Living in a condo in the city of Chicago, I do not have much outdoor space to grow trees and other plants. However, I am lucky to have a roof deck on which I have grown a wide variety of plants. With some careful planning, you can grow almost any plant on a roof deck, including trees. If grown successfully, you’ll love the benefits of mid-summer shade and simple addition of nature trees bring to your roof living space. Here are some considerations for successfully doing so:
1.Mature Tree Size
Be sensible on your species selection, and make sure to choose only small to medium sized trees. You shouldn’t be planting a red oak on your roof deck, for example, as it wants to get over 100 feet tall. As a tree grows, it not only takes up more space on your deck but also requires more water and nutrients. You will have to consider how wide the branches will get, so that you won’t have to prune them back from walkways and seating areas multiple times per year.
Heavier containers (wood, clay, etc.) are a better choice for rook decks than plastic as they are more resistant to tipping over in strong winds. Planting multiple trees in one large container is better for your trees that individual small containers. In a large container, trees can share rooting space and soil.
Your roof deck likely gets a LOT of sunlight. My deck gets basically 100% sun exposure. Therefore, you’ll need to select plants that are adapted to such sunny conditions. Choosing shade-loving plants can lead to severe water shortages and foliage scorching, which can lead to other tree health problems in the future. Another consideration is that, so long as you provide your trees with their needed water and nutrients, the excessive sunlight on your roof deck will cause your tree to have more substantial growth year over year than trees of the same species grown on the ground,
Your roof deck trees are going to need a lot of water. If your deck is like mine, it has 100% sun exposure. That means trees will need use up a lot of moisture every day they are leafed-out. You’ll need to provide water to your trees even when they don’t have leaves. You will need to determine where you’ll get water from for your plants. The source will likely be a hose-accessible spigot or water from a faucet inside your home.
I do not have water access on my roof, so I am forced to carry multiple gallons up from my condo. I sometimes have to do this 3 times per day on a hot mid-summer day. You can also purchase or engineer self-watering containers that will at least store a moderate amount of water.
You’ll need several inches of soil to support fulling grown trees in containers. Small trees need a depth of at least 1 foot, and medium trees will need about 3 feet. The available soil should be at least 4 feet in diameter for small trees and 8 feet in diameter for large trees.
Place a few inches of natural mulch on the tops of your containers to help with nutrient cycling. Mulch will also help to keep the containers from drying out as quickly.
You will need to consider the temperature of your specific roof deck, not just the surrounding area. Your roof deck is likely quite exposed to the wind. This can be especially concerning in winter.
As you can see, there is a lot to consider when trying to grow trees on your roof deck. However, with some thorough planning (and a LOT of watering) you can grow
Urban trees grow in an environment often quite different from their rural cousins. They are generally growing in places where they have not evolved to adapt. Roots grow under pavement. Road salts damage leaves and root systems. Vandals tear off branches and uproot entire trees. Construction compacts soil and tears roots.
Because of the environment in which they grow, urban trees often need our help. Their genome cannot anticipate all that people and cities will throw at them. The entire field of arboriculture is based off the fact that trees are growing in a human-impacted, not-natural-to-the-tree environment. However, the type of help they receive should be based on the needs of the tree, given its species and actual site conditions. Fertilization is often prescribed by tree care companies as one such remedy to improve tree health. However, such a prescription is often unwarranted.
Fertilization and other soil remedies should never be prescribed without diagnosis. Doing so is a waste of money and can lead to environmental problems such as elevated nutrient levels in waterways. Fertilization is useful in some cases, however. But there is only one reason why your trees should ever be fertilized –
Trees should only be fertilized because of a documented soil nutrient-tree need mismatch, which can be improved through the addition of deficient nutrients.
Unfortunately, many tree care companies prescribe fertilization without so much as doing a soil test. There is a simple, likely-obvious reason why they do this – it makes them a LOT of money. Never agree to have your trees fertilized if your tree care professional has not performed a soil test. If an arborist even suggests fertilizing trees or other soil amendments without a soil test, look elsewhere for help with your trees.
There are many other reasons why an arborist may suggest fertilizing trees. Some reasons that are insufficient for prescribing fertilizer include:
1.Trees are newly planted
You should never fertilize trees simply because they are newly planted. Some studies show that fertilizing newly planted trees can impede root growth, and lead to unhealthy top growth.
2.Tree roots have been damaged
A common reason for fertilizing trees is to help improve tree condition after root damage. However, the only way to help recover from root damage is to improve root growth. Fertilization does not aid in root growth, but can often impede such recovery.
3.Soil pH issues
If the trees on your property need nutrients in greater amounts. In this case, soil pH remedies would be a better option. However, the efficacy of such treatments is questionable at best.
As is the case with many aspects of arboriculture, the best answer to the problem is to plant the right tree in the right place. A tree species adapted to the soil conditions present on your property will often eliminate the need to fertilize at any point in the life of the tree. It can also eliminate the need to use other nutrient deficiency correcting solutions as well. Again, if your arborist or tree care professional prescribes fertilization or other soil remedies without a soil test, look elsewhere for help with your trees.
A leaning tree is not necessarily a cause for concern. If a tree has been leaning for most or all of its life, it has likely put on wood in the right places to adapt to the lean. Trees may lean in response to surrounding trees, available light, simple genetics or other reasons.
If you notice things like a change in lean, soil heaving around the base of the tree or cracks in the stem the tree should be further evaluated. If you are concerned about any leaning tree, have an arborist perform an inspection.
Trees with a large number of branches originating from one location can be prone to failure. Such branches have weak connective tissue and branch angles that have difficulty supporting branch weight. When these branches do fail, they often lead to large wounds that the tree has difficulty closing.
Ideally, such a problem would be fixed when the tree is very young. Most deciduous trees should be pruned so that a single leader grows from the top of the tree, at least when young. It gets difficult to prune the tree correctly when it is larger, because the pruning cuts will be larger. Such cuts can be difficult for the tree to close and can lead to decay issues. The best solution is to plant trees not prone to such branching.
Surface roots can lead to problems such as root desiccation, lawn mower damage and trip hazards. They are often a sign of water and soil issues in a property.
Matching a tree to the site is the best way to prevent this, but once it occurs it can be alleviated with the careful application of soil and mulch.