The following is some general information regarding the care of trees. The mature trees in Hancock Park are an important amenity that beautify the neighborhood and increase property values. Unfortunately, some of the mature street trees have either succumbed to disease or have otherwise reached the end of their lives and have had to be replaced. Fortunately, we have a good program lead by the Hancock Park Homeowners Association that plants replacement trees. However, the planting of replacement trees is only the first step in the long process of tree maturation. Think children growing up to become adults. In order for the young replacement trees to grow into the mature trees that we all appreciate and value requires that the young trees receive care and attention. The trees will not flourish without your help. A relatively small investment of your time and money will produce dividends for you and the generations that will come after you. If you do not do what is required for your trees, no one else will – the City of Los Angeles does not take care of street trees. Please do your part. Thank you.
1. STAKING YOUNG TREES
A young tree develops a stronger trunk if it is unsupported and can sway in the wind. (the technical reason is that as the trunk moves in the breeze, it releases chemicals called cytokinins, which cause the cells in the trunk to enlarge and thicken, thereby strengthening the plant tissue.) However, trees that are container grown (almost certainly the type of young tree that is planted in parkways or gardens in Los Angeles) have been closely staked their entire existence and likely do not have the strength to stand alone without staking after replanting. Combine that with the potential for strong Santa Ana winds, and staking during the first six months or year is the prudent choice.
The tree should not be staked with a single stake immediately adjacent to the trunk – even though that may be the way the tree was staked in the nursery container. Beyond not giving the tree the motion it needs to strengthen, a stake driven immediately next to the trunk risks damaging the trunk and/or roots of the tree. Instead, two stakes should be used, placed on opposite sides of the trunk, each approximately 12-18 inches from the trunk (depending upon the size of the tree). Determine where to attach the ties by using your hand to find the place where support of the tree keeps it upright. Attach the ties about six inches above that point. Use soft ties that have broad smooth surfaces – available at nurseries. Leave some slack in the ties so that the tree can move about 2 inches in each direction – that will help strengthen the trunk. Do not use wire, rope or water hose filled with wire or rope – doing so can inhibit growth and girdle the trunk. Remove the stakes once the tree has sufficiently strengthened – approximately 6 months to one year after replanting.
Trees benefit from deep and thorough watering – sprinkling with a hose for a few minutes does not provide adequate irrigation. Likewise, just watering the very top of the soil encourages root growth at the surface rather than deeper in the soil. The frequency of required watering is greatest for a newly planted tree and diminishes as the tree matures. The roots of a newly planted tree have been restricted to the area of the tree’s container – as the tree grows the roots will spread. The following are rough guidelines for a 15 gallon tree (the size of the container) receiving about 15 gallons of water at each watering (a larger tree will require proportionally more water):
First month – water twice per week
Months two and three – water once per week
Months four through seven – water once every two weeks
Months eight through twelve – water once every three to four weeks
Years two through five – once every four to six weeks
After five years, an established tree may only require infrequent irrigation.
The foregoing are guidelines and may have to be varied depending upon actual conditions, including soil type, weather, etc. Too much water can be as harmful as too little. Check the soil for moisture level at a depth of about four inches – if it is very wet, do not water. The growth of your tree will be greatly affected by it receiving adequate (but not too much) water.
Mulching around the base of a tree has multiple benefits: (1) mulch insulates the soil helping to provide a buffer from heat and cold temperatures; (2) mulch helps the soil retain water, reducing the amount needed for irrigation; (3) mulch keeps weeds and grass out to help prevent root competition; (4) mulch prevents soil compaction; and (5) mulch reduces damage to the tree trunk from lawnmowers, string trimmers or other gardening equipment.
Place a 3 – 4 inch layer of mulch around the tree. The mulch should be kept away from the trunk – at least two inches. The mulch can extend out as far as the drip-line of the tree – the outermost circumference of the tree’s canopy. However, recognizing that may be more mulch that you want, a circle or square area of mulch that stretches 2 feet from each side of the trunk will still be beneficial. Mulch is commercially available from a variety of sources, including home improvement stores. Wood or bark chips are good tree mulch and can provide a well-manicured appearance. Use chips that are approximately 1-3 inches in size.
Trees can benefit from feeding (fertilizing) – it will help stimulate growth and better establish the trees. However, a newly planted tree should not be fertilized for a couple of months to let it first get acclimated to its new location. Most of the root activity through which trees draw in nutrients occurs in the top 12 or so inches of the soil. Among the possible ways to feed a tree are dry fertilizer spread on the surface around the tree and liquid fertilizer injected into the soil. Dry fertilizer should be spread evenly over the entire root zone which can extend two to three times the width of the branches. Remember that some of the root zone may have already been fertilized when fertilizer was applied to the lawn or planting bed under or adjacent to the tree. Sprinkle the fertilizer on top of the soil or mulch and water lightly. Since the fertilizer will quickly move through the mulch there is no need to remove it or to place the fertilizer below it. Do not dump dry fertilizer in piles – doing so can cause the roots below the fertilizer to be burned and die. Liquid fertilizer can be injected into the soil using a root feeder – the Ross Deep Root Feeder is available online or at garden and home improvement stores. This is the link to the Home Depot: http://www.homedepot.com/p/Ross-Root-Feeder-12044H/100328642#.UUjKHRdweSo It uses solid fertilizer tablets that are dissolved in water in the feeder and the liquid is injected through the feeder’s injector spike. In Los Angeles, trees can be fertilized once in the spring and once in the fall – the tree roots continue to grow in the winter, even if the leaves fall off or appear dormant. Trees can be overfed – more is not better. Too much feeding can result in too much growth that is weak. Consult with a qualified nursery regarding which fertilizer to use. Do not use so-called “weed and feed” fertilizers that incorporate a herbicide for weed control – the herbicide can harm your tree.
Young trees require proper pruning to achieve a strong structure and desirable form. Among other things, a tree that is not pruned is going to be more susceptible to damage from the wind or other elements. A tree that is not properly pruned when it is young will require more difficult and frequent corrective action as it matures. Generally, the goal of pruning is to establish a strong central trunk with sturdy, well placed branches. Meaningful pruning – beyond the removal of dead or damaged branches – should usually wait for a couple of years after planting to allow the tree to fully recover from the shock of transplanting. Proper pruning requires training and skill and often is better left to a professional. In the case of parkway trees, the city will not prune on a regular basis and the burden is upon the homeowner to ensure that the trees are properly cared for, including pruning.
6. THE RESULTS OF PROPER TREE CARE
The two trees depicted below were planted at the same time, in approximately 2006. The tree on the right has received regular tree care, including watering, feeding, mulching and pruning (it was pruned shortly before the photo was taken). The tree on the left essentially has been uncared for since it was planted. The difference between the trees is obvious. The tree that has received proper care has a larger trunk, is much taller and fuller and has a better form. In seven years it has become a handsome tree that helps beautify its street. The tree that has not been regularly cared for still looks like a recently planted tree and if it can recover from its neglect will take many more years to develop into a meaningful street tree like the one on the right.