For the past two years, I’ve been trying to grow lettuce in my container garden here in Manila but I simply couldn’t get the seeds to germinate. I realized later that I have been using a variety of imported seeds that does not grow well in hot climates like here in the Philippines. So finally I discovered a heat resistant and slow-bolting variety while shopping for seeds at my favorite gardening shop, and voila! I now enjoy my home-grown organic salad, straight from the garden to my table.
Growing Lettuce in Manila
In Manila, the best time to grow lettuce is when the average daily temperature drops below 30 degrees Celsius- or sometime from November to around early-February. Summertime in the Philippines can be very hot which sometimes causes the lettuce leaves to wilt or burn, or the plant to bolt. When lettuce starts to bolt (produce flowers), the leaves may taste bitter and unpalatable.
Sowing the seeds
The first thing to remember is to choose a lettuce variety that can withstand heat and will not bolt easily. Being a cool weather crop, lettuce tends to bolt when the average temperature rises beyond a certain level. Fortunately, some local seed producers had been able to develop slow-bolting and heat resistant varieties that adapt well in our warm environment.
To sow lettuce seeds, simply sprinkle a thin layer of seeds over the soil bed or potting medium. When growing lettuce in a container, choose a medium- sized pot with at least 6 inches in depth. Make sure that the soil is evenly moist. Cover the seeds with another thin layer of soil. Spray the top layer with water to moisten it. Keep the soil moist all the time by spraying water at least once a day.
The seeds will sprout within 5 days. Once the seedlings have grown by at least 2 inches, start thinning or pulling out the weaker seedlings and leave about an inch of space in between. After another 2 weeks, thin out further, ensuring at least 5 cm distance apart. Do not discard the pulled-out seedlings- they are an excellent garnish for sandwiches or salads (as microgreens). During extremely hot weather conditions, lettuce seedlings may look wilted when exposed to the sun for more than 2 hours. Allow the plant to recover in the evening by making sure that the soil is always moist, or does not dry out.
To keep the soil temperature down, find a spot with partial or dappled shade during summer, or with at least 4 hours of full sun in the morning. Maintain a consistently moist soil by watering at least once a day.
Fertilize with compost or organic foliar spray every other week. Water with rice wash to induce a heathy growth of leaves.
Beware of pests.
Lettuce is prone to a lot of soil-bound pests. If available, sprinkle diatomaceous earth on the ground, around the plants, to prevent slugs and other crawling insects. Neem oil is also a useful way of controlling pests organically. Spray a solution of neem oil and water over the plant leaves at night once a week. I also find garlic and pepper solution effective in deterring winged insects, like moths and locusts. For more tips on pest management, visit my blog on organic remedies to control pests in your garden.
Harvesting the Lettuce Leaves
After 6- 8 weeks, your lettuce should be ready for harvest. In hot climates, most lettuce varieties can grow up to about 8 inches. To harvest, cut mature leaves starting from the sides. Alternatively, harvest the entire plant by cutting off the top part from the root base. To ensure a continuous supply, sow a few lettuce seeds in medium sized containers every week.
During summer, I grow lettuce as microgreens by harvesting the young seedlings when they are just 3 weeks old. This way, you can still enjoy your crispy lettuce salad even during summer right from your own garden.