Starting herbs from seed indoors provides access to a wider variety of plants than purchasing nursery seedlings. This method is also significantly more cost-effective, allowing a gardener to produce many plants for the price of one or two mature specimens. Successfully growing herbs from tiny seeds requires careful attention to environmental conditions and specific steps. This guide covers the preparation, planting, nurturing, and eventual transplanting of your herbs.
Essential Preparation and Supplies
Before planting, gathering the correct supplies is necessary. Select high-quality seeds, noting their specific germination requirements; for example, rosemary prefers drier conditions, while basil thrives with consistent moisture. The growing medium is important, and garden soil should be avoided because it compacts easily and may contain pathogens. Use a sterile, lightweight seed-starting mix, typically composed of peat moss, perlite, or coir, which offers the ideal balance of aeration and moisture retention.
Containers must include drainage holes to prevent waterlogging. Ensure containers are clean and sterilized, perhaps by washing them in a diluted bleach solution, to eliminate disease spores. A clear plastic dome or plastic wrap is necessary to maintain high humidity for the initial germination phase.
Sowing Techniques and Initial Germination
Sowing generally occurs indoors six to eight weeks before the last expected frost date, depending on the herb and climate. Planting depth is typically twice the seed’s diameter. However, many tiny herb seeds, such as oregano, dill, or thyme, require light to germinate and should simply be pressed onto the soil surface rather than covered.
After planting, gently mist the surface or use bottom watering to moisten the soil without disturbing the seeds. Bottom watering involves setting the tray in water for 15 to 30 minutes, allowing the soil to wick up moisture. Covering the container with a humidity dome traps moisture, which is necessary for triggering germination.
The ideal germination temperature for many common herbs is around 65°F to 75°F. Consistent warmth and moisture are necessary for breaking seed dormancy, but light is generally not required at this stage. Once the first sprouts emerge, the plastic cover must be removed immediately to prevent fungal issues like “damping off.”
Nurturing Seedlings Indoors
Once the seeds have sprouted, the focus shifts to providing conditions necessary for robust growth. Young seedlings require significant light; a sunny windowsill is often insufficient, leading to weak, leggy plants. Supplemental grow lights, such as LED or fluorescent fixtures, positioned a few inches above the seedlings, provide the required intensity.
The lights should run for 14 to 16 hours per day to mimic summer conditions, and fixtures must be adjusted upward as the seedlings grow. Temperature management is also important; most herbs thrive between 60°F and 70°F after germination. This cooler temperature encourages stockier, healthier growth instead of rapid stem elongation.
The watering regimen must be adjusted as the plants mature, moving to deeper, less frequent watering. Allowing the topsoil to dry slightly between waterings encourages downward root growth, strengthening the plant. When seedlings develop their first set of true leaves, it is time to thin the tray. Snip the weaker seedlings at the soil line, leaving only the strongest plant in each cell to prevent competition.
Hardening Off and Transplanting
“Hardening off” is the process of moving seedlings outdoors, requiring a 7-to-10-day acclimation. Indoor-raised seedlings are vulnerable to sun scorch and wind damage if moved directly outside, as they are accustomed to constant temperatures and filtered light. This transition helps plants develop a thicker cuticle layer and strengthens cell walls, increasing tolerance to environmental stressors.
The process begins by placing seedlings in a protected, shady location out of direct wind for one to two hours on the first day. Each subsequent day, increase the exposure time and gradually introduce the plants to more direct sunlight. After about a week, if nighttime temperatures remain consistently above 50°F, the herbs can be left outside overnight.
Once hardening is complete, the herbs are ready for transplanting into their final location. The final planting site should have well-drained soil, as most herbs suffer from root rot in waterlogged conditions. When transplanting, gently loosen the soil around the seedling’s root ball before placing the plant into a prepared hole at the same depth it was growing in its container.