a zone question for salvias....

kmickleson(z9 CA)March 24, 2014

I'm in a microclimate which is 9a or 9b, I'm not sure--SF Bay Area. Normally we get few enough hard frost days to keep citrus alive with minimal protection. But this last winter, courtesy of unpredictable global warming episodes, we had at least 15 hard frost days in a row, and some others scattered in. It killed a couple of patio lime trees and all above ground growth on a 7' abutillon, which are normally survivors here, among other things.

In retooling the garden, I'm thinking of groupings of salvias, especially blues like vitifolia and other vivids like Salvia canariensis var. candidissima.

My understanding of zones is pathetic, but I'm trying to figure out if 'hardy to Z8' means the plant will return the following season only IF it gets enough hard frost; or, if it means if I'm ABOVE Z9, it will likely behave like a perennial anyhow in my garden.

I'm sure different salvias do different things. But I'm looking for some rules of thumb that enhance my chances of a salvia enduring another long frost period OR not, depending on what global warming delivers next year. I don't want to design a garden around plants that won't keep being there.

Input appreciated.

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rich_dufresne(z7 NC)

The essence of zone hardiness has to do with the plant's tolerance to penetrating freezing. That means how the above ground parts of the plant, including its vascular system and the nodes that will generate new growth withstand both penetration of cold and frequency as well as intensity of thermal cycles. This also applies to below ground parts, which are protected by the ground as an insulator up to the point, depth, and duration of frost penetration.

You will need to know about your microclimates, especially exposure to freezing and drying winds, soil drainage, and soil fertility, including pH (acidic to alkaline).

Most plants that would say hardy to zone 8 doesn't mean they need the cold, since the minimum temperatures refer to the chances of a small number of instances where the lows reach the stated temperature. These figures for a minimal cold tolerance won't work with winters like this last one, and erratic weather patterns will take their toll on plant growers everywhere. It needs to be said that gardens are the canary in the mine for native plants in general, since damage to the this flora does take place, but is not as obvious.

Moving potted plants into a cellar, shed, or garage will become necessary for unusual conditions, as well as mulching beds, covering special plants with cloches.

If your problem is sustained or heavy rains, use raised beds.

Even this can fail. A lot of my friends in Baton Rouge and New Orleans lost plants in raised beds because of sustained high water, which saturated raised beds continuously because of capillary action. Southern Louisiana near the Mississippi River is close to sea level, with really huge levees, which means water retreats slowly after long rains.

There is only so much you can do, so it is important to assess your environment to determine what is possible and draw go/no go lines. Anticipated frequency of unusual events is one of those areas.

    Bookmark   March 25, 2014 at 12:52AM
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kmickleson(z9 CA)

Thanks, Rich. I figured you'd respond and appreciate your expertise and wisdom.

Along with what you say, the question becomes how much one wants to invest in trial and error in these troubled weather times, with almost ensured disappointment sooner or later.

Such is life.

    Bookmark   March 25, 2014 at 1:09PM
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