This has been called 'regreening'. Split seed occurs on severely manganese deficient soils regardless of seasonal conditions. On less deficient soils it usually occurs in spring after a dry spell. Seed appears to set and fill normally until light rain falls, wetting the top 10 to 20 cm of soil. The lupins then start to produce new growth.
Growth then stops and the seeds dry off.
The seed splits long the edge furthest from the pod and the margin of the split seed coat usually turns brown. Many seeds do not split, but stop developing, dry off and shrivel if immature. Pods containing affected seed tend to be conspicuously flattened and slightly darkened. Flower buds and pods that form on new growth usually abort or do not develop. Seed yield losses are roughly proportional to the degree of seed splitting.