Excessive use of plastics in tree planting: A badge of incompetence

Why is plastic harmful?

It’s clear that tree ties often stay in place far longer than they are functionally needed, and drainage pipes stick out of the ground years later, like symbols of manhood. Plastic watering rings are often damaged by mowing until there’s nothing left of them. Many plastics used around trees end up in the soil and spread. All plastics eventually break down into microplastics. This can have consequences for the entire ecosystem.

Watering rings damaged by mower contribute to the forming of microplastics in the soil.

Microplastics can enter animals and plants and, through the food chain, eventually end up in humans. While we don’t eat trees, we do eat their fruits. I realize this is a human-centered perspective. We need to think broader, beyond just the human interest. Microplastics can affect nutrient uptake in plants, reducing their growth. In terms of ecosystems, we contribute more positively by not using plastics in tree planting. This blog focuses on plastics that are effective only briefly during tree planting.

The nursery phase

There may be no action that uses as much plastic as tree planting. Let’s start with the nursery. While guiding young trees with bamboo stakes, binding tubes are used. You can find remnants of these tubes all over the ground at nurseries. The sector would benefit from developing an environmentally friendly alternative. Once delivered, all binding tubes are removed from the trees in accordance with delivery conditions. Trees grown in open soil are sometimes delivered bare-root, but usually with a wire-wrapped root ball of annealed iron and natural jute. Both materials break down quickly—jute within a month in wet soil and the iron is after five years degenerate in pieces. This is environmentally friendly. Synthetic jute, recognized by colored strips, can still be found years later. Think of the conifer hedges from the 70s and 80s; even after years of removal, colored strips remain in the root ball.

Plastic pots, used when trees are delivered in containers, release plastics. Pots must be removed before planting, making them suitable for reuse or recycling. However, reuse rarely happens in practice because cleaning is necessary, and new materials are still too cheap. This is the perverse outcome of an economy heading down a dead-end road. Alternatives such as wood fiber and plant-based pots are available, but they are still not competitive with plastic in terms of cost.

The trunk of the tree is often marked with a plastic tape and label indicating the species. Oddly, many professionals leave these decorations on the tree. Why? Or are you the professional who needs a label to identify the species? Please remove this trash after planting—it’s far from ornamental!

What is the benefit of leaving the label at the tree?

Irrigation and aeration of trees

It’s common to place perforated plastic PVC drainage pipes around the root ball for post-planting irrigation or aeration. Installed at root ball depth, they supposedly aerate the soil, while at mid-depth or higher, they can function as irrigation pipes if regularly filled with water. The pipes are sometimes wrapped in nylon or coconut fiber. The effectiveness of irrigation and aeration with drainage pipes is debatable. For trees with root balls larger than 100 cm in diameter, these pipes do not supply water to the centre of the root ball. Aeration pipes aim to exchange soil gases, but this is limited if the pipe’s cap is blocked or roots grow into it. However, if the pipes are installed in an open soil system, it just indicates poor soil quality, relying on makeshift solutions. Good soil with organic matter can buffer moisture and exchange gases through its open structure. Biobased drainage pipes are now available, claiming to degrade over time, which is a positive development. 

Prideful, non-functional pipes, no ornament among the plants. 

A watering ring is useful for planting, and it can be made from soil or wooden planks. In recent years, it has become common to use 30 cm high plastic rings, 10 cm of which are buried around the root ball and supported by tree stakes. These plastic rings are prone to damage from mowing, making their environmental impact significant. Wooden planks are functional, as they do not erode like soil mounds and contribute organic material when they decay. If you use plastic watering rings, please ensure their removal after the care period. Tenders should make this mandatory in the final delivery. Watering bags, while also plastic, are reusable and effective for slow water release, making them suitable for supporting aftercare with community involvement.

Watering 'rings' of wooden planks, effective and no negative environmental effects in case of damage by mowing.

Above-ground tree anchoring

Several options exist for securing trees temporarily during planting, using either above-ground or underground systems. Above-ground systems typically use poles proportional in size to the tree’s diameter. Fortunately, the era of chemically treated or creosoted poles is behind us. Now, we use durable wood species like Robinia and Castanea, which last up to 15 years. There’s also room for environmental gains by reusing these materials. Softwood (spruce, Picea) poles break much sooner, often in the second growing season, making them suitable only for trees that establish quickly, such as ash or field maple, but not for lime trees, which may need support for up to five seasons. Using wooden poles to plant trees might seem counterintuitive, but if they come from sustainable forestry practices, such as thinning or topwood, it’s not a major issue—provided the tree is given the chance to grow, of course, or the investment is wasted!

Kokos and jute tree ties, environmental friendly but not longlasting enough.

The main plastic used in tree anchoring is in the form of tree ties. A wide range of products is available, but the most common is a nylon seatbelt material. It’s very strong, but as a petroleum-based product, it eventually contributes to microplastics. Better alternatives do exist. Jute tree ties, made from natural fibers, generally last two seasons but require more maintenance than their nylon counterparts. The bioboomstrap, made from bioplastics and natural resources, seems to provide longer support than jute and is compostable, just like jute. 

 Biobased tree ties, longlasting and stil compostable.

Underground tree anchoring

Underground anchoring systems often use the same materials as above-ground systems, including poles with nylon tree ties. These are effective but polluting and are entirely buried in the ground. Another option is using underground anchoring systems with cast aluminium foot anchors and steel cables attached to a turnbuckle.

Underground tree anchoring, in this case a scandalous amount of plastics.

This method is highly polluting. Root ball anchors should never be mounted around the trunk but should run over the outside of the root ball. I remember a specification where the author prescribed removing the nylon straps when after care was complete. A noble goal, but entirely unrealistic. You would need to dig in three places between newly grown roots to reach the straps. Bioplastic materials are now available for underground anchoring, though they remain niche within the industry. Heavier root ball sizes still pose a challenge for bioplastics, and jute straps has proven unsuitable for this purpose. I don’t have personal experience with bioboomstrap for underground anchoring, but given its compostability, I’m curious about its longlasting effectiveness.

An alternative to straps or seatbelt material for heavier root balls is to place wooden stakes over the root ball, against the heads of the vertically installed stakes. This requires close contact with the root ball to prevent any movement.

Tree pit covering

Covering the planted root ball to protect it from strong sunlight and to limit weed growth is beneficial for the tree. Coconut discs are a positive option, as they are plant-based and fully compostable. However, given the source of coconuts, a mulch layer of 5-8 cm of coarse and fine fractions of decomposed wood mulch is a lower-impact alternative based on transport distance and the associated environmental burden.

Some people call this weed, despite that it makes me happy.

As creatures of habit, it’s sometimes hard to change. What we know and trust is not easily discarded, and that’s valuable, but not always the best choice. Our industry tends to be conservative, supplying materials that don’t always align with our growing environmental priorities. I suggest some tender writers spend a day in the field to experience how their paper designs work in reality. However small, you have the power to effect change, and I’m happy to contribute.