Lemon verbena has the most intensely lemony scent of any herb — far sharper and more persistent than lemon balm or lemon thyme. The long, pointed leaves are used in teas, sorbets, cocktails, and as a finishing herb. In Zone 6b it must be grown as a container plant and overwintered indoors; it drops its leaves in response to cold, looking dead before bouncing back in spring warmth.
Bring indoors before first frost and keep barely moist in a cool, bright spot. It will drop most or all of its leaves — this is normal. Prune back hard in late winter, bring into warmth, and resume watering; new growth emerges reliably.
Spider Mites
Fine stippling or bronzing on leaves, faint webbing on undersides, foliage drying out during hot, dry weather.
Spray foliage with a strong jet of water to dislodge mites. Apply insecticidal soap or horticultural oil to leaf undersides; repeat every 5–7 days as needed.
Powdery mildew
White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.
Aphids
Clusters of small soft insects on new growth and flower buds.
Knock off with a strong jet of water. Ladybirds and lacewings are natural predators. Insecticidal soap as last resort.
Thyme Root Rot
Stems blacken at the base, foliage yellows and wilts, and roots turn brown and mushy. Common in heavy or poorly drained soil.
Remove affected plants and avoid replanting thyme in the same spot. Improve drainage with grit or raised beds, and water only when soil is dry.