Flower Breeding and Genetics: Issues, Challenges and Opportunities for the 21st Century (2007) pp. 722‑723
By Neil O. Anderson
6.10 Recurrent Bloom
Non‑vernalization requiring roses that flower continually over the entire growing season are preferred by most rose growers. The market for roses that bloom prolifically for a short season in spring (once blooming), only after flower initiation is triggered by vernalization, has become increasingly small. Fortunately, the inheritance of recurrent bloom is relatively straightforward and is controlled by a major locus with recurrent bloom expressed in homozygous recessive genotypes (de Vries and Dubois, 1978 and 1984; Semeniuk, 1971a, 1971b). Complementation reveals that the same major gene governs recurrent bloom in hybrid china / hybrid rugosa crosses and crosses between the hybrid china descendant 'Goldilocks' and a recurrent flowering variant of R. wichuraiana (Semeniuk, 1971a, 1971b; Svejda, 1974). In addition, minor genes appear to be involved that regulate the expression of recurrent bloom. Some recurrent blooming roses tend to produce distinct cycles of bloom with relative synchrony (e.g. 'Therese Bugnet'), while others tend to be more free‑flowering with plants having at least some blooms open at most times during the growing season (e.g. 'Nearly Wild'). A more free‑flowering, recurrent habit is favored by most gardeners and commercial growers.
https://books.google.com/books?id=kHiAe ... &q&f=false
I first noticed this difference in flowering behavior between 'Mutabilis' and 'Mateo's Silk Butterflies' (Mutabilis seedling). 'Mutabilis' is as continuous flowering as any rose I've seen. In favored locations in California it flowered year-round, though there were fewer blooms in the winter. 'Mateo's Silk Butterflies', on the other hand, tends to bloom in distinct flushes. I don't care much for the pale, lavender-toned flowers, but there is something to be said for recurrent masses of bloom.
Last year my 'Paul's Scarlet Climber' bloomed nicely in the Spring, then put out only a bloom or three over the rest of the season. This year, however, it gave at least five flushes of bloom. The first one was the best, but the repeat flushes were much more impressive than a similar number of blooms scattered over the summer.
I think this synchronous flushing would be a particularly desirable trait for climbers, and for shrubs used in landscape plantings.
I'm anxious to know of other varieties that tend to "flush".