Is Black The New Brown?

Mulch is always an interesting point of discussion as well as the topic of several past GP posts. But I honestly can’t recall if we’ve covered dyed mulch, and can’t search the site, so here goes.

I recently received a request for information from Debbie Dillon, a fine Urban Horticulturist with Virginia Cooperative Extension.  She noted the increased use of dyed mulch in the Northern Virginia area, and has been fielding questions from both landscape designers and homeowners regarding the safety of said mulch and the potential for harmful effects on plants. Black seems to be a fave color of late.

All I could offer her at the time was “Bleccch, I really don’t care for it” and a promise to investigate further. Armed with a bit of spare time and Google – here’s what [little] I’ve found out.

There are several products out there, such as Solarfast MCH and Mulch Magic. They’re used commercially on bulk mulch and are also available to the homeowner without restriction. From the Solarfast website – “Solarfast MCH is a colorant used to restore faded mulch back to its original color. It is environmentally friendly and does not contain hazardous chemicals, heavy metals or other ingredients that are known to be harmful to the environment.”

Is it safe?

The MSDS (Material Safety Data Sheet) for Solarfast was incomplete – it did not list components. The MSDS for Mulch Magic indicates the black contains carbon black, red contains iron oxide, and brown contains diethylene glycol monobutyl ether (as well as carbon black and iron oxide). The composition beyond that (carriers, surfactants, etc.), was not noted.  Diethylene glycol monobutyl ether is a fairly common solvent for paints and inks with purportedly low environmental toxicity, but can irritate skin and eyes. Carbon black can be made from various sources but is basically a petroleum product, used in laser printer and photocopier toner as well as the manufacture of reinforced rubber (i.e. tires).  Most concerns are related to worker inhalation at the point of manufacture. Iron oxide is, well, oxidized iron, and has been used as a pigment for quite a while (i.e. cave paintings at Lascaux, Bob Ross, etc.).

What about the plants?

There are many, many studies on pigmented film mulches (usually polyethylene) in fruit and vegetable production.  Certain colors can alter plant growth and processes, such as flowering and fruiting, stem length, etc., but I couldn’t find a thing regarding dyed, wood-product mulch. Issues of concern might be that the dye is disguising the composition of the mulch. Apparently dyes are frequently used on “pallet mulch” – shredded pallets, usually made from softwood. Another concern might be the increase in root-zone temperature, especially from the use of heat-absorbing black pigments. Could soil temperatures warm to the point of causing a too-early bud break?

Is it aesthetically pleasing?

Apparently “yes”, to some, because there’s a market for it. What do you think?

This photo was taken in April at a local medical center (it was a rainy morning, pardon the low light). The fairly typical commercial landscape surrounding the building is dotted with beds and trees freshly mulched in black. Note the classic mulch “volcano” in the background. No sir, I don’t like it. But that’s just me.

Toxicity information on compounds noted available at the International Agency for Research on Cancer (IARC) – Summaries &  Evaluations,

Building a Better Container, Part Deux: The Ellepot

I enjoyed Jeff’s post on the RootTrapper and thought I’d share another interesting and [relatively] new development in the world of greenhouse growing containers.

Take a tube full of growing media, wrap a paper sleeve around it, and voila – the Ellepot!

It’s bottomless, root permeable, and degradable. Each Ellepot sits in its own cell in a re-usable tray.  The great aeration and drainage makes for a happy, healthy root system.  Another plus is that after transplanting, there are no pots or packs to throw away

I’d say the bulk of Elle Pots are utilized at the propagation end of things – starting seeds and rooting vegetative cuttings – either for greenhouses  to “grow on” themselves or as plug/liner products sold to finishing growers (see student Paul Hutcheson holding a geranium liner above).

Ella and Ojvind Ellegard of Denmark developed the system in the early 1990’s.  Popular with growers in Europe, they’ve made their way to North America. Growers can buy in Ellepots by the pallet from various sources, or can invest in the equipment to make them

Wrap it up, I’ll take it…an Ellepot machine at Battlefield Farms, Rapidan, Virginia.

Sizes run from 15 mm (288 cells per 20” x 10” tray) up to 120 mm – equivalent to a  4” pot, perfect for bedding plants. Landscapers love them if they can find them – less waste from installation sites.

Petunia in an Ellepot. That’s Marc Verdel, head grower at Battlefield Farms.

As far as retail goes, I’m not sure if any market research has been done as to consumer preferences for this “pot-less” system. It’s a slight challenge for a shopper to pick one of this and two of that and transport them – you need some kind of carry tray. Anyone out there experienced with Ellepots (grower or gardener)?

Last-Frost-Date Roulette

We all play the game – at least the more impetuous among us do. You sneak a few tender things out into the garden, or on to the patio.  When the temperature drops and there’s a frost warning, no problem…just cover them up or bring them in.

Unless you forget.

oh, the humanity...
This WAS a rare and neato Pereskia aculeata ‘Variegata’. Paul W., please send me another…

Before dawn on Monday morning, (May 9) the temperature on our little mountainside dropped below freezing for four hours, going as low as 29.5 F according to our weather station. I had tucked everything back into the greenhouse or up under the eaves…except for the contents of a built-in planter on a far outpost of our deck.

Top o' the frosty mornin' to ya...
Dahlia Mystic Desire, edged in frost at 7:00 a.m., May 10.

NOAA has a handy set of maps that illustrate last dates of “Spring freeze occurrence”.  The maps present data averaged between 1951 and 1980.

Walking around the garden last evening with a nice hot cup of martini, I  surveyed the damage. Big, juicy-stemmed bleeding hearts that seem so fragile and succulent? Not a speck of injury – but they’ve been up since March. Newly emerged (and really expensive) Asian Jack-in-the-pulpits looked like wet rats. Annuals and tropicals exposed out in the open didn’t stand a chance. Early-to-leaf-out trees can take a beating, too. Japanese maples are notoriously precocious, flinging their fabulous foliage out as much as 45 days prior to last frost here. They’re in pretty good shape now, having acclimated a bit.  But for our previous hard frost,15 days ago, we had eight little maples individually draped in white row cover (looked like Halloween).

No longer desirable...
Dahlia Mystic Desire, kaput at 7:00 p.m., May 10.

So why the damage on some and not others?  Plants differ in the amount of sugars, proteins, and other compounds that affect the osmotic potential in cells. The lower the content of these compounds, the more likely freeze damage will occur.  Young and unacclimated tissue tends to have a higher ratio of water.  Like an overfilled water bottle stuck in the freezer, something’s got give as the liquid crystallizes and expands (vast oversimplification, sorry).  Cells burst, or are crushed from the freezing of intracellular water, and fluid goes everywhere – hence the limp, dark, water-soaked appearance.

Fog or dew on the plant can delay injury; as external moisture freezes, in gives off heat (an exothermic reaction; one of the amendments to the Laws of Thermodynamics), until all the water is frozen. This is why citrus groves are continually sprayed with water during a freeze event. So it also depends on the duration of the cold; if temperatures just briefly drops below freezing, damage is minimal. Four hours for non-acclimated tissue? See the grim photos for results.  Will I wait until May 15 to plant stuff out next year? Absolutely, positively, not.  We’re due a no-late-frost spring!


oh, the humanity Top o' the frosty mornin' to ya... No longer desireable...


End of the Semester Evaluations

It’s that time of the semester to hand out the lovely SPOT evaluation forms (Student Perceptions Of Teaching) here at Virginia Tech. Students fill in the circles (number 2 pencil of course) as to how you rate as teacher, your knowledge of the field, the value of the textbook, etc. A box is available, though seldom used, for students to hand-write comments – to many of us, the most valuable part of the evaluation process.  So as I was distributing the scan forms, I was thinking about feedback.  It seems that in life, where feedback or comments are totally voluntary and no forms are forced upon you, the energy required to send a letter, email, or comment is often (not always) mustered only for negative feedback.

In the case of this blog (and many others), we have enjoyed amazingly positive and inquisitive comments, even if it’s just two or three for each post, as well as the occasional barb (just fine with me) . Our biggest "commentroversy" came with Linda’s post about International Ag Labs – the ensuing hoo-ha resulted in 102 comments due to a "defend the ship!" email sent out by the company, and many were decidedly in opposition to the post.

All to say: we’ve been at this Garden Professors thing for about 9 months now, and Linda, Jeff, Bert, and me would like to know what YOU, our dear blog-readers, THINK. Some of you  comment fairly regularly – thank you Jimbo, Deb, Hap, Paul, et al. But I also know that’s just the tip of the iceberg.

Please take a moment, if you can, to weigh in: 

– Are you happy with the diversity of posts, or do you want "science and only science" e.g. less garden products/pantyhose posts?

– Do you enjoy reading about our work with students? No? Well, tough! (just kidding).

– What topics would you like to see addressed in future posts by our GP squad? Can be broad or specific. [More on perennials, you say? 😉 ]

– Overall thoughts? The value (or lack thereof) of this blog to you and your garden, nursery, or landscape firm?

Any and all feedback will be appreciated by all of us here at The G-Prof.

So go ahead and comment, even if you’ve never done it before!

Flounder barfs in 3...2...1...
Don’t make us summon you to the Dean’s office! (Note #2 pencils at the ready.)

Flounder throws up in 3...2...1... Flounder barfs in 3...2...1...

Do These Come In Control Top?

For those color-conscious gardeners who can’t bear to have visible tomato ties (or panty lines):

Only $2.99 for eight pieces?  Whatta deal!

Do you know how many tomato ties you can get from a pair of hose? Especially if you are a “long”? About fifty. Of course they’ll be nude or black, unless you bought into that purple trend last season.


ps:   I do like Lusterleaf’s (company responsible for the above) can o’ twine with the handy cutter-top, though. $4 and it has lasted through several seasons.

Oh, Deer…

More from our Ornamental Plant Production class tour across the state.  One of our stops was James River Nurseries, Inc.  Owner Mike Hildebrand has a built a unique and diverse business – they not only grow but do landscape design-build-install, all in the huge market of central and northern Virginia and beyond.

Here’s some arborvitae that spent the past few weeks at one of their job sites north of Richmond, waiting to be planting.  They’re now back at the nursery.  I was going to make this a quiz, but it’s unfortunately just too obvious.

deer nibbles

Wow. Poor things never even made it into the ground.


Just returned from a mega field trip across the state of Virginia with my Ornamental Plant Production & Marketing class. We toured major wholesale nurseries, greenhouses, and retail garden centers over the course of three days. The trip went well, I believe (university field trips are a considered a success if you return with the same number of students you left with).

One over-arching trend is, of course, that growers and retailers are going after the veg/fruit thing in a big way. Bonnie Plants has been one of the few vegetable transplant growers for the big box stores; now others are getting in on the act. Wholesale growers who traditionally supplied woodies and perennials to independent garden centers are including veg plants and herbs in their product mix.

Even the packaging is changing from the ubiquitous paper cup or poly 6-pack.  Coconut fiber (coir) pots are a step up from peat pots – they hold up better for the grower and garden center but are still plantable or compostable.


I can’t decide whether these pre-planted bean cages are ridiculous or genius. The students rated them “very cool”.  But how many beans can you get off of three plants?

bean thingies

Take some galvanized tomato cages, paint them bright colors, and charge three times the usual price. Who on earth would go for this? Oh wait, that would be me. Two. In orange. Cram ’em in the van, people.

I must have eet

Pardon If You’ve Seen This Before…

But it still makes me smile.

First published in December 2005, it’s still up at Red Shirt Knitting.  Seattle yarn artist Erika’s story is posted, as is a chronological progression of photos and events since the original “fitting”. 

She actually got some pretty funny tree questions/comments about potential girdling, the possibility of damage from moisture buildup (I like her response “What are YOUR sweaters made from…neoprene?”), etc.

Tortured urban tree examples abound: poorly planted, pitifully pruned, and other horrors.  I think Miss Erika should get some kind of award for this public display of [tree] affection.

Baffling Daffs

It is daffodil season in the Northern Hemisphere, hurrah!  May their blooms shoo away the gray of winter! It is also the season where everybody and their mother writes something about the wonders of the genus Narcissus, so figured I’d join the fray, but with a bit of a chip on my shoulder…

Miss ‘Barrett Browning’ in the Hahn Horticulture Garden at Virginia Tech

I recently read YET ANOTHER article warning against mixing daffodil stems in with other cut flowers due to “harmful effects from the sap”. If stems are conditioned, that is, placed in warm water on their own for 12 to 24 hours, it’s supposed to be o.k. This is repeated in everything from floral arranging manuals to gardening articles, but they never say what exactly causes the problem. So I’ve combed through many resources, to find a specific study backing this up and identifying what compound is responsible.


1) There is such a thing as “daffodil picker’s rash” which has been reported in the journal of Contact Dermatitis  (Julian and Bowers, 1997).  The authors attribute this rash to the “crystals of calcium oxalate in the sap, in conjunction with alkaloids, [which] act as an irritant, and also cause the characteristic sores.”  Duly noted.

2) Said calcium oxalate crystals are found throughout the daffodil, in the bulb, stem, sap, flowers, etc. Micrographs show that these crystals are needle-sharp, and apparently very painful (I have not gotten up the nerve to give them a nom).  This is why deer and bunnies will not eat your daffs.

3) The list of alkaloids is fairly extensive (as with many other members of the Amaryllidaceae family), including masonin, homolycorine, and a real nasty one, narciclasine- which disrupts cell division (meiosis) much like colchicine.

4) Are daffodils poisonous? Yes. If you (or your cat) hunkered down and consumed an entire bulb, problems would ensue. But the calcium oxalate crystals are, perhaps, nature’s way of convincing you (or Mr. Twinkles) that this is not a good idea.

So is there really an effect and if so, what makes daffodil sap deleterious to the other flowers in the vase?  The study “Effects of Daffodil Flowers on the Water Relations and Vase Life of Roses and Tulips” by W.G. van Doorn appeared in the Journal of Horticulture Science. Dr.van Doorn found the mucilage (sap) was indeed to blame, with just one daff shortening the vase life of both the tulips and roses by almost half.  But what component?

He split out the alkaloid fraction and the sugar fraction of the sap, and then added them as individual components to the vase water.  He drew different conclusions as to the cause: the research indicated that the effect in roses is mainly due to the sugar and polysaccharide fraction of the mucilage stimulating bacterial growth. This clogged the rose’s vascular system resulting in bent neck. You’ve seen this before – the bud, yet to open, flops over, never to recover.

These same sugars didn’t impact the tulips negatively but the alkaloids sure did. Even touching the sap to the tulip foliage produced a yellow spot.  He was not able to distinguish which of the six alkaloids detected were responsible, but at least narrowed down the cause ( sounds like a job for a grad student!).

So there you have it. I feel better. Am off to pick a few daffodils (very carefully) to brighten my office.


Some of my favorite plants are those that “do something” when little else is.
Do we really need more June-flowering perennials? No!
Well, yes. Never mind.

Edgeworthia chrysantha – “Paperbush” is the common name – is a deciduous suckering shrub , native to China. It usually maxes out around 4′ to 5′ tall and as wide.  The large, matte bluish-green leaves resemble those of Magnolia virginia in shape and are also a bit silvery on the underside.  But that’s not what we’re here for…

An oooh-aaahhh-worthy specimen at the Hahn Horticulture Garden, Blacksburg, VA.

Furry, silvery flower clusters dangle like earrings from the cinnamon stems throughout the winter, getting larger by the month.  

Then by late February or March, they open up, all golden and waxy, emitting a light, sweet fragrance on sun-warmed days.

Blooms at Pine Knot a few Springs ago…

Edgeworthia is ideal for the deciduous woodland environment. Hellebore specialists Dick and Judith Tyler of Pine Knot Farms (Clarksville, Virginia), situate theirs among drifts of spring bulbs and, of course, Hellebores. It’s a soul-stirring sight in March.

I believe the hardiness of Edgeworthia may be underestimated, especially if you go to a little effort to select the right microclimate.  Dr. Dirr lists it as Zone 7 to 8(9). Having enjoyed them at the JC Raulston Arboretum during my doctoral work at NC State (Raleigh, North Carolina; Zone 7b), I found Edgeworthia was little-know here in the Blue Ridge (solid Zone 6, alledgedly 6a).  We ordered some in for our Garden and Hort Club’s 2007 plant sale held in late April – despite my pleading and mark-downs, they didn’t generate much interest from shoppers as they were out of flower. We planted the left-overs in a fairly protected position on the North side of our garden pavilion, and they’re thriving. Snow was heaped up around them throughout January and February and we’ve gotten well into the single digits complete with howling winds a few times.  Despite this rotten winter, they look better than ever, ready to burst into bloom any day now.  Readers, please weigh in: Had any success with it in Zone 6?  And why isn’t this fabulous thing more prevalent in the trade?