Quick verdict
Five reusable 30 ml injectors that screw into a small drilled hole in a trunk and deliver fertiliser, insecticide or fungicide straight into the sapwood, where the tree carries it up to the canopy, so a palm with a nutrient deficiency, a tree under borer attack or an ornamental with a fungal problem is treated without spraying the whole garden. Trunk injection is how arborists treat large trees and it puts the product where it works at a fraction of a spray dose. These are the home-scale version; they need a drill, care and a product labelled for injection.
Strengths
- Delivers product into the sapwood for canopy-wide uptake
- No spray drift; a fraction of the dose
- Reusable injectors, five per pack
- Thirty ml each for medium and large trees
- Suits palms, ornamentals and fruit trees
Weaknesses
- Drilling a trunk is a wound; do it sparingly and cleanly
- Only products labelled for trunk injection should be used
- Uptake depends on the tree being in active growth
The overall YardToolLab Score is out of 100. Section scores are out of 10.
Treating the Tree, Not the Garden
Spraying a 30 foot tree for borers or feeding a chlorotic palm from the soil is slow, wasteful and often useless. Arborists inject the trunk instead, and the product travels in the sap to every leaf. Agroject’s injectors are a home version: five reusable 30 ml units that screw into a small drilled hole and deliver fertiliser, insecticide or fungicide into the sapwood.
This review is based on the maker’s specifications and on how trunk injection is practised generally. We have not used these injectors ourselves. Trunk injection should follow the product label and, for valued trees, the advice of an arborist.
The Method
Choose a healthy tree in active growth. Drill a small hole of the stated size and angle into the sapwood low on the trunk, spaced round it as the product label directs. Screw an injector into each hole, fill with the measured dose and leave it. The tree draws the liquid in over hours on a warm day, longer when cool. Remove the injectors, wash them and let the tree seal its own holes.
What It Treats
Borers and scale with a systemic insecticide labelled for injection. Certain fungal diseases with injectable fungicides. Palms yellowing from manganese or magnesium shortage with chelated micronutrients. Chlorotic oaks and maples with iron. In each case the dose is a fraction of a spray and it goes where the problem is.
Cautions
Every hole is a wound. A few per season on a healthy tree close over; a ring of them on a stressed tree is an invitation to decay. Use only products labelled for trunk injection, at the labelled rate, and never on a tree that is dormant or drought-stressed. For a large or valued tree, an arborist with professional equipment is the right call.
Build
Reusable plastic injectors with a thread that seals in the hole and a reservoir that is easy to fill and read. Rinse after use and they last seasons.
Who Needs It
A gardener with a palm collection, a fruit tree under borer attack, or a specimen tree that is yellowing despite feeding. For those, the five-pack treats a tree properly for less than one arborist visit.
Who Should Buy It
- Palm owners with nutrient deficiencies.
- Gardeners with borer or scale on a tree too big to spray.
- Anyone treating chlorosis at the source.
Common Owner Complaints
Slow uptake on cool days. Inject in warm active growth.
Alternatives to Consider
Acecap implants for a drill-and-forget approach. Soil drench systemics for small trees. An arborist for large or valued trees.
Verdict
For a tree that needs treating from the inside, these injectors do what the professionals do at home scale. Drill sparingly, use labelled products in active growth and call an arborist for the trees that matter most.
Full specifications
Agroject Tree Injector, 30 ml Capacity, Reusable, Pack of 5, for Trees and Palms FAQs
Drill a small hole at the specified angle into the sapwood low on the trunk, screw the injector in, fill it with the labelled product and let the tree draw it in over hours or days. Remove, seal nothing, and let the tree close the hole.
Only those labelled for trunk injection: systemic insecticides for borers and scale, fungicides for certain diseases, and chelated micronutrients for palms and chlorotic trees.
During active growth when sap is moving, spring and early summer. A dormant tree takes nothing up.
A few small holes once a season on a healthy tree close over. Many holes, or holes in a stressed tree, do harm. Follow the product label for the number and spacing.
