To determine leaf stage, you count the true leaves only, not the cotyledons. If the plant leaves have an alternate arrangement, then you count each true leaf. If the plant leaves have an opposite arrangement, then you count true leaf pairs. Plant stage can’t be determined by just measuring the plant height. In warm, moist weather plants can quickly move through their growth stages and cotyledons or true leaves might look bigger and more spaced apart than you were expecting.
The trifoliate leaf has to be fully extended before you count it. This soybean is at unifoliate stage. Soybean cotyledons are very thick and spongy. Photo credit: Wendy McDonaldLeft to right. Soybeans at the Vegetative Cotyledon (VC) or Unifoliate stage with two unrolled unifoliate leaves. Soybeans at the Emergence (VE) stage or emergence. The cotyledons have been pulled through the soil but the unifoliate is not fully expanded. And soybeans at the pre-emergence stage. Photo credit: Wendy McDonald
Wild buckwheat in the two leaf stage. Cotyledon are long and narrow and true leaves are alternate and heart shaped. Photo credit: Wendy McDonaldLamb’s quarters has an elongated cotyledon which is attached by a petiole that is very distinctive from the blade. The first leaves are opposite and the subsequent leaves are alternate. This would be at least the four leaf stage, some might even call it the five leaf stage. Photo credit: Wendy McDonaldRed Root Pigweed has an elongated cotyledon (cigar shaped) and the first leaves are rounded to oval, but all true leaves are alternate. This is a two leaf red root pigweed. Photo credit: Wendy McDonaldLupin at the cotyledon stage, the leaves of the first true leaflet (little palm tree) haven’t expanded yet. The cotyledon leaves are wrinkly but thick. The leaflet can have five to 10 leaves arranged in a circle. Photo credit: Wendy McDonald
Peas in the V3 or three node stage. Count the elephant ears that clasp the stem, don’t count the stipule until it is fully unfolded. The top leaf (folded) is called a clam leaf. Photo credit: Wendy McDonald
