G.G.M. van der Valk
During the winter, mulches of reed or straw are used on fields planted with hyacinth, narcissus, iris, etc., mainly for protection against frost injury.

Frost injury can be caused either directly by low temperatures or by processes accompanying the formation and the presence of ice in the soil. As a first approach the effect of low temperatures on several cultivars of tulip, narcissus, hyacinth, iris and crocus was tested in sand-filled containers at various temperatures below 0°C. This was done at different stages of plant development, with different lengths of freezing period.

The effects of continuous freezing and a repeated alternation of freezing and thawing were also compared.

The negative effects of low temperatures increased from tulip, crocus, hyacinth, narcissus, to iris, but temperatures below -1°C seemed to have a harmful effect on shoot formation in all crops. Only the degree of freezing and the total duration were of influence.

van der Valk, G.G.M. (1971). FROST INJURY TO FLOWERBULB CROPS. Acta Hortic. 23, 345-349
DOI: 10.17660/ActaHortic.1971.23.56

Acta Horticulturae