Sites are rarely ideal and often adjustments and modifications must be made to them to provide trees with better growing conditions.
As mentioned earlier, drainage is important for tree health. Trees can drown or develop diseases if they sit in too much water. Conversely, if they are on high ground and have poor drainage, the water will simply run off, often taking topsoil, fertilizer and pesticides with it. Drainage can be improved by creating subtle swells and valleys in the site so the water will move around and slowly absorb, rather than running off or sitting all in one area (2). Also, reducing compaction, which was discussed above, can help correct the soil to absorb more water.
Another tactic is installing French drains. These drains can be used to divert water away from an area with poor drainage (2). The water will absorb somewhat within the trench and then slowly disperse into the area of lower ground. Care should be taken to make sure the drains do not lead to existing trees because this could of course drown them during times of high rains (2). You can perform a drainage test to find out if you need to be improved. It is always best to test first and modify only if needed.
The easiest way to “modify” your tree to your site is to pick a tree that is well suited for your site. As mentioned previously, picking the variety of tree is one of the most important factors. The right tree for your site can save you a great deal of time and money. Another way to modify your tree to better fit your site is trimming it. Pruning a tree could be an easy way to greatly improve how it fits into your site. Great care should be taken as improper pruning can give the tree poor architecture. For example, if you are making the tree fit into a site with a power line and you end up cutting off a large portion of the top and one side you will make the canopy asymmetric, which will weaken the tree and make it more susceptible to breakage and possibly disease (15).
It is important to select a variety of different tree species. A variety of species can help protect you from pests and diseases. Also, there are many types of spaces that you could be planting trees in, certain trees will fit into certain spaces. As always, selecting an appropriate species of tree for a site is critical to tree survival, as well as easy maintenance for you.
Selecting an appropriate species
Species selection is a subject that has been brought up a number of times already, and that is because it is an important point. Nearly all sites could make excellent homes to a number of different species of tree. However, not all trees will do well in a certain site. There generally are several different trees that could flourish in any one space. Research should be done to find out what varieties these are and then you should select at least one of them that you like. Selecting more than one species can be aesthetically pleasing and also help reduce the dangers of pests and diseases. This is because if a species specific disease strikes, such as Dutch elm disease, it is probably going to affect all elm in the area. If you have only planted elm trees on your site, all of them will likely die and you will have a sad and barren site. On the other hand, if you planted two elm trees, an oak tree, a maple tree, and a hackberry tree then you will probably lose your two elm tree and still have the other three trees.
Even when you have selected or designed a perfect site for your tree, you will still have to perform maintenance on it.
Homeowners and the city must take several considerations into mind when they select trees to plant too. Trees planted in boulevards should be generally small trees since there is limited space for the trees’ roots. Trees that are small in stature are also a good choice for planting under power lines. If small trees are planted under power lines then they will not grow to be tall enough to interfere and require the tree architecture to be compromised to accommodate the power lines.
Trees planted by sidewalks and roads that use deicing salt must be tolerant of salt or they will suffer greatly during the winter months. Another important thing to keep in mind is proximity to infrastructure. A tree should not be planted close to a sidewalk or building because it will eventually grow into them. If a tree’s roots run into a sidewalk one of two things will eventually happen. Either the tree’s roots will be cramped and the size or lifespan of the tree will be reduced, or the tree will degrade the quality of the sidewalk and the sidewalk will have to be fixed, or replaced. If a tree is planted too close to a building then it will eventually have to be pruned back or it will grow into the building and do damage to both itself and the building. Properly research about your tree species and the site you are considering are crucial steps to growing a quality tree. With proper care, trees are very long lived and special thought should be put into planning your site.
Longevity of the Site
Trees are a very long-lived group of plants. Since some species can live for hundreds of years and can continue to grow that entire time, people often plant them in an area that is too small or too close to infrastructure. At first the location is fine, and then it might even become perfect as the tree grow into the empty space. But another couple of decades pass after the “perfect” phase and now the tree is running into the corner of a roof, shading a garden, tangling with a utility line, or heavily competing with other trees. The very long term future must be considered when planting a tree. Other unpredictable problems could arise with the site. The area might become polluted, the nutrients in the soil might become depleted, or a natural disaster might occur that would compromise the site. Careful planning should be put into selecting the site and tree species, and over time you should regularly check on the tree and the site and attempt to compensate any parts that have degraded over time.
There are a number of ways that soils can be modified and improved. One of these modifications is changing the pH of the soil. The soil’s pH affects the availability of nutrients. If the pH is too high or too low, the soil will hold on to the nutrients and not allow the tree to absorb them. The ideal pH varies from species to species, but generally plants grow best with a pH of 6.0-7.2 (12).
It is easier to pick a species of tree that tolerates the pH of the soil you have, but you can amend the soil to change the pH. There is no practical way to permanently change the pH of the soil, but temporary correction is possible. If the soil pH is too high, you can add ammonium sulfate, sulfur, aluminum sulfate or sulfuric acid. Out of these options, ammonium sulfate is the least effective but also the least likely to damage the plants growing in the soil. On the other hand, sulfuric acid is the most effective options but also the most likely to harm the plants. If your soil’s pH is too low, adding ground dolomite or limestone will help bring it up (13). Of course you should find out whether you need to change the pH before you attempt to. There are a number of at-home methods to test soil pH, but it is best to hire someone to professionally test it to get accurate results. Here is a link to webpage for the University of Minnesota's soil testing laboratory.
Another way to improve the soil for trees is to lower the compaction of the soil. Tree roots grow poorly in compacted soil. Before the tree is planted, the soil should be tilled or broken up. However, this should not be done if you plan on planting the tree near other trees whose roots could be disturbed by this. Another tactic for lessening compaction is using an auger which removes a cylinder of soil from the ground to allow air and water to seep into the soil more easily. Also, a number of trenches can be dug around the tree, extending out like spokes on a wheel, which also helps air and water make its way into the soil and improve compaction (13). Additionally, the soil can be improved by adding fertilizer to help the tree get the proper nutrients to grow. Adding organic matter can help improve nutrient availability, as well as helping with water retention. Also, adding colloidal phosphate can help sandy soils retain water (13).
Homeowner and Municipal Considerations to Species Selection
As already mentioned, tree species governs what type of drainage, soil, space, and climate they require. Aesthetics should also be considered when selecting tree species. But there are still other considerations to be kept in mind. Some trees are untidy and require a lot of maintenance. Trees such as crabapples will drop their fruit which can create a mess, and this fruit will attract birds, which will eat the fruit and then probably defecate on your yard. Another example of a messy tree is the gingko. Male ginkgo trees are generally nice trees with few issues. On the other hand, the female trees produce seeds which drops out of the tree and has a foul odor that some describe as smelling like “a mix of vomit and putrid cheese” (17). Most homeowners do not want to have to deal with these problems or spend the extra time to clean up so often. Of course the city does not want to either. Trees planted in parks or along boulevards that create a mess or smell bad are going to create issues within the community that the city will have to spend time and money fixing. Often to avoid these problems people will plant the male form of the tree which does not have these problems, but the male trees come with issues of their own, such as pollen. Pollen is certainly not a bad thing for everyone, but having the male trees in yards of people with allergies can make spring unbearable.
Schedule of Maintenance
The timing of maintenance varies by tree species and the growing conditions. The most important maintenance practice is scouting your trees. Every season you should inspect your trees for signs or damage, disease, pests, deficiencies and other problems. Every decade or so it may be a good idea to perform tests on the soil to see if the conditions have changed, this should be done more often if a major site change occurs.These tests could include such the pH test, the fertilizer test, and the drainage test. If you find any issues during the scouting or testing you should act on it as soon as possible. The early you deal with a problem the less expensive and difficult it will be. The other important maintenance that should be done regularly is pruning. If you see a branch that is in danger of falling or creating a safety hazard it should be cut out immediately. After a big storm, you should inspect your tree and prune any branches that need it. In general, your tree should be pruned about once a year when it is very young. Depending on the species, an older tree can be left for a number of years between pruning. The timing of the pruning is affected by the species of the tree what you are trying to accomplish. Winter pruning is the most common time because disease and pest concerns are at their lowest. However, if you purposely want to stunt the tree’s growth, then summer is the best time to prune. To enhance next spring’s flowers, pruning should be done immediately after flowers fade (19). But pruning is affected by growing conditions and species, so research into your specific situation is recommended.
- Kilpatrick, Judy. Providing Good Drainage for Trees. [Online] 2016. http://homeguides.sfgate.com/providing-good-drainage-trees-37025.html.
- All about soil. The Morton Arboretum. [Online] 2016. http://www.mortonarb.org/trees-plants/tree-and-plant-advice/horticulture-care/all-about-soil.
- Soffar, Heba. The Types and Properties of Soil. [Online] 2014. http://www.online- sciences.com/earth-and-motion/the-types-and-the-properties-of-the-soil/.
- Plant Profiles. North Branch Nursery. [Online] 2016. http://www.northbranchnursery. com/plant-profile/plant-catalog.html.
- Field Production of Nursery Crops: Field Preparation, Planting, and Planting Density. NC State University. [Online] 2007. http://content.ces.ncsu.edu/field-production-of-nursery-stock-field-preparation-planting-and-planting-density.
- Right Tree in the Right Space. Arbor Day Foundation. [Online] 2016. https://www.arborday.org/trees/righttreeandplace/size.cfm.
- Right Tree, Right Space. Casey Trees. [Online] 2016. http://caseytrees.org/resources/right-tree-right-space/.
- Blackstone, Victoria Lee. Conditions Required to Grow an Avocado Tree. [Online] 2016. http://homeguides.sfgate.com/conditions-required-grow-avocado-tree-55767.html.
- USDA Plant Hardiness Zone Map. United States Department of Agriculture. [Online] 2016. http://planthardiness.ars.usda.gov/PHZMWeb/#.
- Tree Varieties. All Posters. [Online] 2016. http://www.stylepinner.com/apricot-varieties/ YXByaWNvdC12YXJpZXRpZXM/.
- Soil pH. Colorado State University. [Online] 2015. http://www.ext.colostate.edu/mg/ Gardennotes/222.html.
- Site Modifications. University of Florida. [Online] 2015. http://hort.ifas.ufl.edu/woody /site-modifications.shtml.
- Basement Waterproofing systems. AAA Reick’s Landscaping and Waterproofing. [Online] 2016. http://www.aaareicks.com/waterproofing-systems-for-dry-basements/.
- Albers, Jana, et al. How to Recognize Hazardous Defects in Trees. United States Department of Agriculture. [Online] 2012. https://ay15.moodle.umn.edu/pluginfile. php/1003118/mod_resource/content/1/USFS-TreeDefects.pdf.
- Trees Under and Near Power Lines. University of Florida. [Online] 2014. http://hort.ifas.ufl. edu/treesandpowerlines/.
- Fall Colors in Coconino. USDA Forest Service. [Online] 2016. http://www.fs.usda.gov /detail/coconino/landmanagement/resourcemanagement/?cid=stelprdb5351327.
- Marcelis, David. Gingko Trees Stink up City When Seeds Fall. The Wall Street Journal. [Online] 2014. http://www.wsj.com/articles/ginkgo-trees-stink-up-cities-when-seeds-fall- 1416869012.
- No Evidence that Birds are Harmed by Non-Native Species. Death of a Million Trees. [Online] 2013. https://milliontrees.me/2013/09/06/no-evidence-that-birds-are-harmed-by- non-native-plants/.
- When to Prune. The Arbor Day Foundation. [Online] 2016. https://www.arborday.org/ trees/tips/when-to-prune.cfm.