If you've ever asked, "Why do I have brown leaves on my magnolia trees?" You are hardly alone. These specimens can be magnificent, but they can also experience problems. Brown leaves on magnolia trees could result from several factors, such as frost damage, insufficient water, nutritional deficiency, or disease. Read on to learn why your magnolia might have brown leaves and what you can do about it.
Reasons for Dead Foliage on Magnolia Trees
To diagnose your reasons for dead foliage, investigate. First, identify the type of magnolia that you have. Also, record the time of year and other factors that are occurring at the same time.
Some magnolia trees are deciduous, such as saucer magnolia (M. x soulangiana), and some are evergreen, such as Southern magnolia (M. grandiflora). If your tree is a deciduous type, then you have nothing to worry about if the issue occurs during the fall season: Its leaves are expected to turn brown and fall in autumn.
If brown leaves appear in spring, it could mean that there was frost damage. The good news is that such frost damage or winter leaf scorch is unlikely to kill your tree. The bad news is that it will ruin the plant's appearance for a while, and there is little you can do to prevent frost damage on a mature specimen.
However, if you have just brought a small tree home from the garden center, you can select a planting location that will be more likely to keep frosts off the foliage. An example of such a sheltered area would be one close to your house. If the plant is still small enough, you may also be able to throw a sheet (or a similar covering) over it on a night when a frost is expected in your area (but remember to remove it the following day).
For a mature magnolia tree, your options are more limited. However, you can try taking the following measures:
- Soak the soil around the root zone of the plant. The air temperature above damp ground tends to stay warmer than that above drier ground.
- Set up a patio heater (if you have one) near the plant (but not so close that it heats the foliage). Always follow safety instructions to the letter when running such devices.
- Spray an antitranspirant on the tree's leaves to offer some protection.
If leaf browning appears in summer, inadequate watering may cause brown leaves, although high winds could also be the culprit (they dry out the foliage). The former is a more severe problem, but there is still no reason to be hasty in concluding that your magnolia tree has died. It is best to exercise patience, giving the plant time to recuperate. As preventive measures:
- Plant new trees in a sheltered area if your region is subject to high winds.
- Make sure the soil in the root zone is kept evenly moist.
If the leaves turn brown in spring or summer, do you notice if the brown leaves fall off immediately after the color change? If so, it could signal an "iron deficiency." Get a soil test done to confirm the tree's soil contents. Your county extension office should be able to test a soil sample for you.
If you notice full branches of leaves dying or the entire tree dying off suddenly, it's likely verticillium wilt, a pervasive fungus known for killing mature trees. Cankers or large unusual knots can also do the same, girdling branches. You can attempt to control both diseases by pruning out branches below the site of infection, but in most cases, it's systemic and will likely overtake the entire tree. You must thoroughly disinfect the shears in alcohol to avoid spreading the fungus to your other plants.
Moist environments and overwatering can cause root rot, which allows pathogens to enter the tree's vascular system, killing it from the inside out. Phytophthora infection can cause magnolia leaf browning and drop. If you suspect root rot or Phytophthora infection, reduce watering to allow the roots to dry out and attempt healing.
Don't Panic over Frost Damage to Trees and Shrubs. Michigan State University Extension
Ask an Expert: Why Are My Leaves Turning Brown? Utah State University
Verticillium wilt of magnolia. University of Illinois Extension.
Knox GW, Klingeman WE, Paret M, Fulcher A. Management of pests, plant diseases and abiotic disorders of magnolia species in the southeastern united states: a review. Journal of Environmental Horticulture. 2012;30(4):223-234, https://doi.org/10.24266/0738-2822.214.171.124.