Catnip is a perennial herb in the mint family, grown for its grey-green aromatic foliage, which attracts cats and pollinators alike. The leaves carry nepetalactone, the compound that sets cats rolling, and the plant has a long history in herbal teas. The white-to-lilac flower spikes in summer are busy with bees, and the leaves are a mild repellent to some garden pests.
It is easy to the point of weedy. Sow or plant in spring in full sun or part shade, in average to poor soil that drains, 18 to 24 inches apart, and water only until it is established. Like other mints it spreads by seed and root runners, so plant it in a container or with a buried barrier, and cut it back hard after the first flowering for a second flush and to stop it seeding.
Neighbourhood cats will roll in and flatten a young plant; a cage of wire over it for the first season solves that. It reaches 2 to 3 feet and can be cut to the ground in late fall. Deer and rabbits leave it alone. The ornamental catmints (Nepeta faassenii and its cultivars) are tidier and bluer; this is the species to grow for the cats and the bees.
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.
Rust
Orange to brown raised pustules on the undersides of leaves, with yellow spotting on the upper surface. Heavy infections cause leaves to yellow and drop.
Remove and destroy infected leaves. Avoid overhead watering and improve air circulation. Apply a sulfur or copper-based fungicide if it spreads. Clear plant debris in fall.
Spider Mites
Tetranychus urticae →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.
Aphids
Aphididae →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.