Growing herbs at home offers fresh flavor and aroma, but success depends almost entirely on proper timing. Planting herbs is less about general seasons and more about pinpointing specific dates that dictate everything from seed germination to harvest. A slight miscalculation in your planting schedule can mean the difference between a lush, productive plant and one that struggles to survive. Understanding the precise relationship between your local climate and the herb’s specific needs is important for a bountiful yield.
Understanding Your Local Planting Window
The most fundamental piece of information for any gardener is the Last Expected Frost Date, which acts as the calendar anchor for nearly all outdoor planting decisions. This date is an average estimate of the final spring day when temperatures are likely to dip to 32°F (0°C) or below, which is cold enough to damage or kill tender plants. Knowing this date is paramount because it defines the safe window for moving frost-sensitive herbs outdoors. The broader concept of the USDA Hardiness Zone is also relevant, especially for perennial herbs. Hardiness Zones divide the country based on the average minimum winter temperature, determining whether a specific perennial herb can survive the cold and return the following spring. The frost date remains the practical trigger for when to start the growing season for all herbs.
Planting Timing Based on Herb Life Cycle
The optimal planting time shifts significantly depending on whether an herb is an annual, biennial, or perennial, a classification that describes its life span.
Cool-season annuals and biennials thrive in milder spring and fall temperatures and can be planted early. Herbs like cilantro, dill, and parsley can be sown a few weeks before the last frost date, as they tolerate some light chill. They prefer to mature before the intense heat of summer arrives. Cilantro tends to “bolt” or prematurely flower and produce seeds when temperatures rise, so an early start is necessary for a good leaf harvest. Parsley, which is technically a biennial, is often treated as a cool-season annual.
Warm-season annuals require consistently high temperatures and have no tolerance for frost. Basil is the prime example, as it needs soil temperatures of at least 60°F before it can thrive outdoors. This means planting basil, or transplanting its seedlings, should be delayed until all danger of frost is completely past, often one to two weeks after the last expected frost date. Exposing tender annuals to cold temperatures too early can stunt their growth or cause them to die back.
Perennial herbs, which live for more than two years, are best planted in the early spring or late fall. Planting established perennial plants or divisions in early spring allows their root systems to establish themselves before the summer heat stresses them. Hardy perennials like mint, chives, and oregano often emerge from the ground early in the spring, making them some of the first herbs to be available for harvest. Establishing woody perennials, such as rosemary and thyme, from cuttings or plants in early spring gives them a full season of growth to harden before their first winter.
When to Start Herbs Indoors vs. Direct Sowing
The choice between starting seeds indoors and direct sowing them outdoors influences the planting process. Starting seeds indoors gives gardeners a significant head start on the season, especially for herbs that are slow to germinate or require a long growing season.
For many herbs, including basil, oregano, and rosemary, seeds should be sown indoors approximately six to ten weeks before your last expected frost date. This timeline ensures the seedlings are a robust size, with two or three sets of true leaves, and ready for transplanting once the outdoor climate is safe. Transplanting these hardened-off seedlings outdoors must wait until the soil and air temperatures are appropriate for the specific herb. Tender warm-season herbs like basil should only be moved to the garden a week or two after the last frost date to prevent cold shock.
Direct sowing involves placing seeds directly into the garden soil, a method best suited for herbs that germinate quickly or do not transplant well due to a sensitive root structure. Herbs with deep taproots, such as dill, cilantro, and chervil, are prime candidates for direct sowing. These seeds should be sown directly into the prepared garden bed around the last frost date or slightly before for cool-season varieties. The timing for direct sowing coincides with rising soil temperatures, which is necessary for proper germination. This method bypasses the need for transplanting, which can otherwise trigger bolting or cause unnecessary stress on the young plant.