Grumpy addresses your growing concerns about this iconic Southern tree.

By Steve Bender
May 22, 2020
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Jared I. Lenz Photography/Getty Images

My Southern magnolia tree is blooming. I don’t have to see it to know. I can smell it from 20 feet away. Waxy, white blossoms up to 10 inches across crown its glossy, evergreen leaves. Some flowers may smell as good, but none smell better.

With magnolias in bloom or nearing bloom, I’m getting a lot of question about this native stalwart. I will answer them now to your great delight and approbation.

How big does Southern magnolia tree grow?

That depends on where it’s growing, but the average tree matures anywhere from 60 to 80 feet tall and 40 feet wide after many years. That’s BIG. Fortunately, home gardeners can plant more compact selections that won’t swallow entire an entire yard. They include ‘Teddy Bear’ (16 to 20 feet tall, 10 to 12 feet wide), ‘Brackens Brown Beauty’ (35 feet tall, 15 feet wide), ‘Little Gem’ (20 to 25 feet tall, 10 to 15 feet wide), and ‘Majestic Beauty’ (35 to 50 feet tall, 20 feet wide).

Where can you grow Southern magnolia tree?

It thrives in USDA Zones 6 to 10. It likes acid to slightly alkaline, well-drained soil and full to partial sun. It also tolerates salt spray, so it’s a good candidate for beach gardens.

Is it OK to prune Southern magnolia trees? How and when?

Sure! Where do you think all of those magnolia branches for holiday decorations come from? I use hand-pruners to do the work, shortening branches to the point where they join with another branch, so I don’t leave obvious holes in the canopy. You can prune in spring, summer, late fall, or winter. Keep in mind that if you completely remove the lowest branches of a big tree, they probably won’t be replaced.

What should I fertilize it with and when?

Shocking news! It doesn’t need any fertilizer, so don’t waste your money. Just plant it in a hole that’s three times wider than the root ball, but no deeper. Fill in with the same soil you just dug out.

I planted my Southern magnolia tree five years ago and it has never bloomed. What am I doing wrong?

Probably nothing. Unnamed, generic trees (just says “Southern magnolia” on the tag) can take a long time to start, especially if they’re small. Named selections such as ‘Little Gem,’ ‘Teddy Bear,’ and Bracken’s Brown Beauty’ start blooming much earlier. If you want an absolute guarantee, buy a tree that already has flowers or flower buds on it.

My magnolia has this brown coating on the undersides of the leaves. Is this a disease?

Nope! The brown stuff is made up of tiny hairs and called “indumentum.” Many gardeners, Grumpy included, find the rich, brown undersides combined with the deep-green top sides to be quite attractive.

WATCH: Grumpy Gardener's Guide to Magnolias

Lots of smaller branches on my magnolia have brown leaves on the ends. What’s up with that?

This is damage caused by a small beetle called a black twig borer. The female beetle bores a tiny, round hole on the underside of a twig and lays eggs inside. The larvae hatch and feed inside, hollowing out the twig, which then dies. The dead twig ends don’t threaten the life of the tree, but they sure do make it ugly. Solution? Pick up any dead twigs that fall and throw them out with the trash. Remove any you can reach that haven’t fallen by cutting three inches up from the holes into live wood and throw them out too.

What’s the most common mistakes people make when planting Southern magnolias trees?

Planting them too deeply (top of the root ball should be even the soil surface) or too close to the house (no closer than 20 feet).