A friend who grew up on an acreage tells us how his favorite apple tree — he doesn’t remember what kind — produced clusters of small, undersized apples. Some of the fruit developed brown spots, probably apple scab from the way he describes it. His story made us wonder: why was this his favorite apple tree? (Answer: it was the furthest away from the house and offered him a shady, quiet place to escape his younger siblings and read, either sitting on the ground against the trunk or up in its welcoming branches.)
He goes on to tell how a neighbor suggested thinning the fruit soon after blooming so that only one fruit in the cluster remained. This, he was told, would reduce the number of fruits the tree produced, but would greatly improve their size and quality.
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Our friend talks fondly of scaling the trees branches and picking off the newly emerged fruit, sometimes with the remains of the blossom still poking out from its end, and letting them drop to the ground or tossing them at his siblings if they were nearby.
Sure enough, the tree began to produce larger fruit. Our friend even suggests that the thinning even lessened the effect of the disease, though might have been due to the fact that the neighbor also suggested that all the fall leaves under the tree be raked up and hauled away, not put in the compost pile, before winter set in.
Fruit thinning is a common practice among orchard growers but not always practiced by home growers. After all, it’s hard to pluck potential harvests and send them to the trash. But thinning of apples, pears, and stone fruits makes the harvest more valuable, increasing the size and quality of the fruit. And it also helps the tree’s blossoming the following year. Win-win.
When and how much do you thin? The answer to the first question is now.
Many growers suggest starting early, not waiting until the tree fruits, but plucking the blossoms before they turn. Thinning blossoms reduces competition between fruits as they set stems and extend roots and branches. But it also carries a risk, one that seems to be increasing with current weather patterns, especially for people growing fruit at elevation.
A freeze that comes after blossom thinning can wipe out the blossoms that remain, reducing the crop or eliminating it entirely. This is what’s happened to some apricot growers in the high-country orchards along New Mexico’s northern Rio Grande Valley the last few years where early season warm spells pushed trees to blossom early only to have those blossom destroyed by a late frost. The result? No apricots for two and some places three years in a row.
So it’s good to wait until fruit sets, especially in areas prone to late frosts. But don’t wait too long. As soon as the fruits show, it’s time to start thinning.
How much to thin? Commercial growers work look to leaf-to-fruit ratios. The University of California’s Division of Agriculture and Natural Resources recommends somewhere between a 40:1 to 75:1 leaf-to-fruit ratio for best size and quality production.
Now we don’t expect you to crawl out on every branch of your fruit trees counting leaves before you pluck emerging fruit. But some general principles apply.
Prune fruit to leave only one apple of a cluster. In those clusters, the center blossom, known as the “king blossom” among growers, will usually produce the most vigorous growth. That’s the one to leave. If you have trouble identifying the king blossom, it doesn’t matter. No matter which blossom you leave, it will reap the benefits of thinning.
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Generally, one fruit should be left for every eight to ten inches of branch. Sometimes the selection process is easy. Damaged or irregular fruit should be the first to go.
It’s hard to over thin the emerging fruit. In fact, most of us make the opposite mistake, leaving too many fruits on the tree. The more fruit you remove (and the earlier you do it) the better quality your harvestable fruit will be and the better your blossom production will be in the following years.
Apples, peaches, plums, apricots, nectarines, pears and even grapes benefit from thinning the small fruit says the University of Arizona Extension Master Gardener Manual. Nuts are usually not thinned because the practice doesn’t affect the size of the meat inside the shell.
If you haven’t pruned fruit from your trees yet this season, now’s the time. The longer you wait, the less advantage you’ll see. If you have experience with early season pruning let us know about your experience, either in the comments or over on our Facebook page. Like our friend who learned from his neighbor, we want to learn from you.