While the terms are often used interchangeably, it is botanically accurate to state that all cacti are succulents, but not all succulents are cacti. Succulents are a broad category of plants that have evolved to store water in their leaves, stems, or roots to survive arid conditions. Cacti are a specific family within this group (Cactaceae) with unique adaptations. This fundamental taxonomic difference is the root of their care requirements.
The most critical botanical distinction is the presence of areoles. Areoles are small, cushion-like, specialized branching structures from which spines, flowers, and new stems grow. All true cacti possess areoles. The spines of a cactus are modified leaves that grow from these areoles. In contrast, the defensive structures on other succulents, such as the thorns on an Euphorbia or the sharp leaf tips on an Agave, are modified stems or leaves that grow directly from the plant's tissue, not from an areole. This is the definitive feature separating the two groups.
Most cacti have drastically reduced or completely absent true leaves to minimize surface area and reduce water loss through transpiration. Instead, they perform photosynthesis through their thick, green stems. Many other succulents, such as Echeveria, Aloe, and Jade plants (Crassula ovata), retain their fleshy leaves as the primary organ for both water storage and photosynthesis. This difference influences light needs; leaved succulents often require very bright, direct light to maintain compact growth and vibrant leaf coloring, while some forest-dwelling cacti (like Schlumbergera, the Christmas cactus) are adapted to filtered, indirect light.
Both types require a "soak and dry" method, but the timing and frequency can differ based on their growth cycles. Many cacti originate from environments with intense, infrequent rainfall and have a pronounced dormancy period, typically in winter. During this time, they require very little to no water. Other succulents may have less extreme or different dormancy periods (some are summer-dormant). A Haworthia, for instance, may need more frequent watering than a Desert Cactus because it is adapted to slightly more consistent moisture availability in its native habitat. Overwatering is the primary cause of failure for both, but cacti generally demand a more stringent dry period.
The requirement for excellent drainage is universal, but the ideal soil composition can vary. Cacti, having evolved in extremely well-draining, mineral-rich soils, often thrive in a mix with a higher proportion of inorganic materials like perlite, pumice, or coarse sand (e.g., a 50:50 organic to inorganic ratio). Many other succulents can tolerate a slightly higher organic content in their potting mix (e.g., a 60:40 or 70:30 ratio), as their native environments might include leaf litter or other organic matter. However, a fast-draining mix is non-negotiable for both to prevent root rot.
