The first growing season is just about complete at our chestnut demonstration orchard. It's been a full year with lots of lessons learned and we've compiled a long to do list of things to do this winter to make next year better across many dimensions.
Below is a list of the biggest lessons we learned this year. In no particular order. I'll start with a "good" lesson learned, then focus on all the "bad" ones like usual. Where appropriate, I've also added what changes we're going to make this winter and next year in light of what we've learned.
Lesson #1 - These Trees Grow
Despite the irrigation failures, heat stress, stake rub, pests, and other challenges we've confronted this year (you can read about many of them here), most of the trees we planted in January have grown at least feet 8. Many have grown 10 to 12 feet. They broke dormancy the last week of March, so that means they added 1.25 to 2 feet of growth per month from April to September. It is amazing to see a trees that was 15" tall when planted bare root 9 months ago (you can see them at planting here), now standing 10 feet tall!
Here are a couple close ups of trees that are each >10 feet tall, the first in a 6-foot Plantra tube, the second in a 3-foot Plantra tube.
Lesson #2 - Tree Tubes Influence Tree Shape
This lesson is not a surprise, but it's been really interesting to see how much the trees' growth patterns are influenced by the various tubes. The trees tend to not send out lateral branches until near the top of whatever sized tube they're in. If you use a 6-foot tree tube, expect your first branches between 5.5 and 8 feet up the trunk.
The next two pictures show what I mean. The chestnuts we planted with 2-foot tall blue wraps have a very different shape than those in 5-foot tall Plantra Tubes.
Lesson #3 - Watch Out for What You're Not Watching Out For
We were very thoughtful about the deer pressure we thought we'd have (and then didn't), about designing the irrigation system, about scouting for insects, etc. We weren't thinking that the field mice population would explode in the protection of our cover crop and then start decimating trees in mid-summer.
Rodents feeding on the chestnut roots and enjoying the moisture from the drip emitters has been by far the biggest cause of tree loss. We lost 2/900 trees to heat stress and water issues. 0/900 trees to deer. 0/900 to herbicide or orchard floor maintenance, and 127/900 trees to rodents. It is so painful to see a thriving 6-foot tree get it's roots eaten out from beneath it an be dead in a week!
You can see what that looks like in that picture above of the blue tube row. The tree on the far left was killed by rodents in the early summer.
Next year, we'll terminate the cover crop earlier in the summer so the hawks & owls can keep the rodents in check.
Lesson #4 - Our Irrigation Data is Good, but the System is Too Complicated
The drip setup with single emitter per tree works well and get's the trees plenty of deep watering when we run ~7 hour sets. WiseConn's drop control app and soil moisture sensors are also really good.
We had well issues in the late spring and early summer, so were able to run irrigation sets for more than ~3 hours. The well was fixed in July, allowing us to run longer sets and you can see the impact that had on soil moisture in the Wiseconn chart below.
The black line on the large graph is the cumulative soil moisture percentages of all the sensors from 4" to 36" in the soil. The blue and red areas represent too much and too little soil moisture. The yellow bars on the small chart are the tree's evapotranspiration and the blue bars are irrigations.
Together, these two charts show that as the weather warmed up in June we could not run enough water to keep up with the tree's needs and the soil began drying out. Once the well was online in mid-July, we started running longer sets and we're able to rebuild soil moisture for the trees to draw on through the peak of the summer.
What isn't really good is our decision to put a filter and fertigation port on every zone, rather than a single large filter and port on the mainline. In the current setup (one zone shown below), we have 4x filters that need to be cleaned with each irrigation and lots of little fittings that are unnecessary.
This winter, we'll change this main irrigation manifold to have a single 3" filter and fertigation port before the valves for each of the 4x zones.
Lesson #5 - Think Ahead About the Tree Shape You'll Want in 20 Years
Even with the same tree tubes & stakes, every tree is going to grow a little differently. The photo below is of a row of trees in 3-foot Plantra tubes. Most of them have 90% vertical growth with a single or group of leaders. The tree right in the middle of the photo however, has much more of an open "V" shape.
Two other things to notice in the photo:
- There is a sucker pushing out through the tie hole of the Plantra tube on the tree in the foreground. All of the trees have sent out lots of suckers inside the tubes. Some find a hole to poke out there like this one. We'll remove the tubes and all the suckers this winter.
- The tree in the foreground has several vertical leaders with very narrow insertion angles to the main leader. We're going to prune the trees into a central leader shape this winter. That means removing all those leaders that we don't want to be the main trunk. If we leave those vertical co-leaders, they'll reduce the amount of the tree that receives sunlight and therefore the surface that will produce nuts. The vertical insertion (or crotch) angles of those co-leaders also means that they are likely to break in the future if they set a heavy crop or get battered by a storm.
More on central leader and other methods of nut tree pruning can be found here.
One last thing on pruning - shaping many of the trees into the core scaffold that will form the central leader structure is going to take some major cuts. The tree below is a great example of this. It has two similar-sized leaders that start below the top of the 3-foot tube and reach >8 feet into the air. We will remove one of these leaders this winter and top the other one to encourage lateral branching. In other words, we're going to remove more than 50% of this tree's canopy.
Lesson #6 - Constant Wind is a Constant Problem
The wind hits our orchard from the southwest everyday. This constant pressure in the same direction has broken off the growing tips of dozens of our trees and leaned all the rest towards the northeast.
Trees in shorter tubes tend to resist this lean more than those in taller tubes. That's expected, as the shorter trees "felt" the wind earlier in the year and strengthen against it. As we prune this winter, we're also going to straighten up & re-stake the trees that need it. Allowing a tree to continue to grow at an angle risks it falling over when heavy with fruit down the road and or being a safety concern for equipment moving through the orchard.
Lesson #7 - Chestnuts are Resilient
Despite everything we've messed up this year, >85% of the trees we planted survived and grew at least 8 feet. Some that we thought were dead or at least heavily stunted pulled through as seen in the pictures below. It is a joy to work with trees that can endure some serious punches!
Lots to improve upon this winter and a couple hundred more trees to plant - both Okei pollinizers and replants. We're looking forward to the winter period to make the improvements and prepare for a better 2026.