Native to northern Turkey and Russia, Siberian iris isn’t bothered when the thermometer drops below zero. These super-reliable perennials put on a spectacular spring show of fleur-de-lis shape blue, purple, lilac, yellow, or white flowers. The plants grow 3-4 feet tall and produce thick clumps of dark green, straplike leaves. Siberian iris prefers a rich, slightly moist soil, yet it will still look good even during drought. It’s also more resistant to iris borer than it’s slightly showier co...