6 Crucial Reasons Romaine Lettuce Is Getting Tall (With Expert Comments)

Is this OK?

You wonder looking at your romaine lettuce plant.

Is it supposed to be getting this tall? Or is there a problem?

Your romaine lettuce is tall because of hot weather causing the plant to bolt. The lettuce is developing a flower stalk to set seeds. The rise in temperature, excess sunlight are reasons for causing this. The leaves will taste bitter when lettuce starts to bolt.

In this post, I’ll help you understand what can cause your romaine lettuce to grow tall and how to avoid this problem.

Let’s begin.

What is bolting?

Bolting is a natural process where a cold-season plant will try to produce flowers and seeds. This happens because the plant realizes the environment is not conducive to growth any longer.

This may happen because of a rise in temperature, lack of water, overfertilization, too much sunlight, or irregular harvesting.

The plant will direct all its energy to growing flowers and seeds. This causes the leaves to become leathery, lack taste, and even turn bitter. They may even turn yellow or brown.

Bolting will eventually happen to the cold-season plant, but we want to avoid it happening early. Otherwise, we won’t be able to get the full harvest of fresh, crisp, and flavorful foliage from the plant.

Now that we know what is bolting, let’s look at how this can affect romaine lettuce and what we can do to avoid these problems.

1. Warm weather causes romaine lettuce to bolt

The suitable temperature for growing romaine lettuce is between 60 F to 65 F. This will encourage it to continue developing foliage.

But if the temperature rises above 75 F for several days, the romaine lettuce will bolt. This could happen because of unexpected warm days in spring or fall. Or you may have grown the lettuce in summer when the weather gets too warm.

The romaine lettuce will bolt because the temperature is unsuitable for growth and it will try to preserve itself by going to seed.

You can delay bolting by choosing a romaine lettuce variety that is slow to bolt. These varieties can withstand the rise in temperatures longer.

I would suggest planning your romaine lettuce planting so you can get a good harvest by summer. It’s best to start seeds just after the last frost date in spring. Or you can grow them in fall as the weather cools down.

If there’s a sudden abnormal spike in the temperature, you can cool down the plants by using a shading cloth. If you’re growing the romaine lettuce in containers, it’s good to move them to a shaded location or indoors, if that is possible.

Bolting is when the weather starts to get too warm for a plant, and it goes into a panic of trying to reproduce while it still can. The result is that its remaining energy goes into seed production instead of leaf production. You will notice the plant become more yellow, tall, and skinny. It is trying to flower and make seeds to reproduce, which means the lettuce will no longer be lush and delicious for eating. – Carly MacQuarrie, Founder, The Little Green Shoot

2. Too much sunlight causes romaine lettuce to bolt

The length of the day impacts if your romaine lettuce plants will bolt faster. They’re a cool-reason plant that prefers early spring or late fall to grow well.

The romaine lettuce will grow well with 6-8 hours of sunlight every day. But if it receives 12 hours or more, the plant will bolt. This is because it considers the optimal growing period is ending and it’s time to produce seeds.

As mentioned above, it’s best to grow romaine lettuce just after the last frost date in spring or late fall when the sunlight conditions are optimal for the plant.

You can also grow the plant in partial shade so the amount of sunlight it gets is limited and delays the bolting further.

It’s a good option to grow the romaine lettuce in containers, so it’s easy to move them to an appropriate location with optimal sunlight.

Ironically, a lack of sunlight can also cause the romaine lettuce to grow tall. This is because the plant wants to grow in the direction where it can get sunlight. So make sure the romaine lettuce can get the right amount of sunlight. Not too much nor too little as both will cause it problems.

If the lettuce is being grown in a shady location, it will again attempt to grow taller to reach more sunlight. Lastly, overcrowding can cause the lettuce to grow tall as it fights for space and resources. – Tom Monson, Owner of Monson Lawn & Landscaping

3. Lack of harvesting romaine lettuce causes it to bolt

If you don’t harvest the matured romaine lettuce plant or leaves, it will bolt. This is because the plant has reached maturity and decides it’s the right time to develop seeds.

The benefit of growing leafy plants like romaine lettuce is you can keep harvesting the leaves as long as the plant grows. And the more you harvest, the longer the plant will go without bolting.

If the romaine lettuce plant has developed a bud, you could cut it as soon as possible to slow down bolting. But it does not help with the flavor, as the leaves will continue to lose flavor and even turn leathery and bitter.

Another thing that can cause tall Romaine is if you are harvesting using the “cut and come again method” for harvesting. This is a method that ensures a longer more productive harvest season by harvesting the lower leaves instead of new top inner leaves. When you use this method, the lettuce will grow much taller, but will continue to produce good leaves for eating. – Carly MacQuarrie, Founder, The Little Green Shoot

4. The lettuce variety can cause it to bolt quicker

There are some romaine lettuce varieties that would take longer to bolt than others. This is because they can withstand the higher temperatures longer.

So choose a variety that is optimal for the climate in your region and based on the season when you’re going to grow them. Check out the information about lettuce varieties before buying the seeds. Read the instructions on the seed packets and catalogs to understand the temperature requirements.

I would also suggest growing a romaine lettuce variety that can become large. This would help it take longer to mature and going to seed. So you can get a lot more harvesting cycles.

I’ve listed down some romaine lettuce varieties that are slow-bolting.

• Little Gem: This is a frost-tolerant romaine lettuce variety that takes 20-68 days to reach maturity.
• Parris Island: Frost-tolerant romaine lettuce that takes 21-68 days to reach maturity.
• Rouge d’Hiver: Frost-tolerant romaine lettuce that takes 20-65 days to reach maturity.
• Sunland: Heat-tolerant variety that matures in 56 days.
• Saint Anne’s: Another slow-bolting romaine lettuce variety that reaches maturity in 58 days.

The main reason for this occurrence is “bolting.” Bolting is essentially when the plant stops growing itself and instead prepares itself for reproduction. After it grows tall, it will then flower and release seeds. Romaine lettuce is a cool season plant and will grow best in those weather conditions, so when it gets hot, that’s when you are most likely to deal with bolting. – Jeremy Yamaguchi, CEO of Lawn Love

5. Lack of water can cause the lettuce to bolt

Like most annual vegetables, romaine lettuce needs a good amount of water to grow well. If there is a lack of water for many days, the lettuce will bolt.

This is because it considers the growing conditions are no longer optimal for producing foliage. Instead, it will develop a flowering stalk and eventually seeds as part of survival.

My advice is to check on the romaine lettuce plants every day if watering is required. Stick your finger 2 inches into the soil to check for the moisture. You need to give a good watering if the finger comes out completely dry without soil sticking to it.

Be careful not to overwater the soil as this leads to its own set of problems, such as humid conditions that attract fungal diseases. Make sure the soil has dried out before watering it.

Bolting is a natural phase of romaine lettuce as it matures (and many other plants!), but there are some environmental conditions that can trigger premature bolting. Hot weather can trigger bolting, so utilizing shade cloth or companion planting to provide some shade can help. If you live in a warm climate, limit growing romaine lettuce to the spring or fall when temperatures are cooler. Look into slow-to-bolt varieties of romaine like Cimmaron, Ferellenschuss, Green Towers or Sweet Valentine. If you notice the romaine starting to bolt, harvest it right away. If you wait too long, it can develop a bitter taste and will no longer be good for eating. – Katie Krejci, MS, RD, LD, IFNCP, The Homesteading RD

6. Overfertilization can cause lettuce to bolt

The romaine lettuce needs a good supply of nitrogen and nutrients to grow foliage. I recommend using organic fertilizer for this.

But too much of fertilizer can stress the plant when it’s immature and not capable of absorbing all the nutrients. This stress will cause the lettuce to bolt as it tries to go into survival mode and produce seeds.

If you overuse chemical fertilizers, you risk burning the roots. This is another form of stress on the romaine lettuce plant that would make it bolt.

Start adding the fertilizer only after the seeds have developed into seedlings about 2-4 inches in size. I recommend using organic fertilizer and only adding it every 15-30 days to the soil. You don’t need to use much and follow the suggestions on the fertilizer packet provided by the manufacturer.

Can I use romaine lettuce that has bolted?

You’ve gone out to your garden to harvest your crop and your worst fears are imagined: your romaine lettuce has bolted.

Large stalks of flowers now rest on the tops of what was once your promising buds and all you can think is: well there goes all of my hard work! All this is good for now is feeding the rabbits.

If your romaine lettuce has bolted, not all hope is lost. If you are the avid gardener who checks their veggies every day, then you caught the bolt in time and the romaine may still be usable.

Harvest the bolted lettuce right away and do a taste test; does it still taste like romaine or has the bolting turned your leaves into bitter weeds?

If your romaine still tastes good, you caught the bolt early enough and can enjoy your romaine in salads and sandwiches.

If you tried your lettuce and found that the bitterness has already taken over, you have three options:

Collect the seeds: in preparation for your next planting season, you can harvest the seeds from your bolted lettuce to be replanted.

Cut it: you can cut your romaine lettuce down to the stalk and leave it in the ground to regenerate if your season is still going.

Donate: your local wildlife will thank you for this treat and hopefully by putting it out for them they won’t venture into your garden for an all-you-can-eat buffet.