Originating from the Greek island of Cos, Romaine is one of the oldest and most popular varieties of lettuce. It is relatively easy to cultivate, and from just a handful of seeds, you can be rewarded with crisp, delicious lettuce all summer long. But I find the trickiest part of the process is knowing exactly when to harvest romaine lettuce to ensure you do maximize your yield.
When To Harvest Romaine Lettuce
Romaine lettuce is a cool-season plant that will generally be ready 3 months after planting your seeds. But you don’t have to wait that long to start sampling their crispy fresh leaves You can start to pick the tender, young leaves as soon the plant is around 4 inches high. They will then keep producing leaves and growing. Or you can wait until they are at full maturity and harvest an entire lettuce.
Romaine lettuce will only keep for a few days in a refrigerator and cannot be frozen so to ensure you don’t end up with a glut, I would always advise picking it on a needs-be basis across the season.
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Romaine Lettuce Growing Stages
Romaine lettuce really is a great plant to grow at home, it thrives in pots as well as planted directly in the ground and for limited effort, you can be rewarded with enough salad leaves for the entire summer.
- Germination The germination of Romain seeds typically takes between 7-15 days depending on the environmental conditions.
- Seedlings Throughout the seedling stage the small plants will be prone to attack from slugs and snails. They will also be prone to dampening off if conditions are too humid.
- Lettuce Head Develops After around 6 weeks the cluster of leaves will be forming a dense head. This will continue until the plant is around 80-90 days when the lettuce reaches full maturity.
- Bolting and Stretching If the plant is not harvested, it will continue to grow. Fluctuations in the weather will cause a reaction that pushes the plant to prepare to flower. A thicker stem will form as the plant grow taller and forms a flower head.
- Setting Seed Finally as the flower head matures the plant will set to seed and deposit its tiny seeds in the surrounding soil, ready for the process to start again.
Growing Romaine Lettuce
- First, sow your seeds thinly along a moist, 1cm deep trench spacing each seed out.
- Cover them thinly with soil and ensure you leave 30cm between rows. If growing in pots scatter the seed sparingly over the surface of moist compost and then cover it with a dusting of compost.
- Once the seedlings are well established you can thin them out to give enough space for each lettuce to grow. Be sure to not let the soil get too dry, especially if the weather is hot, or they will bolt.
- If you live in warmer climes, you could mulch the area around your lettuce to seal moisture into the soil. You may also want to give them an occasional liquid feed while watering.
Number of Days to Maturity
Romaine lettuce takes around 80-90 days to reach full maturity. At this stage, you will have a crop of full lettuces ready to pick. But you can harvest sooner if you just want to pick a few loose leaves. You can expect these to be ready after around 2 months.
Signs You Lettuce is Ready for Harvest
You have two options when deciding when to harvest your lettuce, cutting off individual leaves or harvesting the whole head.
If you are opting for individual leaves the plant should be about 4 inches high with at least 3-4 leaves. If you are waiting to harvest a full lettuce head, you will know it is ready once the leaves turn dark green and are elongated and overlapping slightly forming to form a head that is about 6-8 inches high.
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Picking Romaine Lettuce
Picking romaine lettuce is easy because the entire plant is edible. If you are just harvesting the early individual leaves you can pinch them off with your finger or tear them off near the base. You might also like to use a sharp knife to get more precision. If you leave a few leaves in situ, the plant will use that foliage to continue to grow.
If you are ready to pick a full lettuce head, you will need to use a sharp knife to slice it off at the stem. If you leave around 1 inch of foliage and stem the lettuce should start to grow again. If you are reaching the end of the season and are ready to pull them up, you can either pull the lettuce head clean out of the ground then cut the roots off, or cut it as close to the soil line as possible.
It is important to pick your lettuce as soon as they look ripe and ready and not leave them in your vegetable patch as once they reach full maturity it will quickly go to seed and start producing a tall flowery stalk, a process otherwise known as bolting.
How To Avoid Bolting
If you keep a mature romaine lettuce in the ground, then it will be impossible to avoid it bolting at some stage as it is a necessary part of the plant’s growth cycle. But there are some things you can do to stave bolting off for as long as possible.
Picking your romaine lettuces as soon as they appear ready and mature will ensure they do not bolt before you get a chance to enjoy them.
You should try to keep your plants as cool as you can. Planting them in a spot that enjoys a proportion of shade throughout the day will keep lettuce healthy and slow down bolting.
Trimming off any flowering stalk as soon as it appears in the middle of your lettuce head helps to slow the process down too.
You can identify if the lettuce is about to start bolting when you spot extra white sap on or around your lettuce. Once this is evident you can act accordingly to try and slow the process down.
Lettuce growing tall and flowering
Lettuce plants that suddenly start stretching toward the sky and growing extra tall are likely to be bolting too. This sudden growth spurt and appearance of flowers happen when the plant stops focusing so much on producing foliage and starts to turn its attention toward reproduction, sending out a flower stalk that will eventually dry to release seeds.
The leaves are still edible at this stage, but the flower stalk will draw nutrients away from the lettuce leaves making them more bitter.
Lettuce tastes bitter and tough
As described, bolting is the main cause of bitter lettuce. But there can be other reasons. Too little water can also cause bitter and tough lettuce. Lettuce is about 95% water, so it needs large quantities to remain full and sweet. Brown leaf edges are the giveaway that your lettuce needs more water. Ensure you water regularly and don’t let the bed become bone dry.
Another reason why your lettuce might taste bitter is the lack of nutrition. Romaine lettuces grow fast so, without proper nutrients, growth becomes stunted resulting in a harsh taste. Ensure you feed the lettuce regularly with a few drops of liquid feed in a watering can, however, this can be a fine balance too as too much nitrogen can also cause bitter lettuce, so don’t overdo it! Lastly, aster yellow is a disease that can impact romaine lettuce and cause a bitter taste. You will be able to identify if this is the issue if the interior leaves have lost color and the outer leaves have become stunted.
Will Romaine Lettuce Regrow After Cutting
Romaine lettuce is fast-growing and prefers cooler temperatures so you may be able to get a second or even third crop from the heads you’ve already harvested beyond the end of summer and into the Fall. If you cut whole romaine lettuce about 1 inch from the soil line, it will start growing more leaves and eventually form a new head.
When Is It Too Late To Harvest Romaine Lettuce
There is never a time that it is technically too late to harvest romaine but once any lettuce plant has bolted it will then taste bitter and be beyond its best. Always aim to either pick the young, fresh individual leaves or harvest a whole romaine head at the point of peak maturity. Once the plant has gone to seed the taste will be massively impacted but if do reach this stage, especially at the end of the season, you can capitalize on it by saving the seeds for your next crop.
How To Harvest Romaine Lettuce – 3 Ways
You can harvest your romaine lettuce when the core has reached a good solid size. When harvesting, be sure not to disturb the roots as you will prevent them from making new leaves and it will be the end for that plant.
It is always better to harvest romaine 1 inch above the soil line using a sharp knife to get a clean and precise cut. Leaving the white base stalk and then watering regularly will ensure new shoots will appear quickly for another harvest.
1. Picking Individual Leaves As They Grow
Harvesting individual romaine lettuce leaves is a great way to maximize what you get from your crop and also allows you to just pick what you need so it is fresh for dinner that evening. Just ensure you only pick the outer leaves and leave the central leaves to continue growing. You can break the leaves at their base by snapping them or make use of a sharp knife to cut them off.
Also, ensure you water them regularly and give an occasional liquid feed, especially when the weather is hot to promote new growth.
Credit: Marco Verch CC by SA 2.0
2. Harvesting Romaine Lettuce So It Keeps Growing
I like to stack the harvesting process and I also spread out when I plant my lettuce seed across the Spring and Summer so I can enjoy an abundant supply of lettuce all season growing in my raised vegetable beds.
To stack the harvest of your romaine plants, choose a few plants to pick individual leaves from and a few to grow to a full head. Then just pick these one at a time as you are ready (and they are mature) then they will regrow and eventually the plants you have taken the induvial leaves from will reach full size too. Continue to alternate like this until the end of the season.
If you really do want a continuous crop of lettuce to pick, I would also suggest doing some succession planting. Romaine can cope with this as they have such a long season they don’t mind the cooler weather during the Spring and Autumn. You simply sow and germinate your first set of seeds then once they are established and starting to grow sew your new set. You could continue this every 2-3 weeks to provide you with lettuce for multiple meals during the week all summer long!
Where to cut a romaine lettuce head
If you want to pick an entire lettuce and get a second harvest from that plant, you will need to cut it around 1 inch above the surface of the soil using a sharp knife
Regrowing romaine lettuce in soil
My children delight in regrowing lettuce from the one you have previously picked. I can highly recommend it as a fun experiment to try out! You just need to pick full romaine lettuce and then chop the leaves off leaving a few inches at the bottom of the heart.
Then place it in a bowl of water and keep it in a bright room. Change the water every few days and you will soon notice new roots begin to shoot.
At this stage, you can plant it back into a pot, water it regularly and, fingers crossed, watch it grow!
How Often Can You Re-Sprout A Harvested Lettuce
It is advisable to only re-sprout a lettuce once as it will likely lose some of its nutrients through the strain of the process but technically you could keep going on repeat until the plant can take no more!
3. Single Cropping Harvest
Homegrown romaine lettuce lends itself to getting the maximum yield from each lettuce by picking the young leaves, harvesting the whole heads then watching those regrow but it is very feasible to just sew a single crop, harvest them and let some bolt to get seeds ready for the next year.
Simply wait until the lettuce heads have reached maturity and cut the stem at ground level and enjoy your bounty.
