Bloomington, Indiana, certainly has an auspicious name for gardening purposes. The city, located about 50 miles south of the capital, resides near the center of the state. In spite of Bloomington's frigid winters, gardeners among the 72,000 residents can grow several varieties of hardy herbs year-round in their backyards.
Successful gardening starts with a good understanding of the local climate. On the U.S. plant hardiness zone map, which divides North America into regions based on their lowest expected winter temperatures, Bloomington falls into zone 5b, which can drop to a bone-chilling minus 15 degrees F. Many herbs cannot withstand such cold, and therefore could not reside outside during the winter months.
The Sunset Magazine Zone Map for the Great Lakes region provides more information about Bloomington's year-round climate. The city is in Sunset's zone 35, with a growing season from late April to late October. It rains in all seasons, and summers are often hot and humid. Winter lows are around 18 degrees, but arctic blasts can bring lows of minus 20. Some herbs that are sturdy enough to survive those arctic blasts may not be happy in the heat and humidity of Bloomington's summers. Perennial plants there need to be able to withstand a wide temperature range.
Selecting Herbs for Bloomington
When choosing herbs for southern Indiana gardens, the biggest consideration is ability to withstand the lowest temperatures. In most cases, too-high heat will result in tough, dry leaves that may not be very palatable, but the plant won't die as long as it gets enough water. Hardy perennial herbs likely to do well in Bloomington include thyme, sage, oregano, hyssop, yarrow, rosemary, garlic, burnet and sorrel. Annuals include chevril, parsley and arugula. Other annuals that enjoy heat and can grow sufficiently in the six-month Bloomington growing season include basil, chives (a perennial that can be treated like an annual) and dill.
Starting Herbs in Bloomington
Some herbs, like rosemary, grow best from cuttings, but most can grow successfully from seed. Start seeds in pots with fertile soil a few weeks before the last expected frost date. In the indoor environment of even temperatures and steady water supply, seeds should germinate quickly. Nurture them for several weeks while waiting for the weather to warm.
For both annual and perennial herb seedlings, acclimating them to outdoors carefully will best ensure their survival and help them to thrive. Once the weather has started to warm, place potted seedlings outdoors in a sheltered location protected from the wind during the warmest part of the day. Bring them back inside after an hour or two. Each day thereafter, expose the plants to longer and longer periods outside. After a couple of weeks, herbs can be transplanted outside. Annuals will peter out sometime in the fall, but perennials will remain and require little care for years.