We got a lot of questions this week about what looked like lollipops sticking out of the base of several trees around Wellfield. Rest assured, we only have the trees’ best interests in mind. These “lollipops” are actually tree injection capsules, containing chemicals that are taken up by the tree. Small holes are drilled into the tree, and capsule tubes are placed inside the drilled holes so the chemicals are taken up by the tree’s xylem, carrying the chemicals from the trunk to the canopy.
There are several ways to apply chemicals to trees; foliar spray, trunk basal spray, soil injection or drench, and trunk injection or implantation. As you can imagine, it becomes more difficult to spray the foliage of a tree the bigger the tree is. Chemicals that are “protective” coat leaves and branches, protecting them from insects and fungus. These are most often used as a foliar spray. Trunk basal spray involves spraying the lower 4 to 5 feet of the trunk. The chemical is absorbed by the bark into the vascular system of the tree. Not all chemicals can be absorbed by the tree in this way. Soil injection or drench is applying chemicals, dissolved in water, to the root zone of the tree where it is taken up by the roots of the tree. A sufficient amount of water is needed to ensure that the chemical reaches the root zone, and there is a possibility of the chemical running away from the intended area. Trunk injection is the fastest way to get chemicals into the tree, especially the larger the tree is. Tree injection requires special training and certification. Wellfield hires an outside company to treat the trees in this way.
The injections applied this time to the trees at Wellfield consisted of iron and other nutrients. The trees injected are suffering from chlorosis, a yellowing of the leaves resulting from a lack of chlorophyll. Iron deficiency is one of the more common causes of chlorosis. Soils in this area usually are not lacking sufficient amounts of iron. The problem is the tree is unable to access the iron because the pH of our soil is too high. Most plants can access iron at a pH of 5.0 to 6.5. A majority of the soils in our area average 7.0 to 7.5.
At Wellfield, we are always looking for the safest way to solve problems. Tree injections are one of these solutions. The chemicals are confined inside the tree and will not wash off. There is no runoff or overspray. This is especially important with the wells and water features located within the Gardens. Keeping these water sources safe is a responsibility we do not take lightly. So the next time you see these capsules sticking out of the trunk of a tree, you will know what is being done to keep that tree and the environment around it healthy.
Horticulture & Facilities Manager