Parsley (Petroselinum crispum) is a flavorful herb typically grown as a culinary annual. Starting parsley seeds indoors is necessary due to their famously slow and erratic germination, which can take anywhere from two to four weeks. This extended period, often attributed to natural chemical inhibitors within the seed coat, necessitates giving the plants a head start for a substantial harvest.
Determining the Ideal Starting Time
The primary factor in calculating the indoor start date is your local average last expected frost date. Gardeners should aim to sow parsley seeds indoors approximately eight to twelve weeks before this date. This timeline accounts for the herb’s slow germination phase, allowing the young plants enough time to develop into robust seedlings. Counting back ten to twelve weeks provides a reliable window. Starting seeds earlier is generally unnecessary and can be detrimental, as seedlings that spend too long indoors often become leggy or weak.
Essential Preparation and Planting Mechanics
To counteract the natural dormancy of parsley seeds and accelerate germination, pre-soaking the seeds is highly recommended. Submerging the seeds in warm water (around 110°F) for 24 hours helps to soften the tough outer seed coat. This process leaches out the germination-inhibiting furanocoumarins.
Once soaked, sow the seeds into sterile seed-starting mix in trays or small pots with good drainage. Plant the seeds shallowly, covering them with only about one-quarter inch of the mix. Maintaining consistent moisture is paramount throughout the germination phase.
The optimal temperature for encouraging germination is a consistent warmth between 70°F and 75°F. Using a seedling heat mat beneath the trays can help maintain this soil warmth. The soil must be kept evenly moist until the seedlings emerge, which may still take several weeks.
From Seedling to Garden
Indoor Care
As soon as the first seedlings emerge, they must be immediately moved into an environment with strong, direct light. Parsley requires a minimum of six to eight hours of bright light daily to prevent them from becoming spindly and weak. If a sunny, south-facing window is unavailable, using a supplemental grow light placed above the plants is necessary to promote compact, healthy growth.
After germination, the ideal growing temperature is slightly cooler, typically between 60°F and 70°F. Watering should be done carefully to keep the soil moist but never waterlogged, as excess moisture can lead to root rot or damping off.
Hardening Off and Transplanting
Before moving the young plants permanently outdoors, they must undergo a gradual transition known as hardening off. This process, which takes seven to ten days, toughens the foliage against direct sun, wind, and fluctuating temperatures. Begin by placing the seedlings in a sheltered, shaded outdoor spot for only one to two hours on the first day.
Each subsequent day, gradually increase the duration of their time outside and their exposure to sunlight and wind. This slow acclimation minimizes transplant shock.
Transplanting should only occur after all danger of the last spring frost has completely passed. The seedlings should have developed several sets of true leaves and be sturdy enough to handle the outdoor environment. Parsley develops a long taproot, so transplanting must be done carefully to avoid root disturbance, which can cause the plant to prematurely send up a flower stalk and end its productive leaf-harvesting life.