Homesteadin’ in the Tropics, huh? But what if you want to grow something that isn’t a tropical fruit or vegetable? What if you just want a salad with lettuce from your own backyard? There’s good news – you can grow lettuce in Hawai’i – with a few tips and tricks.
To grow lettuce in Hawaii, all you need is nitrogen-rich soil, plenty of moisture, the right lettuce varieties for our climate, and higher elevations. Lettuce does not grow too well in temperatures above 80F, they grow best in the cooler elevations.
Itʻs also a good idea to grow lettuce where Rat Lungworm Disease has not yet taken over, such as in Oahu and Kauai. Raw produce consumed on Maui or Hawaii Island has a very high chance of transferring Ratlungworm to you, a serious disease that can leave you paralyzed.
So what varieties do we need? How do we make sure the lettuce grows well? Read on and I’ll tell you all about it.
Related: Do you want the secret to growing the best lettuce ever? Spray a Fish & Kelp fertilizer on your growing plants every week. Lettuce thrives on nitrogen and trace minerals, and with a regular application, you can have the best lettuce on the block.
GS Plant Foods Fish & Kelp Fertilizer
Best Lettuce Varieties To Grow In Hawaii
The best types of lettuce to grow in warmer weather are thick leafed or heading lettuces. The best variety of those types of lettuces to grow in Hawaii is called Manoa Lettuce or “Green Mignonette”.
This variety of lettuce was specially developed by horticulturalists at the College of Tropical Agriculture and Human Resources (CTAHR) at the University of Hawaii Manoa. It was determined to be the best type of lettuce to thrive in Hawai’i’s climate and weather conditions. It is resistant to heat, slow to bolt and resistant to tipburn, too.
Other varieties to grow in Hawaii
At low elevations (below 2000 ft):
- Manoa Lettuce
- Anuenue Romaine
- Green Tower
- Valmaine Romaine
- Parris Island Cos
At elevations above 2000 ft:
- Red Leaf
- Salad King
- Broad-leaf Batavian
Only in winter months:
- Black Seeded
- Salad Bowl
- Royal Oak Leaf
- Royal Red Endive
- Red Sails
- Super Prize
- Grand Rapids
What Does Lettuce Need To Thrive?
Soil needs
Technically-speaking, you do not need soil to grow lettuce. Lettuce is one of those cool plants that you can grow in water. Growing lettuce hydroponically has also shown improved pest control and sometimes a higher quality result (Itʻs also a great way to control slugs).
If you’re interested in hydroponic growing methods, lettuce is a great way to start. Unfortunately, I havenʻt grown anything Hydroponically for over 20 years so I canʻt help you much there. But I have grown plenty of lettuce in the ground before Rat Lungworm showed up.
If you’re planting lettuce in soil, it likes well-draining, slightly acidic soil with lots of compost. The best compost is a little worm compost mixed into your existing soil. Lettuce loves high nutrition and there is nothing more nutritious than worm compost.
However, building soil in Hawaii is not the easiest thing to do, thatʻs why I wrote this post on the ultimate soil building recipe for Hawaii.
Temperature Needs
Many of the fruits and vegetables grown in Hawai’i thrive in warm temperatures with plenty of sunlight. This is NOT the case with lettuce. It is not a tropical vegetable and doesn’t like heat.
Ideal temperatures vary depending on lettuce variety, but all prefer under 80 degrees F. This means that lettuce grows best in Hawaii’s cooler months, and at higher elevations.
If you are at lower elevations, stick to heat tolerant varieties and think about using a shade cloth to keep the temperatures down. Iʻve seen people make frames out of guava wood or bamboo and put a few coconut leaves on top to act as shade. Solutions can be simple.
Bonus: a shade cloth also helps keep birds away. Birds love to eat lettuce sprouts.
Water
Lettuce loves water. If you are growing lettuce undercover, it may not get all the water that it needs to grow, so you may have to add supplemental water to keep them happy, especially while young.
Lettuce seedlings can benefit from a misting of water 2-3 times per day until they get more established. After that 1 time per day should do it. Preferable during the hottest part of the day to cool it down a bit.
Best Way To Grow Lettuce
You can grow lettuce in several ways: from seed, sprouts, or even leftovers!
Seeds
Growing lettuce from seed is easy, effective, and the most common. It is the recommended method for growing Manoa Lettuce. You can obtain seeds through most garden stores or in person at UH Manoa, but they do sell out often.
You can simply plant the seeds in soil and water them – ensuring they don’t get too warm!
I like to broadcast the seeds where I want them planted and add a light layer of peat moss over them. They should be planted pretty near the soil surface, maybe ⅛” to ¼” down. Because of this, they will need water often until theyʻre juveniles.
Transplants
Lettuce transplants are a good idea if the weather is cool enough and you want to plant your lettuce quickly, in your garden, or at a plot at a higher elevation. Plant in moist soil (not muddy) and be sure to keep your plants well-hydrated, but not drowning.
If you have a tray of transplants, but be too worried about separating the starts, they are pretty resilient. Just rip them apart and stick them in the ground. Keep then watered and thatʻs all there is too it.
Leftovers
You can also plant lettuce from leftover bits of lettuce. Keep the central head and any part of the root that your original head of lettuce came from (It’s best with organic lettuce, but I’ve also had success with replanting super-market varieties of lettuce).
Simply clean the remaining stump or stem and plant it, the head facing up. You can plant the leftover lettuce either in a cup of water or in a pot of soil. Give it water and watch it grow.
You won’t get an endless supply using leftovers, though. I usually can re-grow lettuce from kitchen scraps 2 times before I throw the remainder in my compost bin. It’s still fun to regrow using this method, though.
Pests and Diseases
Slugs
I wonʻt even grow lettuce anymore because of slugs and the whole rat lungworm issue, but if you donʻt have that issue, consider yourself lucky. In that case, slugs are just a minor annoyance.
You can apply some organic deterrents or hand-pick the critters off to save your lettuce, but my favorite method is to use beer.
Yes, beer. Slugs love the smell, so bury a deep, narrow container so that the opening is half an inch above the soil line. Then, pour in a can of beer and wait while the slugs drown themselves.
Another way is to put copper wires or copper tape (sold at garden stores) near your lettuce because copper gives slimy snails and slugs little shocks (serves them right for trying to eat your salad!).
To learn more about these pests and others, be sure to check out this informative post.
Tipburn
Tipburn, or clear spotting on the inner leaves of the lettuce head, has two causes: lack of calcium or hot weather. You can easily add calcium to your soil to deal with the first cause. To do this you can add lime to the soil a few weeks before planting or incorporate eggshells into the soil.
If you have Tipburn because of hot weather, you should plan your planting time to be in winter, provide a shade cloth and hope for the best.
Tipburn is seen mostly when temperatures are regularly over 85F and there are not many cool nights to balance it out (nightly temperatures of 55F).
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