Frost still a threat to fruit trees
Q: How can I protect my backyard peach tree from losing fruit to late frosts? — Submitted via Patrick Kircher, Roosevelt County Extension Agriculture Agent, Portales
A: This is a tough one. There’s lots of advice out there for things that might help (emphasis on “might”). Your options for protecting those precious buds and flowers really depend so much on how old and big the tree is, what stage of development the buds are in, how cold it’s going to get, how high wind speeds get, and how long the cold lasts. Because eastern parts of the state might get a cold snap this week, I’m focusing on what to do to protect existing trees in your yard from late frosts.
There are some tried and true tricks for maximizing fruit load by protecting flower buds, open flowers and developing fruit from freezing temperatures. Covering your tree in some way is likely the best option.
This is just one reason selecting trees with dwarf rootstocks is recommended. If the tree is small enough, you can cover it with a popup tent like those used at farmers’ markets. Just trapping the warm air under that umbrella can keep temperatures more moderate underneath. (This is also a reason to pull back shade cloth or close big umbrellas at night in the summer to allow that trapped heat to escape.)
Depending on how cold it’s going to get, adding an incandescent light bulb can bump the temperature up several degrees into the safety zone nearer freezing temperatures. Safety is key! Do not use heaters or anything with a flame that might catch fire. Depending on how high winds are expected to get, that canopy cover might not work because the warm air won’t be trapped as well.
If you expect high winds, don’t have a pop-up tent, or your tree won’t fit underneath it but it’s small enough to cover with a sheet or blanket, this is a good option. Wrapping the tree canopy without knocking off some of the flowers is impossible. The struggle is real.
Ask a friend to help and take deep breaths.
Avoid plastic tarp as a cover if it will be in direct contact with the buds because plastic isn’t a good insulator, and tissues touching the plastic may still get very cold. Whichever cover you use, be sure to uncover the tree again during the day.
Another idea is watering the root zone a day before the cold sets in so the ground below can hold more heat and keep that microclimate warmer. If there’s enough sun and enough time, painting a 5-gallon (or larger) water container black and allowing it to heat up in full sun during the day, then leaving it at the base of the tree where it can release heat slowly overnight can help
However, again, if temperatures drop very low or wind speeds get high, these techniques won’t work at keeping the warm air near the buds where you need it most. High winds over wet soil may even act like a swamp cooler and lower temperatures even further.
Some gardeners recommend stringing holiday lights around the canopy to help keep buds warm, and this might help, but not with LED lights. Buds that are near (but not touching) a bulb can benefit from the warmth.
When a friend in Clovis texted me for advice on March 2 on how to prepare his peach and plum trees for a cold front that was expected to bring temperatures down to 10 degrees F with a wind chill closer to zero, I had more questions than answers. Are flower buds swelling or opening? How old are the trees?
He said they’re only one year in the ground and sent photos of buds on the plum just barely opening (aka “bud burst” and “first white” stages) and some buds on the peach tree in “first pink” stage of development. Visit nmsudesertblooms.blogspot. com for details on flowering stages, critical temperatures for frost damage, and links to more resources.
The good news is that the early bud growth stages on those plum and peach trees were not as susceptible to freeze injury as they would have been at later stages of flowering or fruit development. Generally, buds are hardier when they’re in an early development stage.
Unfortunately, the tiny developing fruit are even more susceptible to being killed by frost after the petals fall.
Marisa Thompson, PhD, is the Extension Horticulture Specialist for New Mexico State University at the Agricultural Science Center at Los Lunas. Visit the NMSU Extension Horticulture page, desertblooms. nmsu.edu; follow us on social media, @ NMDesertBlooms; or contact your County Extension office, aces.nmsu.edu/county.