The resilient, beautiful Salvia leucantha
It only fears frost (and pruning shears)
Let's leave behind the shady, cool (and hopefully non-radioactive) gardens and transition conceptually to the antipodes, and geographically to the equatorial belt, to explore Salvia leucantha (mexican sage): one of the most beautiful salvias out there. This herbaceous perennial features silvery foliage and stunning two-colored, tomentose inflorescences. Native to Mexico and Central America, it thrives in full sun, well-drained soils (as they always say), and shows a decent tolerance for dry conditions.
However, my intention is not to provide an in-depth description of this plant or delve into the specifics of its cultivation parameters, as that information can be found on the internet. Instead, I aim to clarify why I recommend it and how I got myself into a quagmire of plant physiology when questioning the reasons for its autumn flowering.
First, a quick word on its drawbacks (who doesn't have any?): S. leucantha can't withstand frost, or more accurately, it depends on what you mean by “frost”. A few years ago, I grew a specimen sheltered by a south-facing wall that survived a snowfall but was brutally decimated by my obnoxious neighbor who couldn't stand how its stems, weighed down by snow, encroached upon his sacred walkway. To protect the plant from further mistreatment, I was forced to relocate it to a more exposed area in the garden, and when the next year temperatures dipped slightly below freezing (-3.5°C), the plant perished. To sum it up: S. leucantha starts showing signs of distress below 5°C, can survive at 0°C losing its aerial parts, but cannot endure subzero temperatures, even minimal.
Now, why should you consider growing it? The answer, “because it's beautiful”, doesn't quite cut it, although I personally think it's stunning. First and foremost, it's an incredibly resilient plant that requires minimal care and grows at an astonishing rate. The one that braved the snowfall and then fell victim to the neighbor's pruning shears grew to over 1.5 meters in just five months, from March to August (before dying, the following winter).
Secondly, it's remarkably tolerant of pruning, even severe and repeated, without affecting its flowering (better not to overdo it, though): this “feature” can be useful for keeping plants in shape during the growing season. Given its capacity for exuberant growth, in fact, it's easy to end up with a giant in your garden that you hadn't initially planned for. Once, a client with a garden I designed called me at the end of the summer, reporting some “minor issues” with S. leucantha. When I arrived at the garden, all I could see was a silver-green wall, adorned with purple and white inflorescences, standing at a towering 1.8 meters height. It had essentially devoured the rest of the flowerbed, bidding farewell to lavenders, gaureas, and Calamagrostis.
What's even more intriguing is its ability to thrive in heavy, clayey, poorly draining soils. This defies the oft-quoted mantra I joked about earlier: “it loves well-drained soils”. To be clear, it doesn't tolerate water stagnation, but its resilience in less-than-ideal substrates is a considerable advantage.
Lastly, I recommend S. leucantha just because it blooms beautifully in the autumn, perfectly aligning with the category of “the best plants to cultivate for off-season blossoms” This is akin to what you might find in gardening magazines (or Instagram accounts), those publications filled with photos of flowers captured in soft, dreamy lighting, leaves wafting through the air, people embracing at sunset, golden retrievers bounding through meadows, and breakfast elegantly served on porcelain, atop white tablecloths adorned with lavender and a book (seriously?).
But let's get down to serious business. S. leucantha is a qualitative short-day plant, meaning it only flowers when the daylight hours fall below a certain threshold (12 hours or less for initiating flowering, 10 hours or less for flower development). This is the reason why it blooms in autumn. When cultivated in mild climates similar to its native range, it can undergo a second flowering in spring after a winter hiatus, provided it doesn't exceed its “maximum critical photoperiod”, which I'll discuss in the next article along with other similar concepts (namely the above-mentioned physiological quagmire), and which will be more or less entitled “Are plants metereopathic?”
See you soon.