PlantFiles: Monarch Rosemallow, October Rose, Ruby Hibiscus
Hibiscus radiatus

Positive:
Easy to grow
easy to propagate by cuttings
Gorgeous blooms in fall

Negative:
gangly plant almost always tips over at the soil line, even if kept pruned
stake plants grown for their height of 15 feet
each bloom opens at dawn, closes by 4pm, once
self seeds like crazy
big plant = big dead stalk to clear after frost/freeze
drying seed pods identical to unopened bloom--careful not to trim off buds
PRICKERS--the seed pods are covered with break away tiny prickers

I have not grown this plant. Hibiscus radiatus is often confused with Hibisus cannabinus so I have completed research in an attempt to find distinguishing characteristics that differientiate the 2 plants. Hibiscus radiatus is an allotetraploid of Hibiscus cannabinus and perhaps Hibiscus surratensis. The term allotetraploid refers to an organism that contains four complete copies of the genome, but two (and rarely, one) of the copies are from a different species than the other two copies. H. cannabinus leaves and calyx lobes are glandular and has epicalyx (a series of bracts subtending and resembling a calyx) segments attached to the calyx which are not characteristics of H. radiata. H. cannabinus has an elongate nectary gland at the base of the lower leaf midrib and on the midvein of each calyx lobe as well as a whitish tomentellum on the calyx which H. radiatus does not have. H. radiatus has a tooth-like appendage below the apex on the inner surface of the epicalyx bractlets which is not present on H. cannabinus.. H. radiatus has 3 to 3.5 inch across; whereas, H. cannabinus blooms are 4 to 6 inches across In many references, H. cannabinus is said to grow a little over 3 feet tall; however, in cultivation, it can grow 6 to 8 feet tall. In cultivation H. cannabinus can grow 12 to 15 feet tall. Both can have cerise-pink (mauve-pink, burgandy-pink) that have a dark center. H. radiatus var. flore purpureo is one with rose-purple petals. I have grown H. cannabinus. Judging from photos that I know correctly identify H. radiatus, the leaflets of H. radiatus appear to broaden more in their middle sections as compared to H. cannabinus leaflets. The above information has been gathered from various scientific resources on the internet. Many websites I believe have misidentified H. cannabinus as H. radiata and vice-a-versa. I do not have any books which include detailed descriptions of H. radiatus nor H. cannabinus. Please let me know if any of the above information is incorrect and please add information that may be of assistance with the identification of H. radiata and H. cannabinus.

Note: Hibiscus radiatus is deer resistant due to the tiny thorns on the undersides of its leaves and along its stems.

This is an EASY to grow shrub that propagates EASILY from cuttings - even green stem cuttings will live with little effort! The flowers are beautiful - amazingly deep burgandy red and the plants are covered with them in the fall (zone 9). These grow fast enough to plant in spring and have plants over 10' high by fall and covered with blooms.

Negatives: The seed pods have tiny, clear, barb-like thorns in them that will get ALL OVER YOU and stick in your skin and break off when you try to get them out. Wear not only gloves but GOGGLES, LONG SLEAVES, ETC and don't try to open the seed pods in a windy place or those thorns will be all over you.

These also will spread rampantly from seeds. One bush last year produced so many babies, we had to pull them up like WEEDS. If you leave them too close together they will be too tall and the wind will break them. Space them AT LEAST 2 feet apart or more! Keep the top trimmed during the summer to promote more of a bush than a tall stem to keep the wind from breaking them.

Even with the negatives - I love these plants - they are a show-stopper when in full bloom in the fall!