I know our winters aren't really cold by any means, we don't snow, in fact, we are more likely to have a beautiful sunny day after a frost, and can have a temperature increase of over 20 degC in one day! But this actually makes things trickier because we can ALMOST grow tropical plants, but it only takes one hard frost to knock them back until the weather warms up in spring. Fortunately there are a few tricks we can use to manage frost when we understand what it is and how it behaves.
|frost on broccoli leaves|
The important point is that we can expect cold temperatures to develop on clear still nights, but that if we understand how cold air moves and how frost forms from moisture in the air, we can take steps to prevent frost damage.
|silverbeet with frosted leaves|
- Plant appropriate varieties and understand which vegetables are going to survive and which will need extra protection or if they are just bad choices for your location.
- Protect sensitive vegetables by planting under under cover of trees, close to water tanks or the house (which holds a little heat overnight and can prevent the temperature falling below freezing) or plant in pots that can be moved to safer ground.
- Even though this sounds bizarre, if you water at night before a frost is likely, wet soil will hold more heat and may maintain temperature above freezing (although this can backfire if it does get cold enough to freeze the water on the ground and on leaves).
- If you can circulate the air above your garden using a fan (or a helicopter or a million butterflies) you can mix the cold air near the ground with warmer air higher up - this is used in commercial orchards.
- Cover your veges with fabric or straw/old leaves to try to maintain the air temperature around them. I keep reading to not use plastic, but personally I have had success with using clear plastic all around the plant, and including a bucket of water so the air under the tent is more humid, as this maintains a warmer temperature around the plants.
- Consider where cold air will flow and make sure if can't get trapped uphill of solid fences or hedges in your garden, and also use this concept to direct air AROUND plants but stacking hay bales etc uphill of a sensitive plant.
Frost isn't all bad! It does kill off a number of annoying weeds and bugs, and at least I can grow veges that do like some chill time, like carrots, turnips, swedes and broadbeans, and one day soon fruit trees like apples and stonefruit (or at least I hope I can grow them!).
Do you have frost? How do you manage it?