The Garden Professors™ – Page 111 – Advancing the science of gardening and other stuff since 2009

Why won’t landscapers use mulch?

A few weeks ago I was in Olympia (it misses you Bert!) reviewing grant applications. As I tend to do whenever I have time and my camera, I set out in search of gardening goofs that evening. Here’s the edge of a relatively new commercial site I discovered:

OK, not too bad so far. We’ve got a nice stone mulch next to the curb, then a lovely groundcover, in flower, that also functions as a living mulch. But what’s that we see in the upper half of the photo?

Yes, it’s Canada thistle (Cirsium arvense), an aggressive perennial weed that spreads by stolons and can make dense monocultures of prickly nastiness. In fact, the front is already advancing on our little groundcover:

Had the landscapers continued with mulching the soil rather than leaving it bare, these thistle seeds might not have germinated. But for whatever reason, the bulk of the landscape was left bare:

I’m sorry, but this just looks ridiculous. There was some obvious care in laying the stone mulch and groundcover, but then the landscaper seems to have run out of time and/or money and just plopped in some bulbs and corms. It reminds me of a birthday cake.

I don’t understand the rationale behind this. Was this a real design? Did the client run out of money? Or (as the more cynical side of me wonders) was this done deliberately to create a high maintenance landscape requiring lots of weeding in the future?

Thoughts?

Quiz Plant Revealed

Ha ha hahahaha
*mad scientist-type cackling*

Purslane? Nyet! (but good guess).

It’s an Impatien! Specifically, Impatien repens, common names variously Ceylon Jewelweed, Golden Dragon Impatien, etc. Ours is actually pretty small – can form huge clumps and cascading torrents in warmer zones.

Flower is typical of many members of the genus, and they ALL have the little spur in the rear.

For more weird, wild species impatiens, visit the Cistus Nursery website (I’m pretty sure they used to sell this, but I don’t see it listed currently). We got ours from local plantswoman, gardener, and mail-order-addict Elissa Steeves.

Thanks for playing, all!</d

Quiz Plant!

Ooooh, this is a good one.

Factoids:
– Tropical, but doing well in our campus garden (Blacksburg, VA).
– Succulent stems; alternate, lima bean-shaped leaves.
– Rampant scampering.
– Very cute yellow flowers. (Hee hee, that really won’t help.)
– I hesitate to say this, ’cause it may just give it away: a couple of other members of this genus are common as mud.

Guesses, anyone? Or maybe this one’s already common as mud for you Pacific Northwesterners…
(and P-Dub, do refrain until others have had a chance 😉

I’ll post the "D’oh!" flower photo in the morning.

Hellebore and Hosta for scale. There are flowers, just not in this pic.

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Is brown the new green?

An acquaintance of mine (not coincidentally, an irrigation supplier) brought to my attention a recent editorial from USA today by Laura Vanderkam, entitled ‘’Out of Fashion: Green Lawns.” http://www.usatoday.com/news/opinion/forum/2010-08-17-column17_ST_N.htm?loc=interstitialskip#uslPageReturn The basic premise of the editorial is that we Americans are ruining the environment by maintaining lawns. Now, to be sure, there is plenty of room for improvement in lawn and landscape maintenance, particularly in terms of water management and pesticide use. But, for better or worse, Americans love their lawns. I love my lawn, imperfect though it may be. We’ve got a couple of big oaks in the backyard and I love to lay a blanket in the shade and read a magazine on Sunday afternoon or just doze with the Tigers game on in the background. Love to play croquet and bocce. Love to kick a soccer ball around with my daughter. In the interest of full disclosure, my lawn will not win any awards. At this moment about 75% of my lawn is brown, panting in the heat of our first true summer in several years. I water a small portion of the lawn for the aforementioned croquet/bocce playing, and magazine reading/ Tigers’ game snoozing. For most part, however, I take a lazzez faire attitude to lawn upkeep; I keep a 3” mower height, apply a little bit of Weed-b-Gone every other year in the section nearest the house when the dandelions are ready to drive me to distraction and, if I remember, put down a half rate of fertilizer in the spring. Nevertheless I was taken aback by Ms. Vanderkam’s assertion, “Few parents would light a cigarette at a playground anymore, even if it’s not illegal, and we should start treating the presence of a vast, green, cropped grass lawn in the middle of summer the same way: as a weird and antisocial thing.”

Let the games begin. Mrs. Cregg scores again on the opening day of Cornhole season 2010.

Wierd and antisocial? Really. From May to September, our lawn is the most social part of our place. What’s really needed, and often the hardest to find, is some middle ground. It’s easy to resent people that belong to homeowners associations that require perfect lawns and hire ‘Chemicals R Us’ to maintain their pristine turf. However, lawns and landscapes can provide an array of benefits, some tangible like oxygen produciton and cooler air temperature; and some less tangible, like a perfect croquet shot.. We can, and should, look to reduce water and chemical use on lawns. But Ms. Vanderkam will get me off my John Deere riding mower when she can pry the steering wheel from my cold, dead fingers.

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Dying dogwood diagnosis

Lots of good, thoughtful answers from you over the weekend about these trees. Here’s another photo from a bit farther away:

As Laura pointed out, there’s a relatively new parking lot here. The creation of the parking lot both compacted the surrounding root zone, then covered it with impermeable surface. The dogwoods are huddled on their little island, which is unirrigated, unmulched, and indeed hot in the summer as Daniel said. All of these environmental insults, in addition to the mature age of these trees, have led to what we call a “mortality spiral”: trees are environmentally stressed and then become more susceptible to opportunistic pests and diseases. Jon and Wes both did a nice job of discussing this.

There’s a couple of take-home messages here:

1) If you must disturb a significant portion of an existing tree’s root zone, you should both protect the zone from undue compaction during construction, and then follow up with heavy-duty aftercare of irrigation and mulching.

2) If you can’t follow point #1, then for heaven’s sake just remove the trees when they start their inevitable failure. “Lingering death” is not an attractive landscape theme.

The dilemma of the dying dogwood

Here’s a photo of two mature dogwood trees that are obviously on their way out:

What happened? There’s been no construction in the area since the parking lot was paved several years ago.

Answer on Monday!

Lungs and Plants

As a third grader I distinctly remember my teacher telling our class about how it was bad to smoke because the smoke would make your lungs filthy. She used her aunt as an example. It seems that this aunt was a heavy smoker. One day this aunt was eating popcorn and accidently inhaled a piece. About 6 months or so after she inhaled it she coughed it up and it looked like a little piece of tar. Funny how some stories stay with you.

The interesting thing to me is that my third grade teacher’s aunt isn’t the only one who has inhaled a seed, and that the inhilation of the seed needen’t mean curtains for the plant. Recently a gentleman inhaled a pea (or bean, the exact type of plant still appears to be a bit up in the air — ) which sprouted in his lung http://pagingdrgupta.blogs.cnn.com/2010/08/13/plant-sprouts-in-mans-lung/?iref=NS1 http://pagingdrgupta.blogs.cnn.com/2010/08/13/plant-sprouts-in-mans-lung/?iref=NS1 and last year there was a gentleman from Russia who apparently had a fir growing in his lung (though it seems more likely that the man actually inhaled the tip of a more mature tree — too much vodka? — My question is whether there were roots, and if so, does that make this a novel way to root a fir cutting?) http://www.dailymail.co.uk/news/worldnews/article-1169861/Shocked-Russian-surgeons-open-man-thought-tumour–FIR-TREE-inside-lung.html

After doing a quick search I also found a case where a child had a germinating seed of an apple in his lung, a case where a germinating bean caused a young girls right lung to collapse. And, apparently, both children and adults inhale grass seeds now and again though I couldn’t find much information on how frequently these seeds actually germinate in the lungs.

I wonder, is this the beginning of an interesting coevolution between plants and people? Could a plant evolve so that the seeds were inhaled by humans, grew in our lungs, and then, later were expelled to be inhaled by other humans? Just a random thought on a slow Thursday.

A ground cover I just love

I’m a particular fan of ground covers, especially those that replace bare soil or synthetic mulches (plastics, fabrics, and the sciency-sounding “geotextiles”). That enthusiasm is tempered, however, by those invasive species, like members of Hedera, that seem to take over the world (or at least my little corner of it). So while logic might dictate a preference for native species, I can’t help but love Rubus hayata-koidzumii (often mislabeled as Rubus calycinoides), and commonly called creeping raspberry.

When it comes to ground covers, I prefer species that stay on the ground; I like them low, tough, and dense enough to keep weeds out. Of course they need to have attractive foliage and/or flowers. But the icing on the cake, quite literally, is when they have edible fruits.

That’s why I love Rubus hayata-koidzumii, a high-elevation species native to Taiwan. This USDA Zone 7 plant prefers sun to part shade (as you can see in the photo above), thriving in hot, dry conditions. Not only does it do yeoman’s work in covering and protecting slopes, it bears abundant white flowers which morph into tasty fruits that practically beg to be baked into a cobbler or crisp.

But have I let my heart overrule my head? Are there places where this species has become a problem? I haven’t found anything in the literature to suggest it’s invasive, but am curious to hear from others.

Pigmented Mulch in Paradise

Just back from a quick vacation to Little Cayman island. Truly a dot on the map – the whole island is about 7 miles long and a mile wide. Only 150 locals and a couple hundred tourists are on island at any one time. It’s beyond laid back, with few attractions other than the resident iguanas and red-footed boobies (booby jokes abound).

Airport terminal/post office/fire station.

The big draw is diving – LC is the home to Bloody Bay Wall, one of the most famous dives in the Caribbean. The reef drops off like a sheer cliff, from 40-60′ to more than 1000′.

All the action is underwater!
(Let me know if you want to see more slightly blurry diving photos.)

“Fascinating, Holly. But what does this have to do with painted mulch?”

The extent of the landscaping for most yards: conch shells arranged in interesting designs and/or piles. But as we pedaled past a rather upscale condo, I came to a screeching halt. A gorgeous Bismarckia nobilis had caught my eye, but then I saw what was under it. Egad.

Everything comes to Little Cayman by a weekly barge or little prop plane and is wildly expensive. Four-pack of batteries? $15. A six-pack of beer is $20. TWENTY DOLLARS!!!

So, good readers, what we have here is possibly the most expensive mulch on the face of the earth. I can’t even imagine.

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Need a lift?

One of the topic groupings for our posts is titled ‘Cool research’. The subject of today’s post has actually been around for a few years but I still think it’s pretty cool.

When we think of interactions between plants we usual think of negative interactions such as competition for water and nutrients or maybe allelopathy. But there are cases where plants can benefit each other. One of these is a phenomenon known as hydraulic lift. Hydraulic lift is the passive movement of water from roots into soil layers with lower water potential, while other parts of the root system in moister soil layers, usually at depth, are absorbing water. In essence, plants will large, deep root systems (usually trees) bring soil water from depth to the surface where it can be used by other plants. Hydraulic lift has largely been observed in arid and semi-arid ecosystems, though it can occur in wetter systems as well. For me, the research that went into discovering hydraulic lift is as fascinating as the process itself.

One of the key lines of evidence for hydraulic lift comes from studies of stable isotopes. As you may recall from college or high school chemistry, atoms of each chemical element have a certain number of protons and neutrons, which give it its mass. A small portion of each element has extra neutrons resulting in a ‘heavy isotope’. In the case of hydrogen, approximately 1 in 6400 atoms is heavy hydrogen or deuterium (²H). Interestingly, the amount of 2H in water can vary depending on the source of the water; this ratio is termed an isotopic signature. By comparing the isotopic signature of ground water and rain water in a given location, researchers can actually tell where certain plants are getting their water. One of the classic studies in this area was conducted by Todd Dawson at Cornell in the early 1990’s. Dawson analyzed isotopic signatures of groundwater, rainwater, and water in various plants around sugar maple trees and determined that many herbaceous plants contained a high proportion (up to 60%) of groundwater. But how do shallow-rooted plants obtain groundwater? The neighboring maple trees bring it to the surface from ground water as they are hydrating overnight. An efflux of water from the maple roots results in a localized increase in soil, which can be utilized by other plants: hydraulic lift.

How important in hydraulic lift in most landscapes? Probably not very. Demonstrating significant hydraulic lift requires the proper hydrology (shallow ground water accessible to trees or shrubs but not smaller plants) and limited rainfall. But the importance goes deeper (no pun intended!). Prior to the advent of stable isotope techniques, many would have been dismissive of the concept of hydraulic lift. Since 1993 over 100 papers have now been published on the subject. To me, the ultimate value of Dawson’s work and related studies is showing the importance of keeping an open mind and being receptive to new ideas.

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