Location: Grand Valley of Colorado's Western Slope
posted 5 years ago
It's a beautiful resource.
The hardiness is a little off.
My lemon grass only survives the winter with heavy mulching. Frozen ground kills lemon grass, and bay trees, whether the true laurel, or the west coast tree of many names: California bay tree, Oregon Myrtle, Pepperwood. In my experience basil is not "half hardy", it is one of the tenderest plants I know. And though they say there are frost hardy rosemarys, Arp being one, if you've ever seen rosemary in a mediterranean climate, where it grows 6 feet tall, and you can cut it by the armload, you'll have a different expectation. The plant that dies to the ground and sends up a few sprigs in the spring I do not consider vigorous enough to harvest. In a climate with a frozen soil winter, rosemary is best brought in doors for the winter, or heavily mulched as for lemon grass and bay. I also grow and mulchrose geraniums and lemon verbena to overwinter in the ground.
I group the ones that need protection from freezing. The mulch has to bee deep enough and wide enough at the base that the freezing conditions do not reach to the center where the roots are cowering in fear of the killing frost. It involves building a fence or stacking bales and filling the internal space. If the soil freezes to one foot, then the mulch needs to be at least a foot deep, and extend out from the base of the plants to be protected in all directions at least a foot. And if I am going to all that effort, I leave a margin of safety of ~ 50 %. What if it is the rare event winter, or what if I judged wrong?...
A nice herb that will survive frozen ground, here in western Colorado anyway, is lemon balm.