Starting lavender from seed offers the satisfaction of growing this fragrant herb from its earliest stage, though it presents a unique challenge compared to using cuttings. Lavender seeds possess a natural dormancy mechanism, which means they will not sprout reliably without specific environmental cues. Successfully starting these seeds indoors requires carefully controlling temperature, light, and moisture, beginning with a preparation step that mimics the plant’s native winter cycle. This process ensures a robust start before the seedlings are ready to transition to the garden.
Necessary Supplies and Timing
Beginning the indoor process at the correct time is important for the seedlings to be ready after the last frost. Plan to start your lavender seeds approximately 10 to 12 weeks before the final expected frost date in your area. This early start provides the necessary time for the seeds to germinate, which can be slow, and for the seedlings to develop strong root systems.
You will need a few specialized items to create the ideal growing environment. Essential supplies include sterile, well-draining seed starting mix (neutral to slightly alkaline pH) and seedling trays or small pots. A clear humidity dome helps maintain consistent moisture during the initial germination phase. A seedling heat mat and dedicated grow lights are necessary to provide the consistent warmth and high light levels required for successful sprouting.
Preparing Seeds Through Cold Stratification
Lavender seeds require a period of cold and moist conditions, known as cold stratification, to break their natural dormancy. This process simulates the winter season the seeds would naturally experience outdoors, signaling that spring is approaching and it is safe to germinate. Without this step, germination rates are low and inconsistent.
A practical method involves using a paper towel or a small amount of sand as the stratification medium. Lightly dampen a paper towel so it is moist but not dripping wet, then evenly scatter the seeds across half of the surface. Fold the towel over the seeds, place it inside a resealable plastic bag, and label it with the date. Place the bag in a refrigerator, ideally maintaining a temperature between 35 and 41 degrees Fahrenheit, for three to six weeks.
Alternatively, mix the seeds with an equal part of damp sand or vermiculite, place the mixture in a small container, and refrigerate it. Throughout the stratification period, check periodically to ensure the medium remains lightly moist. This cool, wet exposure primes the seed, allowing it to proceed to germination once introduced to warmth and light.
Sowing and Initial Watering
After the stratification period is complete, you are ready to sow the seeds into your prepared containers. Fill your trays with the pre-moistened seed starting mix, pressing the soil lightly to remove any large air pockets. Lavender seeds are photosensitive, meaning they need light to germinate, so they must be sown on the soil surface.
Gently press the seeds onto the surface of the soil, ensuring good seed-to-soil contact without burying them. You can lightly dust the seeds with fine vermiculite or sand, which helps anchor them while still allowing light to penetrate. For the initial watering, use a fine misting bottle or bottom-water the trays to avoid displacing the tiny seeds. The soil must be kept consistently moist, but never waterlogged, and the humidity dome should be placed over the trays immediately after sowing to lock in moisture.
Managing Light and Temperature for Growth
Proper environmental control is necessary for successful germination and healthy seedling development. Place the seed trays onto the heat mat, setting the soil temperature to remain consistently between 65 and 75 degrees Fahrenheit, the optimal range for lavender germination. Position your grow lights above the trays, as the seeds require light immediately to begin the sprouting process.
Use full-spectrum LED or fluorescent grow lights positioned just two to four inches above the soil surface. The seedlings need an extended photoperiod, so maintain the lights on a timer for 14 to 16 hours each day. Once the first sprouts emerge, typically after two to four weeks, remove the humidity dome to increase air circulation and prevent fungal diseases like damping off.
Remove the heat mat once most of the seeds have germinated, allowing the seedlings to adjust to a slightly cooler ambient air temperature. Continue the long daily light cycle, raising the lights to maintain the two to four-inch distance as the seedlings grow. Reduce watering frequency slightly once the seedlings are established, allowing the top layer of soil to dry before watering again to encourage strong, drought-tolerant root systems.
Hardening Off Seedlings
Before transplanting your lavender seedlings outdoors, they must undergo a gradual acclimation process called hardening off. This procedure toughens the delicate indoor-grown plants, preparing them for the intense sunlight, fluctuating temperatures, and wind of the outdoor environment. Skipping this step often results in plant shock or leaf scorch.
Begin the hardening off process approximately seven to ten days before your intended transplant date. On the first day, place the seedlings in a heavily shaded, sheltered outdoor location for only one to two hours, then bring them back inside. Over the next week, systematically increase the amount of time they spend outside each day. Gradually introduce them to increased sun exposure, moving them from full shade to partial shade, and eventually to direct morning sunlight. This slow, controlled exposure reduces stress, allowing their cell structure to adapt before they are permanently moved into the garden.