The Rose of Sharon (Hibiscus syriacus) also known as an Althea shrub is a mid summer bloomer in white, pink, red, or purple with a red center. You can also find them ruffled in the same array of colors including what many call blue. You can grow the Rose of Sharon as a shrub or a tree and many garden catalogs sell them as a fast growing deciduous flowering hedge.
The Rose of Sharon grows in zones 5-9 (but I have seen a listing for up to zone 11) and can be quite a prolific re-seeder. In my zone (7) it can be invasive and pop up where the seeds may fall or the wind takes them. Many sites will tell you that the height can reach up to 10′ tall and 6′ wide but I can confirm that I have a ruffled purple one that is 8 years old and is well over 12′ tall and 6′ wide. It has never had viable seeds yet and last summer transplanted a purple one to the same area of the yard to see if that will make a difference (sometimes plants need another for cross pollination). It grows in most soils and will tolerate the hot summer sun.
About 3 years ago I discovered under the Oak tree on the front corner of my property along the street quite a few seedlings. Since the seedlings were mixed in with the Wintercreeper Euonymous under the Oak tree, I just let them to see what they would do. Well, last summer 2 purple and 1 pale pink bloomed so I dug up the 2 purple ones and left the pale pink one under the Oak by the road. I transplanted one (purple) on the side of my house where it is hot and dry and I put the other one in my back yard. (I believe) the seeds came from my neighbor 4 houses down and across the street. She has a purple one but no one else on my street has a Rose of Sharon that I have found.
My double ruffle blooms around the 1st week in July and shortly after the others start to bloom. I have one in part shade and it has not bloomed yet but has buds. This is a late bloomer and would not be a good specimen tree for any garden because the leaves emerge much later than most other deciduous shrubs and trees. The Rose of Sharon does make a great hedge and I would think about mixing it in with some sort of conifer, evergreen, or arborvitae for winter interest. The Rose of Sharon can be controlled by simply cutting off thee seed heads before the pods turn brown and burst open. If the seedlings emerge, you can simply pull them out of the ground. I threw down seeds late last summer and this spring they emerged. These are fast growing plants. The first year they will grow less than a foot but by the 3rd year my Rose of Sharon tree has reached over 6′ tall. Now I live in zone 7 so I have a longer growing season and a milder winter but I would venture to guess that a foot a year growth until it reaches maturity is not over stating how fast they grow.
The Rose of Sharon can be pruned to control its size. I am not a pruner so I let (most of my) plants do what they will. If you do want to prune I would wait until the last flower blooms and fall arrives to prune to shape for next year. You can also prune in early spring and shape the plant (some gardener says for bigger blooms). The Rose of Sharon can be a bush, tree, or even an espalier (which is training the plant to grow along a fence or wall).
I have never fertilized my ruffled Rose of Sharon and had any disease problems but that does not mean they cannot succumb to blight, leaf spot, or canker. This year, however, there seems to be an aphid problem which I need to address with a shower of Dawn dishwashing liquid in my fertilizer hose sprayer. It has been written that the Rose of Sharon is also one of the favorites of the Japanese Beetle. (so knock on wood that I do not find this out)
There are new cultivars you can find at garden centers and nurseries which are smaller and are not invasive (because the plant does not produce many seeds). The bees love them which is a plus in my book. The Rose of Sharon also tolerates my dry, red clay soil and life under Oak trees which is another reason I have them.
I have so many seedlings because I do not prune off the seed heads. It is easy to identify them and pictured below I have a close up of the leaves for you to use to identify them on your hunt. I would save the pictures and go for a walk in your neighborhood and see who has them. I would ask the gardener (or property owner) if they would mind if you took some seeds or dug up some of the seedlings. Many people will share and asking is so much better than just taking.
I have transplanted these in the heat of summer with great success. Watering is the key to success and transplanting before, during, or after a rain is my secret. Happy gardening everyone and if you ever have a question, just ask.
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2015 copyrighted material C Renee Fuller @the Garden Frog Boutique