Growing Kale and Other Brassicas in Winter

I just moved to central Texas, after spending most of my gardening life in a tropical, frost-free climate. So gardening in this climate is basically brand-new to me. I know that I can grow kale, collards, and possibly other brassicas (?) through the winter here, but am not sure at what size the seedlings can tolerate freezing temperatures.

I started a whole bunch of brassica seeds (multiple varieties of kale, plus cabbage, broccoli, and cauliflower) a bit late, and now have a bunch of wee babies in pots on my porch. We have not had a frost yet, but I am thinking when we do have one forecast, I should bring them all in for the night, and then move them back out in the morning if it is warm enough. Am I correct in this? And if so, at what size would you plant them outside and let them fend for themselves through a frost?

As I'm typing this, I am thinking that the sudden temperature change of moving them back outside might not be good for them either? We keep our house at about 70 degrees when we have to use the heat, and the warmest it would probably be outside after a frost would be 45 or 50 (I am guessing). I don't have grow lights to keep them indoors all the time.

What is the expected nighttime temp? Here my seedling just laugh at frosts. They do need to be 3 inches tall before it frosts on a regular bases. They'll live, smaller, but don't grow until spring, when they rush to bolt as quick as possible.

Joylynn Hardesty wrote:What is the expected nighttime temp? Here my seedling just laugh at frosts. They do need to be 3 inches tall before it frosts on a regular bases. They'll live, smaller, but don't grow until spring, when they rush to bolt as quick as possible.

That is good to know! Thank you! The forecast for Friday night is 33, which I know isn't quite freezing, but if for some reason it goes a degree or two lower than forecast, then it would be. After that, we go back to high 40s to mid 60s at night, and days in the 60s and 70s, so it's really just that one night (in my 10-day forecast, anyway) that I'm worried about them.

I'm developing a landrace of brassica with the goal of winter hardiness. As Joylynn said they need to have some size to them before hard frost or freezing. I don't know for sure what that size is. Last year I started mine in late summer of 2020. This year I started them a little later and after several nights in the low 20s F have lost some, I don't know how the reminder will do the rest of winter.  

The picture of those from last year was taken on March 3rd of 2021 on a morning with the temp at 11 F.  This is the size they were when it got cold and before the resumed growth this spring.
 
*This family of plants will bloom after having gone through a cold period. It will not make heads or brussels sprouts or whatever it normally makes when grown traditionally. The flower heads, stalks and leaves are all good used like broccoli. In my garden I'm doing this on purpose to have very early harvest of spring greens while it is still too cold for the cabbage worms to bother the crop.

Lila Stevens wrote:I just moved to central Texas, after spending most of my gardening life in a tropical, frost-free climate. So gardening in this climate is basically brand-new to me. I know that I can grow kale, collards, and possibly other brassicas (?) through the winter here, but am not sure at what size the seedlings can tolerate freezing temperatures.

I have Russian Red kale that regularly overwinters just fine here in NE Kansas. The frosts improves the flavor in fall and early winter. When the sub-zero temperatures start to hit, they go dormant until spring when they start to bolt and produce tons of delicious little broccolinis

Hi Lila,
I live in Arizona zone 8b. Growing vegies in winter here is both very easy and sometimes very challenging. Easy because I only have to water about once a week and THERE ARE NO BUGS, MILDEWS OR VIRUSES AROUND!! I love that part. I start lots of  root vegetables in September/October....  carrots, beets, leeks etc. I just give them a little shade and they germinate quickly. Right now the diakon radish and leeks are pretty big, all the carrots and beets are still young teenagers It's been around 40* every night for the last month. We're due for a hard freeze on Friday night. They will continue to thrive and grow slowly all winter and I'll start harvesting probably in March or April or when I get hungry, whichever comes first. The chard that I planted in the spring fed me all summer. Now it will stop growing until about April and then it will bolt to give me more seed. Good stuff.

Brassicas are a little more of a challenge. In my county and most of Arizona the extension services recommend you start your seeds from July 15th to September 15th to have a fall garden.  HOW THE HELL DO YOU DO THAT! From June until about October 1st it's still over 100* here and nothing wants to germinate! If they do germinate they won't grow, ever! The tiny little things just sit there till months later I put them out of their misery. But the fact is once, just once about 5 years ago it worked. I don't know how or why and it drives me crazy!! I had all my seedlings started on a picnic table under a tree in heavy shade (which I had tried before and since) and they grew and were so happy. I had a fall harvest. So I keep trying to do it again every year. But it hasn't worked.

What usually happens is they don't germinate until around late September or early October and then I plant them out with plenty of mulch around December 1st when they're young juveniles, around 8” tall. Then they will grow slowly and happily all winter long. They love the cold and they love snow! I am including pictures that I took back in 2015. The first one  shows the 12” of snow we got on January 1st. The 2nd picture is the same path 6 weeks later on February 19th. You can see all the brassicas on the left now that the snow is gone. They loved it! The problem is that come spring there is a 50% chance that they will just bolt. Some years the cabbages bolt while other years it's the broccoli. Don't know why but it sucks. A few years back I tried growing them under 12 gauge wire fencing tunnels (picture # 3) with plastic.  But we got a heavy snow again which collapsed all the tunnels and after that ½ of them bolted again. They are after all, biennials and they are supposed to bolt and produce seed after going through winter.

And this year once again they just didn't germinate in the heat. So I am just now starting to warm up my little greenhouse and I will start my brassica seeds in a couple of weeks for an early spring garden. Hope this helps. Happy gardening.

Hi Lila, If I were you I would just find a cardboard box or something to cover the trays overnight when you have frost expected. That will protect them just a bit and give you a bit of peace of mind.
Here I would start brassica in April, when there is still a possibility of frost,(although pretty unlikely ) so they may well be OK without protection anyway.

Thanks! Yes, the hot summers are problematic here as well. I think October would have been the ideal time to start them here, as it started to cool down in early October, but life got in the way, and it was early November by the time I got some seeds planted, and almost December before I started the next batch. I figured it only costs me some seeds and my time, though, so it's worth it to try and have some fresh greens through the winter. My understanding of this area is that truly cold weather rarely settles in for long (in a normal year), so lots of nice, warm growing days between cold snaps.

I believe we are in zone 8b here as well, but snow is extremely rare here. Except for last winter, which was before I moved here.

Debbie Ann wrote:Hi Lila,
I live in Arizona zone 8b. Growing vegies in winter here is both very easy and sometimes very challenging. Easy because I only have to water about once a week and THERE ARE NO BUGS, MILDEWS OR VIRUSES AROUND!! I love that part. I start lots of  root vegetables in September/October....  carrots, beets, leeks etc. I just give them a little shade and they germinate quickly. Right now the diakon radish and leeks are pretty big, all the carrots and beets are still young teenagers It's been around 40* every night for the last month. We're due for a hard freeze on Friday night. They will continue to thrive and grow slowly all winter and I'll start harvesting probably in March or April or when I get hungry, whichever comes first. The chard that I planted in the spring fed me all summer. Now it will stop growing until about April and then it will bolt to give me more seed. Good stuff.

Brassicas are a little more of a challenge. In my county and most of Arizona the extension services recommend you start your seeds from July 15th to September 15th to have a fall garden.  HOW THE HELL DO YOU DO THAT! From June until about October 1st it's still over 100* here and nothing wants to germinate! If they do germinate they won't grow, ever! The tiny little things just sit there till months later I put them out of their misery. But the fact is once, just once about 5 years ago it worked. I don't know how or why and it drives me crazy!! I had all my seedlings started on a picnic table under a tree in heavy shade (which I had tried before and since) and they grew and were so happy. I had a fall harvest. So I keep trying to do it again every year. But it hasn't worked.

What usually happens is they don't germinate until around late September or early October and then I plant them out with plenty of mulch around December 1st when they're young juveniles, around 8” tall. Then they will grow slowly and happily all winter long. They love the cold and they love snow! I am including pictures that I took back in 2015. The first one  shows the 12” of snow we got on January 1st. The 2nd picture is the same path 6 weeks later on February 19th. You can see all the brassicas on the left now that the snow is gone. They loved it! The problem is that come spring there is a 50% chance that they will just bolt. Some years the cabbages bolt while other years it's the broccoli. Don't know why but it sucks. A few years back I tried growing them under 12 gauge wire fencing tunnels (picture # 3) with plastic.  But we got a heavy snow again which collapsed all the tunnels and after that ½ of them bolted again. They are after all, biennials and they are supposed to bolt and produce seed after going through winter.

And this year once again they just didn't germinate in the heat. So I am just now starting to warm up my little greenhouse and I will start my brassica seeds in a couple of weeks for an early spring garden. Hope this helps. Happy gardening.

Nancy Reading wrote:Hi Lila, If I were you I would just find a cardboard box or something to cover the trays overnight when you have frost expected. That will protect them just a bit and give you a bit of peace of mind.
Here I would start brassica in April, when there is still a possibility of frost,(although pretty unlikely ) so they may well be OK without protection anyway.

That sounds like an excellent idea. I think I will do that. Many of them only have their first baby leaves so far, so I would feel better giving them some protection, whether it's actually needed or not.

Just a quick updated; we did indeed get a frost, even though it wasn't forecast to get that low. I think it was below freezing for a few hours in the early morning. I had moved most of my baby plants into our unheated garage the night before, and of course they were fine. I decided not to leave them out and cover them, because I  have an 8-month-old puppy that would pull off whatever cover I used and destroy it, pulling down and destroying the plants in the process. He is quite the garden pest.

I did leave a half-dozen or so of my larger kale babies (each about 3-4 inches tall, with 4 true leaves, and in gallon-size pots) out on the porch railing, and they were also fine. A few looked a bit wilty in the first half of the day, but had perked up by evening, and now look just like the others. This tells me they really could go into the ground at this point and be just fine.

Next frost I will leave a few smaller babies out and see how they do. I couldn't stand to risk losing all of them, but I am curious to find out how they handle frost at that size, for future reference, because if I could just direct seed them at any time of year, well, that would be good to know.

This is a backyard garden in Toronto growing brassicas and lettuce. She planted in mid August.

I haven't yet succeeded in growing kale in the winter here in northern Minnesota, but as an experiment I brought two small (6-7 inches tall) plants indoors that I grew in containers on the deck-rail and they went through a couple of dips into single-digit Fahrenheit before I brought them in. One of them seems to be putting on new growth and the other one doesn't look dead, but also isn't doing anything. Anyway, just providing a data point that they're pretty hardy.