Imagine next spring as the ground is starting to become "workable" for sowing seed, you walk out to your garden and find a ready-to-harvest vegetable crop. As summer harvests taper, take advantage of the current season so you can harvest vegetables in early spring! In this post, I will show the best fall vegetables to grow overwinter and how to protect them so you can be eating those early spring vegetables.
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| Pablo lettuce, grown overwinter. |
This post covers:
1 The Basics of Winter Gardening
2 Winter Protection
2 Winter Protection
3 What to Plant
4 Other Spring Benefits of Winter Gardening
Especially in Missouri, where summers get hot very quickly come June, it's nice to have plants established and producing early. Here I describe a method where cool season crops are sown in the fall to develop their roots over winter.
The Basics of Winter Gardening
To get plants through the winter you need to think about each plant's hardiness as compared to your climate zone. Here in Zone 6B, the average lowest temperature in winter ranges between -5-0°F.
Once you have an idea of what the low temperature will be in your zone, consider which vegetables will grow over winter in your area. Even in my zone, the hardiest vegetables, such as spinach, will likely not survive without a cover.
A floating row cover, however, will warm your plot by about 2 climate zones. So if I add a floating row cover over my garden, I can expect a plant hardiness of about Zone 7B, where the maximum winter temperature lows are around 5-10°F. An additional cover adds even more protection. (See a Zone 5 example here.)
Now keep in mind that the minimum temperature is just a proxy for the climate when it comes to hardiness. People have experimented with temperatures under cover and found that the nightly low temperatures can actually be similar at night compared with the ambient temperature or even colder. The covers protect from wind and frost, which are more damaging to the plants than temperature alone.
For example, while winters are fairly mild in January and February in Missouri, it gets really cold about one week in four. Daytime temperatures will be in the mid-teens, and night time temperatures are around 5°F. Yet given a cover, I have had plants "hardy to 20°F" survive. The wind at those temperatures is often what kills the plants without a cover, not the temperature.
When using a cover, most folks in zones 1-8 are limited to cold hardy plants, such as lettuces, spinach, onions, certain brassicas, etc. The frost sensitive ones such as tomatoes and melons are not going to work.
Winter Protection
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| A simple cover will protect your vegetables. |
In the simplest set up, you can protect your vegetables with felted covers, supports for those covers, and a fixture to keep the covers on the hoops.
For hoops, 8 or 9 gauge wire is commonly used for hoops¹. For 4' paths, one would want at least 8' of wire. You can figure out how long you would like your hoops to be by using the old equation for finding the circumference of a circle (Remember ℼd, where d is the diameter?). Since we only need a semi-circle plus about a foot of wire on each side for staking, that would be 1/2 x ℼd + 2 or 1/2 *3.14 x 4' +2, which is 8.28 feet.
The felted covers should have a thickness of about 1 oz per square yard, which provides protection yet also allows enough sunlight to filter through. You can weigh them down with large rocks or sandbags. Use elastic bands (such as hair ties) to gather the ends.
What To Plant
The following vegetable varieties are suitable for growing in my location, Missouri Zone 6B. However, many of these plants are quite hardy and can be grown in more northern climes, especially if properly covered. Similarly, these plants would be suitable for milder climates of the south in winter months.
If the particular vegetable is especially hardy, seed catalogues won't necessarily report the lowest temperature in which that plant can reliably survive, but usually just say "super hardy" or "hardy to 20°F."
In my experience, knowing which vegetable varieties will survive are best gleaned through books by market growers, such as those by Eliot Coleman and Charles Dowding. These gardeners only grow reliable vegetable varieties for their customers when profitably possible. This is why you can trust the information that they offer, bearing in mind that you should shift your strategy based on regional climatic differences.
Hardiness temperatures are from Charle's Dowdings No Dig, unless otherwise mentioned.
Spinach: If you are going to try to overwinter anything, try this! Spinach is hardy to 5°F. When sown in early spring, it can be difficult to get any spinach harvest before the plants bolt as the weather warms. This is where overwintering really makes a difference for a substantial harvest.
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| Lettuce, Endive, and a Strawberry plant, all hanging out in early March. |
Lettuces, Endive, and Arugula: Lettuces are hardy to 19°F. I have had a lot of success with 'Pablo' and 'Merlot' lettuces. Look for red varieties or those with crinkled leaves for winter success. Endive is hardy to 14°F, and makes a lovely addition to your salads. Arugula is hardy to 21°F.
Cilantro: This stuff reseeds itself every year in my garden, so I do not worry about re-planting it once it is sown. Be sure to collect the seed for coriander spice if you want to prevent reseeding. Hardy to 23°F.
Collard Greens: These are very large plants that taste a bit spicy eat fall, yet really start to taste mild after the frost arrives.
Corn Salad: Corn Salad are small, yet very hardy plants that need to be sown en masse to get enough to harvest. These are hardy to 14°F.
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| Broad Beans, from a February sowing. |
Broad Beans: If you are interested in planting something other than lettuces, try broad beans, an exceptionally hardy cool season bean. Start these in mid-to-late October to get them started (or about 5-6 weeks before you expect regular freezing daytime temperatures). They should be young established plants, but not yet flowering. Aquadulce is an especially hardy variety.
Mustards: I guess I should write about these, despite the fact that I don't like them very much. They are quite spicy, and are hardy to 23°F.
Peas: I am experimenting with peas, but I have read that they are not super reliable over-winterers. This is another plant to sow in mid-October or about 5-6 weeks prior to regular daytime freezing temperatures. Hardy to 23°F.
Other Spring Benefits of Winter Gardening
Not only will your new fall-sown garden produce a beautiful early crop next spring, you are also building up the soil. The roots of your vegetables are creating a symbiotic relationship with the surrounding microflora, supporting the natural ecology of your garden soil. Beneficial insects also hibernate within the crops, protecting populations that keep other pesky insect populations in check.
Both peas and broad beans can be planted solely as a cover crop to add nitrogen to your soil in the spring. Inoculating them with appropriate nitrogen-fixing bacteria will ensure the fixation takes place. Rather than picking the beans, cut the plants down when flowering to release nitrogen into the soil.
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1. Eliot Coleman. The New Organic Grower. 30th Anniversary Edition, Chelsea Green Publishing, September, 2018. p. 192.