ST. GEORGE — One of the most fascinating times in Southern Utah is a day affectionately known as “Leaf Drop Day,” some years a solitary day and other years a succession of days when all the mulberry trees in the area seem to lose their leaves at once.
On Leaf Drop Day, Southern Utahns wake up to mounds of green and yellow leaves blanketing their yards, cars and streets. Sometime residents will catch sight of the leaves falling en masse like giant snowflakes and hear them rustling as they let go of their branches and float to the ground. Residents that have mulberry trees on their property might wait with horror or glee – depending on who does the raking – for the unofficial holiday.
“It’s kind of a release that they do,” Bonnie Pendleton said. “They sort of shatter off the trees.”
Pendleton is known in the region as “The Plant Lady.” She is a private gardener who provides consultation to people and helps them plan their yards and gardens.
The almost magical sight is reminiscent of the movie scene from “Harry Potter and the Prisoner of Azkaban” when the school’s whomping willow shakes off all its leaves in one brief moment.
But Leaf Drop Day has more to do with temperature than magic.
As nighttime temperatures fall into the freezing range, the mulberry leaves will fall off, Mark Hodges, a degreed arborist and owner of Arbor Tech in St. George, said. Cold temperatures stress the mulberry trees and signify that it is time for them to go to bed, he said.
Given varying microclimates across Washington County, with each area experiencing different temperatures and winds at any given time, mulberry trees in some areas have dropped their leaves earlier in the fall season while others are just now dropping theirs.
About the mulberry tree
The mulberry tree was first introduced to Southern Utah in the 1860s by then president of The Church of Jesus Christ of Latter-day Saints, Brigham Young.
The hearty trees grew well in the harsh desert climate – mulberry trees are extremely drought-tolerant and can go years without water, Hodges said – and provided an ample amount of shade. The trees’ leaves were also the primary food source for silkworms the early pioneer settlers raised to make silk.
The pioneers would top the trees and feed the cuttings to the silkworms.
Mulberry leaves are rich in protein, Hodges said, adding that people can eat them in salads.
How to make a mulberry leaf salad:
- Collect young, unopened mulberry leaves in the spring – once the mulberry leaf matures and opens it becomes toxic and no longer edible.
- Rinse the leaves in running water.
- Drain the water and pat the leaves dry.
- Mix with other greens and vegetables to create a salad.
According to a post on the Livestrong Foundation’s website, mulberry leaves may reduce blood glucose levels for the treatment of Type 2 diabetes. Leaves from a white mulberry tree have also been used to treat sore throats, eye infections and colds.
Mulberries can grow in most temperate parts of the world. Young imported many of the mulberry trees seen in Utah from France.
Today, the mulberry tree is prolific in Southern Utah. The trees have few significant diseases or bugs that affect them and they have an aggressive root system that can travel up to five times beyond the spread of the branches in search of water, Hodges said.
In 1996, when he was the city forester for St. George, Hodges said, the mulberry tree made up about 11 percent of the tree population in St. George alone and the percentage today is at least a couple points higher.
What to do with the fallen leaves
Residents waking up to massive amounts of fallen leaves have options for reuse and removal.
But first, why not play in them?
Pendleton recalled building forts out of the fallen leaves in her youth and using them as cushioning for death-defying jumps from the roof.
“(The leaves) were pretty well broken down by the time we were done,” she said.
Because the mulberry tree has such big, thick leaves, they make excellent mulch. Pendleton suggested homeowners break them down and mow them into their lawns or mix them with pine needles to create mulch for gardening.
Residents who don’t want to reuse the leaves themselves can take them to the Reuse Center at 575 E. Brigham Road in St. George. There the leaves will be turned into compost that the city uses for planting. That compost is also sold to the public – over 400 tons annually, according to the city’s webpage about the Reuse Center.
“It is the best place to take your mulberry leaves,” Pendleton said of the Reuse Center.
Caring for a mulberry tree
Caring for a mulberry tree is generally pretty easy, Hodges said. Residents can prune them themselves at any time of year. Without overpruning, tree owners should cut the branches so they are clear of houses and give the trees a small thinning.
Precaution: When pruning a mulberry tree or any tree, Hodges said, it’s important to be sure your pruning tools are clean. Tools that have been used to cut other trees and plants could potentially carry diseases to a healthy tree. Of particular concern when pruning mulberry trees is sooty canker, one of the only diseases that affects mulberry trees. The disease is spread through open wounds on tree bark, wounds you create when pruning the tree.
Tools can be easily disinfected by spraying Lysol or other disinfecting spray directly onto the tools. A bleach solution can also be used by mixing 1 part bleach to 10 parts water, and then pouring it into a spray bottle, which you can then use to spray the tools.
If a tree shows signs of disease, the best thing to do is call an arborist who can help prevent the spread, Hodges said.
Homeowners and neighbors should also use discretion when choosing herbacides to control weeds. Pre-emergents containing glyphosates such as commercial Roundup are safe, Hodges said. But herbacides containing dicamba can kill mulberry trees. Because a mulberry tree’s roots can extend so far away from its trunk it is a good idea to ask the neighbors what sort of herbacide they are using as well.
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