A loose-leaf lettuce variety, "Grand Rapids" (Lactuca sativa "Grand Rapids") produces heads of open, randomly arranged leaves with ruffled terminal ends. This cool-season crop will grow in all U.S. Department of Agriculture plant hardiness zones if exposed to temperatures of 60 to 70 degrees Fahrenheit. This temperature range allows the plant to thrive and produce its characteristic crisp, slightly sweet foliage. Growing "Grand Rapids" lettuce indoors allows gardeners to extend the lettuce growing season by controlling the temperature, along with other cultural conditions. "Grand Rapids" thrives in full to partial sunlight and fast-draining, nutrient-rich soil.
Place a 4-, 8- or 12-inch pot with a depth of at least 4 inches on a flat work surface. Only use a container with drainage holes. Fill the pot one-half to two-thirds full of potting soil. Tamp the soil down to settle it. Add more soil if needed to keep the correct level.
Push on the bottom of the "Grand Rapids" lettuce start's container while sliding the plant out carefully. Massage the bottom of the root ball gently to spread the roots out.
Place the plant in the container, positioning it as straight as possible. Plant one plant per 4-inch pot, two plants per 8-inch pot and three plants per 12-inch pot. Space multiple plants 4 inches apart. Add or remove soil from the pot as needed to position the top of the root ball 1 inch below the pot's top.
Add 2 to 3 inches of potting soil to the pot at one time. Tamp the soil down around the plant's root ball. Continue to add soil to the pot until the level reaches 1 inch below its top. Do not bury the lettuce start deeper than it was previously growing.
Fill the pot slowly with water from a watering can. Wait for the water to soak in the soil completely. Fill the pot one to two more times with water to ensure evenly moist soil. Wait for the excess water to finish draining from the pot's bottom.
Place the pot in an area with a constant temperature of 60 to 70 degrees Fahrenheit that receives at least six hours of sunlight per day. Position the pot in direct sunlight, away from heating and cooling vents.
Water the lettuce when the top 1 inch of soil becomes dry. Fill the pot full of water. Avoid splashing the leaves as much as possible. Wait for the excess water to drain out the pot's bottom. Discard any water in the pot's drainage tray if applicable. Water the lettuce in the morning to give wet foliage time to dry before nightfall. Do not allow the soil to dry out completely or become soggy.
Mix 1/2 teaspoon of 10-10-10 water-soluble fertilizer with 1 gallon of water in a watering can. Apply the fertilizer every 14 days. Fill the pot full of the fertilizer solution. Do not pour it over the lettuce leaves. Wait for the fertilizer to soak into the soil. Fill the pot a second time. Discard any solution standing in the pot's drainage tray. Apply the fertilizer in place of watering.
Trim off any dead or dying leaves with pruning shears or kitchen scissors as soon as they appear. Discard the leaves in a trash bin or on a compost pile.
Harvest the outer plant leaves first, once they reach at least 5 to 6 inches tall, to promote additional leafy growth. Cut through the leaves with pruning shears or kitchen scissors, 1 to 2 inches above soil level. Do not cut into the plant's crown, or base, to avoid damaging it and stunting future growth. Harvest the entire head by cutting horizontally through the plant's base.