How to Grow Salad Greens All Year
Salad greens growing under a shade net, where they are protected from intense summer heat.
Though it’s hard to beat the nostalgic CRUNCH of head lettuce, most of us have come to expect much more from our salads than crunch. Today, a top-notch salad contains many different colors, shapes, sizes, textures and flavors. And in addition to lettuces, it may also include the leaves of arugula, radicchio, spinach, cress, mustards and herbs.
As gardeners, we can choose from a rainbow of different lettuces, and dozens of unusual salad greens and specialty blends. What riches!
The tricky thing about growing salad greens is that they are cool-weather crops. Lettuce seeds germinate best at 70 degrees F. When soil temperatures are below 50 or above 80, germination is spotty. Once the plants are up, optimum air temperature for healthy growth and best flavor is 60 degrees F.
If you garden anywhere other than the cool Northwest, it’s unlikely you can offer these ideal growing conditions for more than about 60 days each year. The rest of the time it’s either too hot or too cold to grow decent lettuce.
But gardeners love a challenge, and as a salad-loving gardener I’ve managed to work out a few techniques that allow me to pick salad greens 10 months a year. You’ll need to adapt these techniques to your own particular climate and growing conditions, but I think you’ll find that’s easy enough to do once you have the basics.Varieties
With so many interesting kinds of lettuces to choose from, it’s easy to get caught up in appearances. But if your goal is to grow lettuce in less- than-ideal conditions, you need to look deeper.
For a long season of salad greens, plan on buying at least eight or 10 different kinds of seeds. Start the year with varieties that thrive in cool soil and relatively low light conditions. These include the lettuces Arctic King, Winter Marvel, Winter Density and Black-Seeded Simpson; the arugula Astro and many beautiful cutting mixes blended for spring growing conditions.
As warm weather comes on, reach for heat-tolerant lettuce varieties, such as Red Butterworth, Torenia, Larissa, Craquerelle Du Midi and Rosalita; try the spinach Emu or Tyee and look for cutting mixes blended specifically for warm weather.
Experiment. Ask for recommendations from your neighbors or local market gardeners.Seedstarting
To harvest high-quality salad greens almost every month of the year, you need to maintain a ready supply of young transplants. The only way to do it is to sow a pinch or two of seeds every week, either indoors or out.
Start seeds indoors when it’s either too cold or too hot outdoors. You can grow under lights, in a greenhouse or in a sunroom. Use a potting mix that's blended for seedstarting and plant in small boxes/flats that measure about 4″ x 6″. In a flat of that size you might sow about 25 seeds. If you’re growing under lights, cover the flat with plastic wrap until you see the seeds have sprouted. Fluorescent bulbs should be kept no more than about 2 inches above the foliage; use a timer so the lights are on for 15 hours a day. Once the seedlings have their first set of true leaves, you can transplant them to individual growing cells and grow them for another two weeks before transplanting them to the garden.
When starting seeds right in the garden, I use two techniques. The first involves sowing a few seeds wherever there’s unoccupied space. It may be a spot where a broccoli plant died or beets got harvested. It might be a sheltered nook between some pepper plants. If weather conditions are right, I can return a few weeks later to find a dozen or two seedlings ready to be transplanted. The other technique is to sow seeds right in a bed where I want them to grow. Most of the beds in my garden beds are about 20″ wide, so I plant short, 12″ to 16″ blocks of different kinds of greens.
Sowing seeds every week or two will definitely give you more lettuce than you’ll be able to eat. But seeds are cheap and when weather conditions are variable (when are they not?), frequent sowing is the easiest way to improve the odds of a satisfying harvest.Soil and Moisture
Leafy greens grow best in rich, loamy soil that contains plenty of organic matter. Before you sow or plant out your seedlings, use a trowel or hand fork to dig some compost into the top couple inches of soil. Seedlings benefit from being watered right after transplanting with a weak solution of seaweed/fish emulsion.
Lettuce and other salad greens are shallow-rooted and grow rapidly. They need continuous access to lots of water to produce tender, succulent leaves. Keep the soil consistently moist so the plants don’t get stressed. If your summers are hot and dry, invest in a soaker hose or dripper line.Microclimate
Greens growing under the Garden Quilt.
Hoops to support garden fabric can remain in place while they're not being used.
This is the big lever for year-round salads. The idea is to create miniature growing environments where the soil and air temperature are well-suited to salad greens. Depending where you live, this will probably require hoops (or some other kind of support frame), clothespins, Earth Staples, and as many as four types of garden fabric (row cover).
In late winter or early spring, when nighttime temperatures hover around 25 degrees, sow some seeds and transplant some little transplants into the garden and cover them with Garden Quilt. As the weather warms, switch to All-Purpose Garden Fabric, which doesn’t provide as much cold protection but admits more light. When the weather has settled and the days are long, there will be a brief window of ideal lettuce-growing conditions. Let your plants enjoy it in the buff!
As daytime temperatures rise into the 80s, it’s time for shade netting. This knitted fabric reduces incoming sunlight by about 50 percent. It keeps the soil cool and moist, lowers the air temperature, and shields plants from intense sunlight. Shade Netting is too heavy to rest right on the foliage and should be supported by hoops or a frame.
Once the heat of summer has passed, there’s usually another period of ideal lettuce-growing weather. Hopefully you’ve got lots of young plants (started under shade netting or indoors under lights) that are ready to hit their stride. As the weather gets cooler and nighttime temperatures begin to drop into the 30s, be ready to cover your salad greens with Garden Fabric. Switch to Garden Quilt when temperatures drop into the 20s. When nighttime temperatures drop into the single digits, add a second layer of Garden Quilt. Lay that one right on top of the plants and let the other layer be suspended above on hoops or a frame. In late winter/early spring, remove the layer that’s right on the plants to admit more light, and start the cycle over again.Harvest
Harvesting a head of lettuce by pulling the whole plant from the earth.
There are many ways to harvest salad greens. In all cases, you want to make a clean cut using a knife or scissors. Most greens will re-grow after cutting, as long as you leave about a half inch of plant behind. Individual leaves may be picked, entire heads may be cut, cutting mixes and leaf lettuce may be cropped off with scissors. Experiment and see which techniques you like best.
In the dead of winter, when light levels are low, plants grow very slowly if at all. When lettuces and other salad greens enter this winter dormancy period at a young age – less than four to six weeks old – they usually revive and get growing as soon the light returns. Even in the coldest climates, spinach and arugula will usually overwinter under two layers of Garden Fabric, and be ready to harvest in March.
Too many gardeners plant salad greens just once a year. By planting continuously and thinking creatively about how to establish microclimates, it’s surprisingly easy to eat beautiful, delicious, home-grown salads almost every day of the year.