Summarize this article:

Wait until the soil is dry before you water lavender. When you do water, water for several minutes to make sure the roots get completely soaked. If you live in an area where it rains frequently during the summer, skip waterings when the ground is wet. Lavender doesn't need to be fertilized more than once a year. In early spring, work some bone meal mixed with compost into the surface of the soil around the lavender, then give it a deep watering. Over fertilizing lavender will cause the plant to grow poorly, rather than having the effect you want. All year round, check the plant for dead or dying shoots and remove them promptly with a pair of sanitized pruning shears. Prune the entire plant back by 1/3 in early spring, before the new growth emerges, to tidy the shape of the plant. Pruning encourages healthy new growth to emerge. The lavender shrub will get bigger and thicker as it ages, producing more flowers every season. The first season may not yield more than a bunch or two. By year three, you should have several bunches per season. When the lavender flowers just begin to open, usually in early summer, gather the lavender into a bunch (one bunch is about a handful of stems) and cut the stems. The plant will produce another flush of flowers before the end of the growing season. When you harvest flowers, avoid cutting into the woody part from which the shoots emerge. Cutting this part will damage the plant. Lavender stems may be kept in a vase filled with fresh water. To dry lavender, cut stalks before the flowers open, as soon as the buds turn purple. Tie a bunch using a rubber band and hang it upside down in a dark, dry place for about a week. The lavender flowers may be used in baking and savory recipes, for crafts, or to make essential oil.
Water lavender deeply but infrequently. Fertilize lavender in early spring. Prune lavender. Harvest the flowers.