Putting on a show this week in the garden are the Living Stones. No, not Mick, Keith, and Ronnie, but the horticultural Living Stones, Lithops aucampiae. Our oldest patch starts flowering in early to mid November each year, growing beautifully under an overhanging rock.
For all the articles about how difficult they are to grow, and how they won’t take any frost, we’ve found it all to be completely fake gardening news. These were started from seed in 2018, and have now survived 11F in the ground with no ill effects. We have them planted in a soil mix of 50% Permatill gravel, 25% native sandy loam, and 25% compost, with an open exposure to the south.
We added two more species (L. hookeri and L. lesleii) to the garden almost two years ago and they have thrived equally as well. Sounds like the myth about Lithops being difficult to grow and not winter hardy is completely busted.
I had to chuckle as folks on several Facebook plant groups were wringing their hands in worry prior to the recent cold snap, while we were secretly hoping for even colder temperatures than forecast.
JLBG registered three consecutive nights in the teens recently; 11F, 19F, and 19F. While this was certainly not abnormal for our area, folks with very short memories thought the horticultural world was coming to an end. In reality, we recorded similar temperatures in the winter of 2017/2018, albeit a week later that year.
When we first started the gardens at JLBG, we were squarely on the Zone 7b side of the Zone 7a line. We are now on the Zone 7b side of the Zone 8a line. In order words, we have shifted about 1/4 of a hardiness zone. Since 2018, JLBG has registered three consecutive Zone 9a winters, so it’s not surprising the new gardeners or those with short memories start assuming that all kind of plants are reliably winter hardy, which is not the case.
We long for cold temperatures because we want and need good winter hardiness data, and while mild winters may be enjoyable to us Homo sapiens, we don’t learn anything about plant hardiness from those winters. So, here are a few things we learned this year.
Agave weberi ‘Stone Cold Austin’ is Patrick McMillan’s collection of Agave weberi from Austin, Texas. We’ve tried Agave weberi a couple of times prior, and could never get it through one of our milder winters. Patrick’s original plant at Clemson got large enough to flower there, so we’re hoping for the same. The older foliage is showing damage from 11F, and will most likely be lost, but the bud seems fine so far.
We’ve never had any luck with any of the dwarf Agave lechuguilla mutants we’ve tried in the garden, but this new one, shared by plantsman Hans Hansen, that we call Agave ‘Tater Tot’, had no problem with 11F. These are often sold as Agave x pumila, which actually doesn’t exist. Everyone assumed that A. x pumila was a hybrid, but when one in Europe recently mutated back to the original form, it turned out to be nothing more that a super dwarf form of Agave lechugullla.
Mangave ‘Racing Stripes’ is a plant we had high hopes for in terms of winter hardiness, but we had not had a cold enough winter to get good data. Our only reservation was that it contains genes from the tropical Agave gypsophila. Thankfully, our plant came through the 11F freeze in reasonably good shape. The wrinkled nature of the older leaves are indications of cold damage that will show up in a few more days, but the core seems intact and should re-grow.
We fully expected Bambusa multiplex ‘Green Giant’ to be defoliated after 11F and the stalks killed to the ground, but our fully exposed clump still looks like it’s mid-summer…at least from the north side.
On the south side, the same clump has fried foliage. There are typically two causes for such damage. One is wind desication when the winds are blowing from a single direction and the ground is frozen, making it impossible for the plant to replenish water lost through the foliage. During the time that our ground was frozen, our winds were coming from the West, so that wouldn’t account for damage only on the south side of the plant.
In this case, the more likely scenario is that this is due to sun scorch when the soils was frozen, since the damage is on the south side. If the canes are indeed undamaged, as it appears, new leaves should reflush in spring.
We didn’t hold out much hope for the Mexican palm, Brahea decumbens, but it sailed through 11F unscathed.
Since we know that genetics matters, we will often plant more than one clone of a marginal plant like a new palm. Below are two seedlings of the small-seeded European Fan Palm, Chamaerops humilis var. microcarpa. The first shows significant foliage burn, while the second plant, growing nearby shows no damage after 11F.
The hardiest of all Sabal palmetto forms are those from NC’s Bald Head Island. Our plant from there came through the cold unscathed. We expect many local businesses and even homeowners who purchase large trunked forms directly from Florida growers will probably be in for a disappointing spring.
All of our hardy cycads have assumed the straw-color we see every year when the temperatures drop below 18 degrees F. The plants are fine, but we recommend waiting to remove the dead fronds, since doing so now, can cause the new foliage to emerge in the middle of winter, which is never a good idea. April 1 is our target date to remove the fried foliage.
One of the real surprises was the fried foliage of Viburnum ‘Moonlit Lace’, where it was growing in full sun. The same plant growing in shade looks untouched. The stems are fine and the plant should re-sprout fine, but gardeners who grow this in full sun may be disappointed.
This is the coldest temperatures we’ve seen since planting Patrick’s hardy selection, Opuntia microdasys ‘Dripping Springs’. Our clump looks great after the cold. It’s hard to imagine that this clone is so much more winter hardy than any of the other forms of this species that we’ve tried previously and killed at much warmer temperatures. Although we don’t offer this for sales, I’ll remind you of our great prickly pear cactus giveaway at our Summer Open Nursery and Garden in July.
The Mexican Sedum praeltum looks a bit sad, but actually seems to be fine with sound buds up and down the stem. This little-known perennial forms a plant that looks almost exactly like the tender Jade plant, Crassula ovata.
Lastly, our patches of Living Stones, Lithops aucampiae, sailed through 11 degrees F. I wonder if we can ever get all the disinformation on the Internet regarding their tolerance to cold corrected.
Just like the rock group of the same name, these fascinating living stones also look quite old and wrinkled. The genus Lithops are tiny succulent plants native to the deserts of South Africa. Despite virtually all references on-line, they make great garden plants…as long as you have a crevice garden, and grow them when they will not receive any rain in the winter months. These are 4 1/2 years old from seed.
Our plants of Lithops aucampiae have just started their flowering season last week, having sailed through winter temperatures of 16 F last winter, and seemingly enjoyed our hot, humid summers. We’re hoping for single digits F this winter, so we can really put them to the hardiness test. In the meantime, we’ll enjoy the fall flowering season.
Not only did we have 100% survival on our living stones (Lithops aucampiae ssp. koelemanii) in the garden, despite low temperatures of 15-16 degrees F, but they are now in the process of splitting, which is sort of like giving live birth. Splitting happens after flowering, and followed by a subsequent dormancy. The plant divides and the new plants absorb the of the old foliage…sort of like The Blob movie. We were fortunate to catch the process visually for the first time this week.
We’ve tried growing living stones (Lithops) a few times over the last decade in the garden, but could never get them to last longer than a couple of years. We weren’t loosing them to cold temperatures, but to moisture. So, when we built the crevice garden, lithops were one of the first plants we wanted to try again. We designed the crevices with overhangs to keep water completely off certain special plants, and that’s where we planted our seed-grown living stones.
For those who haven’t grown these irresistible gems, Lithops are South African succulents in the Azoiceae family, native to very dry and mostly tropical regions. They are prized for their odd appearance that consists of only two camouflouged succulent leaves.
We’ve never been able to coax a lithops to flower until last week. In their new crevice home, several finally decided to bloom this fall, with a sucession of flowers that still continues. We are currently growing only one species, Lithops aucampiae, but now that we’ve been successful, we’ve planted seed of more species to try. It takes us about 18 months from seed to get a plant large enough to go into the garden.
Despite everything written about lithops being tropical, we have not found this to be the case. Like so many plants, not enough people have been willing to experiment in colder climates in the right conditions. Of course, if you believe everything written on line, you’ll know for sure that they can’t take anything below 40 degrees F. Hint…ours have made it fine in the garden to 13F, so we expect them to tolerate even colder temperatures if kept dry. Wish us luck and be sure to check out the stones growing in the crevice during our next open house.