Freeze

It is not unusual to have a hard frost in May and that is what we got last Sunday night. I have learned to keep the most frost sensitive transplants like peppers, tomatoes, squash, okra, basil and melons in pots by the house until the 4th week in May or the first week in June.

Several years I got enthusiastic about planting tomato plants early and they got frozen. I had a back-up set of plants to replace them with. But I have learned my lesson. I just don't transplant early to the field.

If you keep those early transplants in pots they grow just as well and you can cover or protect thousands of plants by bringing them inside or covering them.

I was talking to some of the growers at the farmers market and they reported.

Sweeter with Frost - Kale

Kale is one of the most frost hardy of the greens and highly nutritious. It protects it's cells from deep cold by increasing the solids content in the cells. One of the solids being sugar. Mature kale has a heavy leaf that holds up well under repeat freeze and thaw cycles. It wilts after a heavy frost and then recovers during the thaw the next day.

Kale has gained popularity over the past several years as a gourmet green as well as a highly nutritious health promoting and cancer preventing food. I was not aware at the time, but I have been looking for a seed source for baby kale. I finally found a source this year and was taking baby kale to market this spring way ahead of when the full sized kale would be available.

In parallel the cooking magazines were promoting kale as the next hot food item for raw and cooked dishes. Largely due to these promotions kale was highly prized as a farmers market purchase. Some weeks we sold more baby kale than spring mix.

I was wondering if this baby kale would hold up under frost like the full sized plants and so far it has been hanging in there.

Kale also has few pests. The little green worms that love cabbage and broccoli pretty much leave kale alone.

We will see how it goes next season. If kale is a flash in the pan designer green or if it has the staying power of some of the other common greens.

Sweeter with Frost - Spinach

Spinach takes the grand prize of frost hardy and frost sweetened. Spinach will overwinter in Minnesota with a little snow cover. It goes dormant in the freeze up and wakes back up in the spring thaw and will start growing again. The leaves that have been frozen all winter are edible but not good quality, but the new growth is outstanding.

We plant fall and winter spinach between September 1-15 and plant about 3x the amount we would plant for the main summer season. It grows throughout the fall and we harvest as needed. The earlier planting often is harvested twice. The later planting is typically harvested just before freeze up and we often stop harvesting due to snow in early December.

Spinach is always sweet but is especially so after a few light frosts...

Sweeter With Frost - Carrots

Fresh organic carrots are great anytime of the growing season but are amazing once the plants are exposed to several light frosts. I have been picking enough carrots each week to satisfy our customers. The carrots we have been picking have been excellent, but I have been holding back on the main harvest until we get those first few frosts.

Why are they sweeter with frost? When temperatures drop below freezing the starches in the carrots turn to sugars. That is great for those of us that love carrots, but why do the carrots do this? Well sugar in the cells of the carrots is a type of antifreeze to protect the carrot from damage by ice crystals forming in the cells of the carrot. Carrots are a biennial and need to be able to overwinter to produce seed the next year.

We have an excellent late fall carrot crop this year. I planted 7 rows approximately 300 feet long toward the end of July. It took 100,000 seeds to cover this many rows. I use a strip of compost about 8-10 inches wide and 4 inches deep to provide good emergence and a weed free zone. Carrots don't need a lot of fertilizer so the compost is just right for that. It took 20,000 pounds of compost (14 pickup loads) to make the rows, so it took a couple of weeks to get this all ready.

With the stage set we now had to deal with the weather, it was very very dry about this time and I had to water a couple of times to get things started. Carrots are kind finicky that way, they don't like weeds when they are little and it takes about three weeks after planting for germination and the appearance of those first few spindly fronds. You don't quite know the status of your planting for three weeks. You just need to water thoroughly a couple of times and trust that everything is well.

Our teenagers weeded thoroughly between the rows every couple of weeks and I also ran the wheel hoe through a couple of times. So weed control has been excellent. I planted the rows about 20 inches apart so the carrots at maturity will almost shade the ground between the rows. They look beautiful planted that way.

Most of the carrots came up just fine, but I had one area where I must not have watered enough that didn't germinate. It was only about 20 feet long, so I just replanted those rows. These carrots are about three week behind the main group.

Carrots planted for fall like this need to be plated about 90 days before harvest, instead of the normal 60 days due to the shortening of the days and the drop in temperature during the last month before harvest.

We have been monitoring progress (read munching on a few carrots) for the last 3-4 weeks and things are coming along nicely.

Sweeter with Frost - Brussels Sprouts

Brussels sprouts are the king of the frost resistant varieties and can tolerate brief cold to 15 degrees. A few light frosts significantly sweeten the sprouts and remove the bitter taste that is often characteristic of summer sprouts. We don't harvest any sprouts until after first frost and the sprouts take the place of green beans in our market display.

So why do the sprouts get sweeter? The Brussels sprout plant replaces some of the fluid in the plant cells with fructose as a type of anti-freeze. Since these plants are some of the most frost hardy, they are also some of the most dramatic improvements in sweetness.

The Brussels sprouts are planted in late May or early June. About September 1 we remove the growing tip of the Brussels sprout stalk. This stops stem growth and forces the plants to fill out the sprouts. In early October they are pretty much filled and the harvest can begin.

Patients is rewarded with excellent sweet sprouts that we often harvest through Christmas.

Sweeter with Frost - Broccoli

Broccoli is one of those garden crops that get sweeter with frost. In honor of our first frost yesterday I'm going to do a series of articles on frost hardy vegetables. Broccoli can tolerate temperatures down to 26 degrees for a brief period of time. We often harvest broccoli until Thanksgiving here in Rochester, Minnesota.
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But why is it sweeter. Broccoli increases it's sugar content after a few light frosts as a protection mechanism against freezing. It is good it does because sweet fall broccoli is some of the best of the season.

We plant the last fall broccoli until approximately the middle to end of August. The normal 45 day maturity is stretched to 75 days when the days get shorter and cooler.

One of the side benefits of the freezing temperatures is the insect pressure goes away. I have some broccoli that is in full production and some that won't be ready for at least a month. Also, one of the full season varieties has great side shoot production. The side shoots can be as large as a full head of broccoli. We planted 6 different varieties this year. The best fall broccoli is a variety called Marathon. Large heads, small bead and very frost hardy.

I'm going to publish a series of posts highlighting the other frost hardy crops and ones where the produce becomes sweeter. There are quite a few and the mechanism for sweetness varies a bit.