Lettuce is a cool season vegetable. It is characterized by a loose leaves and head. It is easy to grow. You can grow lettuce under a limited space even in vegetable garden, sack garden, greenhouse or hydroponically. It is very nutritious and rich in vitamins and minerals. This is the reason why it is widely used as salad. Apart from salad, it is also used in soups, sandwiches, wraps or grilled.
Apart from being nutritious, it is also low in calories which makes the crop good to be used in weight loss programs. The nutritional benefits and and health benefits makes the crop have a high demand.
Varieties Of Lettuce In Kenya
- Butterhead; has loose leaves and buttery texture. Ready for the first harvest in 45-55 days after sowing.
- Crisp-head; forms tight, dense heads that resemble cabbage. It is the mildest form and valued for its crunchy texture than flavour. Ready for the first harvest in 70-100 days after sowing.
- Loose-leaf; has tender, delicate and flavourful leaves with a loose bunch and is mainly used for salads. Ready for the first harvest in 45-55 days after sowing
- Romaine lettuce; grows to a long head of sturdy leaves with a stout rib almost reaching to the tip of the leaf blade. It is used mainly for salads and sandwiches and is ready for first harvesting in 75-85 days after sowing.
- Chinese lettuce; forms long, tapering, non-head forming leaves and has a strong-flavored the tuff of terminal leaves.
- Summer crisp; forms moderately dense heads with a crunchy texture. The variety is intermediate between crisp-head and loose-leaf varieties.
Nutritional & Health Benefits of Lettuce
Some of the benefits of lettuce include the following;
- Certain proteins in lettuce like lipoxygenase and carrageenan help in controlling inflammation
- Lettuce’s vitamin c and beta-carotene work together to prevent the oxidation of cholesterol
- It helps with insomnia (has Lactucarium which has relaxing and sleep inducing properties)
- It is a rich source of vitamin k which has a potential role in the bone metabolism.
- Fresh lettuce leaves contain good amounts of folates and vitamin c.
- It contains zeaxanthin, an important dietary carotenoid.
- It is rich in healthy amounts of minerals like iron, zinc, calcium, potassium and magnesium which are very essential for body metabolism.
- It is a rich source of the B-complex group of vitamins like thiamin, vitamin b-6 and riboflavins.
- It is rich in fiber and cellulose
- The latex of lettuce has antimicrobial properties that completely deform yeasts using terpenes and cardenolides and enzymes like glucanases.
- Lettuce has anti-cancer properties.
Ecological requirements
Lettuce is a cool season crop that grows best with temperatures of 12-20OC. Temperatures above 27oC affect head development and plant edible quality and also promote premature seed stalk development. Although the crop can thrive on a wide range of soils, optimal production is achieved on well-drained fertile loam soils that are rich in organic matter, have good water-holding capacity and a pH between 5.5-7.0.
Propagation & Planting
Lettuce is propagated from seeds, which can be sown directly into the main field or raised in a nursery bed and transplanted thereafter.
Raising seeds in a nursery
You can sow the seeds in a nursery first then transplant to a ready bed or sow directly in a ready bed. For a nursery you need about 200g/acre and 300-400g in direct seeding It is recommended to raise seedlings in a nursery for a good start and break seed dormancy.
To raise in a nursery:
- Prepare a bed 1M wide, dig out weeds and level well
- Make small drills 1cm deep at a spacing of 25-30cm apart
- Mix seeds with some soil and sow thinly along the drills
- Cover with a light mulch and water
- After 7 days when they have germinated, remove the mulch and make a raised shade 1M high over the nursery bed
- Drench the seedlings while in the nursery with Pearl 50SC to help control early diseases from Damping off and Fusarium wilt
- The seedlings are ready for transplanting after 4-6 weeks when they are about 7cm high
Transplanting
Lettuce seedlings are ready to transplant in 4-5 weeks with 4 to 6 leaves and a well-developed root system. To harden the young plants, the rate of irrigation should be reduced, a week before transplanting, and the shading withdrawn. Before lifting the seedlings, the nursery bed should be irrigated.
Procedure
- Make raised or sunken beds on the prepared land.
- Mix soil with manure and DAP. For efficient and improved nutrient uptake and stimulation of root development, among other benefits, mix 1kg Humipower® with 50kg DAP and /or 1 ton of manure.
- Irrigate the beds to allow for easy planting.
- Plant the seedlings in the beds at a spacing of 45*30cm
Tips!
- To overcome transplanting shock, spray seedlings with Optimizer® 10ml/20L.
- Transplanting is best done early in the morning or in the evenings.
- Transplant only the healthy and strong seedlings.
Cultural practices
Thinning; When seedlings sprout to about 2-3 inches, they should be thinned to 3-4 inches apart. This helps in reducing competition as well as ensuring sufficient air circulation within the crops.
Weeding; Lettuce does not compete well with weeds and therefore weeding should be done regularly until the crop foliage covers ground. Thereafter, it can be reduced to pulling out individual weeds when they appear.
Mulching; The crop should be mulched to retain soil moisture and keep the produce clean. When decomposed, the mulch releases nutrients into the soil which are absorbed by the crop.
Watering/Irrigation; In order to ensure even and rapid growth, the soil should be kept moderately moist throughout the season. Otherwise, lettuce may become bitter and flower prematurely.
Crop rotation; Strict crop rotation should be practised using non-family crops like cereals, legumes, brassicas, among others. This helps prevent build-up of pests and diseases among other benefits.
Fertilizer application; Timely application of both basal and foliar fertilizers is highly recommended in order to achieve optimum yields. Well decomposed farm yard manure should also be added especially for soils with little or no organic matter as it boosts productivity and does not destroy soil structure or pollute the environment. It also has residual effect in the soil which benefits the next season’s crop.
Maturity, Harvesting & Post-Harvest Handling
Depending on the variety and the ecological conditions, lettuce takes 45–130 days from planting to harvesting. Besides, the stage of harvest maturity depends on the variety of lettuce and the purpose for which it is grown. For instance, since lettuce that flowers through bolting becomes bitter and unsaleable, plants grown for consumption are rarely allowed to grow to maturity.
The heading types are harvested when the heads are fully grown and firm while the loose leaf types are picked when the leaves have reached the required size.
Harvesting is done by cutting off the plant just above the soil surface to keep most of the outer leaves around the head and should be done very early in the morning because lettuce wilts rapidly. Generally, harvesting lettuce in cooler weather makes for much sweeter tasting, crisper leaves.
If lettuce is left in the ground for too long, it begins to form a seed stalk, a process known as bolting, and the lettuce leaves will have turned bitter.
After harvesting lettuce, the leaves or heads should be sorted and graded, then packed in crates or cartons. Lettuce can also be stored for up to three weeks at temperatures of 4°c at 95% relative humidity.
Pests and diseases of lettuce
Common pests known to attack lettuce as listed by greenlife.co.ke include aphids, cutworms, diamond black moth, caterpillars and American bollworm which are controlled by spraying with appropriate pesticides and insecticides.
Diseases that infect lettuce are damping off, Downey mildew, leaf spot, powdery mildew, bacterial rot, and lettuce mosaic virus which are controlled by applying recommended fungicides.
Lettuce Prices In Kenya
The price of lettuce in Kenya varies depending on various factors such as seasonality, location, and supply and demand. Generally, lettuce prices tend to be higher during the dry season when the supply is limited, and lower during the rainy season when there is more supply.
In Nairobi, the capital city of Kenya, lettuce prices as of March 2023 range from Ksh 50 to Ksh 150 per head, depending on the size and quality of the lettuce. However, prices may be higher in other parts of the country, especially in areas that are not near major lettuce production regions.
It’s also important to note that prices may fluctuate depending on factors such as transportation costs, input costs such as fertilizers, and availability of labor. Additionally, prices may be affected by market forces such as the demand for lettuce from hotels and restaurants, which tends to be higher during the peak tourism season.
Overall, lettuce prices in Kenya can be quite affordable, especially if you purchase them in bulk from the main lettuce growing regions. However, prices may be higher in certain areas or during certain times of the year.