Fruit trees and frost
Spring is defined by unpredictable weather with wild temperature swings, but this year stands out as especially full of extremes here in Ohio. Home fruit growers are understandably worried about tender blooms being affected by frost, and the consequent reduction of harvest. Spring in 2020 was relatively gentle, but an especially late cold snap zapped all the blossoms and developing fruit, resulting in no harvest whatsoever of any cultivated tree fruit on the farm. For the flowers of fruit trees, it doesn't matter if spring is sweet and mild, or a mix of snow, sleet, and 80 degree days like it is this year. The crucial factors are the date on which the freeze occurs and the lowest temperature reached.
The temperature at which developing buds are killed after exposure of 30 minutes is often called the critical temperature. For most home growers there's no point in worrying about the critical temperature because there's not much we can do about it. Commercial orchards use overhead irrigation to prevent frost damage, and homeowners with a few dwarf trees can cover them on especially cold nights. But with over 20 fruit trees in the orchard, many of which are full size, I can only hope for the best. The most important measures to prevent frost damage have already been taken: planting on a slope so cold air drains away, avoiding known frost pockets, and choosing varieties known to do well locally. Planting on a north facing slope can help to delay bloom until temperatures stabilize, and is something to be considered for those with this choice.
The steps growers can take to prevent cold damage are important, but limited. Fortunately mother nature has designed some safeguards to help ensure the survival of fruit from bloom to maturity. Readers have probably noticed that the flowers of most trees and shrubs don't open simultaneously, but gradually over a period of time, with the first ones being fully opened while the laggards are still in the bud. Not only does this make for a longer show in the case of ornamentals, it also means that one especially cold night won't kill off every blossom of a fruit tree. Even if the first eager blooms are nipped by frost, there's still a chance of a harvest from the slowpokes.
In addition to staggering the opening of flowers, most fruit trees feature many more blooms that are actually needed to produce a good harvest. Not only can they afford to lose a few blossoms, it's often a good thing and makes for fewer and larger fruit, rather than many puny ones. Many growers remove immature fruit, especially on young trees, to promote quality over quantity. Apple trees do this for themselves during the “June drop,” which doesn't always occur in June. The tree is unable to manufacture enough food to support all of the immature fruit, and performs some abortions so to speak, retaining the strongest pomes to nurture to maturity. If you discover some blackened flower remains after a cold spell, don't despair. Some experts say a tree can lose up to 90% of blooms and still produce a decent harvest.
As mentioned earlier, there's little point in worrying about that which you can do nothing about. If you've thoughtfully placed your trees, and made sure they're as healthy as possible, you've done your best. There will be years when much fruit is lost due to weather, and this is out of your hands. The effects of such devastating years can be mitigated by planting as wide a range fruit trees as possible. Growing different cultivars of multiple species will mean there is usually something to eat even in years of the most extreme weather. I try to add a few new trees each year to increase the diversity the orchard. Purchase of large trees can be expensive, so this year I added bare root Barlett pear and pawpaw acquired from the local soil and water district sale. It will be years before they produce, but I'm focusing on long-term property improvement as usual.
Growing a wide variety is beneficial when it comes to other types of plants as well. Planting berry, nut, and perennial vegetable crops as insurance against bad conditions is a good idea, as is planting annual vegetables of many kinds, especially self-seeding ones. Every year I expect at least a few crop failures, like the great fruit fizzle of 2020. The following year turned out to be the greatest apple harvest since I began the orchard in 2001. Every tree bloomed beautifully and produced fruit, some in enormous quantities. It was as if the trees used all the unspent energy from the previous year to create a bumper crop. Perhaps not coincidentally 2021 was a huge mast year not only for cultivated plants, but wild ones from oaks and hickories to spicebush and blackberries. Trees and shrubs all over the area were loaded with nuts and berries. Such enormous plenty makes me wonder if these plants were also storing unused energy from the past year. I can’t know for sure if this is the case, but I'm fairly certain that nothing is ever wasted in nature. What seems to be a loss today, may reappear as a harvest later on. Don't feel like a failure because you lost a fruit crop to bad weather, or if some of your vegetable plants died or didn’t produce. That's the nature of the game. Just be patient and watch and wait for unexpected bounty to come your way soon.