It is cold hardy to about 15 degrees F. Sunset's rating is a little conservative, but as this plant has recently become much more popoular, I'm sure there was much less experience with this plant when Sunset wrote their description.

In Astoria, I would plant it and expect it to survive many average to mild winters, but it will probably freeze out when a really cold one comes along once every 10 - 20 years. That's all right though because you should still be able to enjoy it for a long time (unless we get a really cold one next winter!).

There are a number of interesting Prostanthera species and cultivars you can sometimes find in mail order nurseries. Some of them are a little cold hardier, and are larger growing plants. All of them have that great minty smell.

I planted one on Camano Island. It froze. However, a friend has one in Seattle. I have seen others around Seattle as well.

Every plant has a minimum temperature below which it dies. Only a brief exposure is necessary to kill it. As long as your site stays above the minimum temperature for this one - something that may vary from one seedling or clone to the next - it will survive. As soon as it falls below it, goodbye!

This importance of the minimum temperature is why various tender plants are being hailed by the inexperienced as 'hardy' here, we have had some years of high minimum temperatures. Variations in hardiness between different seedlings, races or cultivars also explains variable results, with what is being considered one plant (but actually isn't) found to be hardy for one person but not another. Often entire species of gums, for instance, are discussed as though they were clones, when in fact these are grown from seed, and sometimes vary widely in hardiness even within the same batch.

the nice thing about the mint bush is that it should be fairly easily propagated from cuttings and it might be wise as a form of "insurance" to strike a few each fall as potential replacements for any the coming winter might do in. as shore acres state park on the southern oregon coast a specimen we grew literally covered itself with flowers and was the most commonly asked about plant by visitors for almost a month!!!

Thanks - I am getting one. I need to re-think my location, as we get huge winds in my sunny front yard - I can give some shelter in Winter as this will be grown in a large tub - some web sites refer to this as a house plant - maybe, maybe not - but yes, propagation seems in order. Again, thanks.

Putting it in a pot will make it more vulnerable to cold, as roots of plants are less hardy than tops.

Saw one this afternoon in NW Seattle. It was loaded with flowers.

Which may explain why some fuschia plants of mine, notably Swingtime, Indian Maid, Lena & Pink Lena are thriving in my Fern Garden - Black Prince is more like a frog than a prince - are doing so well in ground for 3 years & more - these are some that didn't look too promising to be in a hanging basket, but too healthy to discard. But I have no sunny "planting" spot. I use inexpensive black heavy plastic pots - very large - I'll chance it, watching weather as always, and would not mind wrapping the tub - also take cuttings - the ones in my nursery are more blue in flower than the violet/orchid color - our worst month here is February, mostly because of the drying winds combined with the cold - It's a beautiful plant - if enough maritime gardeners love it, we can expect some tougher plants.

Some fuschia plants of mine, notably Swingtime, Indian Maid, Lena & Pink Lena are thriving in my Fern Garden - Black Prince is more like a frog than a prince - are doing so well in ground for 3 years & more - these are some that didn't look too promising to be in a hanging basket, but too healthy to discard. But I have no sunny "planting" spot. I use inexpensive black heavy plastic pots - very large - I'll chance it, with the Prostanthera, watching weather as always, and would not mind wrapping the tub - also take cuttings - our worst month here is February, mostly because of the drying winds combined with the cold.

Saw one today about 5 ft. high that has been growing in NE Seattle for 5 years.