Mid-October is flowering time for the widespread (Canada south to Texas) native oblong aster, Aster oblongifolius (aka: Symphyotrichum oblongifolium). This amazing plant forms a large clump to 2′ tall x 8′ wide. This is the clone Aster ‘October Skies’, which is quite similar to the other widely grown clone, Aster ‘Fanny’. Average to dry soils in full sun is the key to success. Hardiness is Zone 4a-9b.
In our hot, humid climate, we really struggle with keeping most cultivars of Caryopteris x clandonensis alive for very long. A lovely exception in our trials has been Caryopteris ‘Gold Crest’, a recent introduction from the plant breeders at Ball Hort. Here is our three year old clump in the garden this week. The foliage is deliciously fragrant…more so than any other caryopteris we’ve ever grown, and the native bees find it incredibly attractive. We’ll be adding this to the new Plant Delights catalog in January. Winter hardiness is Zone 6a-9b.
I’d grown quite a few eryngiums…49 different ones, in fact, before Patrick shared Eryngium ravenelii with us in 2015. Who knew we were missing one of the best eryngiums in the entire genus! Today, Eryngium ravenelii holds several places of honor in our garden, where we can watch the myriad of pollinators who regularly stop by for a nectar snack during flowering season (mid-August to late September).
Eryngium ravenelii was named for American botanist, Henry William Ravenel (1814-1887). In the wild, Eryngium ravenelii grows in standing water in flooded ditches, alongside sarracenias (see bottom photo). We’ve now seen them in the wild in both North Florida and South Carolina, where they grow in calcareous-formed soils. In the garden, they thrive in an array of slightly acidic soils as long as the soil is reasonably moist.
Looking fabulous in the garden now is the perennial Salvia ‘Big Blue’. This amazing sage has been in flower since spring, and has yet to slow down. It’s also a favorite of the native bumblebees.
Here’s a recent garden combo that we’ve been enjoying with purple eucomis (pineapple lily), Agapanthus ‘Navy Blue, backed with Foeniculum vulgare ‘Purpureum’ (bronze fennel).
There is a “growing” trend toward using groundcovers to reduce the need for bark mulch in gardens. As with any trend, there is a time and place where it is appropriate, and other times when it is not. One plant that we absolutely love for that purpose is the evergreen Carex flacca ‘Mini’. This blue-foliaged sedge is a Mediterranean native marsh grass that spreads very slowly, so it is not a problem in overrunning other plants in the bed, as long as they aren’t placed too close. These pictured below were planted six years ago on 1′ centers, and are just now knitting together.
We have studied a few reports of this sedge being invasive in parts of the northeast US, but our trials have shown quite the opposite, with nary a seedling in over six years. We can find no scientific research that shows this sedge qualifies as being invasive using any commonly recognized definitions of an invasive plant. Our skepticism of these reports comes because some of the ridiculous listings that appear on invasive species lists, which have no scientific basis. Our favorite invasive faux pas was a listing a couple of years ago of the genus Bambusa on a state invasive list. Never mind the plant is a strict clumper and only flowers once every 100 years. Winter hardiness is Zone 4-9.
I hope everyone with a sun garden has grown the amazing Amsonia hubrichtii. It’s certainly looking fine in the garden as this recent image from JLBG will attest. Few people realize it was name after the late American naturalist, Leslie Hubricht. Before Hubricht died in 2005 at age 97, he had published 108 new species of mollusks (snails). His world class collection of over 500,000 specimens is now housed in the Chicago Field Museum.
After an early life stent as a research associate at the Missouri Botanic Garden, Hubricht went on to spend the majority of his career as a repairman for adding machines, and later computers. During his career, he moved constantly, living in 22 different cities. His single-minded focus was studying nature…in particular, mollusks. In his spare time, he published 151 scientific papers. This would be almost unheard of for a researcher who had the backing of a major formal botanical institution, of which Hubricht had none.
Additionally, 25 new species of animals were name after him, along with one lichen, and two species of plants…most notably the amsonia. Hubricht did all this despite a formal education that only included a single semester of high school. We salute the amazing Leslie Hubricht.
Nierembergia ‘Starry Eyes’ is looking particularly dazzling in the rock garden at JLBG. Starting to flower for us in late April, this incredible gem is from our 2002 botanical expedition to Argentina. I distinctly remember walking by as our friends from Yucca Do Nursery extracted a small piece of this nierembergia with only a single flower attached. I remember thinking to myself how poorly nierembergias, in particular Nierembergia repens perform in our climate and how I wouldn’t have wasted my time on such a plant. Two decades later, boy was I wrong!
In our climate, Nierembergia gracillis ‘Starry Eyes’ blooms continually through the summer months. It thrives in full sun and a well drained, gravelly soil. Thank you Yucca Do, for all the great introductions!
For years, we struggled to grow the Mediterranean/Balkan native spurge, Euphorbia characias…until we discovered its secrets. First, it isn’t a long lived plant to begin with…in most cases 3-5 years is it, so you’ll need to plant it where it’s likely to reseed. That would be well-drained slopes that are either mulched or covered with gravel.
Secondly, after it flowers in spring with its stunning show of yellow flowers, remove most of the flower stalks as soon as flowering has finished, except those needed to produce new seedlings (the flowers are also great to use in floral arrangements). If not, the seed stalks use up energy causing the plant to decline much faster. We’ve now allowed this to seed throughout the slopes in front of our house, and here is the result…a smattering of 3′ tall x 3′ wide clumps, photo taken mid-winter.
Although this section of the garden, planted in compost-amended sandy loam is irrigated, we typically don’t recommend irrigation for this spurge without excellent drainage. You’ll also read on-line that Euphorbia characias doesn’t like hot, humid summers…another example of fake gardening news that just keeps getting repeated without any concern for the facts.
We’ve also found Euphorbia characias to grow well in part sun under large trees, which keeps the soil dry. The plants will never be as dense as they are in full sun, but they survive and flowers. There is really not anything else that gives you this evergreen blue color and form in the winter garden.
One of many great attributes of mangaves, compared to one of their parents, agaves, is that they don’t die after flowering. Agaves are mostly monocarpic, which mean that they behave like bromeliads, where each rosette grows to maturity, then dies after flowering. Those species of agave which offset, live on after flowering, by means of un-flowered offsets. Those agave species which don’t offset are a one and done after they flower and reproduce by reseeding.
By incorporating manfreda genes to create xMangaves, the monocarpic trait disappears. After a mangave flowers, it dies to the ground, but like a good zombie, it soon pops back from the dead. Here is a current photo from the garden of two clumps of xMangave ‘Blue Mammoth’. The first, larger clump has not flowered, but should do so next year. The second clump with all the offsets, flowered in 2020, and re-grew to this point in 2021. Next year, the rosettes will continue to re-grow in size.
One of many exciting new introductions for 2022 is Phlox divaricata ‘Blue Ribbons’ PPAF. This variegated version of our wonderful native woodland phlox was discovered here as a single sport in our garden by our plant taxonomist, Zac Hill. Instead of being all green, each leaf is edged with a wide creamy border and flushed with pink during the colder months. In early spring, the entire clumps are topped with sweetly fragrant blue flowers. We think Phlox ‘Blue Ribbons’ is an incredible design addition for the woodland garden. Hardiness is Zone 3-8. The new catalog, with this and many other amazing gems, goes on-line in 2 weeks!
We love the appearance of plants like agapanthus in the fall, long past the season when the showy blue flowers graced the top of each now browning stalk. In fall, it’s more like looking out on a mass of punk rock hairdos. These garden features are so much more interesting than flat beds of mulch, created far too early by garden neat freaks. This is the cultivar Agapanthus ‘Prolific Blue’ which puts on a superb fall/winter show.
The non-weedy Ajuga ‘Blueberry Muffin’ from the breeders at Terra Nova has really put on quite a show at JLBG this spring. We love the non-seeding and slow spreading traits…not to mention the amazing floral show.
Our baptisia introductions are looking absolutely fabulous this week. Here are a few in case you missed the first weekend of our open house. Baptisia ‘Aspriing’ (top) with its long spikes of lavender blue flowers, followed by the incredibly dense flowering Baptisia ‘Blonde Bombshell’. Next is our Baptisia ‘Cherry Pie’, which brings a new color to the genus, and ending with Baptisia minor ‘Blue Bonnet’ with it’s enormous blue flowers. Baptisia are a North American genus of long-lived perennials that can grow equally as well with cactus or as a marginal aquatic…as long as they have full sun.
Earlier we posted photos of wild collected Amsonia tabernaemontana, so here is a closely related species that’s been hopelessly mixed Amsonia tabernaemontana, thanks to mothball-sniffing herbarium botanists. Amsonia glaberrima is a gulf coast species that’s actually quite different…smooth leaves for a start, and different habit and flowering time. Here is our garden selection grown from a seed collection in east Texas. This is a truly exceptional plant, so I expect we’ll get our propagation staff to tackle this after flowering.
Just snapped this photo of the amazing Amsonia ‘Storm Cloud’ in the garden. This was a 2011 discovery in Central Alabama on a botanizing trip with Hans Hansen.
Amsonia (aka: bluestar) are one of the best temperate genera (18 species) of blue-flowered perennials for the spring garden. We’ve offered quite a few different species and selections through the years, rotating them in and out as propagation successes allow and as sales dictate. All but two of the species, (Amsonia orientalis from Europe and Amsonia elliptica from Asia) are North American natives. Most are extremely drought tolerant, while others like Amsonia rigida and Amsonia tabernaemontana can tolerate very wet soils.
Amsonia montana is a commonly grown plant of mystery, having just appeared in horticulture, but never been documented from a wild population. A few of the amsonia species have flowers so pale blue that they appear white in the garden with only a hint of blue on the flower corolla. Amsonia are quite promiscuous in the garden, so if you grow more than one species nearby, you will have hybrids from seed. We hope you’ll explore this amazing genus of perennials.
Baptisias, commonly known as false indigo, are North American native members of the pea family and quite drought tolerant once established. They provide amazing architectural form in a sunny garden or perennial border, and are deer-resistant and a butterfly magnet (See the top 25 flowers that attract butterflies here.).
Not only do baptisia come in blue, which many people are familiar with in the most common species, B. australis, but they are also available in a wide array of colors such as white, yellow, purple, and pink, and new breeding efforts are producing bicolor flowers such as those of Lunar Eclipse.
Baptisias have long been one of our favorite groups of sun perennials here at PDN. Through our trials of new varieties introduced to the market, as well as our own breeding program, we continue to select for improved structure and habit as well as flower color. In 2017, we have introduced 2 new varieties in our Tower Series, Yellow Towers and Ivory Towers. These join our previous introduction, Blue Towers, all having a vigorous upright habit to 4.5-5′, terminating in 18-20″ spikes of flowers, true show-stoppers in the garden.
Due to high demand, we quickly sold out of finished stock of Ivory Towers, but don’t fret, we have another crop coming along and they should be ready just in time for our Spring Open Nursery & Garden Days April 28-30 and May 5-7. And be sure to join us on Sunday May 7 at 2pm for our Gardening Unplugged garden chat series, where Tony will be talking about baptisias. You can also read Tony’s more in depth article about baptisias, here.