San Jose is just as bad. Beautiful temperatures to live in, but not for rooting roses. Tom Liggett studied how Sequoia propagated roses and tried to copy it at his place in old San Jose. I warned him it was too cold and damp, but he had to see for himself. EVERY cutting rotted. Cold and wet permits the cutting to just sit there doing very little while pathogens "eat" them. Hot with high humidity pushes their cellular activity, speeds their growth tremendously so they callus and root, while the high heat inhibits rot. I discovered this when volunteering at The Huntington propagating roses for their sales and gardens. Cuttings would just sit in early spring or in weather like what it was in spring. Warmish days with cooler nights would slow them down so many would rot. Those which did root, took weeks to callus. But, once the days were in the nineties and above and evening temps remained around seventy or above, and most roses rooted in seven to ten days. This was an outdoor mist table, exposed to full southern sun and open above it. Three sides were protected by lathe so the air flow was excellent. Wind would frequently blow the mist off the table, but the cuttings rooted right down the line. The same varieties struck in winter and held in the orchid greenhouse (they turned the mister off in winter to prevent freezing) took three to four months to root. Strike them in summer and the same roses rooted in a week. No kidding!
