Lupines, with their striking spires of densely packed flowers, are a beloved feature in many gardens, instantly lending a cottage-garden charm. These blooms stand tall above distinctive, palmate foliage, offering a vibrant spectrum of colors. Lupines are generally hardy plants that thrive with the right foundational care. Proper attention to their specific needs ensures these stunning perennials return year after year.
Site Selection and Planting
Lupines thrive best in full sunlight, especially in cooler climates. In regions with hot summers, filtered light or afternoon shade helps protect the plants from heat stress. The soil must be extremely well-draining to prevent root rot.
The ideal growing medium is a sandy loam with a slightly acidic to neutral pH, generally ranging between 6.0 and 7.0. Because lupines develop a long taproot, the planting area should be loosened deeply (12 to 18 inches) to accommodate growth and facilitate drainage. When planting transplants, do not bury the crown, as contact with wet soil can quickly lead to rot.
If starting lupines from seed, scarification is necessary, which involves slightly scratching or nicking the tough outer seed coat. This abrasion allows the seed to absorb water and signals germination. Scarification can also be achieved by soaking the seeds in warm water overnight before sowing. Seeds should be sown shallowly, about one-quarter inch deep, and kept consistently moist until the seedlings emerge, typically within 15 to 25 days.
Routine Watering and Feeding
Newly planted lupines require consistent moisture to help their deep roots establish themselves. Once established, they become more tolerant of dry conditions and only need water during periods of drought. When watering, apply moisture slowly and deeply at the base of the plant, allowing the top layer of soil to dry out completely between waterings.
Lupines belong to the legume family, meaning they fix nitrogen from the atmosphere using soil bacteria. This process enriches the soil, making additional nitrogen fertilizer largely unnecessary and sometimes detrimental. Applying a high-nitrogen fertilizer encourages excessive leaf growth at the expense of flower spikes.
If the soil is poor, a light application of a high-phosphorus fertilizer promotes strong root development and better flowering. A layer of organic mulch, such as straw or compost, helps retain soil moisture and keeps the roots cool.
Pruning for Appearance and Rebloom
Timely pruning, often called deadheading, is the most effective way to encourage a second flush of blooms. As the flowers on the tall, conical spikes begin to fade, the entire spent flower stalk should be removed. Using clean, sharp shears, cut the spike back to the next set of healthy leaves or lateral buds near the plant’s base.
By removing the fading flowers, you redirect the plant’s energy away from seed production, which prevents it from completing its life cycle prematurely. This energy is used to create new flower stems, often resulting in a smaller, secondary bloom later in the summer, especially in cooler temperatures. If you wish to collect seeds or allow the plant to self-sow, leave a few of the latest flower spikes intact to mature.
Lupines are often short-lived perennials, sometimes lasting only three to five years. Allowing some seed set can help ensure their continued presence in the garden. Once the growing season ends and the foliage begins to turn yellow or brown, the entire top growth should be cut back in preparation for winter dormancy.
Managing Pests, Diseases, and Winterizing
Lupines can be susceptible to common garden pests, most notably aphids and slugs. The lupin aphid, a distinct grayish-white variety, forms dense colonies on stems and flower spikes, causing the plant to wilt and leaving behind honeydew. A strong jet of water or an application of insecticidal soap manages these insects.
Fungal diseases like powdery mildew and root rot are also a concern, with poor air circulation and excessive moisture being the primary causes. Powdery mildew appears as a chalky white film on the leaves, and proper plant spacing can help prevent its spread. Root rot is best avoided by ensuring excellent soil drainage and being cautious not to overwater, especially in cool, wet conditions.
For gardeners in colder climates, preparing the plants for winter dormancy helps ensure their survival. Once the foliage has been cut back in the fall, apply a layer of organic mulch, such as straw or shredded leaves, around the crown of the plant. This protective layer helps insulate the roots and prevents the freeze-thaw cycles that can cause the plant to heave out of the soil.