Selecting a healthy Lobelia plant, whether an annual (Lobelia erinus) or a hardy perennial variety (like Lobelia cardinalis or Lobelia siphilitica), requires a keen eye for the plant's overall vitality. Here is a detailed guide from a botanical perspective on what to look for.
The leaves are the primary organs for photosynthesis and a clear window into the plant's well-being. Inspect the foliage thoroughly. Healthy Lobelia should have lush, green leaves that appear turgid and vibrant. Avoid plants with yellowing (chlorosis), browning, or wilted leaves, as these can be signs of overwatering, underwatering, nutrient deficiencies, or root rot. Carefully check the undersides of leaves and the points where they attach to the stem for any signs of pests like aphids, whiteflies, or spider mites. The presence of sticky residue (honeydew) or fine webbing is a major red flag.
Examine the plant's architecture. The stems should be sturdy and green, not leggy, spindly, or weak. A healthy Lobelia should have a bushy, well-branched form with multiple growing points. This indicates it has been grown in conditions with adequate light, preventing etiolation (stretching for light). Avoid plants that are already flopping over or appear overly tall and sparse, as they may not establish well in your garden. Gently brush the plant; if a significant number of leaves or buds drop off easily, it may be stressed.
While a plant in full, glorious bloom is tempting, it is often better to select a Lobelia that has more buds than open flowers. A plant with a profusion of unopened buds is poised to continue its blooming performance in your garden after it has acclimated to its new home. A plant that is already covered in spent blooms may be nearing the end of its flowering cycle. For perennial types, energy is being diverted from root establishment to sustaining existing flowers. Look for vibrant, newly opened flowers and a high bud count for a longer display.
If possible, gently slide the plant out of its nursery pot to inspect the root ball. This is crucial. Healthy roots are typically white or light tan in color and feel firm to the touch. They should be well-distributed throughout the potting mix but not forming a tight, dense mat around the outside (root-bound). A root-bound plant may struggle to establish itself. Conversely, roots that are dark brown, black, mushy, or emit a foul odor indicate root rot, often caused by overly saturated soil, and the plant should be avoided entirely.
The growing medium can tell you a lot about the plant's recent care. The soil should be moist but not waterlogged. Soggy soil promotes root diseases, while bone-dry soil indicates neglect and that the plant has been severely stressed. Look for any signs of algae or moss growing on the soil surface, which is another indicator of consistent overwatering and poor air circulation around the roots. Ensure the pot has functional drainage holes.
