Maturity of Peas

Maturity is measured in Heat Units (H.U. °C; in US °F) and development days. The Number of nodes to the first blossom is an additional source of information.

There are various optimum temperatures for growth and development of peas:

The fastest vegetative development takes place at a temperature around 82° F. It leads to much vine development and results in low reproduction rates. The fastest growth or generative development is seen at temperatures of 59-72° F.

Low temperatures during the growing period lead, therefore, to sturdy, fertile plants with high yield potential.

Growth and development are, naturally, influenced by light conditions and water supply availability. Later plantings require an increased heat for maturity. This may be caused by vernalization -which occurs when planted in cold soil &/or inadequate light during the later development stages-.

The H. U. and development days are counted from emergence to harvest at tenderometer readings of 95-100. Indications from planting to harvest are inaccurate as the germination period is influenced by different factors.

Heat units are calculated from the total of mean day temperatures of the air during the growing period of peas minus the minimum temperature for the growth of peas of 40° F per day.

Besides the method of the meteorologically defined H. U., we also use the method of biologically calculated H. U.
As reference we use a standard variety of which at a certain location its readings have clearly been determined. Based on these data a development chart can incorporate new varieties into the cultivation calendar also taking into account the maturity data as given by the breeder for the local conditions.

Average Heat Units of an Early and Late Variety