Let’s consider two ideas for garden plant frost protection that are neither mechanical, nor traditional.
Tender or frost susceptible plants run the gamut, from those that are history when hit (such as annuals) to tropicals that, depending on how long they’re exposed to cold temperatures, are wounded or also become history. Wounded plants should be removed once you get a look at them in the spring, when it’s been warm long enough to encourage new growth. It can be hard to part with plants that are an important part of your landscape, but like old sheepherders say: “A sick sheep is a dead sheep!” You’ll save time and money with early replacement.
Perennials that are hardy will go into a dormant state by reducing sap and conserving water. Make no mistake, there is activity in those seemingly dead branches. Give them a gentle bend and if there is no breakage, all is well. Like a toad buried in the mud, the heart still beats, just more slowly.
There are different types of frost. Horfrost, rime, and black frost are just a few frost types. For frost susceptible plants, frost is bad by any name.
There are also different types of freeze, including:
- Light freeze-temperatures go down to 28 degrees Fahrenheit for a few hours
- Moderate freeze-temperatures go down to 25 to 28 degrees Fahrenheit for several hours
- Severe freeze-temperatures go below 25 degrees Fahrenheit for several hours
Killing frosts for a given area usually refers to events between the average first and last frost dates.
So how can you prevent your plants from succumbing to a deadly frost?
DIY Frost Protection
Mechanical ways of frost protection include watering plants thoroughly before an anticipated freeze. This is done automatically in commercial citrus orchards, whether or not there are wind machines in place. Tender container plants can be brought indoors and a layer of mulch put over susceptible sprouts. Larger shrubs and trees can be covered with any number of commercial frost cloths, old bed sheets, burlap, etc.
Do not use plastic or plastic-lined material. Frameworks can be rigged for draping to keep the drape from touching the foliage. Sturdiness of a frame is key for untoward winds.
Organic Products for Frost Protection
A liquid seaweed (Ascophyllum nodosum) product can be utilized to precondition plants to withstand cold temperatures with less chance of frost damage. A seaweed crème made from the whole kelp plant, rather than being a kelp extract, is best. All of the plant growth hormones including cytokinins, auxins, and gibberellins are intact and unaltered.
This is now beginning to sound like a lesson in plant physiology, so let me explain the function of each hormone. Cytokinins promote cell division, gibberellins regulate growth, and auxins are the great coordinators of nearly all plant growth processes. Remember the age old question of how does a thermos bottle work? You put something cold in it and the something stays cold. You put something hot in it and the something stays hot. How does it know what to do?
Toughen up plant tissues with foliar sprays of seaweed (one ounce in one gallon of water). The cytokinins will thicken cell walls, the gibberellins will influence plant hormonal responses to cold temperatures, and the auxins, like the thermos bottle, know what to do to make the outcome best for the survival of the plant. When applying foliar sprays, good coverage is very important. Apply spray until there’s runoff to foliage, limbs, and trunks.
Soil and microbial heat can be exploited to increase heat transference from earth to leaf canopy. Bare soil, even on cool nights (as low as the 20s), will have a surface temperature around 50 degrees Fahrenheit. Like soils that have active microbial communities containing aerobic bacteria, fucultative anaerobes, yeasts and molds actinomycetes, pseudomonads, and cellulose degraders generate calories of heat. By any standards the amount is miniscule, but soil microbial activity does contribute to the earth’s heat.
Applying a liquid humic acid product under and around and then out to the dripline of trees and shrubs in anticipation of frosty temperatures will result in a two-way action. The carbon-based humic acid is food to increase the numbers and diversity of the soil’s microbial mass, and the black color from the carbon will absorb sunlight, making the soil warmer. Treat the soil with this material (undiluted) to blacken the surface evenly.