Confusion Over Hardiness Zones

‘Sensation’ (Syringa vulgaris ‘Sensation’) is actually a very hardy lilac, fully capable of growing in hardiness zone 5. Photo:

Question: I just bought a ‘Sensation’ lilac, but I forgot to look at the hardiness zone. So here I am with a lilac from zone 3 while I live in zone 5. What will happen? Did I just throw money out the window? Which lilac is more suitable for zone 5?

Annie Bilodeau

Answer: You’ve misunderstood how hardiness zones work.

When some nurseries put only one hardiness zone on a plant label, in this case, zone 3, that was not meant to exclude all the other zones. You’re supposed to understand that the zone given is the coldest one the plant can support, but the plant will also grow in warmer zones. It is the minimum zone the plant can tolerate.

In the case of your lilac, it’s capable to tolerating quite serious cold, down to -40ºF/-40ºC, but will also do fine in milder climates, like your zone 5, where winter temperatures are much warmer. Check the table to better understand.

Now, this confusion would have been avoided if the label provider had given the range of hardiness zones the plant is adapted to … and many nurseries do. In the case of your ‘Sensation’ lilac, for example, as a cultivar of the common lilac (Syringa vulgaris), that would be zones 3 to 7 (common lilacs need a cold winter and won’t readily bloom in milder climates, that is zone 8 and up). As you can see, zone 5 is safely ensconced in the middle of the lilac’s cold tolerance range.

So, when you shop plants and see only one zone on the label, keep in mind that you can buy plants from your hardiness zone (5), but also plants tolerant of greater cold (zones 1 to 4 in your case). So, 1, 2, 3, 4 and 5 are the ones you can choose. It’s those from zones warmer than your own (6 to 13) you need to avoid, as they won’t tolerate the colder winters in your area.

?Helpful Hint: If ever you’re not sure of whether a plant is hardy where you live, why not ask someone from the nursery staff? They’ll be able to direct you to plants that will grow well in your area. 

To answer your second question, “Which lilac is more suitable for zone 5?”, almost all lilacs are hardy in zone 5, so you could pretty much take your pick.

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, will continue its mission of demystifying gardening and making it more accessible to all.

3 comments on “Confusion Over Hardiness Zones

  1. I would like a lilacs, but being in zone 8, I am never sure they would bloom.

    • Yes, zone 8 is not usually ideal for lilacs, but if “your” zone 8 has a distinctly cooler winter, you might want to try one to see.

  2. Incidentally, when we grew French hybrid lilacs, like ‘Purple Sensation’, they were supposedly less reliant on chill to bloom well. However, even the common lilac blooms quite well here, and in climates with even less chill. They really do not seem to require much chill at all, which is why they are not prescribed a range of hardiness zones.

Leave a Reply

Sign up for the Laidback Gardener blog and receive articles in your inbox every morning!

%d bloggers like this: