The crop everyone knows
Lettuce is one of the most popular crops in the world. Here in the US, we use lettuce on almost anything that we eat cold. The cool-weather crop grows sweet and tender, a perfect addition to any fresh dish.
Lettuce grows well in almost any gardening system, whether hydroponic, aquaponic, or traditional soil gardens. It takes up relatively little space, has a short (5-6 weeks from transplant or 9-11 weeks from seed) growing cycle when it’s healthy, and is always in demand from some market or another.
Our favorite lettuce varieties
Hundreds of lettuce varieties are grown around the world.
The common varieties, like red and green Romaine, Iceberg, Oak Leafs, Green Leaf, and Mesclun mixes, can be found in almost any grocery store.
Farmers and consumers shouldn’t forget about the more unique and heirloom varieties, which each bring its own beautiful leaves and special flavors to the table.
Seed companies like Baker Creek Heirloom Seeds offer truly wonderful varieties like Deertongue, Bronze Beauty, Brune D’Hiver, Cimmaron, and Devil’s Ear lettuce.
Ideal conditions for lettuce: (beware of heat!)
- Growing temperature: 45–70º F, ideally in the 60s
- EC: 0.8–1.2
- pH range: 5.6–6.2
- Light: 10–18 hours
Hot temperatures usually make lettuce greens taste bitter and strong – effectively ruining a carefully prepared salad or another dish meant to pair with a sweet, mild lettuce. Keep lettuce in temperatures between 45 and 70 ºF (7 to 21 ºC) but ideally in the 60s to keep the bitterness at bay. (Some varieties are more tolerant of heat than others.)
Depending on the shape and size of a lettuce variety’s head, lettuce can be planted quite closely. Most lettuce plants reach 6-12 inches in height.
Gentle harvests and cold, consistent temperatures extend shelf life.
Harvesting techniques can affect shelf life if the lettuce is handled roughly, bruised or crushed during the process. This makes the produce much more vulnerable to post-harvest decay and diseases, as well as impacting the scalability of the produce.
Quick tips for harvesting and storing:
- Harvest the whole head.
- Store at 32–35º F and keep temperatures consistent.
- Don’t let the lettuce freeze.
- Process the lettuce minimally.
Lettuce can be harvested quickly as a batch by taking the whole head. (Many growers harvest the entire plant, including the roots, which can extend shelf life if the growing technique facilitates it.) For growers using ZipGrow Towers, a harvesting knife used to cut each head where it meets the face of the Tower is best. Horizontal growers should harvest close to the surface of the soil or other growing apparatus.
Lettuce, with so much transpiration and moisture, can be tricky to store for more than a few days before it starts wilting, or worse—gets slimy.
Where basil requires room temperature to stay fresh, lettuce needs cold—almost freezing—to extend the shelf life. 32–35º F (just above 0º C) is ideal, and lettuce can stay fresh for up to three weeks this way. While much of the lettuce bought in stores or from trucks have already been in storage for a while, local and Upstart Farmers can start that three week period from day one and give their customers more time with their lettuce.
Don’t let the lettuce freeze, however. If frozen, the leaf epidermis will separate from the other tissues, and the leaf will decay rapidly.
Lettuce requires humidity to keep from drying out, but condensation or heavy moisture on the leaves is detrimental. The best thing that producers can do to avoid condensation is to keep temperatures very consistent.
Process as minimally as you can.
Different producers may process their lettuce, depending on the market. As a general rule, producers shouldn’t do any more to their lettuce (washing, cutting, etc.) than they have to. The only absolutely necessary tasks are removing the produce from the growing space (keep the plant together as much as possible) and trimming leaves that are dried out, diseased, or which affect the aesthetics of the crop. If possible, don’t wash the lettuce before delivery—leave that to the user to do before food preparation.
Some growers prefer to use a cold water dunk to extend shelf life—there is some debate between different growers and plant pathologists as to whether this helps by closing stomata, or decreases shelf life by spreading the diseases that are already present.
Creating a crop list?
Choosing crops for your farm requires a balance of market information and crop suitability. Growers have to choose crops that have overlapping needs, like:
- pH range
- EC range
- Temperature range
Get this information for the most highly recommended crops for hydroponics in the Recommended Crop List.