Weather: Sun angles are changing; the sun was in my eyes when I was sitting at my desk for the first time this year on Monday. The zonal geraniums on the indoor porch are happier than I; they all are in full bloom.
Last useful rain: 3/11. Week’s low: 23 degrees F. Week’s high: 72 degrees F in the shade.
What’s reviving: Hollyhocks, sweet peas, golden spur columbine, chrysanthemums, brome grass; arborvitae have greened; fern bushes have leafed
What’s coming up: Garlic chives, Queen Anne’s lace, oriental poppies, larkspur seedlings, alfalfa, white yarrow
Tasks: Finished the difficult work on the wall I built to stop soil from eroding into the path of my gate, and keeping it from opening when the ground heaves in winter.
Animal sightings: Small birds. When I was digging out soil for the lower course of the wall, I uncovered an active caterpillar and a grub. Heard geese honking near the river on Monday.
Weekly update: High winds returned Wednesday. Friday night they took down one of the Siberian pea trees. When I looked, one of the stems had no roots and one had a few laterals that tore before they broke.
The trees grow like shrubs here. This one was about 8' high and 5' across, with two main stems. I pulled the interlaced branches apart, and loaded the smaller one onto the wheelbarrow to take to the burn pile. The other was larger and heavier. It took some effort to get it to balance diagonally across a dolly.
Then I looked at the roots. There were none on the smaller stem. The larger one had a few laterals that had torn, and a few tiny ones I had to cut. I pushed them back into the hole and covered them, hoping they would resprout.
When I tried to discover what type of roots the species had, I ran into the usual problems that no one looks, and everyone copies Wikipedia without attribution. All the it said was the root system was extensive, but not how wide or how deep. [1]
My first thought was the ground squirrel, but there was no tunnel. Besides that animal seems to feed on members of the rose family, and Caragana arborescens is a legume.
The second possibility was some kind of root rot. The trees are native to Siberia and Manchuria, [2] but researchers did not include Siberia pea trees in their list of Russian trees affected by fungal diseases. [3]
The question remains what happened. The species is used for windbreaks on the northern plains. [4] The high winds of last week and the snow load in February should not have been a problem.
Canadians indicated Caragana arborescens normally lives for fifty years. [5] This tree was planted as a bare root along with two others in 2001. They are about 18-years-old, so it didn’t die of old age.
The Canadians also suggested the pea trees were "very drought tolerant" but would "not tolerate prolonged flooding." [6]
Last summer was hotter than usual. That amplified the effects of the lack of rain. The first of July I noticed this particular shrub was losing leaves.
Last year was also the time I replaced some soaker hoses that, at the best of times, supplied water in 3" strips with sprayer hoses that provided more water over a wider area. When I was fighting with the older hoses, I had snaked one around the base of this particular tree when I looped it back on both sides of the others. That may have caused the roots to be concentrated in a small area. They then may not have been able to respond to the change in water distribution when it got hot.
When I saw the leaves dropping, which is a normal response of the species to drought, [7] I shifted the hose a bit to make sure it got more water. Maybe I was flooding it instead of starving it. The lack of roots is consistent with too much water.
So it may have been victim of the classic conundrum: is it too little or too much, and did compensating for the one cause the other? Killed with loving care, but which kind?
Notes on photographs: Snow picture taken 23 February 2019; the others were taken 9 March 2019.
End notes:
1. Wikipedia. "Caragana arborescens." The tree was discussed in more detail in the post for 4 May 2008.
2. James A. Duke. "Siberian peashrub." Handbook of Energy Crops. 1983. Purdue University Department of Horticulture and Landscape Architecture website.
3. Evgeny P. Kuz’michev, Ella S. Sokolova, and Elena G. Kulikova. Common Fungal Diseases of Russian Forests. Newtownsquare, Pennsylvania: USDA Forest Service, June 2001.
4. Duke.
5. "Caragana." Agriculture and Agri-Food Canada website.
6. Agriculture Canada.
7. Wikipedia.
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