Answer: Minerva and Diana are both described as reaching to about ten feet tall, while the Lavender Chiffon is naturally a smaller plant overall. (Different cultivars will mature to different sizes.) Keep in mind that the size range is an approximation since actual growth will depend somewhat on the climate and the site where it is planted.
You can keep a Rose of Sharon smaller than the stated size range by annual pruning. In general if pruned very hard (close to the ground) in late winter every year it will stay smaller and will have a shrubby or bushy look. If left to grow to its mature size without much if any pruning, it will take on more of a tree form with one or more trunks. You can also prune it midway if desired. A ball shape would also require annual shaping. It blooms on new growth of the season so annual pruning done in late winter or very early spring does not interfere with flowering.
I hope this helps.
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