Lavender

Spread one to two inches of white sand around the plants, pulled back clear of the crown. Skip sawdust, wood chips, and heavy organic mulches. Heavy organic mulch holds moisture against the crown and feeds the fungal pathogens that rot lavender, and it raises insect pressure too. A light mineral mulch suppresses weeds and dries the crown fast after rain, which is the condition this Mediterranean plant is built for.

Lavender has very low nutrient needs. Work in about an inch of compost at planting, and give established plants at most one application of slow-release fertilizer, roughly a tablespoon per plant, for the whole season. Excess fertility pushes soft leafy growth at the expense of flowers, and that lush growth holds humidity in the canopy and makes the plant more vulnerable to disease. A hungry lavender flowers better than a fed one.

Wait until new green growth emerges from the base of the plant, then cut back one third to one half of the stem length all over. Always leave green leaves and live buds below every cut, and take out any stems that stayed brown and brittle through winter. Lavender is a woody subshrub that will not push new shoots from bare leafless wood, so a cut below the last live bud kills that stem permanently. Waiting for green growth also lets you see what actually survived the winter instead of guessing at dormant wood.

Newly transplanted lavender takes about 1 gallon per plant per week until established. Hold established plants at half a gallon every two weeks until flower buds form, then water one or two times per week from bud formation through harvest. Let the soil dry between waterings and go back to sparse watering once the flowers come off. Lavender is drought tolerant but sets more and better flowers with steady moisture while the buds are filling. The rest of the year, wet soil is the real threat, because Phytophthora root rot follows overwatering more reliably than any pest.

During hot muggy stretches, walk the planting and look for individual plants or single branches that wilt and brown while neighbors stay healthy. Dig out and dispose of affected plants, and do not replant lavender into that spot. Vascular wilt is lavender's most common killer, and it moves in hardest around 90 degrees and 90 percent humidity. It plugs the plant's water-conducting tissue from inside, so once a plant shows it there is no spray that saves it, and English types go down more readily than lavandins.

For dried bundles, cut whole spikes once the first few florets on the spike have opened, taking the stalk just under the first pair of leaves. For fragrance and oil, wait until about half the buds on the spike are open. Cut early in the day before full sun, then bundle 50 to 100 stems and hang them somewhere cool, dark, and airy. Essential oil concentration is highest early in the day before the sun drives it off, and buds cut before they are fully open hold their color and stay attached to the stem as they dry. Fully open spikes shatter.

Once flowering finishes, deadhead the spent flower spikes and lightly shape the plant back toward a mound. Take the spikes and the dead tips only, never cut into bare leafless wood, and do not cut the plant back hard. Deadheading and shaping after bloom keeps the plant compact instead of splitting open and going woody in the middle, and it encourages the plant to bloom again.