When the warm spring sunlight starts streaming into your home, you might be tempted to move your herbs outside. However, moving them too early can harm your plants, sometimes irreversibly. In an exclusive interview, Tiffany Selvey, Onions Australia’s garden editor and master gardener, explains that moving certain herbs outside too early can lead to their death. Whether you’re starting herbs from seeds or transitioning plants back outside after overwintering indoors, tender plants are at risk of being killed by a late frost.
It’s important to note that not all herbs are frost-tolerant. Herbs classified as annuals are particularly sensitive to late-season chills, which is why exposing them to the outdoors prematurely can be detrimental. Selvey mentions that young basil, cilantro, and dill seedlings are likely to be too damaged by a frost to recover. While woodier, frost-tolerant herbs like sage, rosemary, and lavender are better equipped to handle cold weather, they still need time to transition to the outdoors before being exposed to frost. This raises the question of how to determine the right time to move your herbs outdoors without risking damage.
Transfer your herbs outside once the threat of frost has passed
The ideal time to move your overwintering herb plants or newly sprouted seedlings outside is when the risk of late-season frosts is minimal (air temperatures of 32 degrees Fahrenheit or below). While there are estimates for average last spring freeze dates, nature is unpredictable. Selvey suggests waiting for the last expected frost date to pass and checking the extended forecast about two weeks ahead. If there are no low temperatures near freezing, it’s safe to move your herbs outside. However, it’s wise to have a backup plan in case of an unexpected late frost.
Acclimate your herbs before leaving them out for the summer
Knowing when to transition indoor herb plants outside is important, but understanding the process is equally crucial. Selvey advises that mature woody herbs can be moved outdoors without acclimating, while seedlings should be hardened off gradually over about a week. Hardening off involves adjusting plants to outdoor conditions by increasing sun and wind exposure slowly. Failing to do this can be a critical mistake when transplanting seedlings, as young plants need time to adjust to the outdoor environment. Make sure to place young herb plants in appropriate locations and consider the specific needs of each type of herb for a successful transition.
