Maximum vegetative growth rate occurs during flowering. The main stem and each branch usually terminate in an inflorescence, which is a simple raceme with varying numbers of flowers. Even aher the main stem flowering has ceased, the plant can develop lateral secondary as well as tertiary flower sets from a sequence of lateral branches. Species and cultivars differ in ability to set pods on these secondary and tertiary branches. The process is highly influenced by environmental conditions.
Lupine is a cool-season crop, and is relatively tolerant of spring frosts.
The flowering process is affected by high temperatures which cause blasting of flowers and a subsequent yield reduction. In areas which normally experience high temperatures in early summer, such as many parts of southern Minnesota and Wisconsin, the risk to the crop is great. Lupine is adapted to well-drained, coarsely textured, neutral to acidic soils. Iron chlorosis and disease problems often result from plantings on poorly drained, higher pH soils. Reports from Minnesota, New York and parts of New England indicate that many lupine production problems are due to planting on soils too heavy, too wet, or too high in pH. An area of adaptation in central Minnesota on the more acidic, better drained soils has been identified, as have other localized areas in the state.