Romaine and butterhead lettuce are good sources of folate.
From the en.wikipedia.org
Say you sow a row of butterhead lettuce.
From the washingtonpost.com
It is a perfect picnic dish, a beautiful summer lunch, topped with plenty of fresh herbs and served in scallops of butterhead lettuce.
From the post-gazette.com
Gotham grows 5 to 10 types of lettuce including red and green leaf, and baby butterhead lettuce, which it supplies to restaurants and high-end grocery stores in the New York metro area.
From the businessweek.com
His produce included butterhead and mesclun lettuce, pea shoots, basil, watercress and kale.
From the sfgate.com
Butterhead or loosehead lettuce form a loose head of iron-rich, buttery leaves that are somewhat crunchier than leaf lettuces.
From the chron.com
Generally speaking, loose-leaf and romaine lettuce varieties handle cold better than crisphead or butterhead types.