Mid-winter Cold Injury to Peaches

Mid-winter Cold Injury to Peach Flower Buds -- January 2004

Jon Clements

Extension Tree Fruit Specialist

University of Massachusetts Amherst

clements@umext.umass.edu

Peaches and nectarines have become a prominent niche crop for Massachusetts tree fruit growers over the past 15-20 years. Strong demand and high prices for this summer fruit have made it a popular roadside stand and farmers market addition for many apple growers.

But, southern New England is on the edge of the northern limit of peach production territory. Unlike apples, which can survive mid-winter temperatures as low as -30 to -35 F., peach trees start to be seriously damaged (shoot death) when the temperature drops below -20, and fruit bud injury occurs once the temperature falls into the -10 to -15 F. range.

During the third week of January, 2004 an arctic high pressure system sent temperatures to as low as -15 F.(estimate) in parts of Massachusetts. At the UMass Cold Spring Orchard in Belchertown, a low of-12 was recorded on two dates. (January 15-16.) This was as cold as it has been in 20 years. The cold was persistent with daytime temperatures only reaching the single numbers with wind and very low dew points. Some injury to flower buds likely occurred. Fortunately, warm temperatures did not immediately precede this cold spell, although the week just before the New Year was relatively mild. Warm temperatures before a cold snap leaves the trees less acclimated even more likely to suffer damage.

Cold-injured peach fruit bud, January 2004

Massachusetts peach growers are advised to evaluate the extent of cold injury to fruit buds that may have occurred in their orchards. Using a single-edge razor blade, fruit buds can be dissected vertically and then visually examined for browning of the flower parts. Undamaged buds will be uniformly 'greenish' throughout, while cold-damaged buds will be 'browned' to varying degrees in the center. Sometimes slightly browned buds will be OK, but more than likely, any significant browning indicates the flower bud is damaged and will not set fruit upon bloom. (Altough the flower may actually 'bloom,' the reproductive parts are dead.) Usually, it is good to wait until warmer temperatures arrive (above freezing) to evaluate the damage, as the browing will be accentuated. Also, fruit buds should be sampled thoughout the canopy to get an accurate estimate of percent injury.

One week following the above-mentioned cold temperatues, I dissected some peach buds at the UMass Cold Spring Orchard to assess cold injury. Browing was evident in nearly all the fruit buds I cut, regardless of cultivar. Thus, I concluded there was significant injury. In fact, I estimate 90% + of the fruit buds have some degree of injury. Although this is not a good thing so early in the season, in reality only 5-10% of viable fruit buds are necessary to set a decent peach crop. I also suspect cultivars will differ quite a bit on the crop they set this year (assuming it does not get any colder) because varieties differ significantly in cold hardiness of fruit buds. But, by doing the fruit bud evaluation now, growers will have an indication of what kind of peach crop they can anticipate, and adjust their spring pruning accordingly.

Watch a QuickTime Video (10 MB) of how to assess peach fruit bud injury in the orchard.

More pictures of peach fruit bud cold injury.

Pictures of Stellar® (Fruit Acres) peach fruit bud cold injury.