Lettuce is one of our most common cool season vegetables. A close relative of artichoke, chicory, endive and sunflowers, lettuce is a sprinter from planting to harvest but can be a challenge. We’ll take a look at some of the basic types of lettuce and discuss cultural techniques for success. But first a few words about the history of this leafy green.
Lettuce is actually a member of the sunflower family. It is a descendant of the weed Lactuca serriola (prickly lettuce), which probably originated in the region stretching from Asia Minor into modern day Iran. This wild lettuce now may be found in many places around the world.
The wild form is quite bitter, a characteristic that may be attributed to its milky sap. This sap contains lactucarium which is similar to opium in that it has narcotic qualities. There are reports that the Romans ate lettuce to induce sleep. But don’t dive into the salad bar looking for a high. Our modern lettuce doesn’t contain any significant levels of this component.
From the original wild forms, gardeners in various regions selected and bred improved types of cultivated lettuce that was much less bitter. Reports of lettuce cultivation date back to Egyptian tomb paintings that predate 4,500 B.C. Greek writers in the 6th century B.C. spoke of it being served on the table of Persian kings. Chinese writings record its use in the 5th century B.C.
The Romans are credited with developing the characteristics of our modern lettuces that were improvements on the narrow leaved, bitter tasting wild version. This included broad leaves, non-spiny plants, resistance to early bolting, and decreased levels of the bitter milky sap. They also reported growing their lettuce for a brief time in dark conditions (blanching) to make it less bitter.
It was most likely Columbus who brought lettuce to the Americas. Also present in colonial gardens, lettuce has been a prominent feature of gardens in this country from the beginning of our nation to the present day.
Thanks to horticultural work from the Roman period on to the present we are now enjoying around 2,000 years of work in developing our modern improved types and varieties of lettuce. Modern lettuce is divided into 4 basic groups:
Crisphead types of lettuce (also referred to as iceberg types) form large rounded heads of tightly overwrapping leaves. The exterior is green but the interior base of the head is white to creamy yellow. While crisphead types are popular, they generally don’t do as well in Texas as some other types because they are pretty demanding in their growing requirements. We usually end up with loose, poor quality heads. Plus the hard, gnarly pale interior of head lettuce although crunchy is not all that appetizing in my opinion.
Cos types of lettuce (also referred to as Romaine types) are also heading lettuces. But rather than tight round heads they form tall, elongated heads. Romaine lettuce may be firm or rather loose compared to crisphead lettuce. Romaine lettuce has more green leaves and is thus a better source of calcium and vitamins A and C than crisphead types. Many varieties are rather slow to bolt, a good feature for our spring gardens here in Texas. Cos or Romaine types deserve wider use here in Texas.
Bibb types (also referred to as Butterhead lettuce) form a tight rosette of fleshy leaves but do not form a head. They do well in our Texas climate and are popular with gardeners. Most varieties are a medium green color.
Leaf lettuce (often called loose-leaf lettuce) is perhaps the best adapted choice for our Texas climate. It forms loose rosettes of leaves that come in a range of colors from various shades of green to burgundy including speckled types. Leaves may be harvested individually or as with other lettuce types you can harvest entire plants at one time. Another option is to “mow” the plants back part way with scissors and then allow them to regrow for a later harvest.
Lettuce can be started from seed or from plants. Some gardeners like to direct seed their lettuce but many prefer to start transplants and then move them into the garden after they get off to a good start.
Lettuce seed germinates best in moderate to cool temperatures with soil temperatures of 75 degrees being about ideal. The seeds are small and flat so some seed companies now offer palletized seed for easier more accurate seeding and germination. Lettuce seed won’t germinate well if buried too deep so cover them with about 1/4 inch of light sand or screened compost. Press them lightly on the surface to firm soil or growing media against the seed and then mist them well to thoroughly moisten. One mistake many gardeners make when direct seeding lettuce out in the garden is to not prepare a fine textured, smooth seed bed. Scattered into chunky, crusty soil lettuce seed will seldom make a good stand.
Keep the seeds moist until they sprout and get off to a good start. If a seed dries out at any time during the germination process it will die. If you start seed outdoors it helps a lot to place a rowcover fabric over the seed row, suspended to prevent the rowcover from getting pressed into the soil surface with watering or rains. The rowcover helps to keep the seeds from drying out quickly in the sun and drying wind.
Remove the cover to water the seeds once or twice a day to keep them moist. Use a mister nozzle on the water hose to prevent blasting the seeds away.
Gardeners often tend to plant more lettuce than they need. Think about it. How many heads or plants of leaf lettuce do you eat a week? Plant enough to last a couple of weeks and a few extras to allow for some that won’t make it. Scatter the seeds one half to an inch apart. It is really easy to plant them too thick. Then when you try to thin the seeds it’s difficult not to do significant damage to the remaining plants.
I seed leaf lettuce across my wide garden beds in rows about 12 to 14 inches apart, putting about 15 seeds per foot with the plan to thin them later once I can assess the stand. If I’m setting out transplants a spacing of 6 inches is about right. Cos or Romaine types are often larger and can be set out 8 to 10 inches apart in rows 16 to 20 inches apart. If you are growing a patch of lettuce to “mow” or harvest young with scissors you can forgo the rows, scatter seed more densely over the area, and not thin nearly as much.
When the plants have two or three true leaves thin them to about 4 to 6 inches apart. If you like you can leave them at about 3 to 4 inches and plan on removing every other one later in an early harvest, allowing the rest to grow on to full size.
I prefer transplants to direct seeding. Out in the garden it is difficult to control growing conditions and germination is often erratic and the resulting stands poor. By starting your own seeds you can get them off to a good start in ideal conditions and then transplant the right number of young growing plants out into the garden.
In winter start the seedlings by a bright window or beneath florescent lights. After they get their first true leaf move them to a bright outdoor location on mild sunny days. That way they will grow into stocky, strong plants.
In fall start the seedlings in the outer shade of a large tree or beneath the eaves of your home so they will receive good light but be protected from the hot sun. Use a rowcover to slow drying and improve germination. When the seedlings start to get true leaves, gradually move them into more light beginning with the early morning sun.
By the time your early fall planted seeds are ready to go out into the garden the weather should be cooling off enough for them to take right off. Winter started transplants are also hardened off by their increasing exposure outdoors during a time when seedlings in the garden would have struggled with the erratic cold snaps of a Texas winter. Either way you’ll be off to a good head start compared to direct seeded lettuce.
Stagger your plantings about 2 weeks apart to keep fresh lettuce coming on through the season. Lettuce prefers cool growing conditions for best growth and quality. When the weather heats up in spring the quality declines rapidly. The leaves become bitter and the plants begin to “bolt” as the stem elongates into a tall bloom stalk.
Leaf lettuce varieties take about 40 days from seeding to harvest while head types may take 70 days. This is another reason the head types are more of a challenge.
To get more from your garden space, consider interplanting your lettuce with slower maturing crops. Cabbage is slow to mature and makes a good interplanted vegetable with the fast maturing lettuce varieties in the fall. In spring you can start setting tomato transplants in where lettuce plants are being harvested to make double use of the bed area.
Another option is to include lettuce in ornamental beds. The colorful leaf types are downright pretty and make a great addition to any bed. Lettuce can even be grown in containers as long as the soil volume is at least one gallon. Larger containers are even better.
Lettuce performs best if you keep it growing well with adequate soil moisture and moderate fertilization. Water transplants in with a dilute solution of soluble fertilizer according to label instructions. Repeat this application twice weekly for a couple of weeks to ensure the new plants are off to a good start.
A light application of dry fertilizer when the plants have been in about two weeks should take them on through their harvest time. Sprinkle one half cup of a 3-1-2 or 4-1-2 ratio fertilizer per 10 foot of planting row. Then lightly scratch it into the surface and water it in well.
Lettuce is shallow rooted so avoid deep cultivation. Stay ahead of weeds so you don’t disturb the lettuce plants later when removing large competing weeds. Light, shallow cultivation is best. You can mulch the best when plants are well on their way. This will also help prevent soil from splashing onto the leaves during rain or irrigation.
Lettuce doesn’t suffer as many problems as do some garden vegetables. Aphids can be a pest at times but seldom require treatments and when they do a blast of water from a hose or a squirt of insecticidal soap is usually enough to do the trick.
Slugs and snails can be a problem at times if the conditions are moist but I can say I have never had them damage my lettuce plantings. There are some low toxicity baits that work well if these pests become troublesome in your garden.
Lettuce used to be plagued by several diseases that could wipe out plantings. Most modern varieties have some good resistance built in, but at times during wet periods some fungal rots and mildews may show up. I suggest that should such a problem arise just pull out affected plants and keep the new plantings coming rather than resort to sprays, especially since by the time some rot shows up it is too late to do that plant much good with a spray.
Lettuce is fairly cold hardy and will tolerate light frosts with little to no damage. Young seedlings are more prone to freeze damage. I find a cover is usually enough to get it through a freeze. Cold frames are a great option if you want to grow lettuce all winter and live in the northern half of the state where a cold snap can be fatal.
Tip burn is a condition that can occur when a cool rainy period is followed by hot, dry weather. Some varieties are more prone to this than others. Try to maintain even soil moisture to minimize the problem.
Head types are best harvested after they develop a firm head. Bibb lettuce is ready to harvest when the plants have reached about their full size and the leaves are just starting to cup inward slightly as if to form a loose head. Leaf lettuce can be harvested at any time from when you are thinning young plants on. But is it best to either harvest older leaves, leaving the plants to grow for later harvests or cut entire plants out when they reach near full size for the variety.
I generally make harvest decisions based on how much other lettuce is coming along for later harvest. If I have plenty on the way I’ll pull more plants when they are younger. If not then I may just harvest outer leaves to get more later on from the older plants.
Lettuce actually gets sweeter in the refrigerator after a day or so. The milky sap can become bitter and refrigerating seems to improve things a bit. If you are planning on using the lettuce within a day or so you can wash the leaves or harvested plants before placing them in the refrigerator. Then shake off any excess water. If it needs to keep longer go ahead and harvest it dry and store in a plastic bag where it will keep several weeks. Wait to wash it until you are ready to use it or the wet leaves will tend to decay faster in storage.
There are more than 200 varieties of lettuce available to gardeners. I have tried many different ones and find that most do quite well if provided the right conditions. The leaf lettuces and Romaine type in my opinion deserve the top slots for our Texas gardens. I try a few new types each year and really prefer to have several different types growing together so my salads can be more colorful and interesting.
Some common varieties that have performed well in Texas gardens include those listed below. However I would encourage you to experiment with various new varieties of each type. New varieties come on the market each year and most deserve a shot in our gardens. Variety blends are another way to purchase lettuce. These make for some really attractive salad mixes and are especially good for planting thick and harvesting with scissors. You can also create you own blend by mixing seed from several different varieties.
|1, 2, 3, 4, 5
|dark green leaves form small,
compact hearts that blanch to an
appetizing yellow color
|Black Seeded Simpson
|1, 2, 3, 4
|a long time favorite; medium green leaves
|heavily frilled green leaves with dark red edges
|Royal Oak Leaf
|3, 4, 5
|attractive rosettes of dark green leaves, shaped like oak leaves
|compact, fringed heads of deep burgundy red over green
|Green Salad Bowl
|1, 2, 3, 4
|large, lime-green rosettes of delicate, lobed, oakleaf-like leaves
|Red Salad Bowl
|2, 3, 4
|burgundy red, deeply lobed, delicate leaves form a large, full rosette
|intensely frilled leaves add loft and texture to salads
|ruffled, slightly frilled vivid red leaves over a light green background
|1, 2, 4
|tall heads; interior is pale green to cream; outer leaves dark, gray-green
|glossy green, semi-savoy leaves with maroon speckles; a semi-cos type
|Sources: 1 Willhite; 2 Johnny’s; 3 Harris Seed; 4 Burpee; 5 Park Seed