Thinning: Part 1

We're moving right along to spring here in Portland with sun, hail, sun, hail, sun, hail.... last weekend we had sun and 70's. Hum...tough going out there for the wee fruit that is starting to grow. But the trees have been inspired to break bud, and my allergies have been inspired to start as well?!

If you have fruit trees, at what stage are they? Have the leaves emerged? Still flowering? Have the flowers past and now you have tiny fruit? My friends from Chico say their apricot is already leafed out and has grape sized fruit. My, does that sound inviting to us Portlanders. The earliest of apples are breaking bud (picture 1), Asian pear blossoms are in full swing (picture 2), and the plums are in full bloom (picture 3).

I haven't seen any stone fruit blooming, and I suspect that they will be a couple weeks off yet. What is a stone fruit? Well, stone fruits are those fruits with a big pit in the middle like plums, peaches, apricots, nectarines, and cherries. In our part of the world, we want these to bloom later, as they are susceptible to frost. Unpredictable last frost and cool wet weather tends to make growing stone fruits in Western Washington and Oregon difficult. Notable exceptions are plums and cherries which can handle the cooler weather and tend to be self fertile (read don't depend on pollinators trying to fly in cold weather). Apricots and peaches on the other hand, like it warmer and dryer like in Eastern Washington and Oregon and in the Central Valley of California.


Pome fruits on the other hand, are those fruits having multiple (usually 5-7), small black/dark brown seeds in the middle. Apples, pears, quince, and Asian pears are pome fruits. They tend to like things a little cooler without the extremes of Central Valley CA., New Mexico, and Arizona. They do like Eastern Washington because of the cool desert nights and less extreme heat of the summer. Eastern Washington produces the most apples in all of the United States.

So all this talk about pome fruits and stone fruits for what? I want to start talking about thinning. Ah, the art and tedium of thinning?! Thinning is the act of pulling off or hand pruning of fruit from the tree in order to have better fruit quality. What? Fruit trees, especially apples, peaches, pears, and sometimes plums produce way more fruit than they can sustain, both physically and nutritionally. Not thinning fruit has negative effects like broken limbs, small disappointing fruit, and with apples, reversion back to biannual bearing. Fruit thinning is selecting choice fruit and controlled quantities to maximize fruit size and quality. Trees naturally thin fruit, often called June Drop, when growing naturally, without us and is a way a tree naturally selects the best fruit to reproduce itself. But this is often too late for good sized fruit and not enough thinning. So for our use, and remember, fruit trees are about fruit, we control thinning by manually selecting keepers. In the case of conventional orchards, they use chemical thinners that cause the trees to abort a certain percentage of fruit. Organic producers still rely on hand thinning, thus making the fruit that much more expensive. For the backyard fruit grower, the types of fruit most needing thinning are apples and peaches, and secondly important apricots, plums, and pears. Usually apricots, plums, and pears don't need thinning, but there are varieties that need it and you should consult your nursery where you bought the tree or a catalogue. If you like big apricots, plums, and pears, that is another reason to thin fruit.



I want to show thinning in pictures, as it is easier to see than to just explain, so there will be a Thinning Part 2 most likely in May for us in Portland. I will try and get pictures to document the process. For those in warmer climates and ready to thin, which by the way is ideally done when the fruit is about grape sized, a good resource to check is the California Agriculture and Natural Resources web site: http://www.anrcatalog.ucdavis.edu/ for California information and the OSU extension website here in Oregon: http://www.extension.oregonstate.edu/ or for Washington: www.mtvernon.wsu.edu/FruitHorticulture.html.



Good Luck?!