Evaluate your growing site. Choose a field of sandier, dryer soil over one with damp, clay-based soil, where possible. Higher elevations are preferable to lower ones.
Send soil samples to your local extension service for analysis. Lavender's reputation for thriving even in rocky, infertile soil is not unfounded, but it's critical to determine the pH level. Lavender prefers slightly alkaline soil, which is a pH level of 7.5 to 8.5.
Choose one or more lavender varieties. There are dozens of lavender species, and hundreds of cultivars, but the Washington State University Extension Service recommends the species Lavandula angustifolia, also known as "English lavender" or "true lavender." Cultivars within this species possess different merits for varying climates and uses, but in general the English lavender family is the hardiest and most fragrant.
Calculate how many seedlings you will need. Measure the size of your field, then figure on six feet between rows. When you know how many rows will fit in your field, figure a spacing of three feet between plants within the rows to give you plenty of harvesting options. Multiply the number of plants by the number of rows to determine how many seedlings you need to buy.
Order lavender plugs or seedlings. The herb's seed has a notoriously poor germination rate, so simply tilling the soil and broadcasting seed generally fails. Large orders of lavender "plugs" from wholesale growers cost much less than the per-seedling cost at a retail nursery.
Till or spade in 50 pounds of well-aged manure per acre. For smaller fields divide accordingly---25 pounds for a 1/2-acre field, and so on. While this step can be skipped, the small amount of nitrogen provided will get the seedlings off to a better start without making the soil overly rich.
Incorporate lime to raise the soil's pH level, if previous soil tests indicated overly-acid soil. The extension service will recommend how much lime per acre your site needs.
Install weed fabric, if you are using it. Most artificial mulches come in rolls; secure these to the ground with garden spikes or staples.
Prepare "starter fertilizer" in batches. This mixture will go directly into the planting hole. In a wheelbarrow or large container, blend four parts composted chicken manure, blood meal or cottonseed meal with one part bone meal.
If using a landscape fabric, make an "X" in the fabric large enough to dig a hole for each lavender seedling.
Dig a hole with a garden trowel. Make the hole slightly less than the depth of the plug or seedling, ensuring that the planted lavender will sit slightly higher than the surrounding soil.
Add 1 1/2 to 2 cups of the starter fertilizer mixture to each planting hole, and work it thoroughly into the soil.
Set the lavender seedling in the hole. Backfill soil into the hole and press firmly.
Repeat--and repeat and repeat! Work your way down each row, then move on to the adjacent row, taking care to check your spacing as you go.
If using gravel or other non-sheet mulch, spade between plants and between rows, if desired.