Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden. More on Tony O’Neill
Two botanical lettuce varieties grow tall; romaine lettuce (Lactuca sativa var. longifolia) and celery lettuce (Lactuca sativa var. augustana).
All lettuces will grow tall if left to enter their seeding phase. When lettuces go to seed, known as the bolting stage, stalks extend upwards and grow flowers, each producing a single seed. Romaine and celery lettuces grow to about 20 inches (50 cm) tall without bolting.
The Four Main Lettuce Varieties
Lettuce plants have a biennial life cycle, using the first year to establish themselves and the second to produce seeds. They have tiny flowers and self-pollinate to produce a single seed per flower. Botanically, there are four lettuce types in the Lactuca sativa genus:
- Celery lettuce (L. sativa var. augustana) is grown mainly for its juicy stem, but the whole plant is edible. It is also called celtuce lettuce or stem lettuce.
- Head lettuce (L. sativa var. capitata). As the name indicates, this lettuce type forms a compact, crispy head. The class typically has crunchy leaves, and the iceberg is famous.
- Leaf Lettuce (L. sativa var. crispa), with a rosette of leaves that may be buttery, curled, smooth-edged, or oak-leaved in shape. Batavian varieties are a cross with Romaine lettuce.
- Romaine lettuce (L. sativa var. longifolia). Also called Cos lettuce and offers conical-shaped leaves that form a tall, oblong, loose head. Longifolia references the long foliage, and Romaine lettuce is more tolerant of poor environmental conditions.
Several hybrids exist, and scientists are constantly seeking ways to produce better lettuce quicker that can stand winter colds or summer heat without bolting.
Our language is fickle; Poetry is rife with references to early blooms: “Thou yellow trumpeter of laggard Spring,” yet when the same flower, with the same purpose, interrupts our harvest, a color is suddenly a bolt.
Annual cool-season plants such as lettuce and spinach will bolt when the days lengthen in the summer. Bolting in lettuce causes the foliage to turn bitter, as do hotter temperatures and longer days.
Hot weather, as well as dry soil, causes flowers to bloom more quickly. A change in climate (hot weather for cool-season crops or cold snaps for warm-season crops) during a plant’s typical vegetative period causes bolting in several biennial plants. Several of the Brassica and Asteraceae crops are susceptible to bolting.
Romaine Lettuce Bolting
Some biennial plants (focused on producing foliage and roots in their first year and blossoming to release seeds the following year) may bolt in reaction to deviations from their general growing habit—a cold period during the first growing season.
Most biennial plants, such as lettuce, carrots, onions, and headed cabbage, must reach a specific degree of development before they can blossom. However, turnips are cold-sensitive from the moment they germinate.
Bolting cannot be stopped once it has begun, so replace afflicted plants with heat-tolerant summer crops or wait until later in the summer to replant for a fall harvest.
Several factors trigger bolting, i.e., bolting in the first year of growth. Long days, extended exposure temperatures above 85°F/29°C, and dry spells will start the bolting process.
Bolted lettuce tastes bitter, so much so that it’s almost inedible. I do not suggest doing a taste test. Removing the flowering stalks doesn’t solve the problem. Once the lettuce plant has generated a flowering stem, you cannot save the crop even if the weather cools.
The bitter taste sets in once the plant’s chemical composition changes to produce flowers. It’s just a phenomenon unique to biennial plants.
Can We Stop Bolting?
As mentioned earlier, lettuce bolts when temperatures are too, the soil is too dry, or the days are too long. But how do you stop lettuce from bolting? It’s a problem commercial lettuce growers have spent chunks of resources on—both time and money.
Reproduction is a built-in compulsion, a very strong one at that. Likely, we will never prevent bolting. The best gardeners can hope for is to delay bolting long enough to allow a harvest of lettuce crops unsullied by bitterness.
There are several ways to slow bolting, mainly negating the risk to prevent bolting before growers harvest their lettuce. These risks are:
|Cause of Bolting
|High soil temperature
|Keep watering plants and cover the soil with mulch
|High light levels
|Avoid midday sun by using strategically placed shade cloth
|High ambient temperatures
|Use slow-bolting cultivars like Batavian (Nevada or Sierra)
Why is My Romaine Lettuce Growing Tall?
Romaine lettuce is highly nutritious but, for some reason, seems to be less popular with home gardeners. It resembles Chinese cabbage, forming upright heads with wavy, attractive leaves.
Romaine lettuce is a cool-season crop grown in full sun or partial shade. Romaine lettuce prefers well-drained soil with a pH between 6.0 and 7.0 and requires moderate watering.
Romaine lettuce can be started from seed or transplanted as seedlings. Romaine lettuce takes approximately 50 to 70 days to mature and is typically harvested when the leaves are full-sized and have a crisp texture.
How to Stop My Romaine Lettuce Growing Tall
Unlike other lettuces, this variety grows to about 20 inches (half a meter) tall, similar to the less popular stalk lettuce (celtuce). There is no way to stop Romaine lettuce from growing tall other than buying a mini version like the little gem or the Fenburg lettuce.
The mini Romaine lettuce variety is a novelty version of the Romaine lettuce and has a dwarf habit. If you find this Romaine lettuce growing tall, you can safely assume it is bolting. If your Romaine lettuce has a flower stalk growing from the center, it is beyond saving, and the crop can be rogued (unless you want to produce seeds).
A flowing stalk produces one seed per flower, lasting a year. Harvesting lettuce seeds is easy, but you may consider heat-treating harvested seeds to reduce pathogen risks. It is not recommended that beginner gardeners grow lettuce from harvested seeds.
Growing Romaine Lettuce
Romaine lettuce is a nutritious cool-weather vegetable, providing a low-calorie, low-carbohydrate source of vitamins and minerals. A cup of chopped romaine lettuce contains
- Eight calories
- 1.5 grams of carbohydrates
- 1 gram of protein
- 1 gram of fiber
- approximately 30% of the daily value (DV) of vitamin C
- 15% of the DV of vitamin K
- 10% of the DV of folate (essential for pregnant moms)
- small amounts of vitamins A and B6, potassium, and manganese.
Typically planted after the last frost date in early spring, this lettuce plant is more tolerant of warm weather. Still, avoiding too much sunlight and hot weather for cool-season crops is best.
Lettuce plants are happiest if you keep the soil moist, limiting exposure to the midday sun, and too much sun can cause tip burns and trigger bolting. Except for water and light essentials, growing lettuce is easy.
Fresh Lettuce Seeds
Lettuce growing is often frustrated by poor seed germination, more so than other plants. Getting fresh seeds annually is vital as lettuce seeds cannot be stored for the next season.
Harvesting Lettuce Leaves
Romaine lettuce, growing tall, takes about 60 to 80 days to develop fully. Unlike leaf lettuce, the whole plant is harvested once it has grown tall, and it’s essential to gather Romaine before it grows taller (bolts).
If your Romaine lettuces are growing taller than 20 inches/50 cm, they are probably bolting. Plants grow slower if they are stressed.
FAQs on Secrets to Growing Tall and Healthy Lettuce
How do you make lettuce grow better?
To help lettuce grow better, plant it in well-draining soil with consistent moisture and plenty of sunlight. Avoid overwatering and overcrowding. Fertilize with a nitrogen-rich fertilizer every two weeks and mulch around the plants to retain moisture. Harvest lettuce regularly to encourage new growth.
What is the best fertilizer for lettuce?
A balanced fertilizer with a higher nitrogen content, such as a 3:1:2 or 4:1:2 ratio, is best for lettuce. Organic options like compost or manure can also help. Avoid over-fertilizing.
How do you speed up lettuce growth?
To speed up lettuce growth, ensure they receive at least 6 hours of sunlight daily, provide consistent moisture through regular watering, and fertilize with a nitrogen-rich fertilizer. Planting lettuce in raised beds or containers with well-draining soil can also promote faster growth. Finally, choosing fast-growing lettuce varieties and planting them in the right season can help speed development.
Biennials, like the lettuce, have a two-year growing cycle—one for developing infrastructure and one for seed production. If plants face adversity, they rush the process and start seed production in year one.
Romaine lettuces grow taller than other lettuce plants, and though they better manage the summer months and warm days, they still prefer cooler weather. The lettuce plant likes cool weather and should be planted in winter if you live in a warm climate.