Thursday, February 2, 2012

Winter Spinach

Growing spinach has always been a challenge for me. My plants have often been ravaged by leaf miners, making any leaves that do manage to grow to be inedible unless you're a chicken (yum, extra treats in those leaves girls!) - yuck. Other times aphids have taken over and stunted the plants before they can produce a crop. And in some cases the plants have simply failed to thrive or bolted in the blink of an eye. And sometimes I do manage to grow a crop but it tastes just downright awful. I just cannot seem to grow enough spinach to fill even a small salad bowl let alone enough to wilt down into 2 servings.

But I think I've finally bumbled my way to getting a decent crop. I seem to have finally found the correct timing and a good variety for my climate. Winter spinach turns out to be a good bet in my garden. So, this is not a definitive guide to growing spinach, but here's some of the lessons that I've learned about growing it in my zone 9b garden.

Lesson #1. There are varieties of spinach that are considered "winter" varieties which I suppose is due to their cold hardiness. I suspect that I could also grow "spring" varieties in my winter garden because of the relatively mild winter weather we have here. That might be an interesting test, perhaps I'll try growing a "spring" and a "winter" variety side by side next winter to see how they compare. Anyway, my little patch of Guntmadingen Winter Spinach is the most productive little patch of spinach I've ever grown, even considering that at least half of the plants that I set out and perhaps even more were prematurely mown down by sowbugs in the first couple of weeks after I set them out. Oh, and let's not forget the night that a vole got into the patch and mowed half of the plants nearly down to the ground. The plants recovered, the vole is still out there...

Not your typical looking spinach leaf.

Lesson #2, winter spinach (any spinach?) tastes good in the deep dark cold days of winter, relatively speaking, my winter might seem more like spring to some northern gardeners. Well, let's say that winter spinach probably tastes best after a bit of frost, or at least some really cold nights. My first crop of spinach this season, harvested November 28, didn't taste as good as I had anticipated, it produced that furry sensation in my mouth that is so typical of most spinach. That was a big disappointment, the little crop of this variety that I managed to grow last year (more on that in a bit) was sweet and mild, not furry at all. But the next harvest on December 21 and the succeeding harvests proved to be much better, I didn't notice any furriness but all of those harvests were cooked which reduces that sensation. And then last week when I was out inspecting the garden I plucked a big mature leaf and took a nibble fully expecting that furry feeling again, after all it was a BIG leaf. What a surprise to find the leaf to be exceptionally sweet and flavorful with absolutely no hint of fur. Yum, I kept plucking and munching - all good, really good. So what was the difference between the first picking in late November and the latest crop? Colder days and a few frosty nights. We had exceptionally mild weather, quite warm in fact, in November and December and didn't get our first good frost until mid January. Also, the spinach spent most of the fall and early winter under the protection of some lightweight rowcover which probably kept it a bit on the warm side. It was just a few weeks ago that I opened the top of the rowcover to expose the spinach so that the beneficial insects could help me control a developing aphid problem. Wouldn't you know it, as soon as I exposed the spinach to the elements we experienced the coldest nights of the season so far. I went out one frosty morning and found the spinach quite frozen. Thank goodness this variety is hardy enough to take the frost (winter spinach, doh), even after being coddled for most of its life the spinach came through a few frosty nights unscathed and perhaps improved. I think that the cold weather helped to sweeten up the leaves. Actually, after poking around on the web I'm convinced that the cold sweetened up the leaves, do a web search for "Winter Spinach" and you will find more than one testimonial for the sweetening effects of frost on spinach.

Guntmadingen Winter spinach has oak-leaf shaped leaves.

Lesson #3, timing is everything. Winter spinach shouldn't be sown in winter. Winter spinach is sown in the fall to be harvested in winter, or in colder climates to be overwintered and harvested in early spring. That small but tasty crop of spinach that I grew last year would have been a large and tasty crop if I had sown the seeds at the proper time (read, not in the winter). But in my defense, I didn't get the seeds until well after prime planting time but I couldn't resist trying anyway. So, last year I got away with sowing seeds in January (lucky me, we had a really warm January with highs in the 70ºF+ range followed by a long cool and wet spring and early summer). Those plants matured enough to produce a small but tasty crop and were promising enough to encourage me to try to do it right this season.

Prime time to start seeds for winter spinach is in time to get the plants to mature before the first frost which means sowing the seeds 5 to 8 weeks before the first frost. Hmmmph, well, that's a bit fuzzy, isn't it? 5 to 8 weeks? I guess that depends on the variety of spinach you want to grow and how quickly it matures. First frost? Well, around here I thought it was around the end of November or the beginning of December.  Last season it was at the end of November of 2010, earlier than the first week of December the two previous years. But first frost this season was in mid-January, go figure. Anyway, with the end of November or early December as my target "maturity" date and a vacation planned for just the proper time to sow my spinach seeds, I split the baby and sowed some seeds in paper pots on September 4 and stuffed those itty bitty babies in the ground (at the mercy of the sow bugs) just before I left for vacation and then sowed some more seeds in paper pots as soon as I could get around to it after recovering from vacation on October 21 and planted those out a few weeks later. So, the first planting grew like gang busters and produced a big crop right on cue in late November. Actually, it would have been right on cue if that lovely vacation hadn't gotten in the way and I had sowed my seeds a couple of weeks later. Even so, if we had had our first frost when I was expecting it I would have been luxuriating in wonderful sweet spinach for the last 6 weeks or so. Anyway, I luxuriated in spinach that wasn't as sweet as expected, but the plants were fully leafed out when the sweetening frost finally hit. The second planting didn't grow as quickly or as luxuriantly as the first planting, the days were just too short and the nights too cool and the soil too cool as well. But they are looking pretty good now and I think that they will do well for an attempt at seed saving.

Plants sown 9/4/11

All of my harvests have come from the patch shown above, that's 6 pounds 20 ounces so far, most of it weighed after trimming off the stems. When I sow spinach in paper pots I put 2 seeds in each pot and don't thin out the extra plant if both seeds germinate. The two plants per pot seems to work if the plants are set out about 6 to 8 inches apart. The September sown patch is about 12 pots, a few with 2 plants each. The October sown patch is 14 pots, most of them with 2 plants each.

Plants sown 10/21/11

Lesson #4, leaf miners aren't much of a problem in the winter. Yippee! One great reason for growing spinach in the winter, no critters inside the leaves. Nuf said.

Lesson #5, leaf miners may not be a problem, but aphids and their attending ants are. Ah well, it's not absolute spinach growing heaven here, unless you're a chicken, more treats for the girls.

Little black aphids on the spinach leaves.

Above is shown part of the spinach patch just before I harvested it. I had to cut those plants completely down, shown in the photo below, because of an aphid infestation. The aphids tend to infest the young leaves in the center of the plant and the ants attend them so that they can collect the aphid honeydew (a nice word for sh*t), sometimes actually covering them with soil particles to help protect them. I hope I can get the aphids under control now. After I cut the plants down I sprayed what was left with insecticidal soap to kill any aphids and ants that were left. My experience with the aphid/ant combo is that the ants will bring the aphids back as soon as the plants start to leaf out again so I'm trying a new product based on cedar oil that I hope will help to repel the ants. I sprayed the repellent on the soil and the base of the row cover around the entire perimeter of the planting.

Here's one of the plants a few days after I mowed it down, the leaves are regrowing already and the only ants and aphids to be seen are dead ones. The repellent seems to be working here, there's no new ants to be seen. I also sprayed the cedar oil around the outside of the October sown patch, applying it to the soil and the base of the row cover. The ants and aphids had just started to invade that patch of spinach and there was a trail of ants going in that doesn't seem to have reappeared so far.

The white dots in the photo above remind me that there is one other minor pest of winter spinach - sowbugs. They love to get into a clump of spinach and munch holes in the stems. They generally don't do a lot of damage other than at planting time when they may mow down the seedlings. I find that an occasional application of the organic pesticide Spinosad helps to keep the population in check. Sluggo Plus (the white dots) contains spinosad and there are also spinosad concentrates that can be applied as a spray.

But wait, there's another pest that bears mentioning - rodents. The reason my plantings are encircled by row cover is not to protect them from the weather, it's to keep the rats and voles from feasting. It generally works fairly well, although the resident vole has recently burrowed into the September sown spinach patch and I'm trying to figure out how to deal with that...

Lesson #6, spinach is day-length sensitive (see note below), meaning that as the days get longer in the spring the extra light will trigger flower formation. This is important if you want to harvest some leaves before the plants decide to put their energy into flowers rather than those tasty leaves. The magic number is somewhere in the range of 12.5 to 15 hours of daylight, depending on what variety you've chosen to grow. I suspect that this is where the importance of "spring" varieties comes into play, the "spring" varieties are probably selected for their greater tolerance of longer days. If you want to grow a spring crop of spinach you should find a variety that will wait to bolt until day length approaches 15 hours rather than the shorter 12.5.  My garden sits at latitude 36.39º N so day-length hits 12.5 hours on April 7 this year and the longest day of the year will be 21 minutes shy of 15 hours. But keep in mind that there is plenty of light before sunrise and after sunset that will have an influence on the plants. Last year I harvested my last crop of Guntmadingen spinach on April 19 and although I didn't note when it started to bolt I think that it is safe to assume that it was sometime soon after that. I assume that the Guntmadingen spinach is suited to winter not only for its cold hardiness but likely also because it lies on the shorter end of the day-length sensitivity scale.

Temperature also plays a role in making spinach bolt, although not a primary one. Warm temperatures accelerate the blooming process once it has been triggered by longer days. Bolting may also be induced by temperature fluctuations, but again, that is not a primary trigger for flower formation.  So I could conceivably start a new crop of spinach right now for a spring crop and not expect my spinach to bolt until May or June if I select the proper variety. But I won't because I would be challenging what I learned in Lesson #4, leaf miners are definitely a problem in the spring here. And I would also be ignoring Lesson #3, spinach tastes great with a touch of frost and frost is a rare thing here after January or February and besides, there will be plenty of other tasty vegetables in the garden in spring. It works the other way around also, if you start a crop of spinach in summer for fall harvests too early when the days are too long the plants may be prematurely triggered to bolt. But I think that I'll skip the fall harvests of spinach as well because I should be happily munching on summer vegetables well into October and I tend to ignore most green leafy vegetables at that time. So that's it, Winter Spinach is it for me.

One last lesson - #7, there are male and female spinach plants. Not important if you aren't saving seeds but very important if you are. This year I am going to try to save some seeds from my current patch of Guntmadingen Winter spinach because Adaptive Seeds will not be offering them for sale again until 2014 at the earliest and my packet of seeds is running low. This lesson will be continued in a future post as I hopefully successfully bumble my way through my first effort at saving spinach seed.

Yet one final fact about about spinach that I recently learned is that there are two seed forms, smooth and spiny. In general the smooth seeded varieties produce more wrinkled leaves and spiny seeded varieties produce smooth flat leaves. I've also read that smooth seeded varieties are best for cold weather and spiny seeded varieties are best for warm weather, but I'm not sure how true that is, afterall, Guntmadingen spinach is quite spiny. Anyway, you may not be able to discern what type of spinach seeds are in those packets in your collection because most commercial seed producers remove the spines. That's probably a good thing in general, those spines are really sharp!

The spiny seeds of Guntmadingen Winter Spinach

Note: the term "day-length sensitivity" is a misnomer, it turns out that spinach is actually night-length sensitive, it is shortening nights rather than lengthening days that trigger flower formation. This is true of many other "day-length" sensitive plants such as onions. This distinction is important if you are trying to fool plants into doing something that they wouldn't normally do at a certain time of year, such as forcing summer bloomers to bloom in winter by interrupting the night length by using artificial light.


  1. Great post! I learned quite a bit here and I've been pretty successful with spring spinach. I hope this info breeds more success. I have some spinach overwintering in the hoophouse right now. It will be ready to start eating in March I hope.

  2. Michelle,
    Thanks for teaching me a bit about spinach. Never had the problems with spinach you have. We plant the seeds right in the ground. Our spinach in the cold frame has never grown big, most leaves harvested are about 1 1/2 inch long, good for salad but not much for cooking as so little has grown.

  3. Wow thanks for such an informative post. I appreciate the hard work for such a great post.

    One thing that I have found helps with the leaf miners and aphids is to get some row covers over the plants from day 1. There is not much you can do to get rid of leaf miners once you have them so the key is to keep the adults from laying eggs on your spinach. The row cover will exclude the adults which look like a small house fly and will also help a ton with aphids.

    1. The row cover is a tremendous help with the leaf miners but I've found that it doesn't help with the aphid problem, it can actually make an aphid problem worse. Around here the ants farm the aphids, they will actually carry aphids to a good site and then protect them. I"ve found that they really like to farm the ants on plants under rowcover. I have far fewer aphid problems when the plants are exposed so that the hover files, lady bugs, soldier beetles, parasitizing wasps, and other good bugs can help to keep the aphid population in check. Leaf miners can also be minimized if you are vigilant about removing any infected leaves and destroying them or putting them in the garbage, this interrupts the life cycle by not allowing the larvae to get into the soil where they pupate.

  4. I can eat two pounds of spinach in a good day, so growing it is a challenge. The leaf miners attack so many of the beety plants. I can only get about one good crop before they become so active as to be harmful. Your row covers make me sad -- bad rodents! Terriers, you need rental terriers.

    1. Rental terriers for rodent terrorists - what a great idea, maybe, aren't terriers diggers? If I could just get Zeke the Rodenator to get off his fat lazy butt that might take care of the problem, but that cat just wants to hibernate in the winter. Two pounds of spinach a day is a lot, it would be difficult to grow enough to feed that habit. :)

  5. Thanks for a full of information post Michelle, and I think frost would be bound to sweeten spinach up... it certainly does the same to carrots and brussels, so who knows what else too!

  6. Great post. I have always had problems with spinach too. Last fall I planted a lot of it and it looks like we are going to have a good spring harvest!

  7. I used to have such problems growing spinach here too. Now the best spinach I grow is over wintered spinach. I don't know how hardy spinach is but I'm in zone 6 and don't protect it over the winter. Plus winter spinach here produces before the leaf miners come out so a big bonus. spring sown spinach always has to be covered. BTW sugar is a plant's antifreeze so it isn't surprising that spinach gets sweeter after cold weather.

  8. Great post, thanks for sharing. My overwintered spinach bolts in early March no matter which variety I tried, spring grown variety is no go here.


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