Are Your Magnolias in Decline?
May 8, 2018
Southern Magnolias are the epitome of the classic tree for Southern landscapes... and a favorite for large specimen shade trees. But, you may have noticed lately that many magnolias are suffering in our North Texas climate. What is causing so many magnolias to decline? We’ll have to look to seasons past for some of the answers.
Decline in magnolias can be attributed to a number of factors, but a big stressor is drought. Sure, we have had drenching rains the last couple of springs, and even some flooding. But before that, we had some seriously harsh bouts of drought for many years. Large, moisture-loving trees like magnolias need steady, soaking rains to stay happy. Those previous droughts took a big toll on magnolias in our area and the damage is still emerging. Our ‘gully-washers’ that come now and then, rarely benefit these big trees because the water runs off too quickly, before the tree can take it all up. Add a dry winter to the mix, and many trees are feeling — and displaying— their pain.
If you notice your magnolia is thinning and excessive amounts of leaves are dropping from the center and top portion of the tree, low-water conditions may be the culprit. Trees show signs of drought stress first in the top and center because these are the last places to receive water. Larger trees may take months or years of water stress to finally show this kind of damage; by that point, it may be too late. A warmer than normal summer can further intensify the leaf drop because weakened trees cannot recover from stress as easily as healthy trees.
To avoid drought situations, make sure to check and water your trees, especially during dry spells. Even a large mature tree will need a thorough, soaking watering every 2-4 weeks during a drought.
It is important to point out that, like Live Oaks, Southern Magnolias do shed leaves in big batches in the spring as they push out new foliage. But if your tree is shedding leaves irregularly, that’s not a good sign.
Another major cause of decline in magnolias is verticillium wilt. Verticillium wilt is a fungal disease that enters the vascular system of a plant and blocks the transport of water and nutrients, causing the death of branches one at a time. If you suspect verticillium wilt, a clue is to cut a small branch and examine its center; if you notice a brown “staining” in the middle, then your tree may be infected. Of course, a certified arborist can diagnosis your tree for certain.
The bad news is verticillium fungus is always present in our soils, but only becomes a big problem when trees are stressed and unable to fight off the fungal infection. This can happen when trees are water-stressed (either too little or too much), are nutrient deficient, or have other damage or pest infestations that weaken the tree’s defenses.
Verticillium thrives in 70F - 85F degree soils, therefore spring and early summer weather offers up ideal conditions for infection. The best way to protect your magnolias from disease is to water and feed them properly to keep them strong and healthy.
Other causes of magnolia decline:
root rot (caused by Phytophthora) due to overwatering
nutrient deficiency due to high pH soils
construction damage to roots (this happens frequently in our urban environment)
leaf scorch in colder winter climates
Right Tree, Right Place
In general, Southern Magnolias aren’t necessarily an ideal tree selection for the DFW area of Texas. Our soils tend to be heavy clay, alkaline, and have a high pH. Magnolias prefer looser soils with a lower (acidic) pH - just like azaleas and rhododendrons. Couple less than ideal soils with our extended periods of dry heat, and magnolias can often suffer.
Let us help!
If you think your magnolia is in decline, do not hesitate to contact us immediately. We can diagnosis any issues and provide recommendations on treatment, moving forward. If it’s time for a new tree choice, we can help you select the right tree for your landscape and plant it the right way.