The Caragana Control Trials Project is a City of Calgary Parks initiative that began in the fall of 2009 and has an estimated end date of 2011
Caragana (Caragana arborescens) is a woody legume that was introduced to North America from Russia and China. Caragana is widely utilized in North America as a shrub for erosion control on slopes and in agricultural fields. For an indepth profile on Caragana, visit the USDA Plants Profile Database 
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Caragana is a species of growing concern for Calgary's natural areas. When planted in close proximity to natural habitats, caragana has the potential to reduce the biodiversity of that habitat because it spreads in a monoculture fashion. When evaluated by the risk ranking tool in the Invasive Plant Strategic Management Plan 
(501 KB) compiled for The City, caragana was ranked as an invasive species.
The goal of the Caragana Control Trial Project is to test control methods and re-vegetation strategies on two caragana shrub beds in North Glenmore Park. Successes and lessons learned will then be used to formulate potential management strategies.
Test Sites
The main test site is located at the west end of North Glenmore Park just south of the 37 St. SW parking lot. The secondary test site is located near the tennis courts in North Glenmore Park.
A combination of chemical and non-chemical control methods are being tested. During the summer of 2010 and 2011, the effectiveness of each control treatment will be evaluated and control methods may be repeated and/or adjusted.
Control Treatments:
Drowning:
Caragana prefers well drained soil and is fairly drought tolerant. It does not tolerate flooding. By flooding the plants, hostile growing conditions are created. If there is no apparent effect on the caragana after three weeks, efforts will cease in consideration of water conservation.
Stump Treatment – Triclopyr:
Triclopyr is a systemic, selective herbicide. The product used has the brand name Garlon Ultra. It acts as a synthetic growth hormone, mimicking the natural hormones that occur in plants. This product upsets the hormonal balance that regulates processes such as cell division, cell enlargement, protein synthesis and respiration.
Triclopyr will be painted onto the cut surface of the stump where it will be absorbed into the plant's vascular system. This treatment may take up to two years for total control to be one hundred percent effective.
Snapping:
Snapping is a technique that simulates continual heavy browse. It works by draining the energy reserve in the roots of caragana. Eventually, with persistence, this damage will place the plant in a state of stress making it more susceptible to disease, infection.
Snapping is a technique where the stem is broken. Care needs to be taken to ensure that the stem is not broken cleanly but rather left attached. This control method will induce a biological response in the plant where it sends energy from the roots to try and repair the broken stem.
Stump Treatment – Glyphosate:
Glyphosate is a systemic, non-selective herbicide. The product used has the brand name Vantage. It inhibits new plant growth by interfering with aromatic amino acid synthesis.
Glyphosate will be painted onto the cut surface of the stump where it will be absorbed into the plant's vascular system. This treatment may take up to two years to be one hundred percent effective.
Stump Treatment –Accelerated Decomposition:
Most stumps will slowly decompose if left to natural processes. Wet, dark and nitrogen rich environments are ideal for bacterial and fungal colonization. Bacteria and fungi work together to decompose wood back to organic matter. In this trial we will artificially speed up the decomposition process by creating an environment that encourages bacteria and fungal growth.
Stump Treatment – Vinegar/lemon juice /salt:
Vinegar, lemon juice and salt work together to form a contact herbicide. The acetic acid in vinegar and the citric acid in the lemon juice will destroy plant cell membranes. Salt (sodium chloride) draws water out of the cellular membrane and when dissolved in water, the sodium ions can block the uptake of nutrients required for plant growth: potassium, calcium and magnesium. An application of the vinegar, lemon juice and salt to the stump may prevent sprouting suckers from the cut stump, severely hindering the plant's ability to regenerate.
Recipe is as follows: mix the following and make sure all the salt is dissolved.
- 1 cup pickling vinegar
- ¼ cup salt
- ¼ cup lemon juice
Standing Treatment – Glyphosate injection:
Glyphosate is a systemic, non-selective herbicide. The product used has the brand name Vantage. It inhibits new plant growth by interfering with aromatic amino acid synthesis.
Each plant should receive an injection equaling approximately 0.5 ml per 5 cm breast height diameter. This treatment may take up to two years to become one hundred percent effective.
Girdling:
Girdling is sometimes also referred to as ring-barking. In this technique a strip of bark and the cambium layer is stripped from the trunk of a tree or shrub. This stripping interrupts the phloem of the plant which is the vascular tissue responsible for transporting sugars from places such as the leaves to places such as the roots. The above-ground parts of the tree will continue to grow, but the roots starve and the tree slowly dies.
Acknowledgements
The City of Calgary Parks would like to acknowledge the partners in this project, The University of Calgary and The Weaselhead Preservation Society. Thank you, without your support this project would not have been possible.
