This causes problems as it takes more time to lift and clean the crop and can significantly damage the surface of the bed.
Sand-beds are normally re-sanded and levelled every five years at an estimated cost (with labour) of £17,000 per hectare. If this has to be done annually due to rooting through and the extra costs of lifting (four times the norm) are added in, this represents a serious problem to hardy nursery stock growers.
Growers can cover beds with polythene products or woven fabric but these need to be frequently replaced or they can impede capillary action, so until recently many growers used chemical alternatives. However, due to the withdrawal of Gloquat C and now Ardent, the industry needs a herbicide treatment for the surface of the bed.
HDC project HNS 167 investigated a range of herbicide products on a general shrub nursery and a heather nursery. Species tested were the more vigorous Erica x darleyensis cultivars and Spiraea, Weigela, Buddleja and Vinca. Plants were lifted in November and the amount of rooting assessed and a further assessment was made for the shrub species in March.
Chikara Weed Control (flazasulfuron 25% w/w), from Belchin, gave excellent weed control to the species in the study (annual meadow grass and American willowherb) and liverwort. This product has approval for use as a herbicide in this situation. Stomp 400SC is an alternative treatment for heathers, which gave better root development in the pot.