How to Grow Lettuce
Lettuce, scientific name Lactuca sativa, is a member of the daisy family Asteraceae, but is usually cultivated as a leaf vegetable. It is a temperate annual or biennial plant that can be eaten either raw, such as in salads, sandwiches, hamburgers, and tacos and several other dishes, or cooked, especially so in Chinese cuisines.
Different Lettuce Leaf Colours Photograph by Asdfawev.
The plant gets its latin name Lactuca because it produces a milky juice, the name is ultimately derived from “lac” meaning milk.
Types of Lettuce
Lettuce is a fast growing plant with either compactly growing or loose leaves that range in color from reddish brown to light green. There are five different types of lettuce as follows:
- Cos (Romaine lettuce) - this lettuce type needs a fairly long cool season - from 70 to 75 days before it reaches harvest. In areas with very short cool season, lettuce should first be planted indoors. Romaines have a distinct advantage over other types of lettuce as the outer leaves of the head can be harvested as it continues to grow in the garden.
- Crisphead – these are primarily the most challenging type of lettuce to grow; they require a very long cool season before reaching maturity. Crisphead varieties can be harvested approximately 95 days after sowing the seeds.
- Batavian - these are probably the least known type of lettuce. They can be planted and harvested just like the others and mature fairly quickly into crisp round heads, making them ideal for planters who are not fond of waiting a long time for the harvest, or have a short lettuce growing season. Batavians can be harvested as heads in as early as 55 to 60 days after sowing.
- Butterhead – the ‘Boston Bibb’ is generally the most common butterhead lettuce. They are known for having a smooth and buttery texture. Loose heads are formed and mature from 55 to 75 days after planting lettuce seeds.
- Looseleaf – this type of lettuce is the easiest to grow as it can be harvested a couple of days later as tasty baby lettuces by cutting or picking leaves from the plant. Loose leaf are best eaten straight after harvest.
Grand Rapids Lettuce Photograph by Jeremy Bronson.
Lettuce Soil Preparation
Although lettuces are quite easy to grow, they will thrive better in the ideal condition. They need at least six hours of sun per day and loose, good, rich soil to grow well.
Ideally prepare the plot two to three weeks in advance, and amend it with rotted manure or organic compost. The soil should be able to retain moisture to keep these shallow-rooted veggies happy. For gardens with poor soil, build a raised bed and fill it with a mixture of compost, manure and topsoil. You can also opt for planting lettuce in containers or pots that are at least four inches deep.
Planting Lettuce and Spacing
Lettuce is widely known as a cool-season crop that should come to harvest before the warm weather comes. Sow seeds indoors eight to ten weeks prior to the average last frost date in spring and when the seedlings are about four inches tall, transplant then in the garden.
Sowing lettuce seeds in the garden beds directly should be done four to six weeks before the average last frost date. Depending on the variety, lettuces are ready for harvest 55 to 95 days after starting.
As mentioned above the soil should be prepared in advance; as opposed to manure you can also dig in a complete well balanced fertilizer and sow seeds at least ¼ inch deep in wide rows. Lettuce needs to be thinned to stand six to eight inches apart with spaces 18 inches apart.
Seedlings are ready to be thinned out when they are tall enough. Overcrowding of crops should be greatly avoided.
One of the most important factors in successfully growing lettuces is to meet the moisture requirements. This is due to the fact that lettuces are shallow rooted and are mostly composed of water (about 95%), they therefore will not be able to grow and mature in dry soil.
Fertilization is also another important factor that should be considered in planting lettuces. Soil that is rich in organic matter should not need to be fertilized but it is always beneficial to add nitrogen-rich fertilizers to keep the plants well in poorer soils.
A good layer of mulch can also be beneficial when growing lettuce. Place two to three inches of organic mulch layer such as straw, leaves, wood chips or grass clippings around the lettuce, making sure that there is enough space to prevent the plant from rotting. Mulching aids in retaining moisture, in keeping the soil cool and reducing the amount of weeding.
Troubleshooting Lettuce Problems
Lettuces are mostly attacked by slugs, cutworms, snails and aphids. Trap snails and slugs with a saucer of stale beer set flush to the ground and spray aphids with water. Placing a collar around every crop will discourage the occurrence of cutworms. Aside from pests, there are no major disease problems withg this plant.
Lettuce Harvest and Storage
Lettuce plant is ready for cutting as soon as the heart has formed. Gently press down on the top of the heart to check for firmness; this can be done with the use of the back of your hand. When the plant has matured and left in the soil for five to seven days, the heart will begin to grow upwards, which is a sign of bolting. When cutting the whole plant, lift the plant and cut off the lower leaves and roots. Avoid leaving older plants in the garden as they may attract pests.
Although Lettuce is best eaten fresh it does have a good shelf-life; if kept at 32°F (0°C) then Leaf and butterhead lettuce will keep for one to two weeks, Romaine for three weeks and crisphead from three to four weeks.