Mild, bold or sweet, it’s easy to grow lettuce indoors year around when you know a few growing secrets. Temperature and lighting are the critical elements for successfully growing lettuce in containers indoors, but both elements are easy to master with these growing tips.
Select containers that are 12-18 inches deep and equally as wide to allow lettuce to leaf out and grow deep roots. Good drainage is also essential, so ensure containers have plenty of drainage holes in the bottom. Place coffee filters over the drainage holes to prevent soil from leaching out during watering.
Create a soil mixture that is 50 percent potting soil and 50 percent compost. This will create a light, well-draining, well-aerated soil that won’t compact and will keep the lettuce plants well-fed during the growing season.
Seeds or Plants For first time lettuce growers, start with plants for an increased rate of success. While lettuce is not difficult to grow, it has quirks and first-timers are better off starting with plants. Set plants in the center of container, 2 inches deep. Water well. Sow seeds thickly for loose-leaf lettuce varieties, sow sparsely for heading varieties. Thin plants when they reach 4 inches in height. To extend harvest time, plant seeds two weeks apart throughout the growing season for a continual harvest.
Temperature and Light Lettuce is a cool season vegetable and will only grow in cool temperatures. A room that remains a constant temperature of 60-70 degree Fahrenheit is ideal for growing lettuce. Keep containers away from heating/cooling vents and exterior doors which cause a sudden change in temperature. Place growing containers near a sunny window so they will receive at least 4 hours of direct morning sunlight per day. Direct afternoon sunlight may cause lettuce plants to become too hot. When containers are located in a west-facing window, move them out of direct sunlight after 1 hour, but keep them near the window.
Water and Mulch Lettuce likes consistently moist soil and will need to be watered regularly and evenly. Apply a two inch layer of organic mulch on top of the soil in the container to keep soil cool, and help retain consistent moisture. A good mulch to use on inside container-grown plants is shredded newspaper (black and white sheets only).
Harvest Time Harvest loose leaf lettuce at any stage of growth. Encourage more leaf growth by cutting off the outer leaves near the bottom of the plant. For head varieties, like romaine and butterhead, remove entire head from soil to harvest. Wet soil, grasp plant at the base, rock back and forth until it lifts up from the soil. Use a sharp knife to cut off root at base of lettuce head.
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