As an arborist, trees are my favorite plants. And there is a holiday to celebrate my beloved trees, Arbor Day. Arbor Day is celebrated on the last Friday of April every year in Nebraska. This year that falls on April 24th. This holiday is not the same throughout the United States, it is moved around for other states to be in the best planting time for the year for each state that celebrates it.
Deciding what tree to plant is very important and sometimes difficult. Diversity is key when choosing your tree. The general rule is to plant no more than 10% of a tree species, no more than 20% of a tree genus, and no more than 30% of a tree family in a respective urban area.
Diversity has not always been used as widely as today, and we have learned from that. In the early 1900’s American Chestnut trees were wiped out by Chestnut blight. We replaced many of those trees with American Elm trees which were then destroyed by Dutch Elm disease in the 1960’s. Those were then replaced with Ash trees which are now being demolished by Emerald Ash Borer. Also, in the early 2000’s we lost a majority of our windbreaks to Pine Wilt disease.
Diversity of our tree species helps reduce the problems from widespread disease and insect outbreaks. Look around at what types of trees you have and what types of trees your neighbors have before deciding on a new tree, try to avoid over-planting the same few trees throughout the neighborhood. Plus, diversity of trees is more aesthetically pleasing because of the different leaf and bark textures, different bloom times, and overall differences in trees.
Using understory trees
There are many trees that make a great understory trees and can be planted in the shade and protection of larger trees. Those trees would include things like redbud, pawpaw, and some of our dogwoods including flowering or Kousa dogwood. These trees prefer to have part shade so under a larger tree is a great spot for them. This can help mimic nature and help the overall growth of both the understory tree and larger tree.
Care of Trees
Keep newly planted trees well-watered. Always water newly planted trees, shrubs, or any other plant immediately after planting. Trees should be watered every 10-14 days throughout the growing season and even some during the winter on warmer days. Each watering should give the tree 1-2 inches of water. The best way to determine if a tree needs to be watered is to insert a soil probe or 12-inch-long screwdriver into the ground around the tree. If it goes in easily there is no need to water, if it is difficult at any point then water is necessary for the tree.
A mulch ring should be established and maintained around every tree. Mulch helps to keep the roots cool in the summer and regulated to a uniform temperature through the winter. Mulch will also help keep weeds down and reduce competition of water and nutrients from turf and other plants. Mulch also reduces damage to the trunk of trees from lawn mowers and trimmers. Finally, organic mulch is a way to hold moisture for use later by the tree. Mulch rings should be only 2-3 inches deep and in a circle around the tree at least 2-3 feet out. Organic mulches are a better choice than inorganic mulches. This mulch will need to be renewed every year to maintain an effective layer because it will break down over the growing season which will improve the soil.