Citrus — 30 species

Citrus encompasses the fragrant fruiting trees and shrubs grown indoors and on patios worldwide — lemon, navel orange, sweet orange, and the compact calamondin (x Citrofortunella microcarpa) among them. They demand the most light of almost any houseplant: a minimum of six to eight hours of direct sun daily, supplemented by grow lights in lower-light climates. Water deeply and allow the top inch of soil to dry between waterings; container-grown trees are prone to both underwatering and root rot. All Citrus species are toxic to cats and dogs — the essential oils limonene and linalool, plus psoralens found in the peel and leaves, cause vomiting, diarrhea, and depression.