Hakurei turnips – Sustainable Market Farming

How cold can leafy greens and salad crops survive?

Our hoophouse beds after the nights at 2F (-17C) and 8F (-13C). Looking amazing! Pam Dawling

We were luckier with the weather than many people over the weekend (12/23-12/26/2022). And so were our vegetable crops. On Friday 12/23 we prepared for a suddenly very cold night. It was very windy as we battled to stop the hoophouse windows from blowing open. We finally got some shims, a hammer and a stepladder, and wedged them closed. They stayed that way until Tuesday 12/27. We were fortunate in getting no precipitation (I hate ice!) and no power outage.

Pool noodles repurposed as draft excluders.
Pam Dawling

We fortified the doors with our rock collecting buckets, and prevented most of the under-door drafts with our pool noodle draft excluders. They have a rope running through them, which is hooked onto small cup-hooks on the door frame. We repurposed noodles that had been used as props at a party or some other kind of event. They had been covered in tube socks and had glued-on googly eyes.

Rolls of rowcover at the ready in our hoophouse.
Pam Dawling

It was a bit unnerving being in the hoophouse as it creaked and groaned in the wind. In the winter we keep rolls of rowcover ready for any night we think will be below 8F (-13C). We unrolled the rowcovers by lunchtime and laid tools on the ends nearest the doors. I was worried that if we lost power, and therefore the inflation, it would get very cold indeed in the hoophouse.

The DIY manometer in our hoophouse. (the background lines have faded). Pam Dawling

Since we last changed the plastic we haven’t managed to get the recommended 1/3” (8.5mm) pressure difference in the “bubble” between the plastic layers, compared to our normal air pressure. Mostly we don’t even get ¼” (6.5mm). The “bubble” provides thermal insulation as well as physical strength against snow or ice buildup, and strong winds.

It got down to 2F (-17C) outdoors Friday night, and Saturday didn’t warm up much. I don’t actually know what the night temperature was in the hoophouse as our recorded low temperatures don’t make sense: 14F (-10C) for four consecutive nights (Fri to Mon). I suspect we didn’t reset the thermometer correctly. Usually the hoophouse can hold 8 F (4.5 C) degrees warmer than outdoors, but not 12 F (7 C). It looks like it did, perhaps because we didn’t open it all day!

Soil thermometer in our hoophouse on 27 December 2022.
Pam Dawling

The soil is still nice and warm in there: 59F (15C). That really helps. The rowcovers are usually removed in the daytime, either pulled aside if we expect to need them again the next night, or rolled up out of the way. Most of the time they stay rolled up at the east end of the hoophouse. We appreciate not needing to deal with rowcovers most of the time! On Saturday 24th, the temperature maximum for the day outdoors was 24F (-4.5C), and we kept the rowcovers in place over the crops. On Sunday the high outdoors was 28F (-2C) so we pulled the rowcovers aside until the night. On Monday 26^th the night-time forecast was benign enough that we rolled the rowcovers up. And now we get a milder spell.

Hakurei turnips with frozen yellow leaves where they touched the plastic (rowcover protected the plants). Pam Dawling

How did the crops fare? It’s not always obvious at first if a crop has been killed by cold or not, But I can now say with confidence that nothing died. The edge beds are always the coldest. The south edge bed had Hakurei turnips, delicious and notoriously the least cold-hardy turnip variety. Most of the globe of the turnip sits on the surface of the soil. You can see in the photo that some of the leaves, the ones right by the wall plastic, have been killed and turned yellow. But the roots themselves (with rowcover over them) seem fine.

Bright Lights chard with cold-damaged stems in our hoophouse north edge bed after nights at 2F and 8F
Pam Dawling

Over the other side, in the north bed, we have some Bright Lights chard, among other things. Multi-colored chards are less cold-hardy than red ones, which in turn are less cold-hardy than green ones. We know we take a risk in growing Bright Lights through the winter, but we so enjoy the sight of the short pieces of colored stems in our salad mixes that we take the risk. Some of the stems have curled over, probably on their way to dying, but the plants live on, to provide many more salads this winter! And some cooked greens too.

Some of the giant senposai leaves, where not fully protected by the relatively narrow rowcover, have developed tan dead spots, so those leaves can just continue as the plants’ solar panels until we get tired of looking at them and decide they are no longer needed.

Each winter I update my Winter-Kill Temperatures of Cold-Hardy Vegetables list, except this past spring I had nothing new to add. Outdoors, I noticed today that the tatsoi has definitely died, the Vates kale and the spinach have survived (uncovered) and the small garlic leaves don’t seem troubled. The leftover lettuce transplants have been damaged, if not killed.

Mid-winter hoophouse harvests

December 29 hoophouse crops Photo Kathleen Slattery — December 29 hoophouse crops
Photo Kathleen Slattery

Here we are in the shortest days. What are we harvesting from our hoophouse (high tunnel)? Many different crops, mostly leafy greens, but with the addition of radishes, turnips and scallions. I’ll start with those.

White Icicle radish Photo Southern Exposure Seed Exchange — White Icicle radish
Photo **Southern Exposure Seed Exchange**

We’re harvesting our third sowing of radishes, sown on 10/30. We like the vari-colored Easter Egg radishes and the long White Icicle for this time of year. Cherry Belle also works in this sowing, but not later. Like Sparkler, it gets too fibrous in winter.

Our favorite scallions are Evergreen Hardy White, which are extremely cold tolerant. They are also slow to grow. We are starting to harvest the ones we sowed 9/6. The second sowing (which followed the first radishes on 11/18) are just spindly little blades so far.

Hakurei turnips Photo Small Farm Central — Hakurei turnips
Photo **Small Farm Central**

The turnips (and their greens) which we are starting to harvest at tangerine-size, are Hakurei and Red Round, from a 10/14 sowing. We made a second sowing of turnips on 10/26, but we over-watered them and got patchy germination. We filled the gap with a late sowing of brassica salad mix. This is a mixture of random leftover brassica seeds (varieties we didn’t like, seed that is getting a bit old) which we sow and then cut with scissors about an inch above the soil once they get to about 4″ tall.

Baby lettuce mix in the hoophouse. Photo Twin Oaks COmmunity — Baby lettuce mix in the hoophouse.
Photo **Twin Oaks Community**

Just like baby lettuce mix. We are on our second cut of our 10/24 lettuce mix. We buy the mix already made, although if we get close to running out of seed, we have been known to mix in some seed of basic varieties like the Salad Bowls, that do well in the winter high tunnel. We also have lots of big lettuce plants. We take leaves off those for our salad mixes when we don’t have baby lettuce mix at the right stage for cutting.

Ruby Streaks beside green mizuna. Credit Ethan Hirsh — Ruby Streaks beside green mizuna.
Credit Ethan Hirsh

Into the salad mix we add chopped mizuna and its spicier cousins Golden Frills, Ruby Streaks and Scarlet Frills. These add loft, visual interest and flavor. For color we also add chopped Bulls Blood beet leaves and chopped small leaves of Brite Lites chard. As well as mixing the colors and shapes, I try to have at least one representative of each of three crop families: spinach, chard and beets; lettuce; brassicas such as mizuna, baby kale leaves, small leaves of Tokyo bekana, Yukina savoy, tatsoi.

Tatsoi in the hoophouse Photo Wren Vile — Tatsoi in the hoophouse
Photo Wren Vile

For cooking greens we are harvesting leaves of Russian kale (transplanted 10/22), our first chard (transplanted 10/16), spinach (sown 9/6 and 10/24), senposai (transplanted 10/24), Tokyo bekana (transplanted 10/9) and Yukina savoy (transplanted 10/24). it takes 10 gallons of greens to provide 100 people with a healthy serving each. We aim to provide the cooks each day with a choice of two or three different cooking greens.

We are also harvesting some greens as whole heads now. We are clearing our first planting of tatsoi (sown 9/7), which has been getting ready to bolt for a couple of weeks now. Likewise the Tokyo bekana, which starts to bolt at the end of December.

Hoophouse Yukina savoy at the end of November. Photo Ethan Hirsh — Hoophouse Yukina savoy at the end of November.
Photo Ethan Hirsh

We are also cutting big heads of Chinese cabbage and Pak Choy. As we harvest these, we fill the gaps at the end of the day with replacement plants. My current favorite is senposai, as it is very quick to grow and can be eaten at any stage. (And of course, it’s very tasty, otherwise I wouldn’t even mention it!) We reckon 12/31 is the last worthwhile date for us to do this gap filling with Asian greens. After that we use spinach or lettuce transplants up till 1/25, then only spinach (up till the end of February). We’ve found that planting after those dates doesn’t produce harvest, just wasted time!

The Yukina savoy doesn’t really start bolting until the last week of January normally, but with the freakish warm weather we’ve had this December, we might get early bolting. I don’t know if this crop bolts mostly in response to day length or to temperature. I guess we’ll find out.

We’ve ordered our seeds, we’re planning our next hoophouse crops and our schedule for sowing seedlings in the greenhouse. And this is the slow season!

Bulls Blood beets add intense color to salad mixes. Photo Wren Vile — Bulls Blood beets add intense color to salad mixes.
Photo Bridget Aleshire

What’s still standing after two nights below 0F?

Recently I reported on which crops were still alive after two nights at 14F (-10C) and What’s still alive after two nights at 4F? We’ve now had the Polar Vortex, which brought us two nights at 4F, on 1/6 and 1/7. Then it got even colder.We got the Big Round 0F 1/22-1/23, then a few nights at 5F or 6F, and then the big insult: -4F on the night of 1/29-30.

What’s still standing?

The Tyee spinach under thick rowcover has sustained big damage, showing as patches of beige dead cells. It will recover. Meanwhile we can eat from the more-protected spinach in the coldframes and the hoophouse.

The Vates kale without rowcover is still alive, but badly damaged. The big leaves are crunchy and brown round the edges, and some of the inner leaves are dead. I hope it will grow back, but we won’t be able to pick that for a while. The Beedy’s Camden kale looks worse – the big leaves have died and flopped over. Not sure if it will recover.

Many of our strawberry plants look dead – very disappointing!

Our hardneck garlic and Polish White softneck tops are killed back to about one inch up from the mulch. Equally hardy, it seems.

We had the remains of a lettuce nursery bed, still holding surplus transplants from September sowings that we didn’t need for our greenhouse or hoophouse. After the 4F assault we still had life in the centers of the Winter Marvel, North Pole, Tango, Green Forest. Now only the Winter Marvel shows any signs of life. So that variety gets the prize for cold-tolerance here!

Red Round Turnip. Photo Baker Creek Heirloom Seeds — Red Round Turnip.
Photo Baker Creek Heirloom Seeds

In the hoophouse, we covered all the beds with thick rowcover every night it looked like dropping below 10F inside. Almost everything survived – we only got some minor stem freezing on some turnips and Asian greens. We have been eating Pak Choy, Tokyo Bekana, Yukina Savoy, various turnips and their greens (Hakurei, White Egg, Oasis, Red Round), also plenty of lettuce leaves, radishes, scallions, and some spinach. We lost our second sowing of spinach in there to over watering and flooding, and we are really noticing the lack right now. We’re short on spinach. We have small amounts of mizuna, Ruby Streaks, Bright Lights chard, Bulls Blood beets to add to salad mixes, and Red Russian and White Russian kale growing slowly.

In January we have taken to sowing spinach, kale and collards in a hoophouse bed to transplant outdoors in early spring. We back this up with sowing some in flats if we don’t get good emergence for some reason. This year emergence is late. Is it just late, or is there a problem? We’re holding our breath for a few more days. . .

We are not the only people tracking the effects of the unusually cold weather. The February Growing for Market magazine opens with an article by Ben Hartman “Testing the Limits of Cold Tolerance”. He farms in Goshen, Indiana, using two double-layer plastic greenhouses heated to 30F (yes. I said heated!) and two unheated. They planted kale, carrots, spinach, salad greens and arugula in their greenhouses for winter harvest. Their outdoor temperatures fell to -16F on 1/6 and 1/7. I imagine they’ve had worse since. They used mid-weight rowcover over their beds. Ben reports that baby greens and young spinach survived, as did their rosemary and their 3 fig trees (all farmers deserve some thrills!). They lost baby salad greens that had already been cut previously (all those cut edges didn’t do well). Crops in the outer beds were lost. The tips of full-grown kale leaves froze, but the plants survived.

In their unheated, single-skin plastic hoophouses, the soil froze down to 4″. They used two layers of mid-weight rowcover suspended over the crops. Despite this cold, tiny salad greens less than 1″ tall survived. Spinach survived under just one layer of rowcover. The carrot tops froze and the roots may or may not be marketable. The (uncovered) fully mature kale looks dead. The mature salad with two layers of rowcover didn’t survive.

From this experience, Ben points out that salad greens and spinach less than 1″ tall are very cold-tolerant. Spinach and kale once larger, benefit from more protection than they got this time. Beware the outer beds!

My own article in this issue is about matching crop spacing with desired goals, such as maximum yield, optimum size, or convenience for cultivation.

Andrew Mefford has written some greenhouse tips for hoophouse growers, including tomato grafting, trellising. Chris Blanchard has written the second part of his piece on growing herbs – this is about harvest and maintenance. Erin Benzakain has undertaken a 59-variety trial of celosia.

What’s still alive after two nights at 4F?

Recently I reported on which crops were still alive after two nights at 14F (-10C) and several others in the teens. We’ve now had the Arctic Vortex, which in our part of central Virginia, meant two nights at 4F, last Monday 1/6 and Tuesday 1/7 nights. How did it go?

Before the Prelude to the Big Chill, when we got 9F, I harvested the odds and ends of small cabbages left in our main patch. Quite worthwhile, I got two 5-gallon buckets. Between the 9F and the 4F nights, I decided to gather the Deadon cabbage, which we grew with January harvests in mind. There was some freeze damage, so in future I’ll say that Deadon is good down to 10F, but not lower. I got two full net bags and two more buckets of small ones. I left one smaller and one larger cabbage as sacrificial victims in the cause of better information for next year. When we got 4F, the smaller one died and the larger survived.

Deadon cabbage Credit Johnnys Selected Seeds — Deadon cabbage
Credit Johnnys Selected Seeds

One of the other gardeners harvested the last of the outdoor senposai. Another couple of buckets of tasty food.

Senposai, the Thousand Wonder Green, Credit Kathryn Simmons — Senposai, the Thousand Wonder Green,
Credit Kathryn Simmons

I took another walk round the frozen garden after the Big Chill, to see what is still alive. We have Tyee spinach under rowcover, and Vates and Beedy’s Camden kale without rowcover. They are all still alive! There’s some freeze damage in spots on the spinach leaves, but plenty of good meals still to come!

Our hardneck garlic tops suffered some damage but didn’t get killed back to the mulch level. The Polish White softneck tops are considerably smaller and they too are still alive. They will grow back if they have died.

Garlic planting in November. Credit Brittany Lewis — Garlic planting in November.
Credit Brittany Lewis

We had the remains of a lettuce nursery bed, still holding surplus transplants from September sowings that we didn’t need for our greenhouse or hoophouse. A good chance to see which ones are hardiest! Here’s the scoop:

Still alive in the centers – Winter Marvel, North Pole, Tango, Green Forest. No longer alive – Salad Bowl, Red Salad Bowl, Winter Wonder, Red Tinged Winter, Merlot, Red Sails, Outredgeous, Roman Emperor, Revolution.

At nearby Acorn Community, the home of Southern Exposure Seed Exchange, they had some young but mature heads of cabbage outdoors. The Late Flat Dutch, Early Flat Dutch and Chieftain Savoy all survived one night at 6F. (It’s usually two degrees warmer there than at Twin Oaks on winter nights).

Meanwhile I’m tracking the Blue Ridge kale grown by Clif Slade in his 43560 project at Randolph Farm, VSU. The Blue Ridge survived. It got down to 9F there. Not as cold as Louisa County! Blue Ridge is taller than the Vates we grow, and I’d like to try it here, if it can survive our winters. Otherwise not!

In the hoophouse, we covered all the beds with thick rowcover on Monday afternoon, and didn’t roll it up till Thursday, after the warmer weather returned. There was a tiny bit of freeze injury on some turnip greens that poked out the side of the rowcover, and some on some stems of Tokyo Bekana. I think the rowcover saved the crops! Also, a bad thing happened. it was very windy Monday night and the west window blew open. Argh! Of all the nights to have an open window. Memo: fix the latch to make it stronger.

I didn’t enjoy the really cold weather. I was anxious about the crops and the plumbing! But I can see two silver linings: I now have more information about cold-hardiness of various crops, and hopefully some pests will have died. Now we’re getting ready for another two cold nights, tomorrow and Wednesday.

When we placed our seed orders we gave up for this year on our quest for a reliable red cabbage of at least medium size and fairly speedy maturity (90 days or less). We’re having a red-cabbageless year. We’re still open to recommendations (OP or hybrid) – please leave a comment.

What’s still alive at 14F?

Winter garden scene. Credit Ezra Freeman — Winter garden scene.
Credit Ezra Freeman

One of my ongoing topics of interest in the garden is how cold-tolerant various vegetables are. We’ve now had two nights at 14F (-10C) and several others in the teens. I took a walk round the frozen garden this morning to see what is still alive. We have Tyee spinach under rowcover, and Vates kale. The senposai is still alive, but some of the midribs have brown streaks. Sadly we don’t have any leeks this winter, as we lacked enough workers to tend them in late summer. We have a nice bed of Deadon cabbage, and I notice that some small heads of Melissa savoy that missed the bulk harvest are also alive. The Gunma cabbage stumps have some leaves and tiny heads still alive, but the Tendersweet are done in.

Our ongoing quest for a reliable red cabbage of at least medium size and fairly speedy maturity (90 days or less) yielded no success story this year. We grew Super Red 80 happily for many years, but then it stopped working for us – variable heads, slower maturity. If you have any recommendations (OP or hybrid) please leave a comment. We are working on our seed orders now, and this would be a great time to have some suggestions.

Back to today – our chard had all the leaves cut off in November, and seems to be dead. Some winters it hangs on later, if we leave some foliage to help it regenerate. We have also some years deliberately kept it alive for spring by using rowcover on it. We do that if we go into winter short of spinach beds.

The oats cover crop we sowed in August and early September look pretty much dead. All the broccoli looks dead. That’s as expected for the temperatures. Often we don’t get nights this cold till January – the cold came early this winter.

Our hardneck garlic tops look to be in good shape. The Polish White softneck tops are considerably smaller and look like they are suffering. They will grow back if they have died. Some of our Chandler strawberry plants look dead. Either that or they are extremely dormant! The deer were killing them off by eating the leaves. Too many deer!

Garlic shoots emerging through the mulch in November

The hoophouse is still bursting with great food. Plenty of salad greens: lettuce; various kinds of mizuna and ferny mustards like Ruby Streaks and Golden Frills and Bulls Blood beet leaves. And for salads or cooking we have spinach, chard, tatsoi, radishes, scallions, baby Hakurei turnips and their tasty greens, Red and White Russion kales, and more senposai. Soon we’ll start on the heading Asian greens: pak choy, Chinese cabbage, Tokyo bekana and Yukina Savoy. The first sowing of tatsoi (9/7) is starting to bolt, so we’re clearing that. The second sowing (11/15) needs thinning to an inch. The first round of baby lettuce mix (10/24) is ready for its second cut. In a few days we’ll make a second sowing of that. I love working in the hoophouse on sunny winter days. This afternoon I plan to complete the transplanting of an 11/9 sowing of spinach. We just love the sweet nuttiness of winter spinach!

The hoophouse winter crops are an important part of feeding ourselves year-round