Why Is My Magnolia Tree Leaves Turning Yellow?

Magnolias are some of the most wonderful trees used for landscaping. However, sometimes there are problems with them, and we’ll talk about one of those today.

Lack of watering during dry weather is the main reason why magnolia leaves turn yellow. Root rot, nutrient deficiency, and too much sun can also cause magnolia leaves to turn yellow.

These and some other causes of leaf discoloration are detailed in this article. You will also learn how to fix each of these problems.

Nutrient deficiency

Lack of nutrients always has a negative effect on the growth of trees. This is because the minerals necessary for photosynthesis are not supplied in the right amounts, which causes various problems, in this case, chlorosis.

The main symptoms are yellowing of the leaves, but the veins remain green. This way the tree reduces the amount of chlorophyll in the leaves. It can occur on both old and young leaves.

The leaf may also become pale green with dark green veins instead of turning yellow.

The causes of chlorosis are not always due to insufficient amounts in the soil. Very often, because the soil is too alkaline, the minerals are not available to the roots of the plant.

How to fix it:

The first thing you need to do is check the soil pH. Use a commercially available soil acidity test kit for this purpose.

If the soil pH is much higher than 7.0, you need to lower it a bit. To do this, apply a soil acidifier that you can find at the garden center.

Next, apply a slow-release fertilizer with the multipurpose NPK formula. These fertilizers usually contain more nitrogen and less phosphorus and potassium, which is fine for magnolia. Also be sure the fertilizer contains magnesium, iron and calcium.

Read more: How Do You Fertilize Magnolia Trees?

Natural shedding

Sometimes the yellowing of the leaves is caused by natural shedding. The tree changes its leaves continually throughout its life at regular intervals. This applies to both deciduous and evergreen magnolias.

Evergreen magnolias such as Southern magnolia or Little Gem magnolia drop some leaves. This happens throughout the year but is most intense in the spring.

At the same time, deciduous magnolias such as the Jane magnolia tree only drop their leaves in the fall.

In both cases, the leaves turn yellow first before they fall. Sometimes brown spots form on the yellow leaves and this is absolutely normal.

How to fix it:

You don’t have to do anything with the falling leaves except pick them up and throw them away. The main signs of a natural shedding process are that only the older leaves that are placed lower down the branch or deep in the crown turn yellow.

Too little water

Lack of water in sunny and hot weather can cause magnolia to become stressed and dehydrated. As a result, the leaves will turn yellow.

If the sun is too strong, the leaves will dry out and turn brown. The tree will, of course, be dead by then.

This happens most often with newly planted or potted magnolias. In the first case because the root system is not yet developed, and in the second because the amount of soil in the pot is limited.

How to fix it:

To avoid underwatering newly planted magnolias, check the soil moisture regularly. Once the soil is more than 2 inches dry, water the tree with 1 to 3 gallons of water. You should do this for the first 2 years after planting.

The same goes for potted magnolias, don’t let the soil in the pot dry out more than 2 inches. Also, avoid growing magnolias in pots if possible. Once planted in the garden, the magnolia will feel much more comfortable.

Overwatering

If the soil around the roots is wet for too long, root rot can occur. As a result, the roots will die off and the water supply to the leaves will stop.

The first sign of this will be the discoloration and then the yellowing of the leaves. Also, some leaves may turn brown around the edge. Eventually, the leaves will fall off.

There can be a variety of reasons for the soil being too moist. Sometimes this happens from too much rain and sometimes from improper watering.

How to fix it:

If the soil is too wet in the root zone, eliminate all possible causes of overwatering. For example, turn off and reset the automatic watering or stop watering too often manually. A well-established magnolia does not need watering.

If the reason for overwatering is poorly drained soil, repot the tree in a less moist area using well-drained soil.

Do not plant the magnolia tree too close to areas where water accumulates, such as rainwater from the roof.

Too much sun

Direct sun all day can cause magnolia leaves to turn yellow. Not all species in the magnolia family are equally susceptible to direct sun. Some of them need partial shade.

The sun also often causes damage to the foliage of newly planted magnolias. This is due to the fact that the trees are often grown under shade netting in nurseries. If you plant such a tree in full sun, it will get burnt.

Partial yellowing of the leaves is a symptom of sun damage. Also, red-brown patches or dry patches may appear in the center of the yellow area.

How to fix it:

You need to find out exactly how many hours of sunlight your magnolia needs. You can find this out from your supplier. If the tree needs shade from the afternoon sun, then transplant it to such a location the following spring.

If we’re talking about newly planted magnolias, you need to shade them from the afternoon sun. This can be done with a garden umbrella, for example. In a month the tree will get used to the new sun exposure and the umbrella can be removed.

Sucking pests

There is a certain type of insect that does not eat the plant but sucks on the leaves and branches to feed on its sap. As a result, it can be severely damaged and the leaves will slowly start to turn yellow.

Such insects include aphids, mealybugs, and some others. Separate are spider mites because they are not insects, but do the same damage as the previous pests.

Symptoms are slow discoloration of the leaves. After some time the leaf turns yellow and dries out. Aphids can be seen on the opposite side of yellowed and curled leaves.

The mealybugs are noticeable by white, cotton-like marks in their habitat. Spider mites are the hardest to spot because of their very small size; you’ll need a magnifying glass for this.

How to fix it:

If you see insect colonies on magnolia leaves, spray it with an aqueous solution of horticultural oil or insecticidal soap. Repeat the spraying after two weeks.

Against the spider mite, you should use a special product called acaricide (miticide). It is commercially available. Just dilute it as indicated on the package and spray the magnolia.

Diseases

There are a number of fungal diseases that can lead to discoloration of the leaves. At first, brown or black spots with yellow edges appear on the leaves.

Over time, the spots will become larger and the leaves will turn yellow. Subsequently, the entire leaf turns yellow and falls off.

This can happen to both young and old leaves. Sometimes even half of the leaf can turn brown or black.

How to fix it:

Provide the magnolia with several feet of free space for good air exchange. Magnolia should get at least 4 to 6 hours of direct sunlight per day.

Spray magnolia leaves with an aqueous solution of a multi-purpose fungicide. Repeat the spraying with a copper fungicide after two weeks.

Remove any fallen or badly damaged leaves and discard them away from the yard.

Read more: How do you keep Magnolia healthy and thriving?

Stress after transplanting

Newly planted magnolias very often suffer from yellowing of the leaves. This is due to the fact that the growing conditions change when the tree is placed in its new location. As a result, it gets stressed, turns yellow, and can even die.

Stress can be caused by damage to the root system during transplanting. Also, the change in sun exposure causes discoloration of the leaves, as I mentioned above.

How to fix it:

Plant or transplant magnolia only in early spring when the sun is still mild. Also, avoid traumatizing the roots, the more roots left intact the better for the tree.

Water the magnolia with enough water before planting. Choose an overcast day for planting instead of a sunny day.

After planting, shade the magnolia with a garden umbrella or something else for 1-2 months. This is especially true during the hot summer months.

Keep a constant eye on the soil in the root zone and don’t let it dry out more than an inch. Mulch the root zone with organic material about 2 inches thick.