We’ve completed year two of our Bicycle Tree Monitoring internship program. Our 2014-2015 intern, Irona Lee, has been working to monitor recently planted trees. Most tree mortality in an urban environment occurs within the first 2-10 years after planting. The goal of the tree monitoring program is to collect data about trees (health, growth, maintenance needs) through the city, so that volunteers can respond to help trees survive. Check out Irona’s report below to see how our young trees are doing in Davis!
Trees in Davis and other communities are extremely stressed due to record heat and severe drought. Trees are a long-term investment that benefit us in many ways, including shading our homes and reducing energy costs, raising our property values by upwards of 10-20%, providing beauty, and more (We just enjoy sitting under one!). We are encouraged by those who are working to remove grass areas from their yards in order to conserve water, but remember that your tree needs care during the drought to stay alive. Please use and share our infographic using the share buttons below!
If needed, tree support can be provided by staking, which stabilizes the root ball and supports the tree until it can stand alone. Over time, stakes and ties should be progressively reduced in height to a point where the trunk does not bend when unsupported. This adjustment should occur after the tree is in full foliage (bare trees may appear sturdier without the weight of foliage). Bare root trees, which are grown in nursery fields rather than in containers, may not require staking. With a few exceptions, most trees will be properly developed within two seasons and able to stand without staking. Often, short stakes (18″ – 24″) without ties are left or placed around the tree to protect against mechanical damage from mowers and string trimmers.
Pruning and Training
Proper pruning is essential to ensure a structurally strong, attractive, and mature tree. Pruning needs vary by species and not all trees should be pruned in the same manner. Generally speaking, creation of a main stem or leader is desirable, with the scaffold branches spaced vertically and radially on the trunk. This spacing also varies by species: medium sized trees should have 6″ – 8″ between permanent limbs, while large trees should have at least 18″ of vertical separation. When removing a branch, the pruning cut should be in branch tissue just beyond the bark ridge and the collar. Normally, limbs being removed will be smaller in diameter than the main trunk or parent branch to which they are attached.
If your new tree is planted in a lawn, keep turf cleared at least two feet from the trunk. Regular lawn irrigation may supply enough water for young trees, however check the tree in between waterings to make sure it’s not wilting. If it is wilting, water deeply once a week in addition for the first few months. Use caution not to over-water or over-saturate the soil, as this may cause root rot.
Watering is generally not necessary during wet winter months. In spring, wait to begin watering until 3-4 weeks after new growth begins. This will encourage deep root growth by avoiding the over-saturation of surface soil. As the weather warms, water weekly for two months and then every two weeks for the rest of the dry season. Irrigating once every 2-3 weeks the second and subsequent years should be adequate. Remember to increase the amount of water, while watering on a less frequent schedule as the root system develops.
Eliminate competitive grasses, weeds, and ground cover within 12″ of the trunk.
Maintain 3-4″ of mulch around the base of the tree, but not against the trunk where rot can occur.
DO NOT use string trimmers near trees/trunks — it can be lethal.
Remove or shorten vigorous shoots along the trunk, but maintain small branches to strengthen the trunk and protect it from sunburn and vandalism.
Inspect regularly for insects and disease.
Ensure your tree is still properly staked.
Trees usually respond only to nitrogen (N); additional fertilizers are needed only if other deficiencies have been identified. Ammonium sulfate with 20% N generally will provide the necessary requirements when spread evenly above the root zone: 2nd year – 1/2 cup (*); 3rd year – 3/4 cup; 4th year – 1 cup. (*) or equivalent amount of nitrogen (N), e.g. 1/4 cup urea (40%N)
Pull mulch back to fertilize. Replace after application.
Larger tree canopies yield greater benefits. Cities can maximize the benefits of trees by selecting the largest canopy tree for the available planting space. The surface area of a tree’s leaves covers between 2 and 8 times the area directly covered by the tree. As a result, larger tree canopies result in improved air quality, cooler summer air, greater reduction of storm water, better water quality, and reduced demand for summertime peak electricity.
100 trees remove 5 tons of CO2 and 1,000 lbs of pollutants per year.
Water Quality and Runoff
100 trees save $550 annually in storm water infrastructure costs.
Shaded pavement can last 50% longer before needing resurfacing with slurry seal. This saves our communities $30,000 per mile in road resurfacing costs.
Cars in shaded parking lots release 18%-21% less hydrocarbon emissions due to heat-induced leakage. Cabin temperatures are up to 60 degrees Fahrenheit lower.
From: E. Gregory McPherson, James R. Simpson, Paula J. Pepper, Qungfu Xiao, Guidelines for San Joaquin Valley Communities, March 1999
Plants in parking lots have been traditionally used for aesthetics and traffic guidance. Regulations generally mandate the quantity and distribution of plants, including trees, based on the size of lots. Increasing emphasis is placed on the ecological services and benefits of urban vegetation, a trend that can be seen in laws regarding parking lot trees. Davis, a small city about 20 miles west of Sacramento, California, was one of the pioneers of parking lot shade regulations. Davis’ ordinance requires that all parking lots be 50% shaded by tree canopy 15 years after development. Although the regulation has been in place for nearly 40 years, there are been no enforcement of shade coverage. The city partnered with Tree Davis to monitor parking lots in 2006 and 2007, but the project was terminated soon after due to budget cuts. In 2013, a Tree Davis intern revisited parking lot shade regulations in Davis as well as other cities in the U.S. The report titled “Parking Lot Shade Regulations: Review and Recommendations” is a summary of that work.