Cool-season Brassica Culture West of the Cascades

Although I am writing this specifically for a gardening group which is inclusive of the entire Pacific Northwest, I regret that I have absolutely zero gardening experience east of the Cascade range, unless you count a single summer I spent in Colorado in the late ’90s, where I didn’t do any gardening of my own but observed a friend’s attempt at ripening tomatoes at 9000 feet.  Having made this observation, my response was to move back to the milder climate whence I originate.   Apologies to those living east of the Cascades.

Disclaimer aside, now let’s get on with it.  Why are we doing this? There are but a few simple answers:

Because we can! The mere satisfaction of it is enough.

To utilize garden space-time maximally by growing edibles year-round.

Because why grow somewhat boring cruciferous* vegetables in the warm summer months when you have more interesting warm-season things like tomatoes, cucumbers, even melons!  None of those can be grown at all during the cool season.

It’s actually easier: you get to completely side-step a number of major challenges to growing brassicas in hot weather.  These challanges include cabbage worms and aphids, heat, and often, premature bolting.  You will still have to deal with these issues in the late summer, but by the time your first frost date rolls around, things get generally easier.

It harnesses the biennial** nature of the brassica* family.  I would belie my hippified self if I didn’t assert that natural = better.

Finally, just about every plant in this family will actually taste better when harvested during cool weather, preferably right after a light frost.  This is because starches present in the plant’s tissues get converted to sugars when a frost hits.  The plant does this naturally to protect itself from the possibility of water present in its cells getting frozen.  A sugary solution will not freeze as readily as plain water, so the plant’s tissues are less likely to suffer the irreparable damage that results in water contained within cells freezing, expanding, and ultimately bursting cell walls.  Natural plant antifreeze = deliciousness!

*it seems generally accepted that the words/terms “cruciferous vegetable” and “brassica(s)” are interchangeable. Wikipedia says: “Cruciferous vegetables are vegetables of the family Brassicaceae (also called Cruciferae)”.  Nowhere could I find evidence that “Cruciferae” is actually a synonym of the family “Brassiciaceae”; rather it appears to have once been a genus within Brassicaceae.  But everything has been renamed since.  So generally, I’ll use the term brassica(s) but I might use both.

**A biennial is a plant whose life cycle spans two years and who produces only vegetative growth (typically in a more or less basal rosette of leaves) in its first year. After experiencing a period of vernalization (read: winter), it is only then triggered to produce an inflorescence. Typically this looks like a tall flower stalk. Examples of biennials you’re likely familiar with include foxgloves, carrots, beets, and mullein.

I. SEED SOURCES and VARIETIES

Now before you start to tell me you don’t like growing stuff from seed and you’d rather go out and buy starts, hear me out: you might have a hard time finding the varieties you really need in order to make this work.  Winter gardening is still relatively unpopular (which I am trying to change), so it’s probably not all that profitable for nurseries to start a bunch of babies in hopes that New Seasons and Fred Meyer will buy them and their customers will actually know what to do with them.  Actual plant nurseries *may* be a better bet, but my guess is that your chances of getting leftover spring/summer season varieties that just haven’t sold out yet are high — and those will not be what you want.  You can try, but really, it’s better to know the variety and choose it specifically from a seed catalog.

I recommend you seek out seed companies that sell varieties specifically to our area.  There may be more but the companies I know of include West Coast Seeds, Territorial Seed Company, Ed Hume, Osborne Seeds, Adaptive Seeds, & Nichols Garden Nursery.  If you’re accustomed to going to Fred Meyer or the Orange Box and picking up a few seed packets of whatever they have on the seed rack from the big national suppliers, change that habit now and order online from one of the suppliers listed here.

Probably the single most important thing about winter brassica culture is to make sure you get the right varieties.  And perhaps even a variety of varieties…  It seems like more than any other crop or family of plants, there’s a huge variation in how long it takes to get a harvestable crop between varieties.  Spring/summer-sown early-maturing broccoli often only take 60 days (or less!), but true overwintering sprouting broccoli may require as many as 230+ days.

Wait, you say, 60 days? I thought you said these were biennials? How can that be?

The answer is it’s complicated.  Since the days of the ancient Greeks and likely even before, humans have been growing Brassica oleracea.  And yes, you read that right: broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, and kohlrabi are actually all the same species.  Gai lan, too.  We’ve bred them to exhibit varying characteristics into the forms we know, but they are all the same plant in essence, and have much the same cultural requirements (more on specifics of that later).

In addition to all this variation in plant morphology, breeders have also managed to create strains which grow at very specific rates, and/or strains which don’t require vernalization, or winter chill, to set flower (effectively breeding out their biennial-ness and making them annuals).  There is a staggering amount of variation! There are also a lot of differences in cold tolerance, heat tolerance, and what’s known as field holding capacity, which is a measure of how long the crop can wait to be harvested.  Some have a very small harvest window (get it now or it’ll bolt!!) and others can be ready to pick for weeks without deteriorating in some way.  Broccoli and cauliflower tend have shorter windows while the ones we grow for non-flowering parts can usually hold longer.

II. VERNALIZATION

Vernalization is is the induction of a plant’s flowering process by exposure to the prolonged cold of winter. Having an understanding of vernalization is important, even if you don’t grow any varieties that require it.  When we say, “this is a true overwintering variety of cauliflower,” we mean that it requires vernalization.  That’s an inherent trait to the species that we have bred out, for faster harvests, and for summer harvests.  When you choose your varieties, it’s important to know whether the variety requires vernalization or not, so you know when to expect harvest.

Heirloom purple sprouting broccoli requires vernalization.  I’ve recently seen new hybrids of purple sprouting broccoli that don’t.

Truly overwintering cauliflower is a wonderful thing.  I am personally enthralled with it, so I’ll even tell you which varieties our local suppliers currently offer:

From West Coast Seeds,  ‘Galleon’ – $6 for 18 seeds.

From Territorial, both of their cauliflower blends here and here include truly overwintering varieties.  $14-17 for a 4-pack, 60-85 seeds of each of four varieties. They don’t tell you the variety names, but they do separate them into little color-coded envelopes and they indicate which ones will mature first, second, third, and last.  The reason they don’t tell you the variety names is that they get this seed from their suppliers in England, and they can’t guarantee the same exact varieties from year to year.

From Adaptive, ‘Purple Cape‘ may be on the line between broccoli and cauliflower, as some purple cauliflower varieties are.

Osborne Seed has two varieties (scroll to the bottom) which say, as of July 5, they are coming soon.  Presumably they’ll get them in by the time the seeds need to be planted!

On to…

III. WHEN TO PLANT SEEDS

As mentioned, with all the hybridization we have lots of variability between brassica species and within each species’ hybrids in terms of rate of maturation and also in cold-hardiness.  In ANY case, the size of the edible art of the plant is directly related to the overall size of the plant at maturity.  A bigger plant will produce more.  And, as with pretty much all plants, fast vigorous growth during the plants’ early life is crucial for success.  I have noticed this to be especially true of the brassica family.  Any slowdown or stoppage of growth due to stress from less-than-ideal growing conditions (including pest damage), will result in, well, less-than-ideal results.

Overwintering broccoli and cauliflower need to be as big as possible going into the winter, so they come out of winter in a well-developed state, ready to burst into flower when spring temperatures and light levels are high enough to trigger the onset of flower-making.  For non-overwintering types, harvest will be happening during the cool months of October through January, and again, they need to develop as much plant mass as they can during the late summer and fall, while light levels and temperatures are still adequate for the plants to grow.

We all have our own little microclimates, with first-frost dates varying from mid-September to mid-November, and of course the weather is going to vary from year to year.  I recommend experimenting by planting a few seeds each week or two starting in early to mid-July, and continuing into August.  You may never arrive at a perfect formula, with an exact ideal date, so I wouldn’t recommend even trying to nail it down that precisely.  Just focus on growing strong plants.  If, like me, you plan on raising transplants, I’d recommend starting them in at least 4″ pots rather than tiny seedling cells, to reduce the number of times you have to up-pot before setting them out.

I raise transplants for three reasons:

  1. Growing seedlings indoors means zero insect predation during their most vulnerable stage of life.
  2. I can more easily control air temperature inside my house.  Brassicas are cool-weather lovers, and growth tends to slow down above 90°F. This may not be a concern for those in coastal regions.  I live in the northern Willamette Valley where we get more high temps in August than most other areas west of the Cascades.
  3. By growing seedlings in pots and setting them out in September, I can buy more time in my garden beds for other summer crops to mature before I need the space for these guys.

Despite reason #1 above, I still have to deal with insects once I set the plants out.  If you sow direct, you’ll just have more of this to contend with, so on to:

IV. INSECTS

Once winter sets in and the bugs are all dead or hibernating, you can relax, but until then, here’s what you have to look forward to:

Aphids.  Monitor plants very closely for aphid attacks especially in the center, the growing tip, of the plant.  Major damage here will seriously stunt growth.  Stronger, faster-growing plants are, for whatever reason, less interesting to aphids than plants who are already stressed from other environmental factors.  I fight them with water spray, insecticidal soap or castile soap spray, or neem oil spray.

Cutworms. These are big, hungry caterpillars who only come out at night and usually have two life cycles per year, one in the spring and again in the fall.  You’ll want to be on the lookout for both if you overwinter.  They can do an amazing amount of damage very quickly, and in the rainy season, It’s hard to get Bt sprays to stay on the plants if it’s raining all the time.  Hand-picking at night with a flashlight is effective but tedious.  Having grassy lawn-type areas nearby seems to attract them.

Cabbage worms. These are those white butterflies you see dancing around in summer.  They’re awful, but not as awful as cutworms.  Bt is quite effective since they’re only out during the summer when you can actually spray and not have it get washed off the plants immediately by the constant rains of October & November.

I have not had issues with root maggots, or any other pests but the three above.

V. PROTECTION

Here in USDA Zone 8b, protection against winter cold temperatures is rarely going to be necessary.  But it’s nonetheless a good idea to have a sense of how cold-tolerant your specific varieties are, and have a few things on hand to protect them if a cold snap is forecast.  Typically overwintering broccoli and cauliflower can handle it down to about 10°F.  Many cabbage varieties bred for winter harvest can take even more cold than that, with savoyed or semi-savoyed types being the most cold-tolerant. Kale, too, seems to be able to take absolutely anything. Some are good only to around 20°F.  Snow is an insulator, so if you actually get any, relax.  Cold snaps without snow are the ones to worry about.  Have a row cover or two on hand, something like Reemay or similar.  I wouldn’t advocate for a hoop house with plastic, because the humidity tends to be really high under those and it seems it would invite rot.  But you could try it.  Individual plant cloches probably won’t be too useful because these plants will be big. Hopefully.

VI. PICTURE TIME.

Here’s a collection of images documenting my experiment last season.  I had a pretty broad range of plant varieties and growing conditions, and harvests varied considerably in accordance.  Hopefully it’ll be useful to you to actually see the plants in their various stages.  Disclaimer: I am not a professional photographer nor blogger, and these photos were taken purely for my own recordkeeping, so, that means they’re kind of awful photos.  I’m trying to do better, if for no other reason than to not embarrass myself… Anyway, descriptions follow each photo.

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Picture taken August 23. These were started from seed indoors July 15, and set out about 6 weeks later.  Variety is cabbage, January King, seed from Territorial. They should have been bigger going into the ground, but they experienced slow growth before being set out because I let them sit in very small seedling pots for too long.  They also got some caterpillar damage while in those tiny pots.  Nonetheless, all but one of these produced a decent head of cabbage right in the middle of winter.  The smaller plants produced smaller heads, and the one that didn’t really head up was edible anyway, but it was a bit more like collard greens than actual head cabbage.  All that lettuce was harvested before the cabbage really needed the space, so this was a good succession pairing.

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This is actually a picture of a carrot fail, but it happens to show six cauliflower plants of an overwintering variety.  Photo taken August 23, plants started July 15, same conditions as the cabbage in the previous photo.  The early stunting wasn’t as much of a problem for these, I guess because they are the overwintering type and had a lot more time to catch up.  Seed from Territorial, the latest to mature from one of their blends.  The little one in the lower left produced a 3-lb head, earlier than the others, and the rest produced 4- to 5-lb heads in April.

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Also August 23.  All of these were also started indoors July 15.  With the exception of the cauliflower in the center row, they were set out much earlier than the previous two photos, so they didn’t sit around in tiny pots without growing for a couple of weeks.  You can really see the difference that slowed-growth period made!  On left, Brussels sprouts for fall harvest (with arugula in front there).  Most actually got harvested in January.  Aphids are a real problem even in September and they like Brussels sprouts best of all.  In the center, more overwintering cauliflower of an earlier-to-mature variety.  These experienced too much competition and were not able to grow very big.  They produced edible cauliflower right on schedule in February-March, but it was quite small.  On the right, we have cabbage variety ‘January King.’ mixed with some kind of salad greens mix which was a dumb idea.  As you can see the lettuce is just bolting and everyone else is too crowded.  It could have worked as a succession pairing IF I had actually harvested and removed the salad greens. They all got a lot of aphids and it was really hard to keep those bugs out of the centers of the cabbages. The big one in front gave us a 6 lb head in November.  I believe only one of the rest produced a well-formed head.  This was mostly due to aphids.   In the very back is a really fast-growing broccolini-type broccoli, ‘Apollo’ which was shockingly vigorous, but it formed all its florets during weather that was still pretty hot, and we found it bitter and nearly inedible.  If I ever grow this again, I will start seeds WAY later than July 15.  More like September 15.  That variety says it takes 60-90 days and I swear it took no more than 40.  A harvest in cooler weather would probably make for better flavor.  The thing going to seed behind ‘Apollo’ is a bok choi from the same salad mix that is mostly on the right side of this bed with the cabbage.

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Yet another August 23rd photo. Again these are plants who did NOT sit around in tiny pots and stop growing.  On the left we have ‘Apollo’ broccoli again, showing evidence of harvesting already.  And bolting!  Again should have planted that quick-maturing variety a bit later so it could avoid the heat stress and taste better.  On the right with the bluer leaves we have two or three other types of broccoli for fall harvest, and I regret I don’t know the exact varieties because they came from one of Territorial’s blends.  These were definitely a variety that matured more slowly than ‘Apollo’, and they ended up being quite successful although they didn’t produce large heads.  They may have been a green sprouting type like ‘Endeavor’.  Or it’s certainly possible that I just didn’t grow them very well.  There is also kale and komatsuna mixed in here, both of which were a decent succession pairing.  Lettuce was a better match, although komatsuna makes a great aphid trap crop, and I let one plant stand in here just for that purpose.

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Again August 23.  This was the group that languished in tiny pots for the longest.  The six plants closest to viewer are heirloom purple sprouting broccoli, the next 6 are collards, ‘Flash’ hybrid, and the last 6 are Brussels sprouts from yet another blend with unnamed varieties from Territorial.  Those never amounted to much.  The sitting around was NOT good for them, and they aren’t as cold-hardy as the others so they just couldn’t grow enough size while it was still warm to produce sprouts of eating quality.  The one in the far upper left, who appeared to show the most promise of all, became a big, gorgeous plant, and actually tried to form sprouts in the spring, but by then it was too warm and they were all totally loose.  The collards were fine.  They are soooooo easy.  They would have been better had they not been stunted, but they stood through the winter and gave us huge harvests of nice leaves in early through mid spring before they flowered.  The purple sprouting broccoli did very well, each plant giving us more than we could keep up with.  So, apparently the longer maturing time of the truly overwintered types means that these are more tolerant of the abuses the weather – and the gardener – will dish out.

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More cabbage of ‘January King’ variety.  August 23 photo, plants started from seed with all the others July 15.  See the big ones? Those produced really nice, big, well-formed heads.  The smaller plants took longer and produced smaller, less dense heads.  The largest ones were harvestable in late November, the smaller ones took until February or even later.  This very cold-tolerant variety seems pretty flexible, so I think it’d be a good one to experiment with in succession planting throughout the cool season.  You could probably even start indoors in January and set out transplants in Feb-March for a spring harvest.

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January 9.  The long harvest of purple sprouting broccoli has begun, and would continue through April.  This early stuff came from the larger plants who did not get stunted.

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This is one of several Brussels sprout plants that formed only very loose sprouts.  We treated them as collard greens (ate the larger leaves rather than the sprouts).  To avoid this loose sprout condition, I should have grown these plants faster when they were very young. Other than that I’m not sure what went wrong so I’m just going to try it again and see.  Photo from March 3.

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The first of the peas are starting to flower in this photo from April 8.  These are the same cauliflower plants that you see in the second picture on this page.  You are watching them for months, wondering when they will do their thing, and all of a sudden this pops out from the leaves and it’s just glorious.  What I particularly enjoy is being able to bring something in from the garden at this time of year which has real heft to it.  a 5-lb cauliflower just feels wonderful to carry in, when anything else you’re harvesting in early to mid spring is lightweight stuff like baby greens and handfuls of peas.

So, this year, I will take even more pics, and here’s my list of varieties I have on hand that I’ll be trying. Some are leftovers from last year that I’ll do again, most are new this year.  Last year’s mistakesresulted in about 50% success overall, so I figure if I do it right I can get twice as much harvest out of the same space/number of plants, and I really like a LOT of variety in this species.

Broccoli:

  • Purple sprouting (heirloom, not a named hybrid)
  • “Fall Broccoli Blend” from Territorial
  • Rudolph, a green sprouting broccoli hybrid

Brussels sprouts:

  • “Nordic Winter Blend Hybrid”, another one of Territorial’s variety packs, for harvest December through March.
  • “Autumn Harvest Hybrid Blend” – I went nuts with the variety blends last year.  I may have missed the planting window on this one.  It says to sow May-June.  Oh well; it’s long-lived seed.

Cabbage:

  • January King
  • “Winter/Spring Hybrid Blend” from Territorial… I did mention I went nuts with these blends last year…
  • Tundra F1
  • Katarina F1
  • Murdoc F1 – Always wanted to try a conehead cabbage!

Cauliflower:

  • “Winter into Spring” Territorial hybrid blend (I think; can’t find the outer seed packet).  These will surely get planted again.
  • Purple of Sicily
  • Orange Burst

Other:

I’m also going to try peas (Oregon Sugar Pod II), Fennel (Victorio F1) and Chinese cabbage (Soloist).  I had mixed results with Chinese cabbage sown in midsummer along with the other brassicas last year, and decent results with early spring sowings of the same variety, but I didn’t love the looseness of that variety so I’m trying again with ‘Soloist.’

I will be sure to take more pictures this year and will keep everyone updated with progress as we go!

In solidarity against slugs,

Susan