Sunny Slope Orchard

Sunny Slope Orchard
In the coast range foothills overlooking the Sacramento Valley

Thursday, April 14, 2016

Springtime update

After months of high hopes for a bountiful rainfall year to break the four year drought, mother nature has once again disappointed. So far we have received only 85% of our average rainfall to date. That is an improvement over the past four years, but we really needed an above average year to get ground water levels back to what the orchard and native vegetation need to get through the coming hot summer without stress. 

Still, we did get to enjoy a few heavy rains, and have been feasting our eyes on emerald green hills. And unlike last year, we have decided to go ahead and leave fruit on the trees rather than stripping it off. Bloom time was warm and dry, resulting in a heavy fruit set on most trees. 

An apricot tree bristling with fruit
Unfortunately for the apricots, a week of constant wet weather in March set off a raging infection of shot-hole fungus. Shot-hole is one of several fungal diseases affecting cots, leaving brown speckles on the fruit and "shot holes" in the leaves. Many small fruits shriveled and dropped off, some were just too ugly and had to be stripped, and some had only moderate spotting and will be usable. The spots do not affect taste, but this year's cots will not win any beauty contests.

Shot hole damage to apricot fruit and leaves
One regular spring activity is mowing down the legume cover crop. The mowed debris protects the soil from erosion by wind and rain, helps retain soil moisture, provides food for soil-feeding microorganisms, and shields shallow roots from the heat of summer sun. Timing the mowing is always a compromise: I want it to grow as long as possible to maximize the volume of mulch and to provide habitat for beneficial insects. But the longer the cover crop is allowed to grow, the more soil moisture it consumes, leaving less for the trees to use in summer. So this year I mowed a bit earlier than usual to save as much rainy season moisture as possible.

My walk behind sickle bar mower cutting down the cover crop
Another essential spring chore is fruit thinning, which is removing excess fruit from the trees. After lack of pruning, failure to thin is probably the most common chore that backyard fruit tree gardeners neglect to do.

But don't we want as much fruit as possible? Well, not exactly. We would like as much good sized and healthy fruit as possible, within the limits of what the trees can support. With favorable weather conditions during bloom, most stone fruit trees set way too much fruit. So our goal in thinning is to leave some space between each fruit so that insects and fungus problems do not easily move from one fruit to another. Also we want to limit the weight of fruit so branches will not break during a strong wind. And we want the fruit to attain the biggest size and develop the best flavor. Since each tree only has so much energy to put into its fruit crop, an excess fruit load reduces both size and flavor.

As the newly set fruits begin to grow, many will fall off or "self thin" on their own. So it's best to wait until that happens before doing your thinning. But to get the most benefit from thinning, it should be done before the pits harden. That way the fruit left on the tree will continue to expand to the largest size and reach maximum flavor. Test by cutting open a green fruit as shown below. If the pit is soft and jelly-like and no hard shell has developed around it, the time is right. But late thinning is better than none at all, even if done after pit hardening.

This apricot pit is very soft, indicating an ideal time to thin
How much fruit to remove is the next question. Cots should generally be thinned so they will be at least 3" - 4" apart when they reach full size. That means if they are 3/4" size during thinning time, they should be left no less than 5" - 6" apart. On thin weak shoots even more drastic thinning is needed to prevent stem breakage as the fruit sizes up. Below are before and after shots of a section of apricot branch. The original 25 cots were thinned down to 7. This seems brutal when you're doing it, but once the fruit grows to full size we invariably feel that we were not ruthless enough when thinning.

Apricot branch before thinning, with tight clusters of small fruit crammed together
After thinning, no fruits are left touching, they will grow to much larger size,
and the chance of branch breakage is much reduced
Peaches are about the hardest to thin, since they are tightly attached plus we have to imagine the little almond-sized baby peaches growing to baseball or even softball size. In the before and after shots below, 13 peaches are thinned down to just two. After thinning, the ground under the tree is almost covered solid in tiny peaches, but by the time the remaining fruit grows to full size the trees will still have a heavy crop.

Thirteen 3/4" peaches are jammed together on long skinny stems that are
guaranteed to break as the peaches grow to baseball size
After thinning only two peaches remain
So we are busy preparing for the hectic season ahead, excited to taste the first apricot, peach, plum and fig, hoping for kind weather but knowing that mother nature has her own plans. No problem, we know our place in nature and are just happy to be here.