A little over a year after ordering and receiving our citrus and avocado trees, we finally got them planted in the ground. The original plan was to plant them early this past spring, so they would have a long growing season to get established. However, in order to make sure they wouldn't be subjected to freezing weather during shipment, we thought it best to get them before freezing weather in the fall and then overwinter them in pots in the greenhouse. That worked ok, but the rest of the plan was delayed quite a bit. The plan changed when the greenhouse roof design didn't work out, and we knew we were going to have to replace it. Re-roofing would have to wait at least until summer, for mild weather, since the greenhouse would be completely open during construction. Additionally, we knew we wanted to use biochar when we planted the trees, since that would be the best time to get as much into the ground as possible to not disturb the roots later. The slower than expected ramp-up of biochar production pushed back the planting time too.
So, with the new roof on the greenhouse, and enough biochar produced, we finally were able to plant the trees. We have planted a fair amount of trees before, but this turned out to be quite a bit more involved than we expected. The greenhouse is 16' by 77', and after accounting for space for the dumbwaiter and retort plumbing manifold, we figured we had room for 16 trees, if we kept them pruned to a 6' diameter. Since the root ball usually extends out to the dripline, we decided to dig 6' diameter holes, instead of the normal size which is just a little bigger than the current rootball. That would let us mix in biochar throughout the eventual root zone. We also decided to dig the holes a foot and a half deep. Citrus and avocado both have shallow root systems, so we thought that would be adequate.
A hole that is 6' in diameter and 1 1/2' deep holds a little over 300 gallons of soil. I guess that's doable by hand, but to speed the process, and ease the workload, we brought our small tractor with backhoe into the greenhouse. We were lucky, because it fit through the door with 1/4 inch to spare. But it sure made life easier for us, especially on the row of holes near the block wall. The base under the building slab consists of gravel with fist-sized stones, crushed asphalt, and crushed bricks, all compacted very tight. It extends out from the edge of the slab a few feet and into 7 of the holes. Digging through that layer by hand would have been almost impossible. We are glad that we decided to make the holes larger though, because the tree roots would never have been able to penetrate there.
Each hole was backfilled with 4 layers of biochar/compost (50/50 mix) alternating with 4 layers of topsoil, then 3 layers of compost alternating with 3 layers of topsoil. All told, each hole has about 110 gallons of biochar/compost mix (55 gallons of pure biochar and 55 gallons of compost), another 75 gallons of compost, 120 gallons of topsoil, and a 5-gallon tree rootball. After planting the trees, we put down an irrigation line to each tree, sprinkled the ground around the trees with COF, topdressed each tree with a little more biochar/compost mix, and then spread bark mulch throughout the greenhouse.
We have been pinching off all the flowers on the trees this past year, to conserve as much energy for growth as possible. However, 3 of the trees did end up with one fruit each that slipped through. The fruits were already fairly large when we noticed them, so we let them stay- a Ruby Red grapefruit, a Washington navel orange, and a Meyer lemon. They are all starting to ripen, so we should have a little treat soon. Here is the breakdown of all the types of trees we planted: 4 dwarf Hass avocados, 2 Holiday avocados, 3 Washington navel oranges, 2 Meyer lemons, 1 Ruby Red grapefruit, 1 Moro blood orange, 1 Persian lime, 1 Clementine, and 1 Honeybell tangerine.
Having grown citrus and avocado trees when we lived in California, we're anxious to see how fast they grow with all the biochar we added. They already seem to have done well in pots in the greenhouse this past year. So now we wait. Steve
P.S. much thanks to Rich and Ron for doing all heavy lifting while my back was healing.