Mizuna is a very mild flavored crop, with thin juicy white stems and green ferny leaves which add loft in salad mixes. (“Loft” is the word for the “puffiness” of frilled salad crops, helping them occupy space and not collapse in the bottom of the bag or bowl like wet green corn flakes.) This tolerant crop is very easy to grow, tolerates cold wet soil, and variable weather. It is fairly heat tolerant (well, warm tolerant), and cold tolerant to 25°F (-4°C).
We used to just grow just one planting, sowing it outdoors September 24, transplanting it into our hoophouse October 22. It regrows vigorously after cutting and we harvest leaves from November 27 to January 25 or even to March 7, when it becomes a mass of small yellow flowers (edible!). In the winter, once the plant gets bigger and bushier, we switch from harvesting individual leaves to a method we call the “half-buzz-cut.” We gather the leaves on one side of the plant and cut them with scissors about an inch above the soil. Then we chop them into our salad mix harvest bucket. The plants look odd with half their leaves still full-size and half shorn, but this method seems to help the plant regrow quicker. The big leaves can photosynthesize and feed the regrowing leaves.
Next we tried Purple Mizuna, but we were disappointed with the weak color and a constitution less-robust than green mizuna.
Ruby Streaks and other Frilly Mustards
After a few years of growing mizuna, we discovered Ruby Streaks. It has a much stronger color, and I admit, a much stronger flavor. Our diners don’t generally like pungent greens, but this one, cut small and mixed with other salad greens, gained wide approval. We have moved on to include Golden Frills and Scarlet Frills, and for a while Red Rain. We find the Scarlet Frills and Golden Frills bolt (go to seed) later than Ruby Streaks and Mizuna.
Adding a Second Sowing
We added a second sowing, this one direct-sown in the hoophouse, on October 30, and the next year shifted the date to November 9. These direct-sown mustards can be used for baby salads after only 21 days (when thinning the rows, for instance). Thin to 8″–12″ (20–30 cm) apart, to grow to maturity in 40 days. We sow mizuna and the spicier mustards at the same time, usually 6 rows to a 4’ (1.2 m) wide bed, maybe a total row length of 50’ (15 m). This sowing gives us harvests from February 26 to March 24, several weeks later than the September 24 sowing.
When we learned our hoophouse soil had nematodes some years ago, we searched for resistant crops and were happy to learn that Brassica juncea greens were resistant. Although mizuna is not B. juncea, the more pungent frilly mustards are, so we focused on growing those, and ignored mizuna for several years.
Adding a Third Sowing
We were looking for a late winter nematode-resistant crop to follow our Koji, which I think bolts up to a month earlier than my long-time favorite Yukina Savoy. We tried the frilly mustards, sown February 1, and they were very successful. We got harvests from March 24 to April 23, a very worthwhile month of greens! I like greens that are harvestable in March and April, because this is really our Hungry Gap, the time when the stored crops are running out and the outdoor spring-planted ones haven’t really got producing much yet. I’m a bit suspicious of our record-keeping on the April 23 date – I suspect it was really over before that. It seems unlikely that this sowing lasts 30 days when the second one only lasts 26 days.
As part of a renewed effort to manage the nematodes, last year we added in a fourth sowing, on October 30. I haven’t got any records for that harvest to hand. I do remember though, that we had about as much “Frills” (as we now call them) as we could eat. We planted 30’ (9 m) in the first sowing, 50’ (15 m) in the new extra planting, 48” (14 m) in the November 9 sowing, and a whopping 120’ (36 m) in the February 1 sowing.
In April, sadly, our last mizuna and ferny mustards will come to an end. In our hoophouse we do three plantings of these frilly leaved greens, which we use for salads all winter and early spring.
Mizuna (also known as kyona and shui cai) is a Brassica rapa var. japonica, meaning it’s in the turnip family. The other frilly mustards, such as Ruby Streaks, Golden Frills, Red Rain are Chinese Mustards, B. juncea. We tend to treat them as if they are all types of mizuna. True mizuna is available in green or purple (but Ruby Streaks and Scarlet Frills mustards are much better colors than Purple Mizuna.)
All are very easy to grow, can be transplanted or direct-sown, and tolerate cold wet soil. They are ready to be harvested for baby salads only 21 days after sowing in the fall (longer in winter). They grow to maturity in 40 days. They are easy-going vegetables, fairly heat tolerant (well, warm tolerant) and cold-tolerant to 25°F (-4°C). All regrow vigorously after cutting. The ferny leaves add color and loft in salad mixes, as well as an attractive leaf shape.
Mizuna is very mild-flavored. The ferny mustards vary in pungency, but most only become markedly spicy when they start bolting.
Like all Asian greens, they need similar care to other brassicas, doing best in very fertile soils. They are shallow-rooted – pay extra attention to providing enough water during hot weather to prevent bitter flavors and excess pungency, especially with the B. juncea ones. Provide 1” (2.5 cm) of water per week, 2” (5 cm) during very hot weather.
Do close monitoring of pests, which can build up large populations during the summer. Growing these over the winter, as we do, we have not had many pest problems. Flea beetles sometimes, once the weather starts to warm.
Our mizuna schedule
On September 24 we sow these little crops in our outdoor nursery seedbed, which is covered with insect netting on hoops. We sow 7.5′, with roughly equal amounts of Green Mizuna, Golden Frills, and Ruby Streaks or Scarlet Frills. Red Rain is another we like. We are aiming for about 75 transplants on October 20. We transplant them 8″ apart with 6 rows in a 4′ bed. This takes 8′ length of a bed. This first planting will feed us from November 27 to January 25, with light harvests possible from November 5, and flowers and sprouting shoots as late as February 10.
Our second planting is direct sown in the hoophouse on November 9. We sow 6 rows about 6′ long (depending on available space). We thin these into salad mixes several times as they grow, increasing the spacing until they are about 6-10″ apart. After that we harvest by cutting off the larger leaves, sometimes individually, sometimes by “buzz-cutting” (snipping off leaves on one half of the plant an inch (25 mm) above the ground). Leaving half of the leaves growing seems to help the new leaves grow faster. Next time we harvest, we cut the other side. This planting provides harvests from February 26 to March 24 – just one month, although we get the thinnings from January 20, and the flowers and bolting shoots until mid-April.
A couple of years ago we added in a third planting, because we had some open space in the hoophouse. It follows the first Yukina Savoy. I wrote about some differences between the OP Yukina Savoy and the hybrid Koji. Perhaps Koji is less bolt-resistant than the OP. Late January brings it to an end.
We sow this third planting on February 1 and harvest it for a month from March 24 to April 23. This year this third planting is bolting April 15. (We have had a lot of temperature reversals this spring, which encourage bolting in brassicas.) Scarlet Frills and Golden Frills bolt later than Ruby Streaks and Green Mizuna. The timing of harvest fits perfectly with the second planting. We have sown it as late as March 3 and harvested April 10-April 30 (only 3 weeks when we sow that late).
Kitazawa Seeds sell 18 baby leaf mustards, including four red, purple or streaked mizunas. The other 14 are B. juncea, although a few don’t say. Most are frilly or ferny, a few merely wavy. Something for everyone.
Fedco lists theirs under “Asian greens”. Scroll down past Mizuna to Mustards to find several interesting gene pool offerings such as Pink Lettucy Mustard (Variations of greens with pink or purple pigments in midribs) for those seeking milder flavors; and the medium hot Purple Rapa Mix Gene Pool (sold out as I write this): Very vigorous tall serrated green leaves with purple veins and shading.
This is my twelfth and last Asian Greens of the Month series. You can see the others here:
I have written blogposts about growing lettuce in October, September, August, July, June and May. On October 25, I reported that we have covered our last outdoor bed of head and leaf lettuce, and an “emergency” bed of baby lettuce mix with double hoops and rowcover. Now, one month later, we are waiting out this cold snap (19F/-7C last night) until we get a mild spell to uncover those beds and finish harvesting them. We want to move the hoops and row covers to the outdoor spinach beds.
We are now harvesting only winter salad mixes, no more big bowls just of lettuce. We are using leaves from the outdoor lettuce, the outdoor lettuce mix, or leaves from the lettuce in the greenhouse, according to whatever is most ready. We chop the lettuce up as we harvest. I start with about half of the harvest bucket full of chopped lettuce. I notice that it takes 3 half-buckets of harvested greens to fill one bucket! The greens settle, and when mixed they take less space than they started out using.
Lettuce varieties we are currently harvesting include Green Forest, Hyper Red Wave, Merlot, new Red Fire, Oscarde, Panisse, Red Salad Bowl, Red Tinged Winter, Revolution, Salad Bowl, Star Fighter, Tango, Winter Marvel and Winter Wonderland. Last winter we grew some Osborne Multileafvarieties we liked a lot. This year I learned the hard way that pelleted seed doesn’t store well. As pointed out by Johnnys Seeds in their JSS Advantage Newsletter January 2012
“Some seeds, particularly lettuce, are primed before pelleting, which begins the metabolic process leading to germination. Because some of the early steps toward germination are completed before the seed is planted, germination happens more quickly. Germination times can be 50% faster with primed seed. When seeds germinate quickly, they may avoid potential problems including soil crusting, weeds, and soilborne diseases. On the down side, primed seed doesn’t have the same storage life as unprimed seeds, so we recommend that you purchase only enough for the current season.”
I like to mix three crop families in every salad mix: lettuce, spinach/chard/beet greens/brassicas. I also like to mix the colors and textures, so if most of that day’s lettuce leaves are green, I’ll be sure to get some Bulls Blood beet leaves or Ruby Streaks or Scarlet Frills. I don’t make the same mix every day, as variety is the spice of life!
I love the taste of spinach leaves in salad, and we have lots of spinach (outdoors, in cold frames and in the hoophouse). I love the colors of baby Bright Lights and Rainbow chard. I chop those stems small – not everyone likes a big hit of chard flavor in their salad. When I harvest Bulls Blood beets I snip the stems close to the base of the plant, line up a handful of leaves, then snip off the stems just below the leaf blades, before chopping the leaves into the bucket. These stems are kind of wiry, not good food. I don’t like to leave the leaf stems on the plant for two reasons. One is that the stems “cage in” the developing plant, reducing the access to sunlight and photosynthesis. The other is that the stems die back later and rot. Better to remove them right away. I do the same with spinach.
Last month I mentioned the brassica salad mix we sowed in our hoophouse 10/2. We have made three cuts already – very good value for the tiny amount of space occupied. Mizuna, Ruby Streaks, Scarlet Frills and Golden Frills add a ferny shape and some loft to the mix. Mizuna is very mild, the other three are spicy. Other brassicas we are currently cutting small for our salad mixes include tatsoi and Russian kales (red and white). At some point, deeper in the winter, we’ll try to leave the kale alone to grow big for cooking greens. This will happen when we are shorter of cooking greens than salad items, and the kale has become more robust. Some of the crew are more hardcore than me, and include sturdier greens, like senposai. Later in the winter, other crops will come to the fore.
We also include as microgreens any thinnings from recently sowed rows of almost any greens, including radishes and turnips if they are not bristly-leaved varieties.
Our 10/24 hoophouse sowing of baby lettuce mix is almost ready to harvest – maybe in the next week or so. We have made an 11/2 second sowing of mizuna and friends, but the seedlings are still tiny, showing a big difference between the temperatures on 10/24 and those a week later on 11/2.
For cutting lettuce I like the plain steel scissors fromLee Valley. They are sturdy, easy to tighten and sharpen and ambidextrous. They are a traditional Chinese style.
Lastly, for those of you who want to know more about the Twin Oaks garden specifically, let me introduce you to the Twin Oaks Garden blog. It’s written by Wren Vile, one of the upcoming managers. I will be retiring as garden manager on March 1 2017, and Wren and Brittany will take over the day-to-day running of the garden. I won’t be going away, I’ll be around to answer questions, and I will continue to do some work in the garden, around the “edges”, rather than in the thick of the shifts. I’ll have more time for my writing and speaking on vegetable growing, and I’ll have more time off!
This is a long post, but if your weather is set for all-day drizzle like it is here, you’ll have time to read it. I’m also sending a much shorter version to Mother Earth News, where I’m joining their Blog Squad. So if you are very short of time, you can look there in a few weeks.
This season is becoming past-tense, and some of us are already starting to think about next year. Seed companies are putting their catalogs together, and soon we’ll be snuggled beside our woodstoves perusing them, hoping to find varieties that will not repeat this year’s problems. Reading between the lines of the variety descriptions is a science and an art. How not to get carried away by all the positive exclamations and miss some basic fact that would tell you this variety is not for your farm?
Which catalogs do you buy from? See the Safe Seed Pledge list for companies that do not knowingly buy, sell or trade genetically engineered seeds or plants. You may want to buy from local small seed companies who specialize in locally adapted varieties. Crops that overwinter in zone 7 could die in zone 5.
“Adaptable”“easy to grow” are good phrases to look for. Naturally, your climate will affect what grows well. Here it’s too hot for us to grow runner beans, Brussels sprouts, or cauliflower. We don’t buy our okra seed from companies in the north – they are focused on varieties which will produce a decent crop in their climates. Our worries are different. “Requires an attentive grower” is a helpful warning. The size and skill of your labor force matter. Can you pick beans quickly enough to earn a decent living? “Best for organic production” means it doesn’t require lots of pesticides to keep it producing.
Heirlooms, OPs or hybrids?
What does your market want? Are they truly committed to heirlooms, or is flavor actually more important? Those are not the same thing! Some old varieties are rare for a reason! People didn’t like them much! Others are fantastic and easy to grow in quantity. Finding which are which is difficult. Heirloom tomatoes are a special challenge: which ones crack and split? The Heirloom Tomato: From Garden to Table: Recipes, Portraits, and History of the World’s Most Beautiful Fruit by Amy Goldman is not just a beautiful book, but a very useful one. The author spills the beans on which varieties are worth growing. She has books on squash and melons too, but I haven’t had the joy of reading those yet. Another reliable source on tomatoes is Craig LeHoullier.
An early zucchini might be 47 days from direct sowing, but even the late Costata Romanesco is only 52 days. How important is it to have zucchini 5 days earlier? And after your first sowing, is it still as important to have a 47-day variety? Or could you choose a different one (with other good qualities) and simply sow it a day or two sooner?
Raven zucchini has no listed disease-resistance, while Dunja withstands Powdery Mildew, Papaya Ringspot Virus (I had no idea. . .), Watermelon Mosaic Virus and Zucchini Mosaic Virus. Dunja has high yields of dark green zucchini, and so does Raven. Dunja has open plants and only small spines, so harvest is easy. Raven has open plants too. No mention of spines – are they wicked? Dunja is organically grown, Raven is not. How about price? Dunja costs twice as much as Raven! What price organic seed, disease-resistance and short spines?
Spineless Perfection (45 days) and Tigress (50 days) offer the same disease-resistance package. Both are medium green, high yielding, cylindrical zucchini. Spineless Perfection has an open plant, Tigress is only semi-open, and makes no promises about lack of spines. Price is very similar. Risk the five-day delay, the spines and the only “semi-easy harvesting” to save a dollar on 1000 seeds?
Disease resistance and tolerance
Good catalogs have a wealth of information about disease resistance or tolerance of their varieties. Do read their list of codes or abbreviations. (Admittedly the lists can sometimes be hard to find.) Don’t be a vegetable hypochondriac! Don’t let the length of the list scare you off – your plants won’t get everything listed. Johnny’s had 66 items in their Vegetable Disease Code list last time I counted.
It really helps if you monitored your plants and know which diseases you are trying to avoid. We don’t worry about Pea Leaf Roll Virus or Enation Mosaic Virus of peas because our pea season is so short that the plants will be dead of heat stroke before they get sick with anything.
When I was new to Virginia it took me several years to realize our tomato leaf disease was Septoria Leaf Spot. I even bought Early Blight resistant tomato seed one year and was sorely disappointed at the spotty leaves they got.
Beet greens resistant to cercospora will provide beautiful greens as well as roots. Early Wonder Tall Top is rated by Johnnys as the best beet for greens.
Days to maturity
Johnnys gives days-to-maturity from cool weather spring transplanting. They suggest adding 14 days from direct sowing (direct-sown crops suffer no transplanting shock, so grow faster overall, but you need to add in extra time from seeding to transplant size). Subtract 10-14 days for warm weather transplanting (as crops grow quicker then). Fedco lists days from direct seeding for many crops.They suggest subtracting 20 days from date of transplanting. With warm weather crops they list days from transplanting. For peppers the days listed are from transplanting to full-color maturity. Some catalogs list days to full-size green peppers only. “Early maturing” isn’t so useful if the seed rots in cold soil, so check for both pieces of info. Provider bean is cold-soil tolerant and fast-maturing.
Packet sizes: grams, ounces and seed counts
Take a steady look at packet size and seed specs (seeds/ounce or seeds/gram). Alas, this country has not yet fully metricated. Seeds are measured out in many ways. Go to www.metric-conversions.org/ and print yourself some conversion tables, or use the online calculators. Take a dark pen to your catalogs and write in the relevant numbers.
For a particular crop is “mild” better than “rich” or “robust”, or not? There are mild-flavored Asian greens such as mizuna, available in green, red and purple, and there are spicy mustard greens that look very similar: Golden Frills, Ruby Streaks, Scarlet Frills, Red Splendor.
Ruby Streaks is an exceptionally beautiful plant. We tend not to like spicy mustard greens, but cut small into a salad mix, we have no trouble enjoying it.
“Compact”, “Mini” = small. Do your customers cook for just themselves? They’ll want mini. Are you supplying institutional kitchens? They’ll usually want full-size crops, unless they like “snack-size cucumbers” which they serve whole, with less work. If you want big cabbages, don’t buy from catalogs which have carefully chosen small to medium-sized heads because that’s what most people want these days. It can be hard to compare weights with measurements. Small = 2-4lbs, 4-6”. “Mini-broccolis”Santee, De Cicco won’t produce a big head, ever, just florets. Be sure your crew knows what size to pick.
Mache (corn salad) is a very small vegetable, usually eaten when the whole plant is 3-4” across. Even if the variety description says “long leaves” it’s all relative – maybe they’ll be 4” rather than 3” if you let them really grow.
At the other end of the Rampancy Rating are these key phrases: “needs room to roam,”“vigorous vines”: you can’t sell vines! Are they worth the space? Be sure you plant with appropriate spacing. “Needs sturdy trellis”: is it worth the time?
“Will be bitter in hot weather.” “Prefers warm days and nights – expect reduced yields in cooler areas”– you have been warned! Remember to check this. It’s refreshing that some catalogs now are more upfront “Not heat-tolerant” says Fedco about Bush Blue Lake bean. If your spring heats up quickly, you’ll want greens that are bolt-resistant as well as cold-tolerant, so you can set them out early. Giant Viroflay spinach sure grows big leaves, but they don’t last long in our climate. Tyee is more bolt-resistant, much better for us. Big chicory, radicchio and endive leaves are going to be bitter if grown at the wrong time of year and not blanched. And sometimes even if you do: they are not uniform varieties.
“Concentrated Fruit Set” versus“long harvest season”: length of harvest season is best viewed as potential rather than promised. If Mexican bean beetles or downy mildew are likely to take down your crops, you might do better to sow successions more frequently and not worry about long harvest periods. “Uniform maturity” is definitely a plus if you are growing a drying bean, popcorn, edamame or other single harvest crop. “Holds well in the field” is to your advantage if you hope to pick three times a week for a month.
“Easiest for hand harvest” (E-Z Pick beans) means they come off the vine easily; but “better for hand harvest” can mean simply unsuitable for machine harvest (plants sprawl). “Intended to be picked very slender” means tough when big, so be sure you get a high enough price to justify the lower yield and extra harvest time. And be sure you can harvest every 36-48 hours, or you won’t have anything edible.
Some broccoli has “good side-shoot production” (Gypsy, Amadeus, Belstar). If side-shoots aren’t mentioned, it’s likely that variety was bred for crown cuts.
“Short-term storage only” – we usually read this as “not for storage.” Tendersweet is a fine cabbage for fresh use – its leaves are thin and sweet. Thin leaves dry out fast, so it’s not good for storage.
“Retains flavor when frozen or canned” “Best for sauerkraut” “Good for kimchee” “Easy to shell” These phrases are music to the ears of gardeners putting up produce for winter.
Onions and latitude
Latitude makes a difference with onions. Happily, more catalogs now state which latitudes each variety is adapted for. We’re at 38°N. No use us growing Red Bull (43°-65°), as the days never get long enough to initiate bulbing. Nor do we have much hope for Desert Sunrise (30°-36°) – because after the spring equinox, our hours of daylight are more than further south – they will start bulbing before having a chance to grow very big. A few small leaves cannot produce a big bulb.
Some vegetables commonly thought of as winter squash are in catalogs as pumpkins. Many cans of pumpkin pie filling are not made from round orange-skinned pumpkins, but from squash. Choose squash varieties that grow well in your area and make all the pies you want. Or make no pies and serve the squash baked, or in soups. There are four types of squash: Pepo, the classic pumpkins, pattypans, acorn squash, delicata, dumplings, zucchini and summer squash; Moschata, the long-storing usually tan ones with hard five-sided stems, such as butternut, cheese pumpkins and Seminole squash; Maxima, the (often large) ones with fat round corky stems, such as hubbards, buttercups and bananas; and Mixta, less-common older Southern types like Cushaws.
Research at Southern Exposure Seed Exchange this year showed that many Moschata squash varieties, the kind most resistant to bugs, are also tasty at the immature stage as “summer squash”. So ignore what you’re “supposed to do” and do what works!
“Parthenocarpic” plants can set fruit without pollination, so good for hoophouse growing or production under rowcover or insect netting. Some new varieties of cucumbers and squash are parthenocarpic, and higher-priced, but some old favorites also happen to be parthenocarpic, Little Leaf pickling cucumber, for example.
“Gynoecious” plants have only female flowers, so yield can be higher. These plants still require pollination to set fruit, unless they are also parthenocarpic, so some seeds of another (pollinizer) variety are included in the packet. You’ll need to grow some of these, even though they won’t themselves give you the fruit you want. Sometimes the pollinizer seeds are colored, so you can be sure to sow some.
“Monogerm” beets produce only one seedling from each seedball/fruit. Others will need singling. Trade-off price versus time singling.
Warring sweet corn types
Don’t plant any Super Sweet varieties unless you put them at least 100ft away from other kinds, or you make sure they don’t flower within 10 days of each other. Mistakes will lead to horrible starchy kernels in both plantings. Think about this also if you are growing popcorn, dent corn, flint corn. Those dry corns also need to be separated from all sweet corns. Ignore the small print on this at your peril.
Super Sweet corns have other challenging features: the seed is smaller than normal corn, so your planter may need adjusting; Super Sweet seed needs to absorb twice as much water to germinate as normal corn; Super Sweets are more particular about seed depth (they do better at a shallower depth); Super Sweets have twice as much sugar as other corn and get sweeter after picking. It can get too much, so refrigerate promptly after harvest.
Too good to be true
New fancy types are often more risky. They don’t have all the problems resolved. Romanesco Broccoli – I don’t know anyone in Virginia who has successfully grown it. Flower Sprouts – hmmm. Try brand new things on a small scale first. All the fanfare over Indigo Rose tomato, the excitingly evil Deadly Nightshade color of the immature fruit, and then – blah flavor when ripe. “Good” flavor in a catalog may be the lowest rating. “Attractive purple pods” – Do they turn green when cooked? Purple carrots, striped green and white eggplant, white beets – will people buy them readily or will it be an uphill struggle?
Enjoy your winter catalog browsing! Here’s a cheering photo of wonderful fall colors at Twin Oaks. This is from Ezra’s blog A Year In the Woods
This week I’ve been marveling at Ruby Streaks, a beautiful ferny dark red leafy salad vegetable growing in our hoophouse. It brings a smile to winter salad mixes, a refreshing change from all the earnest shades of green. It’s beautiful, fast-growing, productive, easy to grow, cold tolerant, sweet-tasting,slightly pungent, and the seed is not expensive, what more need I say?
Ruby Streaks is so much more colorful and interesting than actual purple mizuna. For the botanists of Asian Greens among us, Ruby Streaks is a Brassica juncea, not B. rapa var japonica, like actual mizuna.
It can be grown and used as a microgreen (cut at small seedling stage), or a baby green after 21 days, and full size after 40 days. You could lightly braise it if you wanted it cooked. The leaves are finely serrated at the baby size and very similar to mizuna at full size. The stems are green and the leaf color ranges from dark green with red veins in warmer weather, to dark maroon in winter. Right now the color is incredible.
We harvest full size leaves by “crew-cutting” one side of each plant with scissors, then chopping them into short lengths. The plants regrow quickly.
It germinates quickly. Fedco warns that it bolts more readily than mizuna. We only grow it in the winter, when nothing is inclined to bolt, so this hasn’t been an issue for us. If you want to sow for spring, I’d recommend starting early in flats or pots indoors, and then transplanting at 4-5 weeks of age, about a month before the last frost date. Use rowcover for a few weeks.
To start in summer for a fall outdoor crops, you could again use flats, or you can make an outdoor nursery seed bed, protected with hoops and rowcover or ProtekNet insect netting from Fedco or from Purple Mountain Organics in Maryland. In hot weather it’s easier to keep outdoor beds damp compared to flats with a small amount of soil in them. We start ours 6/26 – the same dates we use for sowing fall broccoli and cabbage. The last sowing date is about 3 months before the first frost date. Transplant at 3-4 weeks of age, preferably not older. We haven’t tested out the cold-hardiness of Ruby Streaks, but I would expect it to survive at least down to 25F (-4C), the temperature mizuna is good to.
But the hoophouse in winter is where Ruby Streaks really shines! Double layers of inflated plastic provide enough protection in our climate for Ruby Streaks to grow all winter. And I do mean make actual growth, not just rest up waiting for spring! For winter salad mixes, we sow on 9/24 in an outdoor nursery bed, then plant into the hoophouse 10/24 (4 weeks old). We harvest that 11/1-1/25, by only cutting down one side of the plant at a time. After we clear that crop, we sow radishes in the space. We sow a second round of Ruby Streaks and mizuna inside the hoophouse 11/9, thin it into the salad, and then harvest from it 1/27-3/6.