How big do althea trees get?

Twelve feet, which puts an althea at the short end of the ornamentals we plant. Redbud and Texas mountain laurel run twelve to twenty feet, and Mexican plum and chitalpa are the taller ones at twenty to twenty-five. One caveat belongs with any height figure we publish: height and spread are very variable based on environment, and nearby competition and growing conditions will affect a number like this considerably.

Is althea the same as Rose of Sharon?

Here, yes. They are two names for Hibiscus syriacus, and our own planting list prints it as 'Althea (rose of Sharon).' But both names belong to other plants elsewhere. In British and European usage, 'rose of Sharon' usually means Hypericum calycinum, a low evergreen groundcover in a different family. And 'althea' collides with Althaea officinalis, marshmallow, a herbaceous perennial. It matters when you are reading care advice you found online: check which plant the page is actually about before you follow it.

Does an althea need full sun?

Yes. It needs irrigation and it needs full sun. Without those you don't get the flowers, and a flowering tree that doesn't flower is kind of a waste. Nothing about a shaded althea is unhealthy; you simply don't get the one thing the tree was bought for.

What are the cons of Rose of Sharon?

What decides whether you should plant it is the condition it comes with: it needs irrigation and it needs full sun. Otherwise you don't get the flowers, and on a tree bought for its bloom that is the whole purchase. The other thing to hold onto is the shape of an ornamental generally: it is not a shade tree and is not meant to be, it doesn't live as long as one, and one day you are going to cut it down and grow another. That day isn't dangerous or hazardous, and the replacement comes back quick.

The Althea Tree (Rose of Sharon) in Central Texas

Q: Is althea native to Texas?

No. Althea is from East Asia, and the authorities differ on exactly where: Missouri Botanical Garden says China to India, Kew puts it in southern China and Taiwan, and the Korean literature has it in Korea and south-central China. Whether India, Taiwan and Korea are native range or very old introductions is unsettled, so East Asia is as tight as an honest answer goes. It is on our ornamental planting list on its own merits rather than on a nativity argument.

Althea (Hibiscus syriacus) is one of the shorter flowering ornamentals we plant in Central Texas, and it’s a personal favorite of mine. It comes with one condition attached, and that condition decides whether you should plant one at all: it needs irrigation, and it needs full sun. Otherwise you don’t get the flowers, and it’s kind of a waste. It gets twelve feet tall, and nearby competition and growing conditions will affect that considerably.

At a Glance


Botanical name	Hibiscus syriacus. The species name is a misnomer
Also called	Rose of Sharon. Both names belong to other plants elsewhere
What it’s for	Ornamental and flowering
Native	No. East Asia, and the authorities differ on exactly where
Foliage	Deciduous
Mature height	12 ft, and nearby competition and growing conditions will affect that considerably
Lifespan here	50 years, which is long for an ornamental this size
Canopy spread	Normal. Width is decided mostly by what’s growing next to it. Crowded in among other plants, a canopy never gets as wide as one standing on its own
Sun	Full sun. Short of that, you don’t get the flowers
Water	Needs irrigation
Where it sits	The short end of the ornamentals we plant, with redbud and Texas mountain laurel
On our planting list as	“Althea (rose of sharon),” under Ornamental Trees

Full Sun, or It’s Kind of a Waste

Needs irrigation, needs full sun. Otherwise you don’t get the flowers, and it’s kind of a waste. That is the whole of the condition.

It’s a short recommendation and it isn’t a knock on the tree. This is a tree you buy for one thing. It isn’t put in for shade, for structure or for fall color. It’s put in for the bloom, and the bloom is the part your site either supports or doesn’t. Get the exposure wrong and you still have a healthy plant standing there. You just don’t have the thing you paid for.

So the siting question is worth real care on this species, and it isn’t “does that corner get some sun.” A spot that reads as sunny in February can be under a canopy by June, because the things around it leaf out and grow. If you aren’t sure a spot qualifies, settle it before the tree goes in the ground rather than after a summer with no flowers on it.

The irrigation half is the same kind of condition, and it sits alongside our standing position on any new tree: supplemental watering is the single most important factor in a new tree’s survival, there is no single recommendation we can apply to all sites and all trees, and soil moisture has to be monitored. How to water a newly planted tree is the long version.

Two of those things you can do yourself and they’re most of the job. Get water to it, and look honestly at the exposure before you commit. Where it stops being a homeowner job is the judgment underneath: whether that spot will still be full sun once what’s around it has grown, and what belongs there instead if it won’t. That’s what a site visit is for, and it’s on the tree planting page.

Three Names, and Two of Them Belong to Other Plants

Around Austin, “althea” and “rose of Sharon” both mean the same plant, Hibiscus syriacus. Our own planting list prints it as “Althea (rose of sharon),” and when a customer here says althea, that’s the tree they mean.

Both names are taken elsewhere, though, and the collisions are live rather than historical.

Rose of Sharon, in British and European usage, usually means Hypericum calycinum. That is a low evergreen groundcover in an entirely different family. Not a tree, not a hibiscus. A British gardening book explaining how to prune your rose of Sharon is very likely talking about a plant you’d mow around.

Althea collides with Althaea officinalis: marshmallow, a herbaceous perennial, one letter apart in spelling and not a woody plant at all.

That matters the moment you go looking for care advice online. Common names are a big part of why people around here end up wrong about their trees. It’s the same problem as “live oak” covering two different species, or cedar fever getting blamed on the wrong juniper. This one has the extra wrinkle that the confusion crosses an ocean. Check which plant the page is about before you follow it.

The Latin Name Points at the Wrong Continent

Hibiscus syriacus reads as “the Syrian hibiscus,” and it isn’t one. Linnaeus described the species from plants growing in Syrian gardens; it had travelled trade routes long before it ever got there. The mistake is fossilized in the old names, Syrian hibiscus and Syrian ketmia, and in the binomial, which nobody is going to change now.

It’s from East Asia, and that is as tight as an honest answer goes, because the authorities don’t agree past that point. Missouri Botanical Garden says China to India. Kew’s Plants of the World Online puts it in southern China and Taiwan. The Korean literature, and it’s Korea’s national flower, has it in Korea and south-central China. Whether India, Taiwan and Korea are native range or very old introductions isn’t settled. A page that picks one and states it flat is claiming a certainty the sources don’t have.

For a buyer the settled part is the part that matters. Althea is not a native tree here, and we don’t sell it as one. It’s on our ornamental list on its own merits. If native is what you’re after and twelve feet is the size you want, redbud and Texas mountain laurel are both native to Central Texas and both run twelve to twenty feet.

How You Buy One

Ornamental stock doesn’t work the way shade-tree stock does. Privacy and ornamental species are typically only available in 30-gallon containers and smaller, and fifteen gallon is the most common size. Heights are also less precise on ornamental species than on shade trees, so if an exact height is a requirement for you, that’s worth saying in advance rather than discovering it on install day.

You don’t pick the individual plant off a lot, either. We don’t have a nursery you come walk through. A certified arborist meets you at the property, works out the size and species for your site, and hand selects the tree. On this species that visit earns its keep, because the thing being judged is the exposure, and exposure isn’t something you can see in a container. How a planting job actually runs is on the tree planting page.

Our Take

Althea is a personal favorite of mine, and I’ll say in the same breath that liking it isn’t the recommendation. Mexican plum, chitalpa and althea are all wonderful trees for our area. I don’t have a favorite to push on you. I appreciate them all for their unique appeal to certain customers and landscape looks, and that’s genuinely how the choice gets made.

What I’d want you to hold onto is the sun, because on this species it’s the difference between a flowering tree and a green one. Full sun and irrigation, and this is an easy tree to recommend. Short of that, pick something else and be glad you asked first.

Keep the shape of the purchase in mind too, the way you would with any ornamental. It isn’t a shade tree and isn’t meant to be. It doesn’t live as long as one. Its job is to give some scale in the landscape, it’s going to look great for a while, and one day you’re going to cut it down. That day isn’t dangerous or hazardous, and you can grow a new one quickly. You lose a little bit and that’s disappointing, but it comes back quick. Knowing that going in is what lets you plan the replacement instead of being surprised by it.

If you have a spot in mind and you want somebody to stand in it and tell you honestly whether it’s full sun, that’s a short conversation and we’re glad to have it. Call (512) 996-9100 or get in touch.

More Trees for Central Texas

Mexican plum: a taller ornamental, native to Central Texas, and it wants creek water or irrigation
Anacacho orchid: another ornamental, and its flowers come out after the foliage rather than before
Texas mountain laurel: slow growing and very hardy in the heat
How to pick a tree: what to look at before you settle on a species at all
The Central Texas Field Guide: every species we’ve written up, grouped by what you want the tree to do