Fertilizing a Southern Magnolia?

We have a very large, very old Southern Magnolia in our back yard. It appears healthy and blooms pretty well, but it drops leaves ALL YEAR LONG. Not just a few here and there, but probably 25-50 per day depending on what time of year it is. If you look up into the tree, for the most part the leaves are green and glossy but many are yellowing and fall out. We had all of our big trees pruned and they did a "deep root fertilizing treatment" on them about 2 years ago. Is it time to do this again? The arborist guy used an auger to drill 2 or 3 feet deep holes in various places under the trees and filled each one with a granular fertilizer. Has anyone else ever had this done? Is there some DIY method that I could try? I don't want to pay an arborist to come out again but I don't think a surface treatment is going to do anything for the tree either.

The arborist was quick to suggest cutting down some of our trees- two old pecans and a big old redbud for instance. But he did not say much about the magnolia. Just that he pruned it for shape and deep root fertilized it and the 2 live oaks.

Any thoughts?

Thanks,

Jamie

My magnolia is about thirty years old. It has never been fertilized and is doing fine.It also drops leaves all the time. Certain times of the year more than others. I guess that is because it is an evergreen and never goes dormant. Occasionally, it gets something, a fungus or something, and gets black spots on the leaves. When that happens , it drops more leaves than usual. This tree is completely neglected and is doing just fine. It just started blooming again.

Thanks rylaff. I was outside picking up leaves yesterday and noticed they do have black spots on them. Some did anyway. We just laid St. Augustine sod in the backyard on Saturday and we are out there every day to not only water but to pick up all those leaves so they don't kill the grass!

I see lots of magnolias around here that have glossy deep green leaves and no yellow spotted ones on the ground underneath so I am assuming there is something one can do to stop it from happening. But then again, maybe it's the age of the tree. Or the fact that I have 3 huge trees in close proximity that are fighting for the same nutrients. Or... :)

Rylaff is correct Magnolias do shed leaves year round. If the leave drop problem has gotten worse since the pruning, pruning may be part of the problem. Southern Magnolias that have been pruned to allow more light in through the canopy are more suceptible to leaf spot problems. There are different causes of leaf spot, but most are relatively harmless. Just pick up and dispose of all the leaves. Most trees have their feeder roots in the top 4 feet of soil. Anything that distrubs or damages roots will result in a weaker tree leaving it open to attack by pests and diseases. Concentrated fertilizer will kill roots it comes in contact with. The area of root kill may extend out well beyond the bore hole until the fertilizer concentrate is diluted to the point where it doesn't kill. Root damage may cause added leaf drop.

Southern Magnolias love moisture. If you planted St. Augustine grass underneath it, your magnolia will be competing for water. Be sure to give the magnolia deep watering ocassionally to encourage deep root growth.

If you want to know specifically what is causing the black spots, take a few leaves & maybe a photo of the tree and it's surroundings to your local Extension agent.

Thanks Betty! St. Augstine loves water too so I know my water bill is going to be bad in the summer! I would like to think that an arborist would know what he's doing as far as fertilizing and all that, but you never know! The tree has always been like this as far as dropping leaves. But until he fertilized it I never saw it bloom. I can't say that the leaf dropping issue has gotten significantly better OR worse since it was pruned and all that. He didn't do that much pruning on the magnolia. It was mainly on the 2 live oaks.

Back on the watering part- I have read about people putting PVC pipe in the ground next to trees so they get a good deal of water and don't "rob" it from the grass. Have you ever done this? Are we back to the "damaging the roots" thing again? I'm not sure that you can put PVC in the ground and be sure you aren't hitting roots. I would also think you need more than one, and I have no idea how deep you would put them. BTW- I am completely prepared for grass to NOT grow right up to that tree. In fact, I am contemplating a raised bed there. I read in a Texas gardening book where the author said "when someone asks me how you get grass to grow directly under a magnolia tree, I tell them 'you don't.'" :)

We're back to the "damaging the roots" thing. The roots are pretty shallow. and extend out well beyond the crown of the tree. On oaks, for example, that can be 3 times the diameter of the crown. I don't like doing anything that will stress the trees especially my oaks. We've been very lucky in that our county hasn't been hit by Oak Wilt. Back on topic. We used a RainBird drip irrigation system under our trees. We laid out the flexible 1/2 inch hose on the surface around the trees (several times if the tree was large), plugged in the 1/4 inch tubing with 2gph (could use 4gph) buttons and covered with shredded cedar mulch. It's much easier because you don't have to dig. You could have each tree on a separate line so it can be watered independent of the others. The cap at the end of the line allows you to drain the hose during the winter.

How large a raised bed? Damaged roots again. Small ones here and there aren't going to hurt, but one big one all the way around the tree would probably kill it. Raising the soil level decreases the amount of oxygen the roots get. I'm not sure how much added soil a magnolia can tolerate. I know that an inch or two of soil spread under an oak can severely damage or kill it.

Oh tree drama! Ha! :)

The raised bed was just a thought- there is a pond between the tree and the house so I was also considering one of those wrap around iron benches on the side of the tree that is opposite the pond. Or maybe just pots. Who knows? I do have a drip system started anyway so I can just add lines for the trees. Thanks for the suggestions!

Hi everyone! Happy Easter...
I was just outside looking at my yard, and my Southern Magmolia as some yellow leaves on it. It is about 3 years old and about 10 feet tall. We just put in some tree spike fertilizer. Does anyone have any idea why the leaves are turning yellow? The tree hasn't flowered since I put it in, and I hope it isn't dying on me. Any help would be appreciated.

Usually as new leaves are formed the old ones will shed. Magnolias are like live oaks, they will shed most during the spring with the onset of new leaves. Since the tree was fertilized, it may be putting out lots of new growth which may be causing it to shed more than normal. As far as the ground under the tree, I would suggest making a circle around the tree at least 5ft from the trunk. You could apply pine straw to that area and it would be good for the tree. I fertilize mine using 10-10-10 in a broadcast spreader. I usually do it in late February when plenty of rain is expected. If you are going to be fertizing the lawn around it in the future, you shouldn't need to fertilize the tree anymore.

Lots of good advice in this thread. My only added suggestion is to increase Escambia's mulch circle out to the dripline and get rid of the grass under the tree. Then let the leaves fall there and renew the mulch, and use your mower to blow any stray ones back under there. If the tree has been limbed up (I hope not) you could add a few dry-shade plants under it. Otherwise, grow it like a spruce, clothed to the ground with foliage. You could even make a hidden opening to the interior and place a hidey-bench there for meditation.

Guy S.