Romaine lettuce, also known as cos lettuce, is a popular and nutritious lettuce variety. It is a leaf lettuce with more volume than other species including the less nutritious iceberg head-type lettuce. In the U.S. romaine is an important commercial crop as well as a very popular garden vegetable.
There are eight growing stages of romaine lettuce. Like all plants, it starts as a seed that germinates and grows into a seedling. The lettuce plant then reaches the vegetative stage when the leaves grow, and the plant develops its distinctive elongated head. Like all lettuce, romaine needs to be harvested before it bolts, produces flowers, and goes to seed.
What is Romaine Lettuce?
Romaine or cos lettuce is a popular variety of lettuce that belongs to the Lactuca sativa species. It is a type of leafy green vegetable and a member of the Asteraceae family.
Romaine cos lettuce is widely consumed around the world and is known for its crisp texture, and slightly bitter, but refreshing flavor. The taste contrasts well when the lettuce is combined in a salad with sweet salad dressings and other ingredients.
A standout feature of romaine leaf lettuce is its nutritional value. It is an excellent source of vitamins and minerals, particularly vitamin A (in the form of beta-carotene), vitamin K, vitamin C, folate, and potassium.
Romaine lettuce is commonly used in salads, sandwiches, wraps, and as a garnish for various dishes. It holds up well to dressings and does not wilt quickly, making it suitable for preparing ahead of time.
It is widely available in grocery stores and farmers’ markets throughout the year. The folks at the University of Maryland Extension point out that it isn’t commonly grown by home gardeners, but it is surprisingly easy to grow.
Romaine Lettuce Quick Guide
It is relatively easy to grow romaine lettuce, especially because it is slower to bolt than other types. Here’s a quick guide to help you know what to expect when growing romaine lettuce at home.
|Factors affecting plant growth||What to know when you grow romaine lettuce at home|
|Soil||Does best in fertile, sandy, loam soils that contain lots of organic matter.|
|Sunlight||Requires about 6 hours of sunlight every day.|
|Temperature||Resists heat and grows well in temperatures between 60-70 degrees F.|
|Planting||Easy to plant from seed, but commercial growers commonly grow from transplants seeded into seed trays in greenhouses. Home gardeners can buy seedlings.|
|Watering||Romaine needs regular irrigation to maintain moisture in the soil. Drip irrigation is preferred.|
|Fertilizer||Fertilize with 5-10-15 or 5-10-10 (N-P-K) when planting and then again monthly. Maintain soil pH at 6.0-6.5.|
|Pests & diseases||Fungi and foliar diseases can reduce the quality of leaves. Bottom rot and drop can also be problematic. Aphids, armyworms, cutworms, flea beetles, leafminers, leafhoppers, and wireworms can cause problems.|
|Harvesting||Harvest when the heads are fully formed, before it bolts or flowers.|
8 Stages of Romaine Lettuce
There are multiple stages you will experience when growing romaine lettuce. But you may not notice all of them, even though we have included them all here.
For example, the first is the seed stage. But if you grow seedlings, then it’s not going to be relevant to you.
Other lettuce-growing stages you will want to avoid include bolting, flowering, and seed production. Once your lettuce bolts and produces flowers and seeds, it isn’t going to be edible.
No. 1 Seed Stage
All lettuce plants start out as lettuce seeds. You can sow the seeds directly in your veggie garden or in seed trays.
Depending on your climate, you can start your seeds indoors or somewhere outside that is sheltered. Alternatively, you can buy strong, healthy seedlings from a nursery or garden center.
Seedlings are usually referred to as transplants by commercial growers. This is because they leave the seeds to germinate and then transplant them later. You can do the same.
No. 2 Germination Stage
Seed germination will happen wherever you sow the seeds. But it stands to reason that to germinate successfully, they need proper soil moisture, temperature, and sunlight.
Once the seeds are in the soil, they begin to absorb water and swell. Then depending on environmental conditions, after about 7-10 days the seeds will germinate and develop into seedlings.
No. 3 Seedling Stage
As the romaine lettuce seedlings continue to grow, they develop their first true leaves. These are larger than the first tiny leaves (cotyledons) that emerge from the ground.
The seedling leaves resemble mature lettuce leaves but are a lot smaller in size. At this stage, the seedlings are delicate and vulnerable, and they need adequate water and protection from harsh weather.
As the lettuce growth continues, the cotyledons stop growing. They eventually fall off as the true leaves continue to expand and grow.
As the seedlings grow, you will be able to see which ones are stronger and healthier. So, it’s the ideal time to thin your seedlings.
Ideally, leave about six inches between each lettuce plant. Discard spindly, unhealthy seedlings and, if you wish, transplant the others in another bed.
No. 4 Vegetative Stage
During this stage, your romaine lettuce plants put most of their energy into developing leaves and establishing a strong root system. As the leaves increase in size, the foliage will increase.
During the vegetative stage, the appearance of your growing romaine lettuce plants will change. As the leaves increase in size, they begin to form a rosette shape.
After anything from 25-50 days, the leaves will start to curl inward. This is known as the cupping stage.
Even though romaine lettuce is technically a leaf lettuce, within 30-45 days it will form a dense head. Remember that during the vegetative stage, adequate sunlight and nutrient-rich soil are essential for healthy vegetative growth.
No. 5 Harvesting Stage
It’s important to harvest your lettuce plants before they bolt. A good way to test whether they are ready to harvest is to squeeze the plants gently.
If the leaves hold up, you can safely harvest the lettuce. A good rule of thumb is that the leaves will have elongated and overlapped to form a fairly tight head that is 6-8 inches tall.
When harvesting lettuce, use secateurs or a sharp knife to cut the leaves just above the base of the plant. It’s best to do this early in the morning when they are still crisp and fresh.
Alternatively, you can try the cut-and-come-again method of harvest. Be aware that this works better for some types of romaine lettuce than others.
What you do is harvest the individual outer leaves while leaving the central growing point intact. This way you can harvest leaves many times from each lettuce plant.
No. 6 Bolting Stage
At a certain point in the vegetative lettuce growth stage, romaine lettuce may start to bolt. Bolting is when the plant shifts its energy focus from leaf production to flower and seed production.
Bolting can happen due to environmental stress, including high temperatures or long daylight hours. When it bolts, the lettuce plant produces a tall flowering stalk.
No. 7 Flowering Stage
Once lettuce plants bolt, they form small, inconspicuous yellow flowers at the top of the stalk. At this point, the leaves generally become bitter.
Since the goal is to harvest crisp, sweet lettuce leaves, it’s best to prevent your plants from bolting.
No. 8 Seed Harvest Stage
The flowers on bolting romaine lettuce plants will eventually develop seed pods filled with seeds. You can collect the seeds when they turn brown and dry, and plant them later.
Because romaine lettuce is an open-pollinated plant, the seeds will grow into new lettuce plants with similar characteristics to the parent plant.
Romaine Lettuce Care and Maintenance
As with all vegetables, proper care and maintenance will ensure a healthy, high-quality crop. This is important throughout all eight of the romaine lettuce growing stages.
While romaine lettuce needs consistent moisture, it’s essential to avoid waterlogged soil. A drip irrigation system will keep the soil moist without wetting the foliage and inviting foliar diseases.
Applying a layer of organic mulch around the plants will help to retain soil moisture. Mulch will also help to regulate soil temperature and suppress weed growth.
You should have incorporated a balanced nitrogen-rich fertilizer when you prepared the soil before planting. For example, a 5-10-10 or 5-10-15 (nitrogen-phosphorus-potassium – N-P-K) mix.
Once your lettuce plants are established, it’s a good idea to apply a side dressing of balanced fertilizer. Do the same when the plants are actively growing during the vegetative stage.
Weed around your lettuces regularly to prevent weeds from competing for water and nutrients. Also, watch out for pests and diseases and use organic pest control methods to avoid chemical residues accumulating on the edible leaves.
How long does it take for romaine lettuce to grow?
The time it takes for romaine lettuce to grow from seed to harvest depends on various factors, including the variety of romaine lettuce and environmental conditions. But, on average, it takes 60-85 days for lettuce plants to reach maturity and be ready for harvest.
How do you know when romaine lettuce is done growing?
The important factor here is not really when romaine lettuce is done growing. Rather, it is when the lettuce growing in your veggie patch is ready to harvest.
The thing is that if you don’t harvest your lettuce when it’s ready, it’s just going to carry on growing. It will bolt, flower, and then eventually go to seed.
How many romaine lettuces do you get per plant?
Unless you use the cut-and-come-again method of harvest mentioned above, you can expect to get one head of lettuce per plant. When you harvest the outside leaves, you won’t harvest the head, but you will have a fairly constant supply of lettuce leaves.
If you practice succession planting and sow new seeds every few weeks, you can ensure a continuous harvest throughout the growing season. But, of course, you will only get one head of lettuce per plant.
We have detailed eight growing stages of the romaine lettuce plant. These start with the seed and seed germination stages and end with the possible seed harvest stage.
Throughout these romaine lettuce growing stages, it is important to maintain and care for your lettuce plants. If you do so, you will be rewarded with delicious, nutritious, lettuces for the table.