THE BOTANICAL ANCESTORS of our modern spinach–one of the most widely grown vegetables in temperate zones around the world today–were native to the Middle East, around the Fertile Crescent. That’s a place that’s probably very different from the backyard where you’re eager for it to be time to sow a packet of spinach seed, often the first optimistic gesture of a new garden season.

Spinach has come a long way from its point of origin literally and also genetically, but which of the many varieties available today is for you, and when and how can you plant this nourishing green for best success?

I invited Tom Stearns, longtime organic seed farmer and founder of High Mowing Organic Seeds in Vermont, to help me become a better spinach grower—and find my way through the many choices of spinach leaf types, and varieties from heirloom to hybrid. We talked about the oddball reproductive system that makes spinach bolt and other insights, like how among all the vegetable crops it’s the most sensitive to a low pH.

Read along as you listen to the Jan. 18, 2016 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here). This interview is just one of many can-do segments in my ongoing Seed Series (browse them all at this link).

Plus: I’ve bought a gift certificate for High Mowing seeds for one lucky reader; enter to win at the bottom of the page, after the last reader comment.

my spinach-growing q&a with tom stearns

Q. I should first congratulate you: Happy 20th anniversary of High Mowing.

A. It’s strange—I don’t know if it seems that long, or longer. We’ve got a lot more years ahead of us. It has been a great time to think back and share with our customers and our staff some pieces of our history, but the future is what’s most exciting.

Q. And the future includes a new headquarters, and some new land?

A. We’ve been in a lot of rented land and rented buildings as the business has grown over these years, and as a farm-based business it’s sometimes hard to invest long term when you’re talking about somebody else’s place. Of course we’ve left the land we’ve leased better than we found it, but to have our own place to build the buildings we need and the other infrastructure for the farm—it’s going to be pretty exciting.

It’s just a few miles away, so it doesn’t shift things in terms of the communities we’re most connected with, or commutes for our staff. It’s a very, very special property, and it’s a long-term project; it will take many years for us to fully shift over there.

Q. I loved reading about it; it’s so optimistic. I always enjoy reading the welcome letters in the front of the new crop of catalogs, and in yours I have to say this line of yours struck me as a great mantra for all of us to kick off 2016:

‘I ENCOURAGE you to keep working in service to your soil.’

Well-said; I think that’s so important, and I think people forget.

A. Oh, sure. We live humbly on this thin, tiny slice of crust on this earth, and not only are we so dependent on it but I think it says a lot about a culture and a society how they take care of something so basic like that. So unfortunately that points to us not generally being such good stewards of it, but that’s OK; we know how to do it better, and we will.

Q. I appreciated the reminder for all of us.

So let’s talk spinach: I know we want to cover varieties, production, seed production, breeding. I suppose a good place to start is with the physical characteristics, because there is a lot of variety in leaf shape, texture, plant stature.

A. The main things with the leaves: Is it smooth-leaf, is it savoyed-leaf, really wrinkly and folded, or is it somewhere between—which is called semi-savoyed. It’s interesting: There are preferences on the East Coast and the West Coast for these things. Generally the East Coast has always seemed to prefer savoyed, and the West Coast the smooth leaf.

The other issue that has come in is the baby-leaf market—the small leaves that many of us eat now as bunching spinach. The whole plant, or like six plants, with a rubber band around them, like you see in the grocery store—that’s going by the wayside in favor of baby-leaf, individual small 2- to 3-inch leaves.

The baby-leaf growers, almost entirely in California as well, really favor smooth-leaf.  It’s a lot easier to clean, without those wrinkles or folds in there, you don’t have soil or dust getting in. And greens as a food-safety issue—there has been some concern about e coli in spinach and baby-lettuce mix, so those are issues on the cleanliness side. Believe it or not, the shape of the leaf has food-safety implications.

For the home gardener, there are a lot of different benefits to these different leaf types. I prefer the savoyed. I think the texture of the leaf is more pleasurable to eat. There’s more loft to it, when it’s in a salad. You don’t have all these flat leaves kind of laying stuck on each other, like a pile of leaves you rake in your yard, all pancaked onto each other.

Q. With salad dressing sticking them together, no less. [Laughter.]

A. Right. There are issues in terms of insect and disease implications of these different leaves, but that’s less dramatic, I guess. It’s really more of a cleanliness thing, and some personal preference, and maybe some historical and cultural preference issues.

Q. Speaking of cleanliness issues, for the growers who want to harvest and clean it easily, that sort of stature thing I mentioned—some varieties kind of stand up higher than others, too.

A. There is this uprightness, as opposed to being prostrate on the ground. Some of that has to do with the varieties, very clearly; others have to do with how dense you plant it. If you give them a lot of space, most spinach varieties will tend to be flatter. When they’re packed in close together they don’t have the room to do that, so they go up. So yes, it is genetic, and also a little bit how you plant it. [Above, semi-savoyed ‘Butterflay‘ in the field.]

Q. Botanically it’s related to amaranth and…

A. …beets and chard. It’s in the Chenopod family so it has some familiar cousins.  Then you’ve got amaranth, quinoa, lamb’s quarters as a weed that is quite edible and eaten in some cultures.

Q. I mention that because it bears on its reproductive structure…and we’re going to get to how (damn!) my spinach always bolts, and wants to reproduce too soon.

A. Spinach is a wind-pollinated plant. Beets are chard are also wind-pollinated. A big difference, though, is that with spinach you have plants that are female, and plants that are male, and some plants that are hermaphroditic—with both parts.

So that may sound strange, but maybe not so. In most other vegetables, you have a flower that is male, or another flower that’s female in the same plant generally—or you have male and female parts inside the same flower. Those are things that are more different from humans—the spinach is just like us, with separate male and separate female.

You can’t tell that, though, when they’re growing and young and you’re just harvesting the leaves off them. You can’t look at the seed and tell if it’s a male seed or a female seed—and again, when the plant is young, you don’t know. It’s only when it starts to bolt, when it kind of gets into its teenage years, that it starts to show.

Q. You’re making me think of asparagus, when you only see the female plants when they start to fruit and make seeds.

So spinach is wind-pollinated, it has male, female and hermaphroditic plants—so we’ve got the lowdown that way.

In the catalog, as with other crops in High Mowing’s selection, you offer open-pollinated, hybrid and heirloom choices of spinach (besides different leaf types as you mentioned, for customer preference). Why would I choose one over another?

A. We try to find varieties that are improved with the intent for organic gardeners and farmers. Organic gardeners and farmers are facing a whole different range of conditions than a conventional farm, or a garden, or somebody who is using a lot of pesticides or chemical fertilizer. Some of it is fertility-based—more based on compost and the organic matter in the soil, which means the root systems need to be different.

It also may be more around insects and pests—that the plants need to be more naturally resistant to those things, without there being a spray option. There’s been breeding done on both open-pollinated and hybrid spinach, but because plant breeders have figured out how to hybridize spinach and get quite a bit of increased uniformity and vigor and some disease resistance, that has been the predominant way that new breeding has happened in spinach for the last couple of decades.

So this is typical of many different crops, and I know we’ve talked about it before: Once they start developing hybrid varieties, they make a lot of progress, and it comes to dominate the market.

It doesn’t mean that OP varieties wouldn’t also make that kind of progress if they got that attention—but you get what you invest in. Hybrid spinach is predominately what plant breeders have invested in, in part to have people not saving their own seed and instead coming back to them. But really nobody saves their own spinach seed—it’s such a tricky crop, because you need to be in a certain region only to grow spinach for seed.

[Above, spinach seed being harvested in a greenhouse during a High Mowing trial. See the box at the bottom of the page about where spinach is grown for seed and why.]

You’ve got increasingly exacting requirements by farmers, and that’s who drives the breeding—the market for farmers drives the breeding. In many cases the farmers aren’t involved at all, but the seed companies are breeding for the growers, because that’s where the acreage is.

This whole baby-leaf spinach thing has exploded in Salinas and Santa Maria counties in California, and then Yuma in Arizona—that’s where 90 percent of the fresh spinach in the whole country comes from. And that’s where they’re breeding for. The bigger-scale you get the more particular it needs to be: leaf type, leaf shape, disease resistance—it all needs to get dialed right in.

Q. So the product is really being refined to meet the market.

A. Not the consumer market, but the actual producers, the farmers.

Q. Conventional garden wisdom says to sow spinach “as soon as the soil can be worked,” like peas, but is that the ideal moment for direct sowing?

A. Spinach seed can germinate very cold. I have seen some varieties germinate in the upper 30s and low 40s, but certainly in the 40s and 50s, no problem. You can plant spinach really early, and it’s a dense, hard seed so while peas can sometimes rot in the soil if you plant them too early. Certainly spinach can, too, but not quite as bad as peas.

Q. Is that the only time, because I’d like to have spinach more than just early on?

A. Spinach is a cool-loving crop; it prefers it below 80. The times that are most challenging for growing spinach are when it will be maturing or most of its time growing is going to be in the hot season. Here in northern Vermont, even in the summer there are many days when it’s not in the 80s, so we grow spinach successfully throughout the entire growing season up here.

Because it not only is tolerant of cold, but enjoys the cold, it’s very easy to overwinter spinach. You can do it outside with a little bit of row cover or Reemay. We have greenhouses, and people use coldframes. Spinach survives the winter very well, some varieties better than others. Surviving is one thing, but if it doesn’t grow that much or recover in the spring very well, then it’s not necessarily the variety you want.

But spinach is incredible. You can grow it almost any time of the year in the North. The South is trickier, because you have such a long period of time in the 90s and up. In the South, it’s generally grown as a winter crop.

Q. And that really traces to its roots—its ancestral plants were winter annuals in their native land. That shows even today.

I am a Zone warmer than you, a 5B-ish, and I usually do the best with a late-summer or early fall sowing [about 6-8 weeks before first fall frost], and then put it under a blanket, and then it sort of jumps up as soon as the temperatures warm again. Sometimes it even gets protected by snow, I suppose.

It does well that way—as opposed to trying if we have a mucky late spring thaw, sometimes I can’t do a good job of sowing it in the muck [target time for spring sowing: 4-6 weeks before final winter frost].

A. Overwintering spinach is a much more guaranteed way to actually have spinach to eat in April, May. By the time you get into mid-May, or even earlier, it’s bolting and it’s out of there.

Q. So you mean I’m doing something right? [Laughter.] So let’s get the particulars: How thickly and so on do I sow, and in rows or blocks?

A. Rows. It just depends on if you’re harvesting the whole plant, or if you’re cutting leaves. I assume with the home gardener, you’re cutting individual big leaves and leaving a small, tight rosette of little leaves to grow bigger. In that case, you can put your plants 4 or 6 inches apart in the row, and the rows a little bit more, even as much as a foot between the rows.

Again: It’s one of these crops that will take more room, if it has more room, but if not it will grow up, and do really well. But I’d say 4-6 inches apart and a little bit further for the rows.

Q. What makes spinach bolt? I think we gardeners figure it’s heat, but is it heat, or daylength? What’s the trigger?

A. It’s a couple of things. It’s also the plant stage—the stage of its growth. And also stress. There’s a point even if it’s not stressed at all that it will bolt, because it gets to that plant stage—or as you said the temperature kicks in. But yes, it is also daylength related.

Spinach can be pretty finicky. Of all the vegetable crops, it is the most sensitive to a low pH.

Q. I didn’t know that.

A. Yes, it really likes it at 7. A lot of vegetables will say “6 to 7 recommended pH,” and they’ll do fine anywhere in there. Spinach will not.  It really needs to be as close to 7 as you can get it.

Q. And if that’s not your garden’s natural pH, what do you do as an organic farmer to adjust that?

A. Lime. It’s cheap and easy. You can get it anywhere, and you’re talking about even if you have a big spinach patch you’re going to put down 50 pounds of lime, and that’s like 2 or 3 bucks.

Q. Let’s talk about varieties. There are 11 total spinach varieties listed in your 2016 catalog, for instance, including three that have the very famous name in spinach, Bloomsdale, in their names, including a new open-pollinated one, ‘Abundant Bloomsdale.’

A. The ‘Abundant Bloomsdale’ [below] is something that originated back 10 or so years ago with a non-profit preservation seed company in the Northwest called Abundant Life. Abundant Life has evolved—gone out of business to a certain extent, and shifted to another company, and the non-profit arm of it has developed into the current Organic Seed Alliance, with quite a different mission of just preservation. But this variety has been carried through all those processes.

Starting maybe five or six years ago, the Organic Seed Alliance dusted this seed off, and started to select it, grow it with the different farmers, and get feedback—to try to create this really, really vigorous and heavily savoyed, dark green, very sweet spinach variety.

It’s been selected in the Northwest, but we’ve been a partner with OSA for many years, and started trialing it here, and giving them feedback, and visiting other spots where it was grown out there. Starting last year, we got some sample seed from production out there.

We are a company that produces a lot of seed, either on our own farm or with other partners that we work with, but we oversee seed production. That’s not something that a lot of breeders do—whether it’s a nonprofit breeder like OSA or another. So OSA arranged for us to produce this variety for them [with Midori Farms in Washington], and sell it not just in our own catalog but also share that seed with several other seed companies that were interested in it, and approached OSA about it, but didn’t have the seed-production capability themselves.

Q. So that’s an interesting one, and I see the OP heirloom ‘Bloomsdale Longstanding’—sort of the original, so to speak, and also ‘Winter Bloomsdale.’ What about some of the others that are semi-savoyed or smooth-leaf—and what about some that don’t bolt easily. I keep asking you about bolting. [Laughter.]

A. It’s true, the bolting is the issue. There’s one, semi-savoyed, called ‘Escalade’ [top-of-page photo]. This is a new hybrid variety from folks we work with at Vitalis Seeds. This is a variety that was bred for the California market—it’s the new, modern variety. But we’ve been trialing it here, and we’ve also visited some pretty extensive trials up in Quebec, where they actually do quite a bit of baby-leaf spinach production—like thousands of acres of it—and we got to see ‘Escalade.’

We got to see it on a bigger scale, and pushed through the summer, and got to look at these issues around bolting, and heat tolerance and things like that. It is a rock-solid variety; under tough conditions and variable conditions, ‘Escalade’ can really do it.

Q. I might even try it as a summer crop here.

A. In the smooth-leaf, ‘Corvair’ [above] has been really solid for a long time. It’s a hybrid. ‘Verdil’ is an open-pollinated smooth-leaf variety that’s been really vigorous under cool conditions—really growing a lot under cool conditions, not just surviving. ‘Corvair’ came from the same breeder as ‘Escalade’—Vitalis—and ‘Verdil’ came from a really interesting group of biodynamic plant breeders we work with that are mostly based in Germany.

more from tom stearns

• Browse spinach varieties at High Mowing
• Tom on how to grow cucumber, squash and melons
• Tom on growing healthy tomatoes

where is spinach seed grown?

THE PARTICULARS of spinach’s life cycle make growing it as a commercial seed crop too daunting in most climates. Two spots are home to the world’s prime spinach seed operations: a swath of central Denmark, and the Skagit Valley of northwestern Washington. Ideal conditions for getting a good seed crop, says vegetable breeder John Navazio in “The Organic Seed Grower,” call for cool, wet springs followed by dry, cool summers—and then relatively dry fall weather for harvesting.

prefer the podcast version of the show?

MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its seventh year in March 2016. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the Jan. 18, 2016 show right here. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).

enter to win a gift of seeds

I’LL BUY ONE LUCKY READER a $25 gift certificate from High Mowing Organic Seeds. All you have to do to enter is answer this question in the box way down at the bottom of the page, after the last reader comment:

How do you do with spinach in your garden, and when do you grow which kind—like do you prefer savoyed or smooth-leaf, for instance? Details appreciated! (Please tell us roughly where you live—such as region or Zone.)

No answer or feeling shy? Just say something like “Count me in,” and I will, but an answer is better. I’ll pick a winner randomly after entries close at midnight Sunday, January 24, 2016. Good luck to all.

(Disclosure: High Mowing Organic Seeds is an occasional advertiser on A Way to Garden.)