Fruit Thinning: AKA, how to kill the many to benefit the precious delicious few

Spring has sprung, and sprouted, and splattered weeds everywhere, to create the glorious verdant blanket of the season. For the first time ever, I am feeling somewhat on top of the seasonal orchard chores here at Birdsong Orchards, with all our new trees happily in the ground, old trees pruned and fertilized, most of the irrigation (but not all) tested and patched. Whew!

Now it’s time to start one of my very favorite seasonal tasks, fruit thinning. When I started growing fruit trees, fruit thinning seemed like the most counter-intuitive of chores. Why remove any of those tasty little globes of potential deliciousness? And who has the time for such a painstaking task?  More importantly, how can I bring myself to kill my babies??? Over time, as I have gotten to know my tree species better, fruit thinning has become one of the most enjoyable jobs this time of year, helping assure a better harvest of bigger, tastier fruit as well as healthier trees for the years to come.

There are a bunch of solid reasons to thin your fruit, depending on the kind of fruit tree. I will break it down by species a bit more below, but in general, orchardists thin fruit for the following reasons:

  1. to discourage overbearing and thereby improve the size and flavor of the remaining fruits

  2. to prevent rot forming and insects from nesting in between fruits that grow together

  3. to prevent limbs from breaking from too much fruit load

  4. to stimulate next years crop and prevent biennial fruiting

Tiny tiny Imperial Epineuse plums starting to form

Tiny tiny Imperial Epineuse plums starting to form

When to thin your fruit trees will vary year to year a bit according to the weather. This year everything seems early, and I started around the second week in April with peaches. It’s good to keep in mind that thinning is usually not a one time process, but rather a continuous one throughout springtime and early summer, for different fruit species and varieties will need thinning at different times, and even on a single tree, blossoms may form fruits over a month or more.  I generally plan to spend one day a week thinning through the end of June. 

Some growers will thin even earlier, by thinning the flowers themselves. I am too leery of late frosts impacting fruit set to try this method myself.

I generally thin stone fruit with my fingers. Little plums and peaches will twist and roll right off the branch. Pomme fruit tends to grow on tougher stems, so I use  small clippers to help thin them if needed. Some fruit species and varieties will also self-thin, dropping a load of fruit set early in the year, especially cherries, citrus, plums and pears in my experience. I focus on thinning the peaches and apples first, then the pears, and then thin the rest of the orchard as time allows.

There are alternatives to hand thinning, though I do not use them. Some commercial conventional orchards use a foliar application of the insecticide Sevin (carbaryl). Sevin is not approved for organic orchards like mine. Other growers thin by using a large pole or stick or knock clusters and branches. I have not tried this method, though I am told it works with practice. I am still a little too precious to go around bashing my trees with sticks, but as my orchard matures and time constraints grow with it, I might give this technique a try.

Now let’s talk specifics by species. If you have any additional tips to add, please let me know in the comments, for I am by no means a master of this art.

Apples

Apples need to be thinned about a month after they bloom. Most apple varieties bloom in clusters, and the center bloom is called the “king bloom,” which is usually produces the biggest fruit and is the one to keep. Some apple varieties are spur bearing meaning they bear their fruit clusters from spurs along the branch, and those again I thin to one apple every 6-8 inches. I also entirely remove any apples that look like they are going to grow too low on the tree (the bunnies will get them), or will grow into another branch or stem.

These apple fruitlets just set and will be ready to thin in a week or so

The UC Master Gardener Program also has this to say, which I found interesting:

"Standard apple and peach cultivars require leaf to fruit ratios between 40:1 and 75:1 (40 to 75 leaves per single fruit) to reach typical size at harvest. Early varieties need a larger ratio of leaves to fruit. Spur-type apple varieties require a smaller leaf to fruit ratio of 25:1 to attain good crop size. This result seems to be related to the fact that photosynthates and stored food reserves are distributed more for fruit growth relative to vegetative growth in trees of this growth habit. Leaves of dwarf trees seem to be more efficient in exporting photosynthates because they are exposed to direct sunlight for more hours of the day than those on standard trees.” - http://homeorchard.ucanr.edu/The_Big_Picture/Fruit_Thinning/

Pears

Some of my European pears varieties self-thin, and some do not. I am going to try to take better records of which varieties does what this year, and then I will update this post. Pears in general seem to need less thinning that apples, and will support 2 fruits per cluster more readily. Pears can be thinned a little tighter as well, to one fruit for every 4-6 inches. 

Un-thinned Harrows’s Delight pear cluster

Un-thinned Harrows’s Delight pear cluster

The same cluster thinned to two fruits

The same cluster thinned to two fruits

Asian pears need thinning even less. The few I am growing have not yet set enough fruit to even bother, though I am hoping over the years their productivity will increase.

Peaches & Nectarines

Peaches are generally the fruit I thin first in the season, meaning now, or even better last week for some varieties. Peaches seem to overbear the most voluminously and consistently. They absolutely will break branches if not thinned. I thin to every 6 inches, and focus on leaving the biggest, healthiest fruits along the branch.  Peaches that double set are the first to go, and I will also remove most of the fruits at the bottom of the tree that will not receive enough light to ripen with good color.

Un-thinned stem of Mid-Pride peach

Un-thinned stem of Mid-Pride peach

The same peach stem thinned to one fruit

The same peach stem thinned to one fruit

I have read that nectarines follow the same guidelines for thinning as peaches. However, my nectarine trees are all of a year old, and have not set fruit yet, so I have no additional wisdom to offer.

Plums

Ok, this is the year I am really going to thin my plum trees, really, seriously, cross my heart, it’s gonna happen. Sigh, or maybe not, like the 3 previous years.

Plums benefit from thinning for all the same reasons as peaches or apples. However, they are also the most forgiving of my fruit trees if I don’t thin them. The fruits are definitely smaller, but I have suffered from little branch breakage, rot or biannual bearing due to lack of thinning. Perhaps I have simply been lucky so far. My trees are also quite young, 5 years old, so they are just now starting to bear a real crop.

So don’t follow my example! Thin plum trees to 3 inch spacing between fruits. Asian plums will produce more fruits, but are more likely to self-thin. European plums tend not to be as generous in fruit set, and therefore require less thinning. 

Apricots

Apricots are supposed to be thinned to one per every 6 inches.  Because I have a lot of struggles with Eutypa as well as twig and blossom end rot, both fungal pathogens, I rarely get enough fruit set to need to thin my apricots, so I consider this to be more of an aspirational guideline for my orchard.

This rare cluster in my old Blenheim apricot tree should be thinning to 1-2 fruits.

This rare cluster in my old Blenheim apricot tree should be thinning to 1-2 fruits.

Cherries

Cherries are not generally thinned, unless you are fortunate enough to get a truly massive fruit set. If your clusters have more than ten cherries on them, research tells me they should be thinned. I have never had more than a few cherries per cluster on my trees, so I skip cherry thinning entirely.

These few Coral Champagne cherries are too precious to thin

These few Coral Champagne cherries are too precious to thin

Persimmons

Persimmon trees have really fragile wood, and tend to over produce fruit, so thinning is absolutely necessary for the health of the tree. I have gotten greedy, left on too much fruit, and had to cut off entire branches that cracked under the weight.  Persimmons are thinned to one fruit per 6-8 inches, or alternatively, 1-4 fruits per branch. I try to look at how strong the branches are and how much mature fruit they will support, rather than a purely numerical approach. Persimmon fruits can scald in the late summer sun, especially my favorite Saijo variety, so I also look to remove fruits on the outside of the tree, while leaving more of the shaded fruits within. Persimmons are one of the last to set and fruit in my orchard, so I often can put off thinning them until June, or even July.

Chocolate persimmon tree starting to flower

Chocolate persimmon tree starting to flower

Citrus

I have rarely thinned my citrus, but I do give some attention to my overly productive Meyer lemons. Citrus trees generally will self-thin, and drop a lot of their tiny fruits. After that, if fruit development is still underwhelming and small for the season, I will thin them 30% more. I haven’t found any specific spacing requirements for citrus, so if needed I will focus on balance of fruit placement across the trees.

Quince

Fuzzy Aromatnaya quince, no thinning necessary

Fuzzy Aromatnaya quince, no thinning necessary

I have never thinned my quince trees . They tend to set their big luscious blooms far enough apart it’s not necessary. I have read that they sometimes fall into a biannual fruiting pattern, in which case thinning 50% of the fruit is helpful, but I have not yet had this problem. Unrelated to thinning, my quince do get that vicious fire blight, so I monitor these trees very carefully for signs of blight throughout the summer.

Figs

Don’t thin figs. Don’t remove a single figlet. There, that’s easy.

Peter’s Honey fig setting a nice breba (spring) crop

Peter’s Honey fig setting a nice breba (spring) crop