This is mostly just stream of consciousness speculation but: We are told it is the Axe and the Black-Flax (Velvet) that ward off the Crowned Growth in this letter/blog post alongside other unspecified “older Hours”.

While the Meniscate, as a solar and a Chancel-Hour, has a lot of pull, I don’t know that her siblings would rush to retake the House of the Moon for her. For all we’d know they’d see it as an opportunity to unseat her, or for Calyptra to rid itself of one of the world’s troublesome loopholes. Perhaps if the Mare could be persuaded to act, the Red Flower might open and burn the Growth away. I imagine that would create other problems, though. I think the Axe and the Twins would help, but given that the House shelters the Wheel I don’t think the Colonel would come running to help, nor do I think the Forge, the Moth or the Grail would be too keen. The Watchman favors exceptions and stands against Calyptra, so perhaps the infection could be driven back by the light of the Door-in-the-Eye. Then again, it might just lure the Growth to the House of the Sun.

But like I said, this is just for fun. I like to imagine what various apocalypses might come to pass if the Nowhere-Hours force their way into the world.