I have attempted to find out how long (or much) the species Rosa wichurana blooms but only find very vague answers. Is there an approximate period and length of time of bloom, or is this locality dependent?
Locality and intensity of the season dependent, just as it is with many “species”. For instance, along the coast here, Banksiae can flower up to six or seven months because the weather remains “spring-like.” Inland, just a few miles, it may only flower for six weeks, some years only about three, depending upon how long “spring” weather lasts. When I grew Wichurana, it could flower for just a few weeks, or it could last six to eight, depending upon the weather. And, some years, when it would turn summer, get very hot, then cool of and begin to warm again, it would “rebloom.”
I noticed the same thing with Nigel Hawthorne, Arkansana Peppermint and a number of of species and species hybrids at the coast. What appeared to be “rebloom” was really the extension of the “once flowering” period. Obviously, it was dependent upon the weather as the same roses in my garden, more inland, flowered for just a few weeks then stopped until the following year.
I thought this might be the case, but I have 3 plants of the thornless R. wichurana, all from different sources, and while they all bloom for an extended amount of time, one of them has bloomed from the end of June to just this week. I saw the last flower on it turn pinky/brown just yesterday (mid-October). They are side-by-side, facing south down a slope in the same planter with the same soil and the same watering. They are starting to entwine and I will not be able to tell them apart this time next year, and they have grown already to 10-12 ft (they have plenty of room if the rodents do not interfere) from being planted in late July. From what I see on HMF, they do become monsters, but if they bloom this long, so what?
Personally, if the one plant performs so much better than the other two, I’d consider removing the two under achievers and concentrating my efforts (and resources) on the potentially mutated one. Even if it doesn’t pass on any greater repeat tendency, the landscape value of a longer flowering period outweighs anything else in my opinion.