As arborists, landscapers, and homeowners search for effective and low-maintenance ways to maintain landscapes, plant growth regulators (PGRs) have emerged as a popular choice. Paclobutrazol (such as Cabmistat or Shortstop) can be used in a wide variety of scenarios to help keep your trees (and shrubs) healthy and beautiful.
How does it work?
Paclobutrazol alters the growth processes of plants, leading to various physical changes your trees. When used correctly, PGRs like paclobutrazol can improve the overall vigor of your trees and shrubs, leading to healthier trees which are more resistant to many of the common stress factors that lead to tree decline in our landscapes.
Benefits of Paclobutrazol
Using paclobutrazol offers several advantages for both the aesthetics and long-term health of your plants. Here are some key benefits:
Increased Root Density: Paclobutrazol encourages a stronger and denser and more fibrous root system, allowing trees and shrubs to absorb more nutrients as their root systems cover more surface area. This enhanced root system provides also greater stability, potentially reducing the risk of uprooting. In general, a more established root system is of huge benefit to trees, especially in our urban and suburban environments which can be challenging for trees.
(all before/after images from Rainbow Ecoscience) Lusher and Greener Foliage: Plants treated with paclobutrazol often display richer, greener leaves. This growth regulator shifts energy away from excessive height growth to foliar development, resulting in a fuller appearance. Treatment can also cause noticeable changes in the leaves themselves (thicker, waxier leaves with denser leaf hairs) which can even help reduce the chance of fungal infections!
Leaves are noticeably more lush and green Slowed Canopy Growth: Paclobutrazol effectively slows the vertical growth of the canopy. This is especially useful for homeowners who wish to maintain a neat landscape and reduce the need for frequent pruning. Trees can be managed to maintain an ideal height near structures (within reason, appropriate tree species selection based on the location is still important), helping prevent potential hazards. Slower growing trees also tend to be healthier, on average outliving trees which grow faster (especially in places where resources may be limited).
Branches are slower to encroach on buildings or other trees Increased Pest and Disease Resistance: Healthier plants resist pests and diseases better. Trees that are not stressed by other factors generally are more able to put energy into making natural defense compounds, which aids the tree in fending off invading pests and diseases of all sorts. By enhancing root density and foliage quality, paclobutrazol increases a plant’s vitality.
Drought Resistance: More roots means more access to water! Additionally, paclobutrazol helps increase the amount of abcisic acid trees produce, a compound which is used by the leaves to open and close their stomates (tiny "breathing holes" used by leaves for essential exchange of gasses) in response to dry conditions.
Application and Frequency of Treatment
A significant advantage of paclobutrazol is its long-lasting impact. Generally, you only need to apply it once every three years, making it a budget-friendly and time-saving solution for maintaining your landscape. It is typically applied as a soil drench or soil injection for trees, although it can also be applied as a foliar spray for shrubs.
Timing of Application & Efficiency Pricing
Our team offers this treatment anytime throughout the growing season, and it can be combined with your tree work project for best efficiency pricing, or completed as it's own project. For our follow up treatments (year 3, 6, etc) we typically create treatment routes for all properties enrolled in this service in the early spring (around April) and early fall (around September). Being flexible about scheduling to take advantage of these routes, especially if you are treating multiple trees at once, will help us give you the best efficiency pricing.
By taking advantage of this service, you can gain some peace of mind about your landscape’s health, without having to remember to schedule services (we'll take care of that for you and remind you when treatment is coming up) while receiving the best value for your investment. You may also consider enrollment in our Tree Healthcare VIP program, which can be tailored to fit your goals and needs.
Investing in Your Trees
Incorporating paclobutrazol into your property management and tree care plan can ultimately reduce the time and effort required to keep your property looking beautiful and mitigate some of your tree risks. You also benefit simply from having an arborist on site for your treatments at regular intervals, who will notice and inform you of any risks or pest and disease issues you may not have noticed yet.
If you want to learn more or you think this treatment could be beneficial on your property, please reach out! We'd be happy to get you a quote and include your trees on our first route of the spring this April.
The best way to stop pests & diseases of trees is to prevent them before they begin. Paclobutrazol is just one of our many tools to reduce the susceptibility of your trees and increase their overall resiliency!
I’m appreciative of Sosha's recommendation to use Cambistat for some of the trees at my place. She came out to treat a beloved black walnut that had suffered from root damage when my septic system was installed. Others seemed to think the tree was doomed and should come down, so I was thrilled that Sosha had a suggestion for how to support this tree and encourage recovery. I'm excited to see the changes this year when that tree starts leafing out.
Sosha also recommended Cambistat treatment on a giant, healthy willow oak, when I asked if my construction plans nearby would damage the tree. We were adding a tiny home under the tree's canopy, and I knew the stress from…