March Weather Summary and Frost Watch

Although we have been spoiled by unseasonably warm temperatures frost could be an issue for a little while longer.

Keep the winter jacket handy at least for a little while longer. After experiencing summer-like weather conditions during the month of March, most of the state is under a freeze watch for Monday and Tuesday night. These more “normal” temperatures will feel anything but considering the very abnormal spring temperatures to date.

Temperatures in central Iowa averaged 55.7 F during March which is 16.4 degrees above normal. Overall, there were 12 days during March when the daytime temperature was in the 70’s or 80’s. The warmest day of the month occurred on the 16th with a high of 84 F. Now, we must prepare for frost. Historical weather records show that the average last date for frost occurs sometime between mid-April to the first week of May depending on your location in the state.

So what exactly is frost? Frost is the formation of white ice crystals on an exposed outside surface such as leaf blades. Annual plants are often more sensitive to frost and will need to be brought in or covered to be protected from the freezing temperatures. Luckily, our perennial turfgrasses are more tolerant and frost in and of itself will not cause damage to plant tissue. However, damage from frost can occur if there is traffic on the turf while frost is present.

Cart or even foot traffic is enough to cause damage. Because the cells within the plant are primarily water when the temperatures gets below freezing this water can also freeze. Traffic on frozen turf causes the ice crystals to puncture cell walls within the plan. Even though the turf will appear alright the damage has occurred internally. Frost damage symptoms include white to light tan leaves where traffic has passed. In time, the turf will acquire a brown to blackened color. Damage is usually limited to leaf tissue and will remain until new growth replaces the damaged turf. Mowing will help remove some of the damaged tissue and improve the overall appearance of the turf. In severe cases, damage can affect the crown of plant.

Frost damage on a creeping bentgrass fairway.  Here, damage was the result of cart traffic on turf when frost was present.

It’s difficult to prevent frost from occurring and perhaps the best strategy is communicating with the golf course staff. Have them to pay special attention to low-lying areas and shady areas. Cold air tends to settle into these areas and will likely be the last place frost melts. Just because there isn’t frost on the putting green which is exposed to full sun in the morning doesn’t mean the entire facility is clear.

Irrigation can be used to help speed up the melting process through the release of latent heat. When water changes from a liquid to a solid by freezing it gives up heat. In actual practice, surface temperatures will be held around freezing as long as liquid water is available. A light syringing of the turf can aid in this process.

Covers can also be used to protect turf from freezing temperatures although placing and removing covers is a labor intensive process. Newly seeded turf or renovated areas where recovery needs to occur will benefit from the heat trapped under the cover.

Until you reach your frost free date, keeping people off the course when frost is present is the best way to prevent damage.

Marcus Jones
Assistant Scientist