You may better know the butterhead lettuce (Lactuca sativa) group of salad greens by the term Boston or Bibb, but the names can be used interchangeably. The loose-headed greens are prized for their soft “buttery” texture and mild taste. These cool-weather crops go into the ground as seeds or seedlings four to six weeks before the last average frost date in your area. Within a couple of months, they’re ready for harvest.
Timing is Everything
Keep an eye on the loose heads as they reach their maturity date. As a group, butterhead lettuce reaches maturity as early as 55 days, but a specific cultivar might take as long as 80 days. Check your seed packet or seedling tag for specific maturity dates whenever possible.
What to Look For
Boston, or Bibb, lettuces don’t form the tight heads that you see on iceberg, also known as crisphead, lettuce. Instead, look for the outer leaves to be cupping inward, forming the characteristic loose head. Unless you like very bitter greens, you’ve waited too long if the lettuce is sending out flowering stalks.
As you’re harvesting other salad greens in the garden, feel free to pluck the outer leaves from your young Boston lettuce. Even if you're planning to harvest the entire head later, butterhead types can take a little light harvesting before they are ready to be picked as head lettuce. If you're not going to be harvesting the whole head, just keep harvesting the outer leaves by pinching off -- or cutting with kitchen shears -- the outer leaves at the base of the plant during the course of the growing season.
You could just pick the entire Bibb lettuce plant, roots and all, from the ground with a quick turn-and-pull motion at the base of the plant. But because even heading types have been known to sprout some additional, edible leaves after they’re beheaded, it’s more common to simply cut away each Boston lettuce head at the plant's base. Hold the head in one hand to keep the outer leaves from dropping, and use a small kitchen knife to slice underneath the head. Pruners will also work, in a pinch.
Disinfect your knife or pruners with household disinfectant. Do this after you’ve finished harvesting lettuce in the garden. This will keep any potential fungal or bacterial diseases from spreading to other plants.
Keep It Crisp
Lettuce is less likely to wilt if you harvest the heads or outer leaves in the morning, when the air is at its coolest. Store unwashed lettuce heads, or washed and dried outer leaves, in a plastic bag. Put the head or leaves in the crisper of your refrigerator until you're ready to use it. For best results, serve Boston or Bibb lettuce within a week after harvest.