Crops Honesty (Lunaria biennis)

Seedlings

Most honesty plants are biennials, with well-branched and deeply penetrating root systems, on which develop small tubers containing overwintering carbohydrate reserves.

Young plant in winter

Leaves are initially produced in pairs: they are roughly heart-shaped, with toothed margins, bright green in spring and summer but darker during the winter months. Stems elongate in early spring, often reaching a height of 90 cm (or more in the most favourable circumstances); leaves are arranged alternately up the stem. Flowering may commence in late March or April; the flowers, individually stalked, are usually purple but may be white or parti- coloured, and are produced in groups at the top of the main stem and branches.

The flat green seedpods often take on a purple colouration during the ripening process, which is usually complete by early August.

Silver penny stage

The outer cases and seeds then fall away, leaving the intermediate membranes still attached to the plants as the 'silver penny' popular in floral arrangements. Biennial honesty plants have an absolute (and considerable) vernalisation requirement; they will not flower in spring unless they have been over- wintered as well-established plants.

Seeds

Sowing dates must therefore be early enough to allow the plants to grow sufficiently large before winter. Experience at Sonning suggests that a late July sowing is the latest which can be safely recommended (at this latitude), though improved selections may permit later sowings; some growers have attempted to minimise the consequent disruption to customary farming practice by under-sowing the crop in cereals. It is suggested that a suitable target plant density is about 50-60 plants per square metre, which should be obtained by the shallow sowing of 15-18 kg seed per ha, in narrow rows (10-15 cm). No herbicides are yet recommended as being completely crop-safe; fertiliser requirements are expected to be low and may be met by application of 50 kg per ha of nitrogen. The crop stands well and should be combinable without difficulty, probably early in August: few yield assessments have been made but up to 1.5 t per ha of seed should be attainable with present material. The greatest obstacle to commercial growing may relate to the plant's biennial habit: an annual mutant has been reported, but seed appears to be scarce and productivity may not be reliable. Plants often do not thrive in large fields; in the wild they are usually found in sheltered and semi-shaded locations, and honesty may perform best as a crop in shaded portions of fields, around headlands and perhaps as a component of agroforestry systems. Early results from clinical trials suggest that preparations derived from honesty seed oil may be helpful in treating some disabling conditions such as multiple sclerosis.