Interesting Plants – Page 3 – The Garden Professors™

Cool Plants for Late Summer

I thought today’s post would feature two awesome plants that are relatively new or unheard of in the industry. Both of these plants have performed well in my own garden and survived our two hardest winters recorded since the 1970’s. Many plants suffered severe winterburn or even death due to extremely low temperatures, but not these two plants. They may be harder to find in the nursery/garden center, but are well worth it and have huge ornamental impact all growing season.

The first is variegated fiveleaf aralia, Eleutherococcus sieboldianus ‘Variegatus’ (formerly Acanthopanax sieboldianus ‘Variegatus’). I know, a really horrible, long scientific name for such a great plant. Now before I go on about this particular cultivar, I need to let everyone know that this is the cultivar you want, NOT the species that has all green leaves. The straight species is weedy, grows too large for most landscapes and is not colorful. The variegated cultivar is a real showstopper! It is low maintenance, grows slowly and rarely needs pruning. This medium-sized shrub grows about 5-6’ tall and wide in the northern U.S. growing larger in the south. The natural form is upright, rounded with long, arching branches. Suckering at the base of the shrub is slow, hence the plant does not become a nuisance in the garden. Variegated fiveleaf aralia is adaptable to most soils and pH, tolerates sandy and poor, dry, clay-based soils, will stay variegated in shade and will not scorch in full sun. It is quite drought tolerant with no pest problems. Deer and rabbits seem to leave it alone.

The foliage is quite clean with 5-7, bright, cream to yellow variegated leaflets with an emerald green center. There is no fall color to talk about, however, the brightly colored leaves mix well with other yellow, white or purple flowering/foliaged plants. The stems do have 1-2 curved prickles on them at a node, but they are short. Unlike its straight species, ‘Variegatus’ rarely flowers or fruits so the plant does not become invasive.

This plant is native to Japan and was highly promoted as an outstanding urban tolerant plant by my former graduate advisor, the late Dr. J.C. Raulston of North Carolina State University. He tested and evaluated thousands of landscape plants for adaptability to the southeastern U.S. and a few of those plants are actually hardy up in zone 4b.

Another great plant that I am more and more impressed with each day is a relatively new release from Iseli Nursery, Boring, Oregon. It is NORTH WIND^® maple (Acer ‘IsINW’). This smaller, 15-20’ tall, ornamental maple is part of Iseli’s Jack Frost^® series of hardy, ornamental maples. Through testing across the country, this maple has proven hardy to zone 4a without any dieback, unlike Japanese maple (Acer palmatum). One of the parents of this great hybrid is the Korean maple (Acer pseudosieboldianum), which is also zone 4 hardy.

NORTH WIND® maple (Acer 'IsINW') — NORTH WIND® maple (*Acer* ‘IsINW’)

The beauty of NORTH WIND^® maple is that it combines the cold hardiness of Korean maple with the outstanding leaf qualities and deeper leaf lobes of the Japanese maple, one of the suspected parents, but with one exception. NORTH WIND^® maple new leaves are bright orange! The color of these leaves lasts longer in the growing season in cooler climates. I have a young tree in my yard and the leaves are still orange, even this late into August. The older leaves gradually fade to green in midsummer. The orange-red fall color is superb and makes a real eyestopper in the autumn landscape. For best color, plant the tree in full sun to partial shade.

Closeup of leaves of NORTH WIND® maple (Acer 'IsINW') — Closeup of leaves of NORTH WIND® maple (*Acer* ‘IsINW’)

NORTH WIND^® maple is pH adaptable and grows best in a moist, well-drained soil. I do not know yet how heat or drought tolerant this species is, but if anyone is growing this plant in southern climates, please let me know how it is doing.

Laura Jull, Ph.D. aka The Lorax

Perennial Funday: Rudbeckia grandiflora ‘Sundance’

Just back from the always-inspirational Perennial Plant Association Symposium, this year held in Baltimore. The theme celebrated the massive influence of German plantsmen and designers on both the mid-Atlantic and the perennial business as a whole. Whether a grower, garden center owner, or landscape designer, the names historically associated with Mid-Atlantic horticulture – Kurt Bluemel, Oehme, van Sweden & Associates, etc. – resonated with all attendees.

The history of the “perennials movement” was recounted – where the Germans (and more than a few Dutch) admired, utilized, and selected cultivars of our fabulous summer and fall-blooming native perennials – long before we North Americans ceased relegating them to ditch weeds. And then they taught us how to use them in “New American Garden” style – sweeping herbaceous plantings (fewer species but larger quantities of each), mixed with ornamental grasses and non-native but pollinator-friendly beauties such as Salvia nemorosa and Perovskia atriplicifolia.

'Sundance' massed with Rudbeckia triloba 'Prairie Glow' in the Bluemel garden. — Rudbeckia grandiflora ‘Sundance’ massed with Rudbeckia triloba ‘Prairie Glow’ in the Bluemel garden.

But this was my first encounter with Rudbeckia grandiflora ‘Sundance’. This seed strain was introduced by Jelitto® Staudensamen seven or eight years ago. It has a pretty broad native range… Midwest to South-Central United States. USDA cold hardiness zone ratings listed as 5-8 and 4-9 from various sources. Always full sun. Didn’t see a speck of powdery mildew.

The flower habit is a bit like Ratibida pinnata – the slightly drooping petals give the sensation of movement (even with zero breeze, 90% humidity, and 96° F). The clear yellow color works with just about anything. Around 4’ tall, the sturdy stems showed little sign of flopping. I’m sure the cones will persist, adding texture as the fall progresses.

'Sundance' in action at Emory Knoll Farms. — ‘Sundance’ in action at Emory Knoll Farms.

‘Sundance’ will never impress in a nursery container in May. It’s one of those you-must-see-it-in-the-garden plants. OR or you can take my word for it. And that word is “Yowza!” (Followed by “gimme gimme gimme.”)

An unexpected cactus

Crazy plant of the day is this: Pereskiopsis spathulata! Which, I’ll admit, looks like a fairly generic succulent, but the cool thing is this is actually a cactus. A cactus with leaves. Most cactus have of course lost their leaves to increase their ability to survive in extremely dry conditions and rely on their stem for photosynthesis, but the genus Pereskiopsis is a bit of living evolutionary history with photosynthetic leaves still intact.

Joseph Tychonievich

Perennial Monday: Monarda ‘Raspberry Wine’

It’s been a great summer for perennials here in the mountains of SW Virginia – plenty of rain, warm days, cooler nights. We’ve been enjoying this wonderful bee balm in our home garden for the last few weeks. ‘Raspberry Wine’ is tall (up to 5′), vigorous, and a bit ramble-y; not for the carefully-curated border, but great where it can take up some space. For those who fear Monarda’s tendency to spread, know that is shallow-rooted and very, very easy to pull up. I don’t know much about the origins of ‘Raspberry Wine’ other than it’s a Monarda didyma selection or hybrid and a “White Flower Farm introduction” – Joseph may be able to shed some light.

Monarda didyma is plenty hardy (at least USDA Zone 4) and is included on just about everyone’s plant list for either pollinator gardens or “gardening for wildlife.” The species is bright scarlet, but ‘Raspberry Wine’ has rich magenta bloom with dusky purple bracts subtending the flowers. Speaking of wildlife, it doesn’t seem to be the first choice of deer, so I’d rate it as reasonably deer-resistant. There are a couple of very-territorial hummingbirds making their home next to it – can walk by any time of the day and they’re slurping away. Interestingly, they seem to be ignoring the red ‘Jacob Cline’ down the way. My photography skills aren’t such that I can snag a feeding hummer, but did catch a less-frantic bumble bee making the rounds (above).

The clump pictured is part shade (afternoon) and the foliage is still fairly clean. I have another batch in full sun that has a bit of powdery mildew. The red ‘Jacob Cline’ is frequently touted as powdery mildew resistant but I’ve yet to see ANY Monarda didyma species or hybrid that doesn’t end up with it eventually. Just chop it back to the ground ASAP; you’ll get fresh new foliage and sometimes another round of blooms.

When Size Does Matter: Dwarf Conifers for the Home Landscape

I just returned from another great “Addicted Confer Syndrome” conference. In reality, ACS stands for the American Conifer Society. The meeting I attended was the Central Region chapter of the ACS held in Green Bay, Wisconsin. You might be thinking that only white spruce and tamarack are the only conifers that can be grown this far north, but you would be wrong. There are many outstanding conifers that can grow up here and throughout the U.S. Not all conifers are evergreen as there are deciduous conifers, like larch and baldcypress, but most dwarf conifers are evergreen.

According to the American Conifer Society (www.conifersociety.org/conifers/conifer-sizes), dwarf conifers are those that grow between 1-6” per year with an approximate size after 10 years between 1-6’. In contrast, large evergreens grow over a foot a year and are 15’ tall or more after 10 years. Size can vary due to climatic, environmental and cultural conditions. These smaller than usual evergreens are a fraction of the size of their species and fit nicely into the landscape often requiring very little pruning or shaping. Dwarf conifers can provide food and shelter for birds and other small mammals as well as year round interest due to their bright colors and interesting form and texture. An otherwise bleak, winter landscape can be accented with dwarf conifers that come in a variety of colors besides green such as blue, blue-green, silvery-blue, yellow, and purplish.

Below are a few of my favorite dwarf conifers that are available at many garden centers and nurseries.

Foliage of 'Silberlocke' Korean fir — Foliage of ‘Silberlocke’ Korean fir

‘Silberlocke’ Korean fir (Abies koreana ‘Silberlocke’, a.k.a. ‘Horstmann’s Silberlocke’) is a unique dwarf conifer that looks spectacular all year round. The soft needles are different than most conifers as they curve upwards, revealing the bright, silvery-white, frosty undersides. The silvery-gray twigs also add to the plant’s interest. ‘Silberlocke’ Korean fir grows slowly up to 5-7’ in height with a 4-5’ spread eventually growing into a small, compact, conical tree. Firs, in general, require a sandy-loam, moist, well-drained soil and are intolerant to heavy, poorly-drained, clay soils. This cultivar prefers morning sun, but some afternoon shade. ‘Silberlocke’ Korean fir is hardy to zone 4b.

'Blue Shag' white pine — ‘Blue Shag’ white pine

‘Blue Shag’ eastern white pine (Pinus strobus ‘Blue Shag’) is a dwarf conifer shrub with a compact, rounded form that reaches 3-6’ tall with a 6’ spread. The bluish-green, finely textured needles are very soft and pliable. ‘Blue Shag’ has a slow growth rate and a dense, mounded form making it a great choice for use as a foundation plant instead of the all-too-common yews (Taxus spp.). Like all cultivars of eastern white pine, it grows best in a sandy-loam, slightly acidic to neutral soil. It is sensitive to drought, heavy-clay, poorly drained soil, and road salt. ‘Blue Shag’ eastern white pine is hardy to zone 3a.

Foliage of 'Bergman' Japanese white pine — Foliage of ‘Bergman’ Japanese white pine

‘Bergman’ Japanese white pine (Pinus parviflora ‘Bergman’) is an outstanding, dwarf conifer that forms a dense, compact, wide, rounded to upright shrub. ‘Bergman’ Japanese white pine is a slow grower eventually forming a 4-6’ tall with a 6’+ spread shrub. The blue-green needles are soft, long and twisted. In spring, the immature cones are bright carmine-red contrasting dramatically with the blue-green needles. It is hardy to zone 5a and is adaptable to most, well-drained soils and pH. Unlike many other five-needled pines, Japanese white pine is road salt tolerant.

'Gold Drop' arborvitae — ‘Gold Drop’ arborvitae

‘Gold Drop’ eastern arborvitae (Thuja occidentalis ‘Gold Drop’) adds bright color to the landscape. This dwarf conifer shrub grows 4-5’ tall and 3-4’ wide and is shaped like a teardrop; narrow at the top, wider at the base. The soft, aromatic foliage is bright golden yellow when grown in full sun turning a deeper yellow during winter. ‘Gold Drop’ arborvitae is hardy to zone 3b and is adaptable to most soils and pH, but grows best in moist, well-drained, loamy soil. If grown in shade, the golden colored foliage will turn green.

Even though dwarf conifers are often more expensive than other deciduous shrubs, they are well worth it. They have a slow growth rate, require little maintenance and provide year-round color and texture in the landscape.

Laura Jull

Uncommon Clematis

– Holly Scoggins

Here’s a couple of clematis (clemati?) you may not be familiar with. Both are easy to grow but differ from the more common large-flowered form. There is a great deal of hybridization within the genus, so many cultivars are placed within “groups” rather than described as a cultivar of the species.

Clematis ‘Princess Diane’
Texensis Group

Clematis ‘Princess Diana’ in the author’s garden.

Crossing a large-flower clematis cultivar with Clematis texensis (scarlet leather flower) resulted in this lily-shaped beauty. Pointy little buds open as four hot pink tepals; bright yellow stamens grace the center. The buds on this rebloomer just keep coming; mine has been blooming for 40 days at this point and doesn’t seem to be slowing down. The princess seems pretty happy in her part-shade (sun in the afternoon) situation in my garden.

I swear there’s a lovely wire tuteur under there…

Some catalogs/sites describe ‘Princess Diana” as reaching only 8’ in length; mine’s wrapped up and down a 6’ tall tuteur/trellis thingy at least 4 times. Guess I need a bigger tuteur (doesn’t everybody?). Cold hardiness seems to be up for discussion – some sources state USDA Zones 6 to 9, others 4 to 8 (I’m a solid 6a here in the mountains of SW Virginia, recently warmed-up from 5b).

Various pruning strategies are associated with different groups of clematis. This one dies back to the ground and blooms on new wood, so I just cut it back in early spring to clean last year’s vines out of the wire supports.

Clematis xdiversifolia ‘Blue Boy’
Herbaceous/Integrifolia Group

Clematis ‘Blue Boy’ scrambles through a deciduous azalea.

‘Blue Boy’ is one of the herbaceous clematis, resulting from a hybrid of Clematis integrifolia and C. viticella. Multiple stems arise from the crown and scramble, flop, and otherwise meander through and over anything in the vicinity. Lovely blue-violet blooms festoon the stems from early June through frost (“festoon” is one of my favorite words – need more opportunities to use it!)

The rosy stems contrast nicely with the ornate foliage of Ligularia japonica.

Despite its delicate appearance, this is a very tough and cold-hardy (Zone 3!) clematis. Enjoy all summer, and then chop ‘Blue Boy’ back with the rest of your die-back perennials in winter.

Linked is a wonderful, detailed piece by Julie Lane-Gay on the herbaceous clematis group:
http://www.pacifichorticulture.org/articles/better-in-relationship-herbaceous-clematis/

Plants for winter interest: Going for the Gold

Winter appears to have a death grip on the eastern half of the U.S. for the second year in a row. The thermometer on my car read -6 F on my way into work this morning; with lows of -5, -11, and -2 predicted for the latter half of the week. And to my Northwest friends that have been out mowing their grass already, may the bird of paradise fly up your nose. At this point I don’t even remember what my lawn looks like.

Evergreen conifers provide one horticultural escape from the winter blahs. But evergreens don’t have to be green. One group of conifers that can brighten up a winter landscape are yellow or golden conifers. I will acknowledge these plants are not for everyone. But when sited properly (avoid winter sun is a common admonition among conifer buffs) and used judiciously (a little yellow goes a long ways) these conifers can add a contrasting element that can set off a garden. Note: Hardiness zone and size based on the American Conifers Society Conifer database.

Picea orientalis ‘Skylands’ (Skylands Oriental spruce) Zone 4. Size: Large (> 12” per year). This tree is a guaranteed show stopper. The combination of the narrow upright form and golden needles is tough to beat.

Picea orientalis ‘Firefly’ (Firefly Oriental spruce) Zone 4. Size: Intermediate (6’-12” per year). Firefly was selected as a sport off of ‘Skylands’ and is a recent introduction from Iseli nursery. So if you like Skylands but don’t have room for large conifer, this could be for you.

Chamaecyparis pisifera ‘Filifera Aurea’ (Golden thread false cypress) Zone 5. Size: Intermediate (6”-12” per year). This a tough plant that can make a good contrast specimen or can also serve as a foundation plant.

Golden thread false cypress as a foundation planting at the Missouri Botanical Garden

Picea pungens ‘Lutea’ (Golden Colorado spruce) Zone 4. Who says blue spruce have to be blue? Lots of concerns with blue spruce in the Midwest these days (more on that in later posts), but if you’re in an area where blue spruce are still doing well, this is an option for a winter bright spot.

Pinus contorta ‘Taylor’s sunburst’ (Taylor’s sunburst lodgepole pine) Zone 3. Ok, I’m cheating a bit here – the yellow comes on the new growth in the spring and then turns green. ACS database lists as a large conifer but I think they are referring to the straight species. When I have seen this plant it’s more in the intermediate range (6” – 12” per year).

Organic insecticides that will get you high

Plants are crazy chemical factories, synthesizing a whole host of compounds that we use for flavoring and dye and medicine and… getting high. And why are they making all these chemicals? They’re certainly aren’t doing it for our sake… no, quite often they’re trying to kill something – usually insects — and it just so happens that sometimes our brains and bodies react differently enough that instead of killing us, they make us high. Well, and sometimes they kill us too.

Nicotine, the addictive force behind cigarettes, is a potent natural insecticide. if you’ve heard of neonicotinoids, the pesticides that some are concerned with in relation to honey bee health, they’re synthetic insectides based on the chemistry of nicotine, and like it, they effectively kill insects. No word on if anyone has tried smoking them yet.

Opium poppies are full of a thick latex loaded with chemicals like morphine and codeine, to name a few, which are obviously used as pain killers, and of course opium is taken directly or processed into more potent forms like heroin. The research on these chemicals indicates multiple possible functions, acting to prevent damage by herbivores (like insects), and possibly also acting to prevent pathogen damage and maybe even a more structural function in strengthening cell walls in response to damage (see: http://pubs.acs.org/doi/abs/10.1021/np020583l) I didn’t find any research looking directly at opium’s ability to kill insect pests. Probably because that type of research is usually aimed at a practical solution to pest problems, and even if heroin proves to be a potent insecticide, I doubt anyone would issue and extension bulletin recommending you use it to control your whitefly…

But that lack of practical application didn’t stop a researcher from publishing a paper titled Cocaine as a Naturally Occurring Pesticide in which they found that cocaine was highly effective in killing tomato hornworm! Organic growers, take note! Maybe THAT’S why organic tomatoes are so expensive at the farmers market…

In any case, it is fascinating to note all the interesting, sometimes useful, often dangerous chemicals that have evolved thanks to the on-going chemical arms race between plants and the things that try to eat them. We’re the accidental beneficiaries – and sometimes victims – of that very, very old battle.

You CAN grow it, but is it worth it?

As winter sets in here in Michigan, I’m seeing gardeners deploying winter protection. Like this, which I saw on a visit to Hidden Lake Gardens with some friends recently:

Well. Isn’t that attractive? Come around to the far side, and you see this:

Pinus contorta ‘Chief Joseph’ which is a stunningly beautiful conifer, green in the summer, this brilliant shade of gold in the winter. Sadly, those gold needles are also incredibly prone to turning a less brilliant shade of brown if exposed to too much winter sun and wind. Hence the ever-so-attractive sun-and-wind shade they’ve installed here.

Call me old-fashioned, but the point of a garden is to be pretty, and though you CAN wrap delicate shrubs in burlap or upend styrofoam cones over tender roses or even (yes, I’ve seen it) put little roofs over your hardy succulents to keep excess rain off of them, but is it really worth it? For me, if I have to put something ugly on my plants to keep them healthy, it isn’t worth it. In my garden, I’d lean towards something else I also saw on that visit:

Chamaecyparis obtusa ‘Crippsii’ No, it isn’t quite as stunning as the pine… but it will grow and not turn brown, with no fuss.

What about you? Are there plants you are willing to make your garden ugly to keep happy?

Cool plant of the day: Canary Bellflower

I’m such a plant nerd that a few years ago I actually decided to get Canarina canariensis, the Canary Bellflower, for no other reason than that it is one of the very few members of the campanula family that has red-orange flowers instead of the usual purple-blue ones.

A Platycodon showing much more typical coloration for this family

Okay. Maybe that isn’t the most normal reason to add a plant to one’s garden, but I am VERY happy I did.

That color!

I’ll admit, it isn’t a plant that is particularly well adapted to life here in Michigan… as the latin name suggests (twice!) it is native to the Canary Islands off the West coast of Africa, where the climate is consistently dry, fairly cool, but never freezes. The summers are extremely dry, with a short rainy season in the winter. And the Canary bellflower has adapted to that by dying back to the thick fleshy roots in the summer, and then sending up the long trailing stems and flowers in the winter when the rains come.

That isn’t ideal for growing here in Michigan, but I’ve found I can get it to grow here pretty easily, actually. It is growing and blooming like crazy right now, and once it gets cold, I’ll move it inside, and let it dry out. As the soil dries, the plant goes dormant, so it can sit there patiently until spring and more settled weather when I can water and set it off into growth again. It works, and though it is a bit more work than most of the other plants I grow, it is worth it. I like looking at the lovely flowers, and speculating about the unique evolutionary path that caused this one genus to develop orange flowers while the rest of the family largely stuck with the tried-and-true purple.