Figure 1. The brown and shrunken pistil (L) indicates the flower is dead; a green and upright pistil indicates that the flower is alive. Photo by H. Gohil.
The below-freezing temperatures on Wednesday (4/8/26) and Thursday (4/9/26) early mornings are likely to cause frost damage in several peach and a few apple orchards in New Jersey. It got down to 25°F–28°F in Southern NJ, and 22°F -27°F in Central and Northern NJ, and those temperatures could have killed vulnerable blossoms. The night of April 8th saw wind speeds above 10 mph, which mixed the cold air at the bottom with the warm air above. This prevented cold-air stratification and reduced the heat loss from the soil surface and plant tissues. The night of April 9th was even colder, and the wind dropped below 5 mph, almost coming to a standstill for a few hours. This causes the rapid loss of thermal energy from the soil and plant tissues. Most unprotected peach and a few apple orchards were affected by these conditions on the night of April 9th. In several parts of New Jersey, peach flower buds were at full bloom, the most susceptible stage to frost (Fig. 1). In Apples, though most orchards were in the tight cluster or earlier stages of bud development, and few varieties were in the first pink. The critical temperatures for 90% bud kill at these stages are 21°F for the tight cluster and 24°F for the first pink; hence, only a few apple orchards in South NJ were vulnerable to significant frost damage (Fig. 2).
Figure 2. Frost damage to Apple bloom at first pink
In Peach, not all flowers bloom at the same time, which makes frost-damage assessment a little more difficult. Often, many flowers look damaged, but they still bear fruit. This estimate can be even more difficult in some varieties, simply because they bloom so much that even 90% damage can yield close to the full crop. The natural tendency is to look for open flowers, which can easily lead to overestimating the damage. The developing flower buds will quickly die once damaged by a freeze. You can’t tell what will happen just by looking at the flower. The browning of flower petals doesn’t mean the ovary is dead.
You can do a quick, destructive assessment of loss by randomly opening 10-20 flowers per tree; do this on 5-10 trees across an acre or block for each variety. This can give a relative estimate of bloom loss. If you take a more systemic approach, you may get more accurate results. Due to cold-air stratification, cold air settles to the bottom, so more buds are damaged at the bottom; therefore, you want to sample from both the upper and lower branches. Sometimes, the loss of flower buds could be as good as natural thinning. So, flower bud loss may not result in a crop loss.
After opening the flower, if the pistil is shrunken and brown, consider it dead; and if completely green, consider it alive (Fig 1). The pistil is sticking out, and you see it is brown; it could have been pollinated and is in the senescence stage. It is not brown because of frost, but it’s brown because of the normal progression of development. In another scenario, the pistil is brown because it has frost damage, but it still may have done its job of pollination. It served its purpose and senescence because both frost and pollination are over. After pollination and fertilization, rapid hormonal changes enhance fruit development and make them slightly more cold-hardy. So even the destructive analysis is a close approximation.
Figure 3. Uneven development of peach due to frost injuries, represented by very small ripe fruits in PF Flamin Fury 24 (Left) and Silverglo (right), and a significant number of green unripe fruits in Lady Nancy (middle). Photo by H. Gohil.
If frost occurs at the shuck-split or shuck-off stage, the seed/pit will be damaged. But the fruit looks normal. However, they will not reach full size because the nonviable seed cannot produce the hormones required for fruit growth (Fig. 3). Even if they do grow, they may still face other problems. For example, the pit may have sustained damage, predisposing it to shatter during phase III of fruit growth. If you wait for a week to 10 days, it will be easier and more accurate non-destructive assessment. The live flowers will develop normally, and the dead flowers will be shrunken brown mummies that can be flicked away easily. You will still have plenty of time to adjust fruit thinning to achieve a near-normal crop. You should not be in a hurry to do fruit thinning this year! If you see some fruits that have stopped getting bigger and are distinctly smaller, will you want to thin? Maybe after the June drop.
