Edible PlantsVegetables

Romaine Lettuce Growing Guide

romaine lettuce

Romaine Lettuce (Lactuca sativa var. longifolia), known as Cos Lettuce, is native to the Mediterranean and Middle East. The Cos Lettuce is the most nutritious lettuce available, making it a perfect addition to your meals.

Romaine Lettuce is mostly eaten raw but can also be cooked and added to any dish you wish. The Romaine lettuce has green leaves with creamy white veins and roots. The tips of the leaves are dull. Romaine Lettuce is famously known and used for the Ceaser Salad.

A whole head of Romaine lettuce should last in the fridge for about ten days. The Romaine lettuce can grow to be 20 inches (50 cm) tall and usually matures in 60 to 80 days.

Types of Romaine Lettuce

There are many different varieties of Romaine lettuce available with different growing patterns and tastes:

  • Sparx – this one is dark green colored and very heat tolerant.
  • Jericho – this Romaine has bright green leaves and can be very tall, about 24 inches (61 cm).
  • Coastal Star – has dark green leaves, heat tolerant.
  • Paris White- this is a slow-growing variety that matures in 75 to 85 days.
  • Vivian- the largest Romaine variety with a 6-inch (15 cm) wide head, matures in 70 days.
  • Little Gem- has a sweet, nutty flavor, grows six inches (15 cm) tall, and matures in 50 days.

How To Grow?

Sow 10 seeds per foot directly into the soil. Make sure to place your rows of seeds 12 to 18 inches (30 to 45 cm) apart. These lettuce seedlings require being six to eight inches (15.24 to 20 cm) apart. Ensure the plant’s soil is always moist, but not soggy.

Never place the lettuce plant in full shade, as this plant loves and thrives on full sunlight. The Romaine Lettuce grows best in cool weather and can be grown as a winter crop. It can be grown as a winter crop outdoors in the USDA Hardiness zones eight and above.

Romaine lettuce is happy to grow with other salad greens and some other plants. Check out our lettuce best companion plant guide, to know which plants grow well together with Romaine lettuce.

romaine lettuce grown in a cage
Romaine lettuce grown in a cage to prevent bigger pests Source: Seahill

Water

Romaine lettuce will need constant watering because of its shallow roots. Check the plant’s soil twice a week, and if the first inch (2.5 cm) of the soil is dry, water it. Growing your Romaine lettuce in a container will need more frequent watering, especially on hotter days.

Make sure to keep the soil moist but not soggy. This means you might need to water your lettuce more than expected, especially if living in a hotter climate. If you notice that your plant’s leaves are yellow and limp, it might indicate overwatering. When your lettuce leaves are yellow and crisp, it might indicate underwatering.

Light

Romaine lettuce tolerates shade well but requires a minimum of four to six hours of direct sun daily. A good spot for your lettuce can be where your plant can get morning sun and a bit of light in the afternoon shade. The fact is the more sun your lettuce can get, the better.

big leaves of romaine lettuce
Big leaves of romaine lettuce Source: Marco Verch

Climate

This does not mean it won’t survive cold weather. Romaine lettuce indeed thrives in temperatures between 60 to 65 °F (15.5 to 18.3 °C), but if thoroughly hardened, it can survive temperatures as low as 20 °F (-6.6 °C).

Because of its cold-adaptive abilities, it can sometimes survive colder temperatures. You can harvest at least two times in warmer climates, once from spring to summer and the second time in early winter, when planted in mid or early fall.

During periods of very high humidity, Romaine lettuce can get fungal diseases, if you’re growing them in a green house, guarantee good air flow during these times.

Soil & Fertilizer

The best soil for your Romaine lettuce would be well-draining and loose with adequate nitrogen. Make sure that incorporating compost will improve your Romaine lettuce’s growing conditions. Romaine lettuce prefers slightly acidic soil with a pH of 6.0 to 6.5.

The ideal fertilizer for your lettuce is fish emulsion. You can grow your Romaine Lettuce without any fertilizer, but only if you grow it in organic soil. If you want a healthy crop and a thriving plant in other growing mediums, fertilizing is a must. Make sure to use a balanced fertilizer, feeding the lettuce once every two weeks.

Red Romaine Lettuce
Red Romaine Lettuce Source: Starr

Harvesting & Cutting

The Romaine Lettuce is ready to be harvested when its leaves look big enough to be used in salads or other foods. It’s recommended to cut the Romaine lettuce heads before they turn too firm.

You can harvest the whole lettuce head at once by pulling out the entire head with roots. You can also harvest it by cutting off the lettuce head near the base. The third option is to cut away the bigger outer leaves and let the smaller inner leaves grow and mature.

You can cut the outer leaves within 30 days; to harvest the whole head of lettuce, you must wait about 60 or 80 days. When cutting your lettuce leaves from the outside of the head, make sure to use clean and sharp scissors or shears. The Romaine lettuce can be cut three to four times during the season if it does not bolt.

Propagation

You can easily grow lettuce from its stem:

  • First, remove the leaves surrounding the stem
  • Then, place the remaining stem in a shallow container of water
  • Place the container with the stem on a windowsill or where the plant can get enough sunlight
  • Change the water in the container every two days
  • Lastly, watch your lettuce grow
  • If you want to you can replant it into the soil after it has grown its roots

Repotting

Sadly, repotting your lettuce is something that can not happen. The root structure of this lettuce is too fragile to be repotted and regrown.

Transplanting

Transplanting should be done when the lettuce gets to be two to three inches (5 to 7.5 cm) tall. Make sure to harden the leaves of the lettuce for seven to ten days before transplanting it. You can do that by placing the lettuce pot outside and increasing daily time in the intense sun.

Prepare the bed, where to transplant the lettuce, with loose soil and compost. Make sure to start the seeds indoors and after they have grown for about three to four weeks, start the transplanting process.

Diseases

Many diseases could attack your Romaine lettuce: downy mildew, leaf spot, lettuce mosaic virus, bottom rot, drop, bacterial disease, and more. To treat these diseases, make sure to use a fungicide. Maneb is the most recommended one. Apply the fungicide every seven to ten days.

You can also use sulfur sprays or copper-based fungicidal to treat these diseases. The one disease that cannot be treated is bottom rot, so prevention is key. Tamping the soil when planting the lettuce can help prevent the main lettuce leaves from touching the ground.

Pests

The most troublesome pests you might encounter are caterpillars, especially in the fall. Keep an eye on your lettuce to spot the pests early and to have an easy removal. To disinfect your Romaine lettuce mix a dash of salt and soap into cold water and spray the plant wholly.

Final Thoughts

This delicious lettuce can be grown by anyone ambitious enough. Growing and caring for this plant will widen anyone’s gardening skills. This lettuce won’t only bless you with its looks but also with its tasty and nutritious leaves, which can be used fresh or cooked in any meal of your choice. Make sure to follow the main steps on how to care for your Romaine Lettuce, and you will be satisfied with the outcome.

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