Growing culinary herbs can be a profitable niche market, but not much research has focused on growing culinary herbs on a commercial-scale in our area. Most of the information in this primer is from available research, as well as from Tony Ricci of Green Heron Farm in Three Springs, PA and Deb Brubaker, Jackie Swihart and Allison Glick of Village Acres Farm and Foodshed in Mifflintown, PA.
Getting Started
Do your research and establish a market before planting. Herbs are very labor intensive, particularly in planting and harvesting. Start out small and let your market help determine your packaging. For wholesale markets, herbs can be packaged in boxes whereas for direct markets, bags and clam shells are more common.
Many growers select cultivars based on experience. Having done some marketing research will also be helpful in determining what to grow. Seed catalogs are a good resource for studying the characteristics of various herb cultivars. As with other crops, disease resistance or tolerance is an important consideration.
Plants and Planting
A mix of direct seeding and transplants are used to start herbs. Cilantro and dill can be started by seed; however, transplants can also be used for these herbs. Many herbs are started from transplants to get a good stand or when soil conditions are not favorable for germination, (for example, dry and shaley). Additionally, some perennials, such as members of the mint family, are not true-to-type from seed and are vegetatively propagated to maintain the desired characteristics.
In general, herbs are grown similarly to other vegetable crops. Raised bed production systems are common. At Village Acres Farm, herbs are grown outside or in high tunnels, depending on the herb. Basil, rosemary, thyme and fall parsley are grown on bare ground perennial raised beds using drip irrigation in high tunnels. Dill and cilantro are grown in fields outdoors. In the summer, herbs at Green Heron Farm are grown outside. Green Heron Farm also uses a plasticulture system with raised beds, one or two drip irrigation lines and black plastic mulch. A thick layer of straw mulch is placed between rows to suppress weeds and add organic matter to the soil. Research at North Carolina State University found that using black plastic mulch results in high yields and clean product. While the straw mulch helps manages weeds, slugs can become a problem. Fresh wood mulches may decrease yields compared to black plastic mulch and straw mulch.
At Green Heron Farm, perennial and biennial herbs are produced in the same way annual herbs are: in a plasticulture system. At the end of the growing season, the plastic mulch is removed. With this method, weeds are suppressed until the herbs can get established. Removing plastic mulch can be tricky for certain herbs, such as oregano, because it has a mat-like growing habit. Experimenting with biodegradable mulch may be a possible solution for such cases. Many perennial and biennial herbs can also be treated as if they were annuals, an approach that can help with both weed and disease management. Treating some herbs as annuals can also help with crop planning and timing. Many perennial herbs start to grow in the very early spring, and the plants tend to flower early on in the season. When grown as annuals, it’s possible to delay flowering until later in the season.
Annual herbs including basil, dill, cilantro and sweet marjoram are succession planted because these herbs bolt. At Village Acres Farm, succession planting on a 2-4 week schedule is used for herbs including dill and cilantro. Three to four plantings of basil are made over the growing season. Parsley, a biennial, can also be succession planted.
High tunnels and row covers can be used to extend the season for annual herbs. They can also be used for rosemary, a perennial sensitive to low temperatures. A 3-year-old rosemary is growing in a high tunnel at Green Heron Farm and a 5-year-old planting is growing in a high tunnel at Village Acres Farm. The key is to avoid overwatering.
Other Important Production Considerations
The target soil pH for growing herbs is 6.5 and the optimal range is between 6.0 and 6.8. Penn State’s Agricultural Analytical Services Laboratory has a recommendation of 35 lb/acre nitrogen for most herbs. With an additional 35 lb/acre nitrogen sidedressed 4-5 weeks later for chervil, fennel, lovage, parsley and summer savory. Phosphorus and potassium recommendations are based on the amount of these nutrients existing in the soil.
Irrigation is necessary because periods of drought are a problem. As Tony from Green Heron Farm says, “Irrigate, or don’t grow herbs.” At these two farms, as well as for herbs grown at Penn State’s horticulture research farm, drip irrigation is used. If possible, don’t water herbs overhead. Some herbs including rosemary and thyme, are sensitive to overwatering and keeping leaves dry helps avoid having certain disease problems.
It is important to harvest herbs when leaves are dry. This is after the dew dries in the morning, but before the heat of the day when plants can wilt. If temperatures are high, pick in stages to bring herbs into a cooling area. To maintain the shelf-life, handle herbs as little as possible.