Q: Can you give me some hints and tips for growing lettuce?

A: Lettuce is a cool season vegetable which means that it can be planted very early in the spring, as much as 2-to-4 weeks before the average last (spring) frost date. It survives frosty nighttime temperatures and grows with daytime temperatures as low as 40 degrees. Freshly picked lettuce has a delicious taste that is far better than grocery store lettuce.

There are four different general varieties of lettuce though leaf lettuce, rather than head lettuce, is the most common for home gardens as the leaves can be harvested as needed, leaving the plant to regenerate more leaves.

Crisphead is a head lettuce usually started as transplants indoors or in a cold frame. Iceberg is medium size, forming a firm head with a crisp texture, tender hearts and leaf edges tinged light brown. Iceberg is the most commonly grown commercial lettuce variety. Ithaca tolerates heat; resists bitterness and is slow to bolt. Head lettuce usually matures in approximately 70 days.

Butterhead lettuce also forms a head, but the texture is soft and pliable with less distinct veins. Bibb is an heirloom lettuce. Buttercrunch is an American cousin of Bibb, but more tolerant of hot weather (65 days maturity). Marvel of Four Seasons is a popular European variety having green leaves tipped with red. This variety can be planted in late spring as well as late summer and fall (68 days maturity).

Green Leaf varieties include Black-seeded Simpson, the earliest to harvest. Grand Rapids lettuce has frilly edges, and Oak Leaf is resistant to tip burn and good for hot weather.

Red Leaf lettuce includes Red Fire, which has ruffles with red edges and is slow to bolt. Red Sails is the slowest bolting red leaf lettuce. Ruby is the darkest red and resistant to tip burn.
Cos or Romaine lettuces include the Cos type, Cimmaron, that has unique dark red leaves. Green Towers is an early, dark green, large leaf lettuce.

Mesclun is a French name for mixed young leaves for salads. Generally these are harvested while young, so succession planting is essential. Approximately one foot is needed for a salad. Most Mesclun mixes are “cut and come again” varieties, so cutting an inch above the ground with scissors will keep the lettuce growing (35-45 days until maturity).

Planting Your Lettuce

Plant lettuce seeds ¼” deep when the soil in your garden is on the dry side; then keep the soil surface moist until seedlings appear. The plants should germinate in 4-to-10 days and be ready for harvest in 60 days. Crowding reduces air circulation and increases disease susceptibility so thin seeds or set transplants so they are 10-1/2” apart for head lettuce and 7” to 9” apart for leaf lettuce.

Seeds can be planted indoors 6-8 weeks before they will be planted outdoors. A week to ten days prior to planting outdoors, begin hardening off which means acclimating the plants to outdoor temperatures by gradually exposing them to longer times outdoors.

Lettuce is shallow-rooted and is intolerant of dry soils so a dry spring can affect your harvest. Water needs are critical during head/leaf development and quality suffers if the plants get dry. Plant only the amount of lettuce you can use so you are not watering too many plants. Ideally, start a few plants at weekly intervals for a continuous harvest.

Other Tips for Growing Lettuce

• Amend the soil with organic material and fertilizer. Apply one pound of nitrogen and phosphorus per 1000 square feet before planting and another pound July 1st.
• Use mulch to reduce irrigation needs. Organic mulch reduces the soil temperature which makes for sweeter produce.
• Regularly check your soil moisture and practice efficient irrigation by using a drip system or soaker hose.
• Plant in small rectangular beds or blocks rather than in long, single rows. Controlling weeds, fertilizing, and watering are simpler with smaller plantings.
• As temperatures warm later in the summer, lettuce will often bolt or go to seed. Try planting a new crop in late July or early August.

Like any garden plant, lettuce can be affected by insects or diseases. Slugs, root aphids, gray mold, cutworms, and downy mildew can affect lettuce. Remove affected leaves and wash or pick off insects. Use chemicals cautiously and wash the leaves thoroughly before eating.

Lettuce has attractive and often colorful foliage. Consider mixing lettuce with flowers for a striking and functional bed or border, rather than planting lettuce in rows in the garden. A lettuce crop is ideal for raised beds-it matures rapidly, can be planted close together and be planted in succession every 7-10 days. Or try planting a small quantity of lettuce seeds in a patio container and snack on the leaves as they mature.

Contributed by Deb Ross, Certified Colorado Gardener