The most critical factor for successfully planting different succulents together is ensuring they share the same fundamental environmental requirements. From a plant's perspective, its primary concerns are light, water, and soil. Succulents from similar native habitats (e.g., arid deserts vs. semi-shady cliffs) have evolved to thrive under comparable conditions. Grouping a high-light, drought-tolerant Echeveria with a lower-light, moisture-preferring Haworthia would create an unsustainable conflict. The Echeveria would etiolate (stretch) and potentially rot if watered to satisfy the Haworthia, while the Haworthia would scorch and desiccate under the intense light the Echeveria craves. Therefore, compatibility is determined by aligning these core physiological needs.
Water is a central concern for succulent roots. Different species have varying capacities for water uptake and storage, and their roots are adapted to specific wet-dry cycles. Planting a fast-drying, shallow-rooted Sedum with a deep-rooted, water-retentive Aloe presents a problem. To adequately water the Aloe, the soil must remain moist at a deeper level for longer, which can cause the Sedum's roots to sit in dampness, leading to rot and fungal infections. Conversely, watering only for the Sedum's needs would leave the Aloe chronically underwatered and unable to access sufficient moisture. A harmonious arrangement groups plants with identical watering frequencies and soil moisture preferences.
Succulents compete for space, both above and below the soil. Their growth habits must be considered to avoid one plant overwhelming another. There are two main types: clumping growers (like Sempervivum or many Aloes) that produce offsets around a central point, and solitary or trailing growers (like Echeveria or Sedum morganianum). Placing a rapid, ground-covering clumper next to a slow-growing solitary rosette will result in the faster grower quickly colonizing the entire pot, shading and crowding out its neighbor. The root systems will also compete for space and nutrients, potentially stunting the growth of the less aggressive plant. A successful combination accounts for growth speed and form, allowing each plant adequate room to develop without excessive infringement.
Many succulents have distinct dormancy periods, typically in summer or winter, where their growth slows or stops entirely. During dormancy, a plant's water and nutrient requirements drop significantly. Co-planting a summer-dormant succulent (like some Aeoniums) with a winter-dormant one (like many Cacti) creates a problematic mismatch. When the summer-dormant plant needs very little water, its winter-dormant partner may be in its active growth phase and require more hydration. Watering to satisfy the active grower could drown the dormant roots of its neighbor, making it highly susceptible to rot. Grouping plants that share the same dormancy cycle ensures their seasonal needs are synchronized.
All succulents demand excellent drainage, but the specific composition can vary. The universal need is for a gritty, porous, and fast-drying medium that prevents water from pooling around the roots. While a standard cactus and succulent mix is a good base, some species prefer even grittier substrates (like Lithops), while others can tolerate a slightly more moisture-retentive mix (like some Sansevieria). Planting species with divergent soil preferences forces a compromise that may not be ideal for either. The soil must be mixed to suit the needs of all inhabitants, often leaning towards a faster-draining formula to err on the side of caution against overwatering.
