It doesn't look like what it is named for, but the butterfly bush (Buddleja davidii, USDA plant hardiness zones 5-9) is well liked by butterflies, bees and hummingbirds. Like other plants, it can be vulnerable to environmental problems or insect infestations. Butterfly bush problems can appear as curled leaves, few or no flowers and brown wilted leaves. When you don't control these diseases, these deciduous shrubs can get spread out significantly, which has resulted in them being categorized as a noxious weed in Washington and Oregon.
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Butterfly Bush Leaves
The butterfly bush is a perennial plant native to thickets on rocky stream banks, mountain slopes, forest clearings and limestone outcrops in China. It can get to be 6 to 15 feet high and 4 to 15 feet wide and is known to have a bushlike growth with graceful, arching stems and pretty, fragrant flowers. The leaves are 6 to 10 inches long, sage-green colored on top and white and wooly on the bottom. The leaf shapes can be elliptic (an elongated circle) or lanceolate (narrow oval, tapering to points at the ends), with finely toothed edges.
The attractive flower clusters appear in the early to late summer and form into dense, cone-shaped clusters that can be 6 to 18 inches in length. Ones that grow in the wild can be lilac to darker purple with orangish-yellow throats, but named cultivars can be red, yellow, pink or white. The smell is sweet yet mild, and butterflies love them.
Butterfly Bush Leaves Curling Up
Butterfly bush leaves can curl up for a few different reasons, and not all are that concerning or indicative of more severe issues. For example, if you have new leaves, they are at their most vulnerable and will typically survive well in cold weather. These smaller specimens may curl up as a protective measure when temperatures are too cold, which is generally below 25 degrees Fahrenheit. These plants can tolerate light freezes and bounce back, but you might want to cover them or bring potted ones indoors when a frost is expected.
Butterfly bushes should be watered well during their early spring growth seasons and often during dry spells. If the curled leaves appear brown and shriveled, the plant may be dried and may simply need a good watering. If the leaves look shriveled but are still green, it could be a reaction to an herbicide that you used on them.
A Butterfly Bush With Yellow Leaves
Insects like aphids can attack these bushes, causing issues like butterfly bush leaves turning yellow or showing tiny brown spots. The plant will often employ its defensive curling-up mechanism when these infestations occur; it is common for the leaves to fall off too. These insects are tiny, but you can still see them if you look hard enough. They can be red, yellow, white, pinkish, gray, orange, black, green, brown or white and are oblong with a wider base.
Mealybugs produce the same symptoms but look like cotton balls; these pests absolutely love young butterfly bush leaves. They hang out on those surfaces but also on stems, trunks and roots. You can spray off aphids and mealybugs with a garden hose or use natural neem oil, insecticidal soap or horticultural oil to get rid of these pests. Another option is to use a homemade spray from 1 tablespoon of mild dish soap, 1 tablespoon of vegetable oil and 1 cup of water.