Magnolia trees can be as tall as 5 meters (15 feet), or as small as 2 meters (6 feet). Therefore, they make great feature trees, as well as, filler trees depending on the variety. Today I will explain what to do when a magnolia tree is not doing very well.
Poor soil, soil with the wrong pH, pests, overwatering, the climate, and not enough sun cause magnolia not to grow. To revive magnolia ensure the soil has a pH of 5.0 to 6.0, add compost and fertilizer, move it out of the full shade, water once per week, and treat pests with neem oil.
Interestingly, some magnolias are dormant in autumn and winter so they won’t grow at all during these seasons. When a magnolia doesn’t produce much new growth or none at all in the spring and summer though, it’s a sure sign there is an issue with them.
Below, I will explain the symptoms to look for that indicate what is causing the issue, as well as, the precise solutions for each of these factors to get your magnolia to start growing.
It’s common for the pH of the soil to be out of a good range for magnolias. One magnolia tree can the thriving in one area of the garden, and just a short distance away another magnolia can really be struggling, and not growing at all.
Signs that the soil pH is not in a good range for magnolias are stunted or no growth, and discoloring of the leaves. The leaves should be a healthy green color. The ideal pH for magnolias is pH 5.0 to 7.0.
- Buy a soil pH testing kit from your garden store or online to test the soil pH
- If the pH is too high – above 7.0 add sulfur and organic material
- If the pH is too low – below 5.0 add lime (made from limestone)
Once a magnolia is established it can survive a mild drought, and you don’t need to water it at all. In particularly hot weather they can do a lot better when watered. Watering them too many causes water to stay in the soil and roots, and the roots can begin to rot.
It’s generally not a good idea to dig up a magnolia if you can help it. Therefore, it’s best to observe if this is one of the issues, by the way, the leaves and plant look. If your magnolia has wilted leaves, stunted growth, and discoloring of the leaves it likely has root rot.
It’s also much more likely if the soil is very clayey. If you observe these signs you should dig it up preserving as much of the roots as possible.
Magnolia roots should be firm and soft. If they’re mushy and floppy these areas should be cut away. But if there are hardly any healthy roots left the plant will usually die. And you should get a new one.
- Dig up the plant and remove any roots that are mushy and soft – not rigid at all
- Replant it where there is free draining soil, not clayey soil.
- Only water twice a week if there hasn’t been any decent rain
Not enough or too much sun
As you may know, sunlight gives plants energy that they use to grow. Some plants can do perfectly fine in full shade. But, magnolias do not. Each variety of magnolia is a little bit different but as a general rule magnolias that are evergreen do best in full sun and partial shade.
But, do not do well when in permanent shade. Also, deciduous varieties of magnolias do best in partial shade but can do ok in full sun. But, also do not do well in full shade. Identifying this issue is quite simple because you can see how much sun it’s getting. But, it’s important to identify whether you have an evergreen variety or one that drops its leaves.
- Replant evergreen magnolias in full sun to partial shade
- Replant deciduous magnolias in partial shade but not full sun or full shade
- Move potted evergreen magnolias where they’ll get full sun or partial shade
- Move potted deciduous magnolias where they’ll get partial shade but not full sun
Some insects can eat the stems and leaves of magnolia plants. As they colonize a magnolia plant they can also leave a residue. Common pests are mealy bugs and scale. Some will latch on to the plant and suck out the juices leaving brown dead and crispy spots on the leaves.
As well as, a thick brown crusty residue along the stems and base of the leaves. Other times you’ll need to look quite closely to see the bugs. Crawling on the plant in large colonies, or as individual insects can remain in position their entire adult life. They are very easy to treat.
- Dab them with a cotton bud dipped in rubbing alcohol and they will die
- Spray them with neem oil (horticultural oil)
- Trim off any leaves that are particularly chewed but remove as few as possible
Magnolias can die when the temperature falls below 20 °F (-6 °C). Magnolias in general can survive in most temperatures apart from desert-like conditions and below freezing. But, certain varieties can withstand temperature extremes more than others.
It’s possible the magnolia variety you’re growing isn’t hardy enough for your climate and is struggling due to the temperature being too hot or too cold. The signs that the climate is too hot are leaves drooping, and the stems on new growth bending.
The branches with bark that are hard and rigid will not droop even in extremely hot conditions. In very cold temperatures the leaves can ‘burn’ this is where the edges become dry and crispy. The magnolia society provides a list of the magnolias and what hardiness zone they are suited to.
- Apply a thick layer of mulch in extremely cold temperatures to insulate the roots
- Wrap the trunk and branches in blankets during freezing temperatures
- Water them every day in extremely hot temperatures
- Move potted magnolias into full shade during midday in extremely hot temperatures
- Move potted magnolias into the partial shade in extremely hot temperatures
The soil is too nutrient-poor
Magnolia needs a good amount of nutrients in the soil. Regular garden soil and clayey soil are often too nutrient-poor for magnolias. These types of soil can cause stunted growth. Also, all the leaves can become dry and crispy and the whole plant can die. The leaves can also be yellow which indicates overwatering, underwatering, or not enough nutrients in the soil.
- Replant the magnolia, after putting it in the hole fill the entire hole with store-bought or homemade compost rather than soil
- Apply a regular acidic garden fertilizer in autumn and winter
Another reason for a magnolia’s lack of growth can be transplant shock. This often happens when transplanting a magnolia from pot to ground or when transplanting from one place to another. Roots are usually always damaged after a transplant, and the new location has different growing conditions. All of this together leads to stress and the plant may not grow for one or even two years after planting.
There have been cases where a tree bought in a nursery and planted in the garden can show good growth in the first year. But the next year it does not produce new branches and does not grow. This can go on for another year.
Unfortunately, transplant shock is very common and some plants do not survive it. Always remember that when you buy a new plant you have no 100% guarantee that it will take root in your garden. The same applies to transplanting from one place to another.
- Shade the plant after transplanting. Use netting or an umbrella for this. If the plant doesn’t grow, keep the shade on throughout the growing season.
- Water the magnolia in moderation. Allow the soil to dry 1-2 inches between waterings. A stressed plant is less resistant to disease.
- Avoid fertilizing and pruning magnolia in a state of transplant shock.