How can I prevent lettuce from becoming bitter?

Preventing bitter lettuce requires an understanding of why lactucarium develops in the leaf. Upon exposure to heat stress and overmaturity, this milky sap builds up, resulting in a bad taste. Harvest early in cool afternoon hours when nitrates tend to be down. Offer the plant consistent row moisture and avoid stress. I have rescued entire crops on this basis and literally saved them!

Harvesting time, pick the young leaf varieties while still tender; if left too long, they become tough and coarse. If they are of the heading type, pick them when the head feels firm but has not started forming a heart. Do not pick them in the morning, as this is the time when they contain the most nitrates. Studies indicate that if picked later, they contain about a third less bitterness.

Control temperature exposure during heat waves by installing hoops covered with 30% shade fabric when daytime highs are above 24°C (75°F). Order the hoops in advance, and water the soil in the early morning to cool the root zone. "Heavily mulch with straw," which calms the plants quite literally, causing strong cultivars to slow lactucarium production drastically.

If you got bitter lettuce towards the end of the season, put the leaves in ice water for 10 min. (add 1 tsp. Add 1/2 teaspoon of salt to every liter (quart) of water. Dry them off before using. If you plan to incorporate them into cooked dishes, fry the bitter salad greens with a little garlic in oil to mask their inherent bitterness. I do that every late crop.

Choose slower-bolt varieties such as Winter Density or Jericho, which tend to resist bitterness in warm weather. Seek out a location with some afternoon shade and rotate the location of your plants annually to minimize the potential for disease stress. Applying a balanced fertilizer will also help avoid the nutrient stresses that can result in bitterness.

Read the full article: When to Harvest Lettuce for Best Results