Suicide in the Garden
When I visit friends’ homes, being asked to diagnose plant problems is not uncommon. I entered one friend’s front door only to be escorted outside to diagnose the cause of a groundcover juniper’s death. My friend had planted three junipers in 2009; one had died in June.
I told him that I would have to dig it up and perform an autopsy. He found it hard to believe that I could not diagnose the problem by simply looking at it. I replied that I could give him a number of possible causes but not the exact cause without examining the roots.
Upon lifting the plant from the ground I saw the cause of death: girdling roots. It was evident that the plant had been grown in an eight-inch container because the shape and the size of the root ball had not changed during its three years in the ground.
I asked if he had cut or pulled apart the root ball at planting. He assured me he had, but it was clear from the circular pattern of root growth that the roots had continued to grow in the original growing medium and had not established themselves in the surrounding soil.
Only three roots near the top end of the root ball had grown beyind the original growing medium. These top roots had already circled the stem when the plant was very young, and they grew at the same time and at the same rate that the diameter of the stem was enlarging. As both grew, they came together sometime late last year. When the roots started to grow again this year, they girdled, or strangled, the stem, causing the juniper’s death.
Avoid this problem yourself by slashing a plant’s root ball five or six times from top to bottom at planting. Using a sharp knife, cut an inch or two deep into the sides of the root ball.
Your cuts both stop the circle pattern of growth resulting from container culture and cause new roots to emerge from the surface of the cut roots. This practice also encourages the plant’s rapid establishment in the soil.
For container-grown plants, nurseries generally use a rooting medium that’s a blend of milled pine bark, peat moss and sand or some other aggregate. This type of blend encourages early and rapid root development because it has an abundance of air and drains well. To thrive in the ground, container-grown plants need encouragement to stretch out their roots.
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