Studies have shown that most often the cause of the death of city trees is not even pests, but problems with the root system - the roots simply do not have enough space to grow in compacted soil on city streets, they are suppressed by reagents used to prevent asphalt icing. The forecast is negative: despite the fact that urbanists have taken a course for the maximum greening of cities, scientists warn of the need to radically change the approach and technology of planting and caring for urban plantings. The life span of a tree, which in the natural environment can live for 50 or more years, has been reduced to 7-10 years in modern urban conditions.
Lyudmila Beloded, landscape designer, director and founder of Beloded Landscaping bureau
The landscape designer, director and founder of the Beloded Landscaping bureau Lyudmila Beloded tells us that the solution to this problem is not on the surface, but literally underground, in our regular "Lykbez" column.
Tree vs infrastructure
Most often, ecologists use 8 main arguments in favor of greening gardens. I will simply list: aesthetics, air quality, health and well-being of residents, stormwater management (remember the flooding in Kyiv this summer? Who will say that this is irrelevant for us?), capitalization of real estate, cooling, reduction of wind load on buildings, and even improvement of the criminal situation (proponents of this argument refer to a number of social studies).
Sycamores and lindens in front of the Metropolitan Museum of Art in New York, planted after the large-scale reconstruction of the square in 2013. Image source: deeproot.com
In countries with a developed economy, all these arguments have already been translated into the language of numbers. For example, according to the US Forest Service, every dollar invested in green plantings turns into savings of $2,7. And research by the British organization Natural England says that every pound spent will save as much as 7 pounds. One adult tree gives the same cooling effect as 10 standard room air conditioners — and for countries with a hot or sharply continental climate like Ukraine, you must agree, this is very relevant. These figures may seem unreal to a layman, but it is hardly possible to consider such unanimity of authoritative scientists a "world conspiracy of gardeners".
The life span of a tree in urban conditions has been reduced to 7-10 years
A tree after a transplant is the same as a person after a stomach operation. It would be naive to demand from him a healthy blush on his cheeks, bright eyes and activity. Therefore, one of the main goals of a landscape designer and gardener is to create comfortable conditions for the plant for several decades, so that the trees are healthy, develop, so that we do not change them every hour. Despite the fact that there is less and less free space for green plants in cities, our designers are increasingly using modern design techniques, planting seedlings "in the pavement".
The reconstruction of the square in front of the Metropolitan Museum in New York by the project of the landscape-architecture company Olin Partnership provided for the creation of ideal conditions for trees. Image source: deeproot.com
Yes, it is justified from a design point of view and frees from such an irrationally expensive covering as a lawn. Seeded or rolled - it is extremely expensive to maintain, requires a weekly haircut, fertilization, regular watering, but even if all these requirements are met, it still feels bad on the side of a busy road. Paving is ideal for expanding public spaces. But copying the techniques of European landscapers, Ukrainians probably don't even think about what kind of preparatory work was done before planting trees.
Roots of trees, deprived of nutrition, break open spaces, pavements and roadways
What do we face in practice when we come to the site to assess the work front? Most often, the soil is a mixture of construction debris, sand, and clay. Ideally, it requires a complete replacement with a fertile mixture. But very rarely, the customer listens to the opinion of a specialist, demanding to limit the replacement according to the old standards - 2,5 cubic meters. m per tree. For example, for planting trees on the boulevard in the Rybalsky residential complex, our colleague Maksym Kotsyuba managed to convince the customer to deliver 4 cubic meters of fresh soil for each tree - we treat this fact as a small victory, but this is a rare case. According to European standards, when planting large-scale plants in an urban environment, a minimum of 10 cubic meters of saline and compacted soil must be replaced with fertile soil.
This is what the park on the roof of the Lincoln Center parking lot in New York looks like now. The zone intended for planting trees was equipped with a modular system of suspended roofs, which allowed the roots of plane trees to develop freely in the fertile soil. Image source: deeproot.com
The volume of the root system of a tree can be calculated, knowing the diameter of its crown at maturity. When we say that we need 10-15 cubic meters of fertile soil, enriched with organic nutrients, with a specific acidity suitable for a specific species and variety, we often face misunderstanding. Trees that were grown by careful gardeners in nurseries, where they were provided with full care, we are offered to plant in a hole - what is there and fill it with what is there. Similar projects are known to be unviable. We doom the tree to disease and inevitable death in a few years.
One of the main goals of a landscape designer and gardener is to create comfortable conditions for plants for several decades
But the moral side of the issue and the costs of replacing plants that we could not protect from anthropogenic load are not all negative consequences. Trying to survive, our doomed plants destroy the infrastructure. The roots, deprived of nutrition, break through the area, pavements and roadways. They destroy underground engineering communications - water pipes, grow into storm sewers, clog drains, tear wires. In practice, we are even faced with the fact that the roots grow into the nodes of the irrigation system. The roots of plants that fight for life are so aggressive that they easily penetrate metal, plastic, asphalt, granite, and damage existing foundations. Repair, replacement of road surfaces and destroyed engineering networks is an extremely expensive pleasure, and if we strive for rationality, we would like to avoid all this.
Suspended sidewalks: creating an "underground landscape"
Arborist companies in Europe and America have been implementing a special approach to the organization of seating in cities for more than a decade. They not only use specially prepared soil for planting, but also equip planting pits with irrigation, aeration and "soil cells" systems. Sometimes they are also called "suspended sidewalks", "structural cells" — structural cells TREE PARKER, GREEN MAX company, Netherlands. And there are still several dozen commercial ones named. But the principle of operation is the same: modules made of polypropylene (a non-toxic and recyclable material) create a rigid frame that prevents soil compaction, allows roots to develop, guiding and limiting their growth.
Pedestrian embankment of Chicago after the completion of reconstruction in 2016. Under the stairs that go down to the water, there is a modular system of suspended decks, which provide the development of planted "in steps" viewing platforms. Image source: greenblue.com
A plant in an urban environment creates conditions for long-term development, while there is no conflict between green and conventional architecture. At the University of Greenwich, for example, they are conducting a long-term study of different types of systems for rooting trees in cramped urban conditions. The project started in 2014, and now systems from 12 different manufacturers are being tested there.
The rigid frame prevents soil compaction, allows the roots to develop, guiding and limiting their growth
The use of suspended sidewalks is such a widespread practice in the world that the customers of services - developers or municipalities - do not even think of saving at this stage, on equipment, on labor costs. Surely, during your trips abroad, you have seen how the preparation of planting sites for trees takes place, but you did not even guess what exactly the workers do - the process is so different from how everything happens in our country.
Planting trees in a pit equipped with a system of suspended covered trees.
Image source: deeproot.com
Area landing pit, in which polypropylene modules are first mounted, and then corridors for communications are created, can reach 10-12 square meters. m. The root zone and covering are protected by installing ROOT BARRIER and ROOT GUIDING barriers produced by the GREEN MAX company, Netherlands. Such an intervention looks large-scale, but it is fully justified by the fact that it provides plants with a comfortable living space for many years and effectively protects the infrastructure.
Suspended sidewalks provide plants with a comfortable living space for many years
By creating an underground frame that can withstand the load of pedestrians and cars, we leave the opportunity for the root system of the tree to develop in loose soil. These cellular structures are supplemented by irrigation and aeration systems. Moreover, irrigation systems are often combined with storm sewers, so we can use clean, nitrogen-rich rainwater to maintain our urban gardens.
We completed an internship at the GREEN MAX company, in the city of Heeswijk-Dinter, in the Netherlands, and made sure that the assembly and installation of such systems does not require special labor costs or specific skills. These modules can be mounted in any configuration, which makes it possible to use different corners of the city square for landscaping, while leaving the space available for pedestrians and motorists.
Kiev chestnuts or plane trees?
Currently, we are working on the "Greening" section in the Project of the National Memorial Complex Heroes of the Heavenly Hundred - Museum of the Revolution of Dignity, Reconstruction of the Heroes of the Heavenly Hundred Alley in the center of Kyiv. It is necessary to plant 8‑meter lindens with a root ball 0,9 m high and 1,5 m in diameter on an extremely difficult site, where important communications are laid in the ground, which must not be damaged under any circumstances. In Ukraine, this will be the first greening project implemented using modern technology — if we are talking about public urban territory. But, I am sure, in the very near future, a similar approach will become widespread in our country.
Scheme of using a suspended sidewalk along a busy street
For example, there is now a discussion about what trees will be planted on the main street of the capital Khreshchatyk, where the dead chestnut trees are to be replaced, on which, if you remember, in 2013 the city hall spent more than a million hryvnias. Recently, KSGA officials announced that a hybrid sycamore was chosen as a replacement by public voting.
Platanus acerifolia (hybrida) is a fast-growing tree that reaches 30-40 m in height with a crown radius of up to 25 m. Platanus needs sufficiently moist and well-drained (water-permeable) soil. And it reacts extremely aggressively when it is limited - if the roots lack moisture or the soil is too dense (and we remember that Khreshchatyk is a street with busy traffic, and the load on the road surface is maximum here), then the powerful roots of the sycamore easily break the most durable road surface covering
If the choice finally falls on the sycamore, then the place for its planting simply needs to be organized according to all the rules - with the laying of a mesh sandwich system, root control, limiting barriers, aeration and watering systems. And the area of the planting hole for one tree should not be less than 3 x 3 m.
The proposed greening of Khreshchatyk with plane trees must be carried out using modern technologies
I do not consider a public competition appropriate when it comes to such a responsible decision as landscaping the city's main street. If Kievzelenstroy is not ready to plant sycamores today, having provided them with a comfortable environment for development, then perhaps it would be worthwhile to reconsider the decision, consult with specialists and choose less aggressive species? If the decision is final, then it is necessary to take into account advanced experience and apply modern technologies - in the end, it would be rational and economically justified. In any case, the people of Kiev should be informed about the prospects and options for solving possible problems.
In Ukraine, municipalities and developers are not yet ready to implement long-term and thoughtful projects in the field of urban landscaping. More often, they are focused on obtaining the fastest possible effect — the trees must retain their "marketable appearance" until the housing is sold out, and in the city hall - until the end of the mayor's term. This is extremely sad, and I would like to reverse this trend.
Dying chestnuts planted in Khreshchatyk in 2013. Photo: Danyl Pavlov
And of course, we need to carefully monitor the experience of foreign colleagues. Since 1993, all innovations in this field have been presented at the International Conference "Landscape under the ground" in the university town of Lyle, Illinois, organized by the International Society of Arborists ISA. Participants of the annual events share their experience in solving infrastructural conflicts and the latest scientific developments.
Creating a favorable environment for trees in the city is the task of interdisciplinary teams
In Europe, special societies and unions, such as the European Arboricultural Council, the European Tree Worker, and others, conduct large-scale research on the return of trees to cities, train specialists for professional work with trees in cities, and conduct educational work with construction companies.
Creating a favorable environment for trees in the city, sustainable green infrastructure is the task of interdisciplinary teams. Undoubtedly, landscape architects remain the main providers of the idea of greening cities. But their efforts are doomed without the assistance of city designers, planners, construction engineers, utilities and, of course, the citizens themselves.
