We have long been enamored by the elegant, evergreen fern, Polystichum neolobatum, but have failed countless times with the commonly sold material in the horticultural trade. It was not until we grew spores from a Hans Hansen Chinese collection from 7,000′ elevation in China’s Sichuan province that we met with success. Below is a specimen from that trip, taken here at JLBG last week.
As is the case with so many commercially sold plants, their origin is lost. While the commercial material of Polystichum neolobatum may be fine in the cool temperatures of the Pacific Northwest, that is simply not the case here in the hot, humid Southeastern US. This species has a wide native range from the Himalayas all the way to Taiwan, where it can be found from 4,000′ elevation to 10,000′ elevation. Both elevation and origin location matter when determining the adaptability of many plants. We are finally getting good spore set, and hope to be able to make this form available through Plant Delights in the near future.
The cold and raw weather of late autumn and winter provide the perfect opportunity to sit down with the dissecting scope and put our ferns through the identification mill. Often gardens and nurseries receive a plant into their collections from an exporter or collector who has put their best guess on the identification. After many years in cultivation, we realize what we thought was the right species name for our specimens is incorrect. Today’s nasty weather provided the opportunity to examine, in detail, one of our favorite evergreen fern groups – Dryopterissection Variae.
These firm-leaved evergreens produce thick-textured, durable, medium-sized fronds of varying shape but all display a noticeably longer basioscopic pinnule (that’s fancy talk for the lowest, innermost segments of the divided leaves). All members of the section that we have grown have proven to be very adaptable to our hot, humid summers and unpredictable winters if grown in shade or partial shade in moist woodland garden conditions. The fronds tend to burn if they receive too much light. They are late risers in the spring often not producing a new flush of leaves until late spring or even early summer.
At the beginning of the day, we started with 8 accessions of Dryopteris varia, 2 accessions of Dryopteris bissetiana, 6 accessions of Dryopteris formosana, one accession of Dryopteris saxifraga and a couple of unknowns. From these numbers you would expect that the one plant we would know best would be Dryopteris varia.
Well…it turns out all the plants we had received or had identified as D. varia were actually representative of other taxa. If you’ve never tried keying ferns using The Flora of China or The Ferns and Fern Allies of Taiwan, you would have no idea just how difficult a process this is. The floras of these areas are notoriously difficult to use and often contradictory or difficult to assess using illustrations or pictures (yes even plant taxonomists google names to find images). Very quickly we became intimately familiar with the nature of the stipe and rachis scales, frond outlines, and disposition of the vestiture (yeah you think that sounds easy, right?).
We found most of our collection was actually composed of Dryopteris bissetiana, which are mostly from collectors who sent us tentatively identified wild-collected material. The majority of these were from Sichuan in China, however one very beautiful, deep green and glossy selection that is only half the size or less of the others was Tony’s collection in Korea, and has tentatively been identified as Dryopteris saxifraga. All of these are remarkable garden plants, but we are very excited to some day offer the choice dwarf from Korea which we have named ‘Cheju Dwarf.’
It was a pleasant surprise to find that our collections of Dryopteris formosana were correctly labelled, but we weren’t prepared for there to be two distinctly different looking plants represented in our garden that are the same species.
One of these is the plant that has been shared among fern enthusiasts for some time that is the typical sexually reproducing diploid. The other is an apogamous triploid that looks like a completely different species. In a diploid (like you and I) the pairs of chromosomes uncouple and one copy of each goes into making the male and female gametes.
Thus, each gamete has only one set of each chromosome (haploid) and when combined with those from the complementing sperm or egg results in another diploid. Plants sometimes have a mistake in their cells that lead to the production of gametes with twice as many chromosomes as they would normally have and when such tetraploid plants breed with a diploid the result is a gamete with 2 copies of each chromosome combining with a gamete with only one—thus triploid. In your average plant this triploid is a dead end for reproduction by seed or spore because they have an uneven base number 3—which can’t be divided into an equal number of chromosomes, so it is sterile.
This triploid avoids the curse of having an uneven number of chromosome pairs by avoiding sexual reproduction and producing spores that will result in new plants without the traditional interplay of sperm and egg on a germinated gametophyte (yes apogamy in ferns is still legal in all states and countries). We were puzzled when two very different looking ferns keyed to the same species. Everything that was in the key matched. The bullate hairs, the shape, the color, the basioscopic pinnae and the overall shape.
Our taxonomist, Zac Hill, very quickly uncovered a recent paper by Kiyotaka Hori, et al (2017) which explained and beautifully illustrated our conundrum. The triploid produces a wider, far more pentagonal frond with a less erect nature in the way the blade is held, and a deeper green, highly pleasing color—now that’s pretty darn cool! This new discovery we have named ‘Yushan 2 X 4.’ A new plant for us all to grow in the years to come and now you know why we chose the name diploid (2) X tetraploid (4).
Now that we realize we grow seven different forms of Dryopteris bisettiana, each collection will be given a cultivar name, which will refer back to their specific origin and uniqueness.
Every day brings discovery when you manage a collection of 30,000 taxa but one thing we know for sure, these are amazing, well-behaved, slow growing woodland plants that are the essence of what makes Juniper Level Botanic Garden so amazing.
Patrick McMillan, director of horticulture and gardens
Hori, Kiyotaka, L. Kuo, W. Chiou, A. Ebihara and N. Murakami. 2017. Geographical distribution of sexual and apogamous types of Dryopteris formosana and Dryopteris varia (Dryopteridaceae) in Taiwan. Acta Phytotax. Geobot. 68 (1): 23-32.
Nurses and plant taxonomists are among the few fields in which you would run into the term, anastomosing veins. Having been in the plant world all my life, I had never even run into the term until trying to key our some bamboo ferns in the genus, Coniogramme, almost a decade ago. It turns out that to distinguish between species, you need to determine if the spore patterns on the back of the leaf have an anastomosing or parallel vein pattern. Anastomosing veins are those which diverge and reconnect forming a pattern like a snake skin. We’ve grown quite a few ferns, but none have the amazing vein patterns of coniogramme. Below are the leaf backs of Coniogramme japonica in fall.
Adiantum capillus-veneris ‘Bermuda Run’ is looking exceptional in the garden this fall. Actually, it looks exceptional most of the year for us. Until the temperatures drop below 12 degrees F, this amazing fern remains evergreen. This fern has a huge native range, being found on every continent except Antarctica.
Adiantum capillus-veneris, along with a couple of pteris fern species are often found growing in mortar cracks in many of the Southeast coastal cities and adjacent tropical islands. It is thought that some of these populations may have been spread along the early trade routes. This particularly dense form is our collection from the mortar walls on Bermuda. The same species is native to North Carolina, but only in a solitary population. Winter hardiness is Zone 7b-10b.
One of our favorite ferns is the Lady fern hybrid, Athyrium ‘Ocean’s Fury’. Created in Pittsboro, NC by plantsman Thurman Maness, this patented gem was offered for years through wholesale channels, but sales were not strong enough, so the sole producer discontinued it. So often, great patented plants suddenly become unavailable if sales don’t warrant.
In Europe, any grower can petition the PVR office to request permission to propagate such protected plants, but no such program exists in the US. Fortunately, Thurman has generously granted us permission to propagate his amazing introduction and make it available. That said, division is a very slow way to make ferns available, but since this hybrid between Athyrium filix-femina and Athyrium nipponicum is sterile, it’s our only option.
If you’re a nursery, and you’d like to offer ferns, the plants at your disposal are somewhat limited. A large majority of ferns sold in America are still sadly dug from the wild. When you see a catalog listing primarily these ferns together…usually an very inexpensive prices, you can be pretty much assured they were dug from the wild: Osmunda regalis (royal fern), Osmunda cinnamomea (Cinnamon Fern), Polystichum acrostichoides (Christmas Fern), Matteuccia Matteuccia struthiopteris (Ostrich fern), Adiantum pedatum (Maidenhair fern), Athyrium filix-femina (lady fern), and Onoclea sensibilis (Sensitive Fern). These ferns are often sold bareroot, to save the nursery the expense of having to pot the collected plants, many of which are so large, they won’t fit in small containers.
The other majority of ferns in the market are produced by tissue culture, either by a couple of labs in Florida, one in Texas, and one in Holland. Without the amazing work of these labs, the fern selections available to homeowners would be limited to the wild collections. Even with their amazing work, these labs must focus on well-known ferns that sell in very large numbers.
While we make use of the lab offerings, we also made a commitment over 30 years ago to grow many of our own ferns from spores. Outside of a few small fern specialists, there are few nurseries who grow their own ferns from spores, since this is the most costly and time consuming option. The reason we do this is so that we can offer fern species and selected forms that are otherwise unavailable.
Below is a quick summary of how the process works. Fern spores (fern equivalents of seed) are collected through the summer, and are dried in paper envelopes until they separate from the foliage. They are then sown in pots with potting soil that is sterilized here, and then sealed in ziploc bags. The spore takes from 1 month to 6 months to germinate. Once the spores germinate, they are ready to have sex…a process that is reversed from more modern evolved flowering plants.
To assist the ferns have sex, we gently add water to the newly germinated sporelings, since ferns (other than desert ferns) only have sex while they are swimming. The water is swirled around to mimic the feel of a whirlpool, then the bags are then resealed, and put in the dark where they are subjected to a near constant montage of Barry White music.
Within a few weeks, tiny fern fronds begin to emerge. At this point, the ziploc bags are opened to allow the humidity to equalize with the ambient air. After another couple of weeks the pots are removed from the ziploc bags. If the spore were viable and cleaned well without contamination, and if germination was good, there will be up to several hundred plants per pot.
After a few weeks, the sporelings are transplanted into a cell pack flat. Here they grow out for another few months until they are ready to be planted into our 1 qt. pots, in which they will be sold. In all, it’s about an 18 month process, and a good bit of labor. We’re really quite passionate about our fern collection at JLBG, which the visiting British Fern Society declared one of the largest/most diverse in the world. We hope you find the results worthwhile.
Indeed the old proverb about a rolling stone is correct, but a stationary stone, especially in the water, gathers all kinds of amazing things. This rock in one of our garden streams has not only gathered moss, but several young maple trees, a carex, a couple of sanguinaria (bloodroot), and a handful of various ferns. Isn’t nature just grand if you stop long enough to pay attention.