mastering microgreens, with kate spring of good heart farmstead

A “NEW YORK TIMES” column I did recently happily put me back in touch with organic farmer Kate Spring, who in our past conversations has always taught me how to think smarter about when to start seeds—like how to time succession sowings of vegetables for an extended harvest well into fall. This time she gave me a 101 on another kind of seed-sowing, but indoors, preferably under lights, and starting right now as winter descends: mastering microgreens.

Kate Spring, and her husband, Edge Fuentes, founded Good Heart Farmstead in Vermont in 2013, which serves up to 100 customers each season who subscribe to their CSA share program. Their farm is a hybrid business structure called an L3C, a low-profit, limited-liability company, where part of the mission is to support Vermonters in need of food access.

Kate’s also a writer and the only person I know with her very own brand new yurt, which I couldn’t wait to hear about after having seen it be constructed on her Instagram.

Read along as you listen to the December 14, 2020 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here).

mastering microgreens, with organic farmer kate spring



Margaret Roach: Welcome back, Miss yurt-owning Kate. How are you?

Kate Spring: [Laughter.] I’m doing really well. I’m very excited about the yurt, too. Thanks for having me back.

Margaret: It’s beyond cool. And you guys built it. I was just so impressed. [Below, screenshot of the yurt grabbed from video on Kate’s Instagram.]

Kate: Thank you. Yeah, so we actually used to live in a yurt a little bit bigger than the one I posted about on Instagram. So this yurt is going to be my own office so I can close the door and, hopefully, not be interrupted during this winter’s homeschooling, and have my own creative space. So, I’m excited about it.

Margaret: Cool. I see you’re doing lots of interesting things, like you’re facilitating workshops for farmers who are also, like you are—speaking of interruptions—parenting and homeschooling young children. You’re facilitating workshops with NOFA of Vermont. Is that right?

Kate: Yeah, the Northeast Organic Farming Association. There’s been such a big need for support for farming parents, especially this year with the pandemic. So we have put together a series of conversations for folks to join in virtually.

Which one benefit of the pandemic is that in our first farming-parenting forum session, we had folks tuning in from Canada and Massachusetts. And so it’s opened up a wider community where we can get together and talk and listen, and give each other support and tools as we run businesses and have kids during the pandemic. And some of those kids are home this year and some are doing flex schools and some are still really little, so it’s been good to connect.

Margaret: Well. So, microgreens. The first time I read up on them was a few years back. I think you were working for High Mowing Organic Seeds at the time and wrote a complete how-to on their blog, which is why dot, dot, dot years later, when I was going to do the “New York Times” story, I thought of you and called you.

So before we get into the process, can we just identify what’s a microgreen? Because it was very interesting for me in the comment section on the Times story, a lot of people were like, “Why did you put them in germinating mix, in seed-starting soil? Why didn’t you just do them in water?” They didn’t know the difference between a sprout and a microgreen. And then there are shoots, and the same plant can be grown to many stages of its life by different methods. So can we kind of say what’s a microgreen together? [Above, just-harvested arugula microgreens.]

Kate: Yes. And it’s a really important distinction because with a sprout you don’t need any growing medium. It’s really just wetting the seed and you can do it in a Mason jar at home. All of this you can do at home. But with a sprout you’re also eating the seed. Whereas with a microgreen, you’re growing it in soil, in a growing medium, and you’re growing it just past the point of where the cotyledons have opened up and then you get the first true leaf.

And that can take anywhere between 10 days to 25 days, depending on the crop. And when you harvest, you’re harvesting the stems and the leaves. So you’re not eating the seeds, unlike with sprouts.

Margaret: Right, the root as well.

Kate: Exactly. Exactly. So it’s just the stage beyond the sprout.

Margaret: Right. Exactly. And yeah, so both are possible, but they’re different. The nutritional value is different. What you’re getting, as you said, like with the sprouts, you’re getting the root and the seed that’s opened up and germinated, but you’re not cutting that off, but you’re not getting as much green typically there. I mean, you’re not getting those true leaves.

Kate: Right.

Margaret: Yeah, yeah. So it was very interesting to read a report. And I think it was done in a 2012, I believe, evaluating the microgreen forms of certain crops relative to the mature-leaf forms of those crops and how nutrient dense these little first true leaves were. From 4 to 40 times as much nutrition per volume as their mature counterpart, depending on the crop. So very, very interesting.

Kate: Right. And I think with microgreens, I think you can really taste that, too. Because the flavor is really potent. And so with basil [photo top of page], for example, which we talked about basil for the “New York Times” piece, and we just did a basil harvest for our last CSA delivery of the season, and when you’re harvesting them and when you’re eating them, the flavor and the smell is so potent, it’s really delicious and delightful. So yeah, it’s just like a stronger flavor all around.

Margaret: So speaking of what you’re growing—and I should have said at the beginning, thank you for making time to talk today, because I think this is your only month of the year that you have “downtime,” which I know on a farm is never really downtime, but you’re not preparing CSA shares for people to deliver or pickup this week, and then for the next few weeks, you have a month off, quote unquote, off.

Kate: Yeah. That’s right. It’s nice. We’ve built that into our year. And as you said, there’s also plenty of other things going on. So it’s really nice to just sit down and talk rather than doing all the extra cleanup that inevitably still gets piled up outside.

Margaret: Yeah. So you just mentioned basil, now that would be, if we bought basil in the store in the offseason, we might find it as a whole stem, a more mature thing that was maybe bagged or in a clamshell plastic box or whatever. And it could be quite expensive relative to what you’re getting. And with some of the microgreens, you might find them in a clam shell or plastic bag or whatever. They’re super-expensive. And again, especially in the off season, they’re super expensive. These are not a cheap crop if you buy it finished, right? I mean, it’s a premium item.

Kate: Yes, that’s right. And so you’ll typically, at least around here, you’ll see it being sold by the ounce. So it might be like $2 or $3 an ounce.

Margaret: Whoo!

Kate: But when you compare that in pound prices, it can be anywhere from like $36 to $48 per pound. So it’s a lot more expensive to buy compared to a salad mix, but it’s also really easy to grow. So it’s one of those things that it’s a great thing to do at home if you don’t want to be buying it every single week. And for farmers it is also a great thing to add into CSA shares or farmstands, things like that.

Margaret: Right. So we could choose to grow herbs, a few different herbs, which I think you grow some—you just mentioned one. We could grow certain greens, we could grow some of the root crops as microgreens. What are some of the ones maybe besides basil that you grow pretty regularly or that we should think about starting with?

Kate: Yeah. So along with basil, we grow cilantro. Those are the two herbs that we focus on. And then we also really love kale, arugula, mizuna, broccoli, radishes. The ones I just mentioned are in the faster-to-grow category. So those ones can be ready in 10 to 15 days. So those are nice to start out with, because you get to harvest a lot faster. And they’re all delicious by themselves, but you can also mix them all together, too.

Margaret: And now, a little bit counter-intuitively, we’re not growing salad—we’re not growing microgreen lettuce.

Kate: Right.

Margaret: This isn’t instead of baby-leaf lettuce, you know what I mean? We’re not trying to fill the whole salad bowl with microgreens, are we? And actually you didn’t mention lettuce and I don’t think you grow lettuce as a microgreen, is that correct?

Kate: We don’t grow lettuce as a microgreen. We do have some lettuce that we overwinter in our greenhouse, but you’re right. So we use this more as something to add to. You can add it to your baby-leaf salad, or you can add it on top of tacos or eggs or into pasta sauce. It’s really something that we use as an ingredient for the meal rather than the main meal.

Margaret: So the basic 101: So I know I have to probably get lights of some kind, because the windowsill, it’ll work, but they’re going to be a little weaker, I think, unless you have an incredible windowsill [laughter], which I don’t in the North.

And so I’m going to use my seed-starting light, which I can fit it on a particular part of my kitchen counter or somewhere else like that. What do I want? Like a room that’s around 60-something degrees? Like not hot, not cold? Is that the idea?

Kate: Right. Yeah, I think 65 to 70 degrees is the ideal range.

Margaret: O.K. And so I’m going to get out my light and I’m going to get a seed tray. So tell me kind of what’s the basic 101?

Kate: So you can do two different ways. So one is using a tray that has … Starting with a general 10 by 20 tray. And we use trays that have drainage holes in them because we bottom-water once the seeds have emerged. And that’s mainly because the microgreens tend to be very delicate. So it’s easy for them to get fallen over if you’re watering them, if you don’t have a mister or a spray bottle. So if you want to bottom-water, make sure that you have a tray that has drainage holes. Otherwise you can get whatever tray that you use typically, or flat that you typically start your seeds in.

And then you’re going to use about 1 inch of potting soil and scatter the seeds pretty thickly on the soil. And that is you basically, you do want to see the soil, but what we’ve read up on and have done is about 10 to 12 seeds per inch. And this is the part where you really can put on your “trial mindset,” and it doesn’t have to be perfect. You’re just going to get more used to it and more comfortable the more you grow microgreens.

And from there you just keep them moist and they’ll emerge within usually three to five days. And then from there you’re going to just keep them watered, either with a misting nozzle or again, with like a spray bottle, or you can bottom-water with a tray underneath.

Margaret: So when we say per inch, so the tiny seeds we might be on that upper end, like 10 per square inch or whatever, and it’s sort of a square inch … I loved seeing some of the pictures in your greenhouse of some of the trays [above]. It’s almost like you had—maybe you did have—like a dibber or some kind of something that made almost like a grid of little recesses, as if I’d poked my finger on a perfect grid throughout the tray. And into each one of those things, which is an inch apart in each direction, so within a square inch, you put a little group of seeds and that made the spacing perfect.

We don’t have to be totally obsessed, but like you said, you have your “trial mind” on, be open to observing your first time. Was it too thick? Was it too thin? Was it too sparse? What didn’t work?

And the watering, too. I think the bottom-watering, you put like a quarter of an inch of water in the bottom once they’re up so that you don’t smash them down. Or otherwise, I love that hand pump—it’s like a vacuum pressure. It’s an inexpensive thing from Solo, and you pump it a few times, and then you just… the trigger, you just spray and you can mist a whole tray. But anything stronger than that, boy, they do get flattened. [Laughter.]

Kate: Yeah, they do. And yes, when we started out growing microgreens, we did scatter it and then scatter the seeds on the soil when we were sowing them. And we have switched to using a seeding plate that we have that, just as you said, creates a perfect grid, and then we put multiple seeds within each little dibble hole.

But again, you don’t have to do that. That’s just more of our efficiencies as a farm and growing for many CSA shares. But again, if you’re growing for yourself you can just test it out and try different thicknesses and have fun with it.

Margaret: So let’s say I wanted to have… and I remember you told me, you put the cilantro microgreens on top of black bean and sweet potato tacos, which sounded so amazing and just imagining that flavor in February, to have that flavor would be so great. And the basil of course, I can imagine a lot of things I’d love to put that on top of.

But if I’m a one or two or smaller household, I don’t need a whole tray of each one. Can I do partial trays? And I assume I have to sow it all at the same time, because when you were just talking about they might germinate in three to five days, then the lid needs to come off.

I guess we should have said either you might use one of those humidity domes, or you might just use a piece of moist toweling, like paper towel, to keep the seeds moist before they germinate. And then you remove that, either the lid or the towel. And when they sprout, they have to go under the light. They don’t go under the light until they sprout, but once they do, they need to, right?

Kate: Right. That’s exactly right. Yeah. And you can definitely sow different varieties within the same tray. And when you do that, you just want to pay attention to the days to maturity. So if you want to have maybe two or three different herbs in one tray, you would just want to pick varieties that are going to be germinating and at harvest in generally the same timeframe, and that way you can treat the tray in a uniform way. And you could also seed partial trays, if you want to.

The thing about microgreens is you can eat a whole tray pretty quickly [laughter], even though it can seem like a lot, but then they’re so good. And they don’t take up too much space. But yeah, it’s really fun to mix and match different varieties together.

And then you can kind of create your own mixes or if you want to try a pre-made mix, there are some great pre-made mixes too, that you can get from High Mowing or Johnny’s or different seed companies. [Above, Edge Fuentes and the couple’s son Wayon in the seed room at Good Heart Farmstead.]

Margaret: I think both High Mowing and Johnny’s… To figure out which ones are what days to maturity and how long to germinate and so forth, they tend to have a lot of, because they both sell to farmers, they have a lot of technical information, growing information, a lot of details. So if you want to make good matches—which is quick, which is slow, which would be good in a mixed tray or whatever, or to get some sense of the timing of your stuff—I think those are both good resources for a little research.

And how many hours of light a day am I using, do you think is good? You’re in a greenhouse, but …

Kate: Yeah, so we have a greenhouse and then we also have a seedling room where we will do seeds when it’s really cold out and we’re not wanting to heat the greenhouse all the way up to the 60s when it’s freezing outside. So we do have indoor lights that we use that are LED lights and have them on a timer. And so we’ll have them on for 16 hours a day, which can sound like a lot, but again, it will just make them grow so much stronger. And that consistent light is really, really helpful to get them where you want to go.

Margaret: So years ago, as I said in the intro, you taught me some of the finer points of succession sowing outdoors, in the vegetable garden. But we could kind of practice that here to have a steady supply, too.

Like I could imagine that if I’m getting set up, I don’t want to just have one tray, even if my light stand could only accommodate one at a time. I might want to have a second tray and have that starting to germinate just before the other one is starting to be ready to harvest. You know what I mean? Like staging, like moving them through.

Kate: Yeah, for sure. And that way you get to … You don’t have to have a break in your microgreen supply. So you can, just as you said, if you know that it’s going to take three to five days to germinate and you have one tray already under the lights, then you’d want to start your next tray three to five days before you harvest the current one, and you can just sort of keep a cycle going like that.

And the other thing, too, is that if you wanted to extend your harvest, you don’t have to harvest the entire tray at one time. So this is another way you can kind of bring your “trial mindset” to microgreens. And you might harvest a third of the tray at one stage, and then see … You can find what your favorite harvest stage is at, because there can be a multi-day window where they might still be growing, and you might find that you like them a little smaller or a little bit taller. And in that way you can extend the harvest just from one tray by harvesting it just when you’re ready to eat it.

Otherwise, if you do harvest a full tray, you can keep them in a plastic bag or clamshell in the fridge, and you’d want to eat them within a couple of days.

Margaret: Right. And harvesting is with a sharp scissor, or … I love those knives. And again, both Johnny’s and High Mowing sell them, it’s an inexpensive knife with a serrated edge, a harvest knife. It’s a great thing to have for cutting small things like this. But the scissor will work great also.

So you just said you might like them smaller. You might like them bigger. One thing that gets a little bigger, and in the last couple of minutes I wanted to just talk about pea shoots because, oh my goodness, what a flavor and oh—it just tastes like late spring to me. So pea shoots, that’s a little bit different, right? It’s a little bit farther along.

Kate: Yeah. So these are harvested … They definitely take up more space and are a little heartier than the microgreens. And we typically harvest them around like 4 inches. But just like you said, they really taste like spring.

And the way you grow pea shoots is just with the seeds from field peas. And we soak those overnight. And then we sow them very similarly to microgreens, with the exception that the density is even higher [above]. So we will prepare our tray of soil and then fill the entire tray with pea shoot seeds, with pea seeds, and so you don’t really even see the soil.

And then we’ll cover them again while they’re germinating. Once they germinate, we’ll take the cover off and have them either under lights or in the greenhouse. And again, if you don’t have a light, you can try it on a windowsill, though they get a little leggy in that light, when they’re just like leaning towards the light. But they are so delicious. And those can really stand in as a salad on their own just because they are bigger than the microgreens.

Margaret: Yes. So, Kate Spring from Good Heart Farmstead in Vermont—you’re an organic farm, and just in closing, I’m going to say people should use organic, certified organic, organically grown seed for all of these, I think. For everything, I think, but especially for this. I think this is one…like with those field peas, which are also sometimes used as a cover crop, you want to just make sure this is really good and the best possible quality. Well, thanks for making time. And now go back to your “rest.” [Laughter.]

Kate: Yeah. Thank you.

more on microgreens and with kate

(All photos from Kate Spring, used with permission.)

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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 11th year in March 2020. 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 December 14, 2020 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify or Stitcher (and browse my archive of podcasts here).

  1. Ann says:

    If growing microgreens in my kitchen, as a beginner who doesn’t want to invest in a lot of new stuff, can I place them under the lights under my kitchen cabinet? Is so what kind of bulb should the fixture have?

  2. Margaret Manzke says:

    What a great way to extend the growing season! I have a large (for me) bag of broccoli seeds sold for sprouts, but I’m going to take one of those clam shells and create a small microgreens tray. Wish me luck!

  3. This works even better when you use your own seed. We collect seed from kale, lettuce, chard, mustard, etc. After cutting the crops become a cover crop to turn into the soil followed by a summer crop like tomatoes or sweet potatoes. We also mix in lambsquarters and edible flowers. This works into our agroecology program. We are continually doing research in this area.

  4. Stephanie says:

    Hi Margaret. I read your Times article and listened to this podcast about microgreens. I really appreciate the detailed instructions. But neither of you talked about whether you can use your own leftover seeds for growing microgreens, rather than the “special” seeds sold by the seed companies. I did an internet search and found a few articles that said that using “regular” seeds would work fine. It’s kind of an important point, since I – and I assume every gardener – always have leftover seeds, and this seems like a good use for them. I wonder if you could add something to your website about this. I’ve been gardening for years here in Central Vermont but I always learn something new and interesting from your podcasts.

  5. Pollyalida says:

    Perfect timing! I’m picking up bags of potting soil and seed starting mix tomorrow and planning to sort through all my seeds leftover from the summer to get some micro-greens going soon. Winter peas will go in my one raised bed that has a cold frame, totally agree about that magic taste of pea shoots in January, can’t be beat. Question, can the trays of soil be reused a couple times? Or best to start with fresh soil each time?

    1. margaret says:

      Yes, you can compost the potting soil (doesn’t take too long) till the little roots break down and maybe then mix it with half fresh — so sort of keep a bucket somewhere for this and a trowel to mix it a bit every so often.

  6. Louise says:

    I’ve been growing microgreens for 3 years. My favorites are cutting celery, several types of basil, cilantro and chervil. These flavors really jazz up meals all winter. Some micro greens thrive outside in hanging pots. That surprised me, zone 5B.

  7. Hannah Nendick-Mason says:

    I grow winter microgreens and herbs under lights in those clear plastic containers that tomatoes come in at the grocery store. They are convenient for small quantities and you can use the lid to keep in humidity. I also use them for indoor seed starting. The challenging part is remembering to buy potting mix while it is still available in large bags in the fall. In winter you’re lucky to find the small bags and they are far more expensive.

    1. Alissa says:

      Just got a baggie of fennel micro greens from a local farm and they are now one of my favorites! They are amazing on salad and would be delicious as a garnish for non-oily fish. I sprout in the winter sometimes but haven’t tried micro greens since my countertop space is dominated by houseplant propagations! It is a fun way to support my local farmers in the winter and we are lucky to be able to get them delivered.

    2. Alissa says:

      Whoops, sorry, Hannah! Not sure why my comment was a reply to yours… but good point on securing your potting soil before winter starts!

  8. Kari says:

    Is the Solo sprayer you are referring to the same one you recommended a few years ago for fungicides and foliar sprays? I need one for Greencure, a biofungicide for tomatoes, Septoria Leaf Spot and Early Blight. Is a specific size needed to get good pressure?

    I didn’t get enough growth in my previous microgreen trials for all the work to be worthwhile. Now I think, not enough light. Going to try the pea shoots too. But do you get more than one cutting? Thank you.

  9. Denisa @BreadNewbie says:

    Margaret, such a wonderful discussion with Kate! It was a pleasure to read every word! I’m glad that you covered the part where growing microgreens can become a lucrative business, especially if there are people who are looking for a side income. Your discussion can serve as the perfect place to start. Thanks for everything!

  10. Rebecca says:

    Can you seed another layer of seeds after harvesting one crop of microgreens?micrograms?? What do you do with the used soil? And what is your soil mix?

    1. Jamie Risley-Hall says:

      So once you cut your microgreens, they won’t grow back again, correct? That tray is done? Could you sow another batch of seeds in that same tray & soil?

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