Control of undesired shrubs – Lands For Nature: Hands-On Restoration Instruction & Collaboration

Date last revised: March 2023

Placement in Hierarchy: US-Midwest-> Undesired species->Plants

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Plants with thin bark: multiflora rose, barberry, autumn olive, and smaller honeysuckle using a very quick squirt on the stem bases near the ground has been effective at least during the growing season. Testing dormant season spraying is planned. Overspray is close to non-existent and exposure of the person applying the herbicide is much reduces compared to foliar spraying. The concentration of triclopyr has been dialed down to about 3% (this is a 19:1 mix using 61% Garlon4 from the jug). An excellent resource for chemical and non-chemical options is the Woody Invasive Control website. For a carrier, diesel or unused burn fuel is cheaper and more at hand than bark oil or crop oil. Some folks find that the diesel odor is unpleasant. The oils, rather than water, improve the hang time and penetration. Additionally the oil leaves an oil stain, like on the garage floor, so one can see what has and has not been sprayed. Dyes can be added and that is being evaluated at this time. The same formulation can be spritz onto tiny plants via their leaves. My experience is that it is not necessary to spray the entire stem circumference. The fan tip used is a Teejet 2501. Typically the tip is less than 4-6 inches from the stem or stem crown. Small plants get a very quick squirt, about 1/4 second (about 1.2g), larger stem clusters get about a 3/4 to 1 second spray. For multi-stem shrubs, it is essential to get every stem. My guess is that stem A has its root connection, stem B its connection, etc. The stems of plants that need to be retreated have most of their stems dead, but a few survived possibly due to having been missed. If left the plant will recover the following year.

Die back is noticeable in about a week to 10 days if you look closely. Browning can take another 10 days.. Generally in heavily infested areas, I find that my 100% attempt yields about a 70% kill. Mostly this is due to missed plants, but sometimes the spray was not fully effective. For these areas I plan two passes. Pass 1 (70%) and a pass 2 (70%) about 3 or 4 weeks later which results in about 90% kill (70% +30%X70%). Of course the second pass works best during the growing season when green leaves gives them away. The trade off is to spend more time and use more spray on the first pass. Overall it seems to be more effective and take about as much time to plan on successive passes.

Plants with thick or rough bark: Larger honeysuckle, larger buckthorn, et al in which the bark is coarser and in strips herbicide penetration is less effective. One option is to use more spray to soak the bark and for that I’d try to get more circumference treated. Another method is chop ‘n squirt which is used for saplings and trees (aka by foresters as hack’ n squirt). Use a hatchet to break into the green cambium layer and spray with a higher concentration (9:1). One hand carries the hatchet the other a hand sprayer. Again a fan tip sprays the stem more precisely. Usually 2-4 chops is enough. Sometime larger honeysuckle stems droop and root along the stem. For large plants (stems over 3-4″) that have stem rooted, cut the stem with a small chain saw and treat the cut “stump”.

Deadwood, a shrinking habitat . Once dead, small tree size honeysuckle, buckthorn, autumn olive, et al will remain standing for along time. For aesthetic reasons, some people cut and burned the dead wood. Consider leaving them to rot either standing or fallen. I have dead apple trees that have been popular with sapsuckers, bees, wasps, beetles, moths, fungi, and more which have been standing for 10 years. Depending on the area and its restoration plan, standing or on the ground dead wood is a rare habitat for a large number of species. Modern forestry practices “clean harvesting” leaving little down and standing wood . At least consider leaving patches to see how this very limited resource gets used.

*Notes–Terms and abbrev: Because Garlon 4 comes in a 2.5 gal jug, the 19:1 comes to 1 pt Garlon topped off to 2.5gal with diesel. The 9:1 is 1 qt Garlon topped to 2.5gal with diesel. Standard spray hoses are not stable with diesel. Here is a link to where I bought hose and a short description, but automotive places might have it. https://www.mcmaster.com/catalog/129/153/5187K73 The standard hose softens over time, so it will work fine for a period of time. Empty the diesel before storing to keep the hose in better shape. My handheld sprayer and 5 gallon backpack sprayer from Solo has lasted for years with diesel. Hard plastic seems impervious to diesel.