How long do hibiscus seeds last in a bed?
About 6-8 years ago I bought 2 hardy deciduous hibiscus plants in pots from a local nursery, one pink flowered, the other red flowered. Within 2 seasons after planting them they'd become enormous, with between 22-30 stems per plant. There were so many and they were so heavy that the outermost stems would fall over, touch the ground, then grow straight upward from there.
They got lots of sun, so they didn't just grow a few flowers on the tops of each stem, they also produced lots of lateral branches from each stem, and there would be at least 5-8 flowers on each lateral branch as well. The flowers are huge at 10-12" diameter. So they produced amazing numbers of flowers for probably 6 weeks straight! But they also start blooming a little later than most varieties.
Anyway, these plants were so thick and wide and heavy that they grew very wide(8-10 feet diameter each), so they were falling into the sidewalks and driveway, and even with much staking and tying it was too much. So I dug both plants up and attempted transplanting, but as I dug them up I noticed how their roots grew about 2 inches below ground and spread out in all directions across the bed! I couldn't prevent severing these long thick roots, and they died later after transplanting.
But, then about 2 years later we start seeing new hibiscus seedlings popping up in the original bed, and in other nearby beds, so I finally decided to let 2 of them grow in 2 different beds, away from the walkways and driveway. It's been 2 seasons now that these 2 newer plants have been growing, and undoubtedly dropping hundreds of seeds everywhere, but I don't see any new hibiscus seedlings popping up yet.
Does it always take a few years for the seeds to finally grow, and how long will they remain viable sitting out in the flower beds, covered by new mulch each season? Also, anyone know the name of this variety that grows this large with 10-12" wide flowers?
Thanks in advance.