinegar brine and add enough pepita meal to make a thick cream. While still hot, I may add some dried dill weed, parsley, chives, paprika or whatever else goes with the particular type of salad. Allowed to sit in a cool place for a day, the dressing only improves. To me it evokes Green Goddess.

Also, a dip made with pepita meal (raw or toasted), miso and salsa will likely be well received – otherwise adjust your guest list to include people with better taste. In fact, I’m hard put to think of any entrée, salad or dessert that cannot be improved by the addition of some pepita seeds in some form; the only limitation is how many you can grow.

About the author: Will Bonsall lives in Industry, Maine, where he directs Scatterseed Project, a seed saving enterprise.

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