How to protect fruit trees from frost: frost fleece, thermal blanket and heaters

There are two strategies against frost: cover the crop so it keeps the heat from the soil (frost fleece or thermal blanket) or add heat to the plot (frost heaters). Covers suit crops that can be covered, such as vegetables or newly planted fruit trees; in orchards and vineyards in bloom, which cannot be covered, heaters are used: the Wiesel heater raises the temperature by 2 to 3 °C with 200 heaters per hectare and by up to 6 °C with 300, according to its datasheet.

Which protection suits each case?

Sources: Novafrut frost fleece and Wiesel heater datasheets and the Criado y López thermal blanket datasheet.

Frost heaters: how many per hectare and how long they last

The Wiesel stainless steel heater is designed for late spring frosts, when the orchard is in bloom or fruit set and cannot be covered. Data from its datasheet:

• Density and effect: with 200 heaters per hectare the temperature rises by 2 to 3 °C; with 300 heaters per hectare, by up to 6 °C.
• Burn time: 3 to 5 hours with a half load (10 kg) and 6 to 8 hours with a full load (20 kg) of wood briquettes, preferably hardwood. At the end of the cycle the heater stays incandescent and keeps giving off heat.
• Lighting: with the lid open for the first 20 minutes, closing the air damper after about an hour and a half to extend combustion. It can be refilled on long nights or consecutive frosts.
• Service life: up to 20 years; a reusable alternative to paraffin candles.

Density is set by the degrees you need to gain: according to the datasheet, from 2-3 °C with 200 heaters per hectare to 6 °C with 300.

Thermal blanket: floating cover, hoops or second roof

The Grupo Criado y López thermal blanket is a white, UV-resistant fabric laid directly on the crop (floating cover), on hoops or as a second roof in greenhouses. Besides frost, it holds back morning dew and small insects, and its manufacturer states that it brings the harvest forward. For newly transplanted fruit trees such as avocado, lemon or orange, it comes as a tube that wraps the young tree.

What if the orchard already has anti-hail netting?

Anti-hail netting is not designed to protect against frost, so one of the solutions above must be added. Its structure does allow protections to be combined, for example with a rain cover on the same posts and cables.

How we help

We advise you on protection according to the crop, the growth stage at which your frosts usually arrive and the size of the plot, and we supply frost fleece, thermal blanket or Wiesel heaters. Ask us for a quote or see how we work with fruit growers.