Lettuce & Salad Greens

Lettuce and leafy salad greens — including leaf lettuce, romaine, butterhead, kale, spinach, Swiss chard, and arugula — are among the most nitrogen-hungry crops in the garden because their entire harvested product is vegetative leaf tissue. Unlike fruiting crops where nutrition shifts from nitrogen to phosphorus and potassium at flowering, lettuce and greens benefit from consistently available nitrogen throughout their rapid 30-60 day growing cycle. The ideal NPK ratio emphasizes nitrogen at roughly a 3:1:2 pattern (such as 12-4-8), which promotes the lush, rapid leaf expansion that produces tender, flavorful salad crops. However, the nitrogen source matters significantly for lettuce quality. Ammonium-based nitrogen sources can contribute to tip burn — the crispy brown edge discoloration that ruins entire heads — because ammonium interferes with calcium uptake. Calcium nitrate is the preferred nitrogen source for lettuce production, simultaneously providing nitrogen and the calcium essential for crisp, tip-burn-free leaves. The short growing cycle of most lettuce varieties means pre-plant soil preparation with compost and organic amendments often provides most of the nutrition needed, with one or two light side-dressings as insurance. Lettuce is also an excellent candidate for succession planting every 2-3 weeks for continuous harvest, and New England's cool spring and fall seasons provide ideal growing conditions — the crop actually benefits from temperatures that would stress warm-season vegetables. Soil organic matter is particularly important for lettuce because it retains moisture in the root zone; inconsistent watering stress triggers bolting (premature flowering) which makes leaves bitter.