Greenhouse Temperature for Herbs

Reasons to Grow Herbs in a Greenhouse

• While a fresh supply of herbs is useful for a kitchen garden, fresh herbs also make a good cash crop. According to the Ohio State University Extension, local fresh herb suppliers are constantly on the lookout for organic farmers who can supply fresh herbs year-round. Since dried herbs are more potent than fresh herbs, those who cook with herbs need more fresh product to achieve the same flavor in the things that they cook. Typically 1 tsp. of dried herbs is equal to the potency of 3 tsp. of fresh herbs. Fresh herbs are also higher in antioxidants than dry herbs.

Herb Temperatures

• All herbs have an optimal temperature range in which they will thrive. This optimal temperature range varies based on the environment in which the herb grows in the wild. Herb seeds also have an optimal temperature at which they will sprout. This temperature may be different than the growing temperature. Most herb seeds germinate best if left covered in soil that is between 70 and 75 degrees Fahrenheit. The herbs themselves will grow well in temperatures that range from 65 to 70 during the day and from 55 to 60 at night.

Too Warm

• The optimal temperature for herbs varies from that of warm-season vegetables such as tomatoes. Because of this, the plants should not be kept in the same greenhouses. Herbs slow in growth, produce smaller leaves, fail to produce leaves, and may bolt (produce seed heads) if the temperatures are too warm. Perennial herbs may produce new leaves once the temperatures return to their optimal range for herb development.

Too Cold

• Tender herbs such as basil or tender lavender will often die if the temperatures in a greenhouse are too cold. Hardy herbs that are perennial will go dormant in cool temperatures and will cease to grow, drop leaves, or may even die back to the soil line until the temperatures warm again. Hardy herbs that die back will re-sprout from their roots once temperatures warm again.