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Sunday, March 24, 2024

Summer lilac, Buddleja davidii

Summer lilac, or Buddleja davidii, is a versatile and widely cultivated plant known for its attractive blooms that draw in butterflies. Originating from China and possibly Japan, it's a species with a large range of variability, reflected in its alternative name, B. variabilis. This plant can vary from a small sub-shrub to a large spreading shrub or even a small tree with deeply fissured brown bark. The leaves also show a range of sizes and shapes, from large, elliptic dark green to small, narrowly ovate and glaucous leaves, typically with a white tomentose underside. In temperate regions, it's generally semi-deciduous, with the extent of leaf retention over winter depending on both the environmental conditions and the cultivar​​.

Cultivation-wise, Buddleja davidii is appreciated for its ornamental value and the nectar provided by its flowers, which attract numerous butterfly species. However, it's noteworthy that the plant doesn't offer nourishment for butterfly larvae, and there's a concern that it might out-compete the host plants required by caterpillars. The plant and its cultivars thrive in USDA zones 5–9 and cannot withstand the severe winters of northern or montane climates, as temperatures below about -15 to -20°C (5 to -4°F) can be lethal. Pruning in spring is common practice to encourage more floriferous new growth. Despite its beauty and utility in attracting butterflies, Buddleja davidii is considered invasive in several temperate regions due to its capability to spread rapidly in disturbed soils and urban areas​​.

In response to its invasive nature, horticulturalists have developed several "non-invasive" cultivars of Buddleja, designed to either be sterile or produce a minimal amount of viable seed. These cultivars come in various sizes and blossom colors, offering alternatives for gardeners and landscapers who wish to enjoy the benefits of Buddlejas without the associated risks of invasiveness​​.

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