Here’s how he approaches late-season gardening, and his suggestions for the best flowers to plant to get us past the summer doldrums. Here, the eight best flowers to grow in late summer. “It’s a really good plant because it seeds all around, but not too much, and has wonderful blue flowers,” he says. Culver’s Root, Veronicastrum virginicumAlex Manders // Getty ImagesCulver’s root is another of Hayden’s summer favorites, and “a good example of a Piet plant,” he says. Million Bells, CalibrachoaFaina Gurevich // Getty ImagesAnd some classic summer annuals remain Hayden favorites, because they’re reliable, “tried and true.”