Even here in south east Queensland, our lawns can be affected by frost – radiation frost. This is when the ambient air and the ground cools down by the loss of heat to the atmosphere – or when warm air rises and cool air near the ground drops below zero – causing frost. It most often occurs when there is little or no wind and clear skies overhead. During a light frost the ground doesn’t actually freeze so it is easier for your grass to survive.
Frost can also occur when the overall temperatures have plunged and the temperature overnight is zero or below. Essentially, the frost is the result of dew freezing on your lawn – typically in the early hours of the morning. Why is this a problem for your lawn?
Grass blades move water throughout the length of the plant for nourishment, but when a frost comes, the moisture freezes inside (This is what causes the frosty look of the grass). When the water freezes it expands, rupturing plant cell walls. A light frost that does not freeze the ground won’t cause severe damage because the grass roots below the soil remain above freezing point. This may result in some blade damage but the roots often have the chance to heal the damage as the grass continues to grow.
The frost can freeze the leaf blade and cause significant discolouration – this discolouration is a signal that the frost has damaged the cell walls of the grass which, in turn, slows the process of photosynthesis.
The damage and discolouration that can be caused by frost will often come down to the type of lawn variety you have. Cool season turfs such as Rye and Fescue contain certain proteins which prevents them from freezing – clever huh? However, warm season turfs such as Couch, Kikuyu, Zoysia and Buffalo don’t contain that protein and therefore as much more susceptible to frosts and frost damage. Of course, due to the Queensland climate, warm season turfs are the most common.
Before frost strikes
Ensure that your lawn is in good overall health so that it is able to tolerate any frost better. Consider applying a fertiliser with increased iron before any frost hit to strengthen your lawn for the months ahead.
Give your grass a deep watering the night before an expected frost. The watering allows moisture to slowly evaporate overnight, causing friction and heat around the grass blades. As the night air drops below freezing, you turf will have a slightly higher temperature from the evaporating heat process, allowing your grass to not reach the freezing temperature that causes plant cell wall damage.
Move the mower blades up 1.5 cms, allowing longer leaves to help shelter grass crowns from frosts.
Avoid mowing right before a frost. Mowing creates a wound on the plant, making it more susceptible to frost damage.
If you’re installing a new lawn talk to your local turf supplier and even your neighbours (if you’re new to the area) to determine how likely frost is in your area and therefore the best variety of turf.
If frost strikes
If the temperature plummets and there’s frost on the lawn, the most important thing to do is to stay off it – if you walk on it you will cause the blades of the grass to break and cause even more damage. Obviously, you should never ever drive on lawn that has frost on it.
Give your lawn a light watering just before the sun rises to remove any frost from the leaves. This will help to melt the frost more quickly and evenly – and you’ll be less likely to end up with brown patches in your lawn.
Mow only after your lawn begins to grow again and not looking discoloured. Move the mower blades up 1.5 cms, allowing longer leaves to help shelter grass crowns from future frosts.
Wait to fertilise for up to a month after damage since extra nitrogen from frost dehydration can cause more damage.
Rake yard of dead grass if the frost has been particularly hard in your area. Too much dead grass can lead to excessive thatch.
To learn more about the right variety of turf for the climate in your local – contact the team at Daleys Turf – your turf specialists in South East Queensland.