1 Water proximity:
Southern Ontario’s asparagus production region is widely bordered by 3 of the Great Lakes. This fact alone provides a moderating effect on temperatures and reduces the likelihood of lethal frosts. So, planting fields closer to these (or other) bodies of water can provide significant benefits. During frost events, temperatures can be 3-4 degrees warmer in fields that are within 2-3km of a lake than in fields further inland.
2 Field location:
Higher portions of a rolling field will always be less prone to frosts than those in lower areas where the cold air drains into.
3 Use of an overwintering cover crop:
Many of Ontario’s asparagus fields are autumn-planted to cereal rye. Besides the reduction in erosion and the benefits to the soil, this cover crop acts to slow the warming up of the ground in the spring and thus delays spear emergence. (There is limited benefit to attempting to hit early local markets given that they are usually flooded with very cheap Mexican imports during the start of our season.) Delayed emergence means a reduction in crop exposure to a killing frost.
4 Use of mulch:
We are currently experimenting with the use of a straw mulch which we place over the top of plants early in the spring. Similar to the use of the rye cover crop, the straw acts as an insulating blanket and keeps the ground from warming up, thus delaying emergence.
5 Varietal selection:
Due to the relatively cold and hard winters in Ontario, there are virtually no differences in terms of emergence between varieties from various asparagus breeding programmes. Nevertheless, Fox Seeds is currently investigating varieties that can produce a larger proportion of total spears later in the season to avoid the significant impact of an early frost and to offer growers a more even production profile.
Read also: Don’t freeze in the face of late frosts!