Why did only one of my hollyhocks flower?
In the spring, I bought three hollyhocks from a reputable greenhouse and planted them near my deck. They were all the same size, and had a well-developed root system when I planted them. The tag that came with them said that each of them was a perennial.
The one that bloomed was labeled alcea rosea “Mars Magic” Spotlight Series Hollyhock. The other two were labeled alcea rosea “Mars Magic” Spotlight Sunshine Hollyhock” and alcea rosea “Blacknight” Spotlight Series Hollyhock.”
Why did only one of them put out a flowering stalk? Is it possible that these are really biennials (not perennials) that do not flower in the first year? Should I just be patient and wait until next year when, if they are biennials, they might bloom?
You are correct in your speculation that Hollyhocks are biennial and not perennial. Some people consider them perennial because they do tend to come back year after year. However, when they come back after they flower and set seed they do not come back in the same place. What happens is birds move the seeds around and they re-sprout in a new location, and as a biennial, grow a short plant like the two on the right in your garden photo, then go dormant that winter and regrow and flower in the second year. Usually when they come back in a new spot they will not resemble the original parent, often changing colors due to hybridization with the flowers cross pollinating with other hollyhocks.
As to why one flowered and the others did not, it is possible that of the plants you bought only the one that flowered was in its second year. The ones that remained shorter and did not flower were probably in their first year of growth and will flower next year.