Confessions of a carbon sequestration skeptic

One of the potential environmental benefits that came up in our discussion of the pro’s and con’s of turfgrass was carbon sequestration.  The basic premise of carbon sequestration is to take CO2 out of the atmosphere and ‘lock it up’ in a form that won’t contribute to further global warming.  One of the fallacies floating around these days is that any plant that photosynthesizes, takes up CO2 and thereby sequesters carbon.  What we need to realize is that leaves give off CO2 at night via respiration and all non-photosynthetic (non-green) plant parts such as roots and stems give off CO2 virtually all the time.  Turfgrass has some potential to sequester carbon, primarily as soil C. If we consider that a 7” deep layer of soil weighs 2 million pounds, increasing soil carbon by 1% can sequester 20,000 lbs of C per acre.  How long does it take turfgrass to increase soil C by 1%?  Don’t know, but I’m sure it takes awhile.  Also, there is a limit to amount of carbon a give soil can store as C is respired away by microbial activity so eventually a steady state will be reached.  (Plus we haven’t even subtracted out fossil fuel carbon to maintain turf).  Some plants, such as trees, do have the capacity to sequester carbon in wood for long periods – think redwoods, sequoias and redcedars.  But these trees cover only a small fraction of the world land area.  Intensively managed forestry plantations can take large amounts of carbon out of the atmosphere and sequester it into wood.  The question then becomes what do you do with the wood?  If we burn it for biomass energy; Foof! All that C is right back in the atmosphere.  Still better than burning fossil fuels but also a little less than carbon neutral at best.  We can build houses with the wood from the plantation – the carbon will be sequestered as long as the house lasts.  My home and barn were built in the 1890’s so the carbon taken out of the atmosphere by those trees is still locked up.  If we really want to get serious about carbon sequestration, however, our best strategy would be to convert the entire Upper Peninsula of Michigan to fast growing poplar plantations, harvest the wood every 15 years, and sink the logs in Lake Superior where the cold water will prevent decay.  Sound funny?  I’m not the only person thinking this way.  See Strand and Bedford 2009. Ocean Sequestration of Crop Residue Carbon: Recycling Fossil Fuel Carbon Back to Deep Sediments Environ. Sci. Technol., 2009, 43 (4), pp 1000–1007.  


Bottom line: carbon sequestration is a very complex process and sequestering carbon for more than a few decades takes more creativity and brain-power than most of us can muster.  However, trees and landscape plants do have important role to play in mitigating climate change and it doesn’t require heroic feats of engineering.  Trees and landscape plants can effectively cool buildings, thereby reducing air conditioner use and save fossil fuels – see the USDA Forest Service Urban Forestry Research site for a few examples   ultimately this is landscape horticulture’s contribution to climate change.  Carbon sequestration?  It’s a drop in a very big bucket.


Dog Spots

There is a general misunderstanding among the gardening (and yard owning) community about dog spots.  It seems that some people believe that dog spots occur because of a high or low pH or because of some sort of poison in a dog’s urine, but that really isn’t the case at all.  Dog spots occur because of something that I pointed out a few weeks ago in another post.  Urine contains a lot of nitrogen.  When a dog pees on your lawn that extra nitrogen isn’t used and so ends up being poisonous to the grass which is peed upon.  You’ll notice that around the periphery of a dog spot the grass is particularly bright green.  This is because the extra nitrogen helps the grass in that location rather than poisoning it.  If you want to get rid of a dog spot the best thing to do is to follow your dog around carrying a five gallon bucket of water and pour it over the spot as soon as the dog pees — this should stop the grass from dying, but will probably not get rid of all the extra nitrogen and so you’ll end up with a bright green spot instead of a brown one.

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?


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. 

– 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.


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.”  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.


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.

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 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?)–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.