|By Skip Richter
exas gardeners are fortunate to enjoy a long growing season. In fact, in most parts of the state we can grow something in the vegetable garden 12 months out of the year if we are willing to provide the plants a little protection.
Our northern neighbors have a short to moderately long growing season followed by a truly brutal winter when everything pretty much shuts down in the garden. In most of Texas we have two short optimum growing seasons, spring and fall, each followed by two erratic dormant seasons, summer and winter.
The summer dormant season is one in which a few brave vegetables can survive and produce, but most others either shut down or drop in production or quality. The winter dormant season is relatively mild but is interrupted by a few serious cold snaps that usually knock out most of our fall garden vegetables if they are left unprotected.
The good news is that in most of the state the cold snaps are few in number and usually not severe enough to be unmanageable if a gardener is willing to take a few simple steps to protect a crop for a brief period of time.
Cold Tolerant Vegetables
It would be helpful to have the exact cold tolerance of each vegetable so you would know just what minimum temperature they could withstand and when you would need to protect them. While a lab experiment might yield such results, in the real garden world such numbers are elusive and rather meaningless.
There are several reasons for this. First of all, our landscapes and gardens are a series of microclimates making the television weather forecast rather unreliable. Reflected heat from an adjacent wall, a hedge or building that deflects cold winds, or any tall plant or structure that shades the soil affects temperatures at plant level. Dark soil heats up faster than light-colored soil. Moist soil holds heat longer into the evening than dry soil. Mulches decrease a soil’s ability to gather heat during the day for release over the cold nighttime hours. These are just a few of many site-related factors affecting the temperature at plant level in the garden.
Cold-hardy vegetables such as broccoli or spinach that have been acclimated to the cold are much more able to withstand a freeze than the same plants that have been growing in warm temperatures right up to the arrival of a hard freeze.
Most gardeners are aware of the fact that there are warm-season vegetables and cool-season vegetables. Warm-season crops such as green beans and tomatoes can’t take a frost or freeze. Cool-season crops need cooler conditions to thrive and vary in their ability to take very cold weather. Most can take a frost and some can tolerate a fairly hard freeze, even down to the mid-20s or below.
Really “Cool” Salads
My favorite groups of cool season crops are the leafy greens. More specifically I’m thinking about the cool season salad vegetables. A long while back I fell in love with this diverse group of veggies and here’s why. Prior to my “discovery” of these leafy crops my salads consisted of taste-challenged chunks of iceberg lettuce with some cucumber or tomato slices tossed in and perhaps a broccoli sprig or two; you know, the stuff offered at many restaurant salad bars. I had to toss in bacon bits, grated cheese, garlic dusted croutons, and black olives, and then slather the mix with tangy salad dressing to provide some flavor. In the process I ended up with a not-so-healthy salad.
Enter the new kids on the block. I began trying out any kinds of new greens I could find in my garden. This is the stuff from upscale food markets and restaurants! Radicchio, arugula, cress, mache, sorrel, plantain, and a wide variety of new leafy and Romaine lettuces were all tested and tasted.
Let me tell you that my salads have never been the same, and winter has become a much more productive gardening season for me. When you build a salad from a mix of these tasty greens much of the seasoning is built right in. Hot, lemony, nutty, and a host of other unique flavors are all available in the mix of cool-season greens.
So what are some of the best cool-season greens to try in your fall and winter garden? Well, here are a few that I think you should try this season to spice up your cool season salads.
We should start with lettuce, the foundation of most salads. I like to use the leaf-type lettuces, choosing a mixture of types from green to burgundy to speckled to provide visual variety to a salad. Bibb types and romaine types are also well worth growing. You can extend your lettuce harvest by either planting a small section at a time every two weeks, or by harvesting individual leaves from the plants and leaving the plants for additional harvests over the coming weeks.
Spinach provides nutrition in a tasty package. Spinach salads are great on their own but spinach also works well mixed with other greens. This cold-hardy vegetable deserves a place in the cool-season garden. Provide good drainage, especially if your soil is a heavy clay.
Kale is perhaps the most cold hardy of our garden veggies. For some reason many years ago collards made it as the favorite of the south and kale was more embraced by northern gardeners. I think we need to rethink this. Kale is not only cold hardy but also about the most nutritious thing we can grow in the winter garden. It is great cooked lightly or picked very young and used fresh in a salad. It kicks a salad into high gear when it comes to nutrition and health-promoting compounds. ‘Red Russian’ and ‘Lacinato’ (or Dinosaur) Kale are two good choices.
Radicchio or Italian chicory forms a gnarly white and burgundy head, and provides a rather bitter, spicy zip to salads. You would not want to use it alone but it blends well with a number of other salad ingredients.
Corn salad or mache is easy to grow and forms a rosette of soft leaves with a buttery texture. The flavor is mild and rather nutty.
Arugula or roquette grows quickly and provides a tangy, nutty addition to salads. It is best harvested young when the leaves are tender and the flavor is mild. Harvest it too late and the flavor can get too hot and skunky!
Sorrel brings a tangy, lemony flavor to salads. It is easy to grow and produces well in the cool season. Like most of the highly flavored greens it is best used sparingly, like “seasoning,” in salads, soups or other dishes.
Cress comes in several forms including broadleaf and curly cress. The broadleaf types tend to be a bit less pungent, but note that cress packs a peppery hot punch!
Mustard provides a very strong, sharp and pungent kick to salads. The variety ‘Osaka Purple’ is especially colorful and may be used in salads if harvested when the leaves are still quite small.
Now some of these great greens will be damaged by temperatures below freezing. But even those that can take bitter cold will benefit from milder growing conditions. Therefore, I set my cool-season salad patch up with some cold protection in place. The fact that most of these plants are short-statured makes covering them easy and cold protection very simple.
The easiest way to protect these vegetables is with a cover. Rowcover fabric works great and provides about 4 degrees of protection. Allow the sun to warm the soil all through the day and then at sundown place the cover over the plants to help hold in the heat. Remove the cover again the next day as the sun comes out and temperatures rise above freezing.
Lightweight row covers can be left on for weeks at a time because they allow plenty of light in and are permeable enough for air and water to pass through. Lightweight row covers minimize the work of taking the cover on and off through the winter, and the light covers keep temperatures a few degrees warmer, resulting in more growth during the cold months of winter. However, the lighter covers don’t provide as much cold protection on a bitter cold night. Heavier rowcover fabrics can’t be left on for more than a few days but provide more cold protection.
For extra cold protection you can use sheets, tarps, or blankets to cover plants. These materials are much heavier and can crush tender greens, especially if weighted down by rain. You’ll need to provide some support to hold these up over the plants. A simple way to do this is to place sections of 1/2 inch gray PVC pipe bent into a low arch or hoop over the row forming a Quonset type structure. You’ll need to weigh down the edges of the plastic sheeting, tarp or blankets to keep them from blowing off.
I’ve also cut livestock panel into 4 to 6 foot lengths with a bolt cutter and bent them to make a low support rack for covers. These are easy to set over the row and provide long-lasting, durable support for heavier covers.
Forget the idea of running a sprinkler all night to protect plants. While this can theoretically work if done right, in a garden setting it really can’t be done right and ends up doing more harm than good. Water enough to moisten the soil so it can hold heat better, but no more. Soggy conditions create their own problems.
If you are particularly adventuresome you can really stretch the productive season by growing your cool-season greens in a temporary greenhouse structure or a cold frame. One twist on the cold frame idea that is fast and easy is to place bales of hay in a rectangular shape around a planting bed. Then cover the hay with clear plastic sheeting to create a temporary cold frame type structure. Then in spring the hay can be used for mulching around the garden.
These cool-season greens prefer a moderately moist soil but do not respond well to soggy wet root-zone conditions. Because the cool season can be rainy at times, raised planting beds are helpful, especially in eastern parts of the state. Mix a half cup of a turf type fertilizer (3-1-2 or 4-1-2 ratio of nutrients) per 25 square feet of garden bed into the soil prior to planting.
Barely cover seeds and keep the surface moist to ensure good germination and seedling establishment. When the seedlings have 5 true leaves feed the plants again by carefully working another half cup per 25 square feet of bed area into the surface half inch or so of soil and then water it in well.
Watch for hungry caterpillars or other pests that might decide your garden looks tasty. Sprays containing Bt are a low-toxicity natural alternative for caterpillars and work quite well if applied when these pests are still young.
Don’t give up on gardening just because winter is coming. Try a few of these cool-weather greens and provide them a little protection on a cold night. You’ll be enjoying fresh, nutritious, tasty salads on through the winter season and into spring.