Magnolias have remained desirable trees in many gardens over the years. This article will provide you with answers to the most common questions related to the problems of growing this tree.
Drought stress is one of the main causes of magnolia leaves turning brown. Root rot, pests, mineral deficiency, and scorching sun can also cause magnolia leaves to turn brown.
Potted and newly planted magnolias are most prone to drought stress. This usually happens during the hot and summer months.
Sandy soil can make the situation even worse. If a magnolia grows in this type of soil, it can suffer from dehydration very often.
Symptoms include browning of the leaves. This can start from either the edge or the middle of the leaf. Magnolias with soft leaves may droop during drought stress.
How to fix
During the hot summer months, check the soil around the magnolia roots several times a week. If it is more than 2 inches dry, water with at least 1 gallon of water.
This is especially true for potted magnolias and magnolias that were planted less than a year ago. Once the magnolia is established (2-3 years old), you can stop watering. As for potted magnolias, you should not keep them in a container for many years.
Be sure to mulch the root zone. Use only organic materials such as pine bark or compost.
Read more: Planting And Caring For Magnolia
Black Twig Borer
Black Twig Borer is an insect that lays eggs inside branches. When the larvae hatch, they begin to eat the branch from the inside.
The symptoms of this pest are the browning of leaves on just one branch. If only one cluster of leaves is brown and the rest are green, it may be a Black Twig Borer infestation.
Also, many different sucking insects can cause a change in the color of magnolia leaves. Usually, the leaves will slowly become pale and discolored. After a while, they turn brown.
How to fix
If you see symptoms of Black Twig Borer, cut off the branch with the brown leaves where they attach to a healthy branch or to the trunk. Throw the damaged branch as far away from your yard as possible.
If you see an insect colony on the leaves, spray them with horticultural oil. If the insects are still active after a week, spray the magnolia tree with a systemic insecticide. Read more about this in How do I keep bugs from eating my magnolia leaves?
Lack of nutrients
Nutrient deficiencies usually occur in very poor soils. It can also occur if the pH of the soil is too high because the roots are then unable to absorb minerals.
This can cause the leaves to discolor first and then, depending on the weather, turn yellow or brown. If the weather is hot and dry, the yellowing of the leaves will soon turn brown. Also, the growth rate of the tree will slow down.
How to fix
The first thing to do is to check the pH. To do this, buy a kit that is designed to measure this parameter. You can easily find these kits at your local home improvement center.
If the soil around the magnolia tree has a pH much higher than 7.0, you need to lower it. Use soil acidifiers to do this.
Next, apply a slow-release fertilizer. Make sure the nitrogen number is no more than 15. Phosphorus and potassium should be less than nitrogen. The product must have magnesium and iron.
Fertilize once a year in early spring. Avoid fertilizing in late summer or fall. Also, do not exceed the amount of fertilizer listed on the label.
During periods of extreme heat, hosta leaves can get scorched. This usually happens during the summer months in the southern part of the country.
This happens because the sun is too strong on the leaves and they evaporate moisture very quickly. The tree does not have time to deliver water to the leaves and they turn brown around the edge.
The soil may be wet enough, but the burn will still happen.
Newly planted magnolias and some varieties that require partial shade are the most susceptible to scorch.
How to fix
Water the magnolia once with 1-2 gallons of water. Do not over-water it as this will have negative consequences.
If the tree is up to 7 feet tall try to shade it for the heat. Use a garden umbrella or something similar for this purpose.
Mulch the root zone with organic material to prevent the soil from drying out quickly and overheating.
If possible, transplant the hosta to a location with some shade in the middle of the day.
Natural aging is one possible cause of leaf discoloration. It happens to both evergreens and deciduous magnolias.
The leaves of deciduous magnolias change color in the fall. The leaves stay on the tree for a while but eventually fall off.
With evergreen magnolias, it’s a little different. Not all of their leaves age at the same time, but only some do. This happens mostly in the spring. The older leaves are usually closer to the middle of the crown while the younger ones are at the periphery of the crown.
Some leaves may turn yellow before they turn brown. Once the leaf is dry and crispy brown, it falls to the ground.
How to fix
You don’t need to do anything to the old leaves. It’s all a natural process that repeats every year. All you have to do is remove the fallen leaves and throw them away from the yard.
Root rot is a serious disease in which the roots lose their ability to absorb water. The supply of water to the leaves stops and they turn brown.
This is very similar to drought stress because the leaves start to dry in both cases. Usually, first the edge and then the whole leaf plate turns brown.
Root rot in most cases is due to overwatering or planting magnolia in a place where water collects.
How to fix
Only water the magnolia when the soil is 2 inches or drier. Do this in the first 1-2 years after planting.
If your magnolia is growing too close to where water collects or flows, try to divert the water to the side. Next spring, transplant the magnolia to a less wet location with well-drained soil.
Frost can turn magnolia leaves brown in two cases. The first is when young leaves are damaged by late spring frosts.
In this case, the leaves become watery and turn brown if the weather is sunny. This can happen to both evergreens and deciduous magnolias throughout the spring.
The second case is damage by frosty draughts during the winter. This only applies to evergreen magnolias.
How to fix
If possible, cover the magnolia with protective material for the duration of the frost. The magnolia usually recovers quickly after such damage.
In the case of a frost draught, you will need to transplant the magnolia to a more sheltered location in early spring. For example, it could be between two buildings.