Why architects should stop drawing trees on top of skyscrapers

Vanessa Quirk Tim De Chant argues that the practice of drawing trees on top of skyscrapers in architectural renderings should stop. First, because pretty, high-altitude foliage is the first thing that cost-conscious developers jettison when the actual building is underway; but secondly, because trees can't really survive at that altitude:

There are plenty of scientific reasons why skyscrapers don’t—and probably won’t—have trees, at least not to the heights which many architects propose. Life sucks up there. For you, for me, for trees, and just about everything else except peregrine falcons. It’s hot, cold, windy, the rain lashes at you, and the snow and sleet pelt you at high velocity. Life for city trees is hard enough on the ground. I can’t imagine what it’s like at 500 feet, where nearly every climate variable is more extreme than at street level.

Wind is perhaps the most formidable force trees face at that elevation. Ever seen trees on the top of a mountain? Their trunks bow away from the prevailing winds. That may be the most visible effect, but it’s not the most challenging. Wind also interrupts the thin layer of air between a leaf and the atmosphere, known as the boundary layer. The boundary layer is tiny by human standards—it operates on a scale small enough that normally slippery gas particles behave like viscous fluids.

Bottom line: if we're going to have skyscrapers, let's build them without the illusion that they'll harbor high-altitude forests.

Can We Please Stop Drawing Trees on Top of Skyscrapers? (Thanks, Fipi Lele!)

(Images: “Le Cinq” Office Tower / Neutelings Riedijk Architects, Rendering by Visualisatie A2STUDIO, Pentominium / Murphy/Jahn. Image courtesy of Murphy/Jahn.)


    1. You’re sort of right, but Cory is mostly right.  Conifers survive just fine in the cold, but not up on top of towers stuck 500ft up into the air where wind speeds are gale force a lot of the time.  Most green roofs in my experience are brown for most of the year due to lack of water, and the only thing that reliably survives here in Southern Ontario, Canada is Sedum, a desert plant.  All of you who are saying “trees survive just fine in my high / cold climate” are forgetting the “at ground level” part of it, aka. the boundary layer, which he addresses in the latter part of the article.

      1. Wind isn’t gale force most of the time just because you’re on the top of a building. A friend of mine lives on the 42nd floor (about 400 ft up in this building) and has a fully exposed balcony that faces the SF Bay. It isn’t that windy. More often than not, it doesn’t seem to be more than a light breeze.

        Mind you, this is partly because he’s not in any kind of wind tunnel caused by a bunch of surrounding skyscrapers and partially the fact that they did a wind analysis first and designed the building such that it wouldn’t be a problem (fire codes in San Francisco usually preclude operable windows and balconies that high because of smoke control).

        1. When it gets uncomfortably cold or windy, your friend has the opton of coming inside and closing the door. When a tree gets uncomfortable, it just dies.

          1. This is San Francisco. At all of 500 ft, the temperature isn’t going to drop below -50 F which is what your average Elm tree is hardy to. As far as wind is concerned, let’s look at The Strata which was designed to have its own wind turbine at the top of a 485 ft tower. It was designed for 35 mph gusts which an Elm would just brush away (they are pretty wind resistant).

            If it gets worse than that, then there is always the option of erecting a glass wind shield like most of these drawings seem to have.

          2. Go to Strybing. Proceed to the redwood grove, which is in a hollow. Look at the tops of the trees. They’re almost sheared off. You can see one level where they were topped by the wind and then twenty more feet of growth above that from after the Sunset was built up, and then they’re topped by the wind again. If you don’t believe me, walk over to the nursery and ask Don to explain it to you.

  1. My assumption was always that the trees got put in to add some color and a sense of scale. Everyone knows how big a tree is, so if you see one in a concept, you can get a feel for how big the structure is.

    As for the color part of it.. put “concept skyscraper” into GIS. You’ll see two hues.. white and green.

    1. Everyone knows how big a tree is

      So how big is a tree?

      Are we talking dogwoods here?  An eastern white oak?  Or perhaps a California redwood? 

      Besides if a tree is over 15′ or so it is just adding excess weight.  I’d imagine the +42″ diameter oak trees I have in my yard would require quite a bit of structural reinforcement.

  2. Well, that totally explains why at 7000′ here in Colorado, it’s a barren tree-less wasteland. /sarcasm

    I also have to point out, in the two pictures, the trees either have a substantial hedge windbreak, or full glass panels, to protect them.

    It’s nice to see at least one smart Norwegian calls the writer out on this idiocy, instead of praising his ‘brilliance’. 

    Aspens do just FINE at high elevation, and are all interlinked via a massive root system.. considered the world’s largest single organism actually. Cover a skyscraper with aspens and they’ll do just fine. http://en.wikipedia.org/wiki/Aspen

    1. Any tree with a large (single) root ball would have issues..pines will spread out flat seeking moisture..look in any pine forest and you see them tipped over exposing a spread out root area instead of a ball like deciduous trees..aspens you could grow in trenches formed into the concrete buildings..the interconnected root mass would be simple to water, because you don’t have to water each individual tree.

    2. It’s not about elevation – it is about altitude (which are different things). I live in CO too, and if you go to the places in CO which are actually like a skyscraper (very tall compared to their immediate surroundings, and disconnected from any watersheds) – there are no trees.

      In structural terminology it is called “Exposure Category” which has to do with the surface topology, and your height relative to it (among other things). A skyscraper in NY that is 500 feet above the surrounding topology is a totally different scenario than a protected mountainside at 7000 ft.

      1.  LOLWUT?  In this case, elevation and altitude are one in the same.  Don’t get all semantic and pedantic on us, Sam.  I live in Colorado, too.  I have seen trees that simply bend at the strong gusts (60-80MPH) that Boulder seems to get.  They aren’t doing any worse for the wear they receive.

        What I haven’t seen ANYONE address with this ridiculous issue is the fact that tree roots will utterly destroy the building’s infrastructure just like they do to a foundation if planted to close to a structure.  Plus, the weight and watering would be continual issues.  A 50′ cottonwood can suck in and perspire over 100 gallons of water in a day.

        If people want trees inside a building, but don’t want the care and cost-based issues, then use museum-quality sculptures instead.

        1. In this case, elevation and altitude are one in the same.

          No. Just no. Elevation above ground level and elevation above sea level are not the same thing. The top of a 200 foot building does not have the same local conditions as a point 200 feet up a slope a mile away.

  3. As an architect i can fully subscribe to this. It’s become such a lame selling point. Like putting lipstick on a pig.
    I am not against skyscrapers per se, I am even working on one right now. But the energy efficiency or sustainability is not the strongest argument to go high rise (density and reduced land consumption are).
    So please stop dressing up your skyscrapers pretending they are something that they can’t be.

  4. The two images in the boingboing post show what looks to be a 5th-story roof terrace, and trees completely enclosed in glass higher up.  The original blog post shows an image of what they’re complaining about, but a) that building is clearly goofy and unbuildable, and b) where’s the epidemic of such images if that’s the best they can come up with?  The angle of the final image makes it unclear how high up we are, but if those terraces can be pleasant to hang out on, the conditions are probably OK for trees.

    The thesis would be more impressive with some actual examples.

    1. The terrace wouldn’t work because the design didn’t actually leave any space for roots. Planners of all sorts need to understand to what extent trees live underground. Funny that she doesn’t mention that, the other concerns don’t apply to the trees behind glass. I guess it’s part of maitenance.

      In the comments gbot offers this nice example of a Vancouver building with a tree. Not as tall as what she’s talking about, but it suggests it’s not impossible, just takes much more thought than pasting trees on an existing structure.

      1. They could sink the container into the concrete so it would look like the drawing. There are a couple varieties of trees that can grow quite large in a 1.5 cubic meter container (about 400 gallons).

        An apple tree for instance can hit 20 ft. Heck you can buy 20 ft live oak in a 200 gallon container from a nursery. If you’re willing to put in an even larger container, about 2.5 cubic meters (670 gallons), you can put in a 25 ft magnolia, elm or cypress tree. Though you probably won’t get much more height out of them.

      2. The trouble with isolated trees is that they tend to fall over in high winds. One 30 foot tree falling off a tall building will be the end of rooftop gardens after the lawsuits are done.

      3. Why would they have to be real trees? Fake trunks with built-in irrigation, branches draped with real ivy or something. Might work.

  5. It’s great that the real challenges of greening are being brought to light. I do think that these concept drawing have been a way of greenwashing new building projects. However, if architectural concept artists are putting trees in their designs, it’s safe to assume that there’s a demand for greening our vertical spaces. Let’s meet this desire with ingenuity.

    Yes, Venessa Quirk lays out the challenges succinctly and expertly, but I think the statement should be “let’s stop treating this like it’s not an investment, like it will be easy or automatic.” I’d hate to see the baby thrown out with the bathwater (especially from such a height…) maybe the drawings have to be more accurate, and more honest, and we have to be honest about the possibilities, but I also think the idea shouldn’t just fade away. Very few things that humans have set their minds to has proven altogether impossible, even is they don’t come out looking the way we originally dreamed them.

    1. You can hire this guy. Patrick Blanc. I think he’s a genius and he did some amazing things on walls that are breathtaking elements of great architecture.

      It needs to be said though that non of this is ecological. The effort that goes into keeping these walls alive are not sustainable for the majority of building projects around the world and unless you develop gentically modified plants who don’t care about proper soil nutrition and sun exposure these examples will remain singular and exclusive.

  6. Am I missing something here? Trees (even deciduous ones) survive at high elevations (thousands of feet) on cliffsides in arid conditions as well as on more rainy/windy mountaintops. Is there any actual evidence this doesn’t work or is this just “let’s rip on an idea” time?

    Also [ducks].

    1. Trees stop growing here at 11,000 feet (what we call the timber line).

      The author is saying that trees on buildings will be stripped of their microclimate that protects them. I say BS. They are shown in microclimates that will protect them. Cities themselves are large micro-climates in whatever setting they were built in..look at Las Vegas, Phoenix  Dubai..if anything, the trees will do BETTER at a raised elevation because they aren’t subject to low level vehicle exhaust, and will catch pollen and fresh breezes, and be exposed to greater sunlight levels.

      let us look at some facts on actual altitude changes: http://www.engineeringtoolbox.com/standard-atmosphere-d_604.html

      I may be grumping at architects as a former field land surveyor who often had to explain to people drawing pictures that they needed to actually GO OUTSIDE and walk the land before drawing pictures of stuff to build on it.. ;)

      1. The problem with growing trees on skyscrapers isn’t related to air pressure at elevation, it is related to the wind effects when you are very high relative to your surroundings. If you go to the mountainous areas that are actually like skyscrapers (very tall compared to their surroundings, no watersheds, and no large topographic protection), they either don’t have trees, or they have little scraggly trees that took a very long time to grow there (IE, not a pretty park scenario). The altitude is not relevant – it is the relative height above the surroundings which causes the wind to change dramatically.

        The microclimates shown in the renderings above are totally insufficient to protect trees – you need more than just a single wall windbreak to change the wind behavior of an area.

        1. Okay, I get what you’re saying about microclimates, but we’re talking about trees that can thrive at say (conservatively) on a 6,000 foot mountain versus a 500 foot building? I know it’s a bit like apples and pears, but c’mon!

          1. Dense, tall building areas can produce consistent 40+ mph winds.  Natural environments like that have horizontal, dwarfed, shrubby trees, nothing like what’s in these pictures.

          2.  Which leads to the obvious question – what about planting high-altitude mountain shrubs on the roofs? Dwarf birch or mountain junipers should crawl nicely along the windbreaks … given some decades or centuries of growth. :)

        2. ” If you go to the mountainous areas that are actually like skyscrapers (very tall compared to their surroundings, no watersheds, and no large topographic protection), they either don’t have trees, or they have little scraggly trees that took a very long time to grow there”

          Is this because of a little wind (trees are used as windbreaks in very harsh areas and have been for centuries) or because a rocky, dry peak with little top soil is a poor place to grow a tree?

  7. There are trees on top of a couple buildings in San Francisco. One at 1 Front Street has 4 floors of terraced trees and plants with a large glass wind break. They start about 36 stories up (around 480 ft on that building) and seem to do just fine.

    You can kind of see them here: http://goo.gl/maps/wB78o

  8. I see many people beat me to the punch…but not only can trees survive at that “altitude” (Jesus, really? ALTITUDE? It’s not Everest. You’re not flying a 787 with Douglas firs in potting plants strapped to the wings.) 

    But furthermore…green rooftops should be mandatory for all new construction. There are several in San Fran. There are even more in NY. There are even greentops in Minneapolis, MN, where it’s not just the “altitude” that’ll kill ya…it’s the 4ft of snow and the -30º F. 
    That green tops are “jettisoned” first is just a lack of foresight. The energy savings over even 5 years offsets those initial costs. 

    1. And like everyone else, you are kind of missing the point – altitude isn’t the issue – it is the height relative to the surrounding topology. I do structural analysis for solar electric systems on rooftops, and the scaling factors for wind forces go up by orders of magnitude as the building gets taller and taller. Wind forces are directly impacted by the number of things at that height that will interrupt it or cause it to go turbulent – up at skyscraper height there is nothing like that, so the forces are way more dramatic than they are at ground level.

      I’m not opposed to green roofs, but I’ve seen first hand how difficult it is to pull off – the whole building needs to be designed around it. I think the point is that many renderings just get them “slapped on” to look good and be progressive looking, even when there has been no serious analysis or intent to actually do it.

    1. Ever seen kudzu?  Now just imagine it in tree form….

      -well on one hand China would never run out of chop sticks
      -at the same time I’d probably make shitty firewood and furniture.

  9. I think part of it is the over subscription to the latest “save the world” fad of green roofs.  In the aftermath of Hoboken being submerged by the Sandy tidal surge floodwaters, people opposed to the mayors initiative to build a floodwall suggested the answer was green roofs. WTF???  There was lots more PC “ideas” floated.

    1. I hope you were ok in the storm. I live far enough inland that I only had the power outage to deal with, but my girlfriend lives in Hoboken.

      Anyway, I didn’t realize trees on roofs were a green initiative. I always assumed that watering/feeding/maintaining a tree in such an unnatural habitat wouldn’t end up being that ‘green’ — except aesthetically. In other words,  I always thought people drew trees on buildings because trees are pretty, and who wouldn’t want to live surrounded by trees?

      1. If you get enough greenery, you can affect local microclimates and end up saving energy. In a dry climate, for example, if all the roofs were greened up, you could create a widespread evaporative cooling effect and humidity cover that would reduce cooling costs.

  10. Trees might not enjoy the exposure much but a specialist plant would thrive.  If the building had a brick skin then a shrub like buddleia would be all over it in no time.

    1. Anyone who’s grown even a petunia in a pot will know that you can’t grow trees like that in those containers.

        1. Give it some time for them to grow larger than expected or for a heat spell to dry out the roots faster than they can moisten them. Plants can really get the Jurassic Park vibe once they interact with the environment.

  11. I love this thread. As a botanist and farmer I think all this talk about plants not being able to cope is hilarious. Of course rough conditions will kill most plants, and of course a plant can be found for any of the conditions listed that will do wonderfully. Junipers and ceders, cyprusses and aspins. They are all a working pallet from which to pull options for windy/ cold/ uncomfortable situations. As an aspiring engineer I find all the limitions to be just obstacles to be overcome through calculation and trial and error. Trees are awsome and buildings can be awsome. The only real question here is why would you put a tree on a sky scraper?, and the answer is beause it would be awsome. Pigs should not be forced to wear lip stick, it should not be in the rule book, and maybe it is a very over used rendering cliche. But, in practise it could be awsome. Awsome. Awsome. Awsome (now officially over-used). 

    1. Trial and error is problematic when lives are at stake, and the engineers and architects are never actually in the buildings that collapse.

      1. That reminds me of a story that we heard in design school. There was an interior bridge in a hotel(?) that collapsed. The hotel naturally tried to blame the architects and engineers. But it turned out that the hotel had simply added a bunch of potted trees to the bridge without having engaged an engineer to see if the bridge could take the weight.

  12. B.S.-currently its possible and should be implemented where ever possible in climate specific methods. if anything just to beautify our world.
    In areaswith high winds and to make buildings work with nature…
    Even if high winds-
    3D printed buildings could act as “reefs” slowing winds and having specialized “voids” specifically for plant life.

    -by son.

  13. The Bald Cypress is very adaptable.  As a city tree it has a nice Christmas tree shape, but  and where it grows in area that are buffeted by hurricanes it sheds limbs freely and adopts a big wind contorted bonsai tree shape. Under harsh conditions it looks more like a Dawn Redwood.

    1. Cypresses are really top-heavy. Wet plus wind equals topple if they don’t have massive root systems.

      1. Bald cypresses send their roots huge distances allowing them to withstand hurricane winds even when they rooted in muck, The trunk tapers severely from base to tip (which it can shed without damage), then as it gets older the base become. butressed.  They easily  live 1000 years.

        “The Senator” cypress tree stood 125 feet tall and lived about 3500 years in Seminole County Florida, where it probably survived dozens of direct hits from hurricanes.  


        1. That’s not going to happen on a roof. In fact, ‘gardened’ plants will have a radically different history and structure than naturally grown plants, no matter where they are.

  14. ” I can’t imagine what it’s like at 500 feet, where nearly every climate variable is more extreme than at street level.”

    Someone needs to get out of the city more and up into the mountains.  Or even *look* at pictures of trees growing on mountains, some of which are even higher than 500 feet if you can imagine it.

    I think even San Fran has a couple of *hills* higher than 500 feet and they seem to handle plant growth just fine.

  15. Well up the 4th floor, you could just plant a strangler fig and sned the roots down to the parking lot.

  16. How about knocking some buildings down and planting trees on the ground?
    But seriously, last year the residents where I live managed to get this block shelved: 
    It was in Dalston, London. Most of the objections were about inappropriate height, and bad design. But my partner did a study of the footprint of the building and average rainfall to prove that the plants on the building could not be watered by natural means. He’s a landscape architect. 
    These are the people that know about trees and where to plant them, and if architects want to dress up their buildings in this obvious ‘greenwash’ way, they should consult those who understand the issues.

  17. In the first picture, it appears that the architect has accounted for the “trees up too high” problem by giving the building a scissoring, pantographic exoskeleton.  When the trees freak out from the height, they can simply elect to contract the building, lowering it to Tree Relax Norm 1.  When all the trees are cool, they can re-extend the building to an appropriately skyscrapery height.

  18. Cory, you’re missing the point completely.
    Its not about dressing up a building, in fact I find it really depressing that you think of architects as so shallow. 

    Its generally about the occupants of the building, its about the clients.

    For anyone who has lived in a hi-rise or works in one all day, it can get really de-humanizing and depressing.  It would be so much nicer to have trees and birds outside my window, even on the 30’th floor.   Typically you have to get up, go into the corridor, wait for the elevator, avoid eye contact with strangers, walk out and down the street to the closest park to sit under a tree.

    To eat lunch on a terrace under a tree, or even to sit at a desk, and see a tree outside is what its all about. By the way it the clients who ask for all those trees anyways, not the architects.Some trees can handle the wind, gray water (sink water) can be harvested to water them.I am currently designing 12 hi-rises with multiple balconies, each balcony has full-sized trees on them.  We are not using green roofs (too expensive), rather large stainless steel planters, 4m x 4m x 1.5m, that are externally bolted into the concrete structure. 

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