Category: Interesting Plants

Friday Physiology Fun Followup

Astute readers pointed out several morphological adaptations found in drought-tolerant turf weeds:  fleshy taproots, reflective leaf surfaces, etc.  What we can’t see is what many of these plants do physiologically – and that’s photosynthesize using a biochemical pathway that temperate turfgrasses don’t possess. 

This pathway, called C4 photosynthesis, contains some extra preliminary steps not found in plants using traditional (C3) photosynthesis.  The downside:  it takes more solar energy for the plant to photosynthesize.  The upside:  these extra steps allow the plant to "fix" carbon (transforming it from gas to solid) faster, especially when it’s sunny, warm, and droughty.  Practically speaking, this means that C4 plants do not have to keep their stomata open as long and they conserve water more efficiently than C3 plants.

So in the summer – when it’s hot, sunny and dry – the C4 plants in your lawn are operating under optimal conditions, while the C3 grasses go dormant.  The tables turn when the seasons do:  cool, moist conditions favor traditional photosynthesis, and the C4 plants are overtaken by the turfgrasses.

Cool, huh?

Friday physiology fun

It’s still cold and wintery, so let’s imagine ourselves in a happy place…warm, sunny, dry…with dead lawns.

As the photo shows, the turfgrass is dead; this happens every summer during the Pacific Northwest’s droughty summers.  Yet many of the weedy species are obviously thriving.  Why?

Remember, this is a physiology quiz.  You can discount herbicides, fertilizers, etc.  This is a cool (no pun intended) adaptation that many species native to dry, subtropical to temperate environments possess.  And there are serious implications for water use related directly to this adaptation, or lack thereof.

Let’s see lots of brainstorming on this – no points deducted for trying!  (And if you are a true ecophysiology geek, let other people try first before posting the answer.)

Friday fun, part 1

This posting is for Holly, who I am sure is desperately trying to finish her annual review.  I feel your pain!  And I’m going to add to it today.

 

The poinsettia in these photos is not from this Christmas, but from 2008.  You can see it thriving happily in its office environment.  I’m told by its caretaker Nick (a nongardener) that it has no bugs or other problems, and seems very happy.  And it’s blooming, without the benefit of the extended night period.  (The post-it notes are instructions to its care when Nick is away.)

Apparently SOME people can easily grow poinsettias well past their expected holiday life span.

Baptisia: Beyond the Blue

The Perennial Plant Association recently released the identity of the PPA Plant of the Year – for 2010 it is Baptisia australis (False Blue Indigo).  Various blogs have noted this (including Garden Professor fave Garden Rant) and I’ve read some interesting comments, both pro and con.

True story: I asked for Baptisia at a small rural garden center years ago; the owner said “Don’t have any; but I think I have a Methodist running around here somewheres…”  Badda-bump.

Me? I think it is a truly wonderful native perennial. I’ve had great success with it in both Zone 7b and 6a and teach it as a “bread and butter” component plant for the mixed border. As a PPA member, it certainly got my vote on the last ballot (beats the hell out of last year’s Hakonechloa macra ‘Aureola’ – hard to say and even harder to grow in the Southeast).

The great thing about the PPA “Plant of the Year” program is not just in the promotion of that particular species, but that it opens the door for other cultivars and hybrids.  Two of my favorites:  Baptisia x ‘Twilite Prairieblues’ [sic] and B. x ‘Solar Flare’. Both were bred and/or selected by that delightful genius Dr.Jim Ault, of the Chicago Botanic Garden, and introduced through the Chicagoland Grows program.  Pictured are plants that are have only one full year of growth after purchase and planting (nice full gallons to start with; from Saunders Brothers nursery, located in the greater metropolitan area of Piney River, Virginia).


Baptisia x ‘Twilite Prairieblues’ is a cross between B. australis (our PPA winner) and B. sphaerocarpa – a shrubby, tough little guy with yellow flowers. This fortuitous romance yielded quite a jaw-dropping color combination of dusky violet with a yellow keel petal. These puppies are in our campus horticulture garden.

Now take a gander at B. ‘Solar Flare’ – a “complex hybrid, probably open-pollinated” of B. alba (white-flowered), B. tinctoria (yellow-flowered), and B. australis. This is what can happen when a whole bunch of species and hybrids are planted close together (cocktails and/or bees are usually involved). From my own garden:

Buttercup-yellow fades to warm apricot, then to plum – the thing absolutely glows in the late afternoon sunshine.  Gosh, I miss summer…

Sigh.

Better Red than Dead!!!

David, one of our newer readers, asked why his red-stemmed roses seem to be more cold hardy than the green-stemmed cultivars.  So today’s blog will be dedicated to a brief discussion of why it’s better to be red than dead.

The brilliant red, blue, and purple colors seen in flowers and fruits are due to anthocyanins (and the closely related betacyanins).  These water-soluble, non-photosynthetic pigments are also commonly found in stems, leaves and other vegetative tissues.  In 1999 I wrote a review article exploring the reasons that leaves and stems might turn red.  A few years later I wrote another review, more specifically looking at how anthocyanins might influence plant water relations.  (This last phrase is plant physiology-geek jargon, and I have to admit that the class I took on this topic during my PhD work was the hardest, and probably most hated, of all the classes I took.  And now it’s turned out to be one of the most valuable.  Go  figure.)

While you hard-core types can read the review articles that I’ve hot-linked above, what I’ll try to do is summarize my hypothesis for why leaves (and stems) turn red.  Some leaves are red when young, then turn green when older.  Green, deciduous leaves turn red before they fall off in the autumn.  And some plants are genetically programmed to have red leaves all their lives.

The environment can also influence leaf reddening.  Drought, nutrient deficiency or toxicity, salts, heavy metals in soils, cold temperatures, low soil oxygen, whew!  All of these environmental factors have been attributed to temporary reddening.  What do these factors have in common?

It turns out that all of these environmental stresses directly or indirectly affect the ability of plants to take up and/or retain water. Because anthocyanins are water-soluble, they effectively dilute the concentration of water in the plant.  Look at it this way: any limited area will only hold so many water molecules.  A test tube of pure water has the maximum number of water molecules possible.  A test tube of water plus sugar (or salt, or anthocyanins for that matter) will have fewer water molecules, because the other substances take up space, too.  So effectively, anthocyanins reduced the apparent concentration of water in plant tissues.

Why is this important?  Well, anthocyanins in leaves helps reduce water loss, because the concentration of water in the leaves is reduced and evaporation slows down.  They also could serve as antifreeze compounds, allowing red leaves (and stems, David!) to be more cold hardy.  And if anthocyanins aren’t amazing enough already, they also (1) bind and transport sugars during fall leaf color change, (2) protect tissues against high levels of solar radiation, and (3) are natural antioxidants.  (That’s why you’re supposed to eat red fruits!)

I could go on and on, but I hope this might help explain why David’s red stemmed roses might be more cold hardy than the green variety. (And my thanks to my daughter Charlotte for allowing me to use her photos here.)

I think about these things as I peer into my coffee cup…

This winter, we’re working on renovating part of the campus Hort Garden. We’re tossing around lots of ideas/themes, but I’m leaning towards a garden full of “Plants with a Purpose”. Edible, fiber-producing, medicinal…you get my drift.  Which brings me to today’s bloggerific topic: beverages.

Mankind has, throughout history, infused or fermented just about every species of flora in an effort to get either perked up or calmed down.  These plant potions are often classified anthropologically as, ahem, “ceremonial beverages”. The species that we currently rely on for our daily ups and downs are not native to North America.  But that’s not always been the case.

Way before the joys of coffee hit these shores, there was the Yaupon holly (and I am partial to hollies). This thicket-forming evergreen shrub likes “wet feet” and is usually found in marshy areas in the piedmont and coastal plains of the southeast.  Translucent red berries grace the female plants in winter – hollies are dioecious, meaning male and female flowers reside on separate plants.  The fact that Yaupon is one of few native plants to contain caffeine was picked up on very early by Native Americans – a potent tea brewed from the leaves was called the black drink.  Though the scientific name Ilex vomitoria might indicate some unpleasant side effects, it only exhibits emetic properties when a ridiculous amount is consumed.

Sassafras (Sassafras albidum) has been used as both a flavoring and as the main ingredient in teas and soda.  The sassafras is a sweet little understory tree, with oddly and variably shaped leaves – with one, two, or three lobes – Dr. Dirr at UGA pointed out to us that they often resemble “racoon mittens”  Native throughout the Appalachians, the tree roots were dug up in early spring before while still loaded with sap (where’d ya think they got the name “root beer” from?!).  Safrole is the  phenolic compound that produces the characteristic flavor.  However, safrole is now considered a carcinogen and the FDA banned the sale of sassafras for human consumption in 1976.  Extracts used in food and beverages have to be “safrole free” – produced through a commercial process. It’s also a psychoactive compound.  This may explain Yosemite Sam’s obsessive-compulsive tendencies and Saturday morning profanity (and I quote)  “Rassan, sassan, sassafrasan…”.

Last in today’s line-up of stuff from the woods: Humulus lupulus (the vowel-heavy name for hops).  Mmmmm, hops.  Here ye, the one or two people that may not know this, that from hops cometh the essential oil that maketh beer yummy. Speaking of oils, get close enough to hop vines on a really warm day and you’ll get a whiff of why it’s in the family Cannabaceae.  This perennial vine is native to most of the Northern Hemisphere.  The European beer-making strains have naturalized – that is, has spread from plants brought over by colonists in the mid 1600’s.  Hops are also dioecious – the female flowers are papery cones about the size of a quarter and the source of all hoppiness (the male flowers are basically useless and just sit around with their feet on the coffee table).  The leaves are sandpapery and most have three lobes – sort of reminiscent of a grape leaf.  Not only useful to make ceremonial beverages, the vigorous leafy vines provide an excellent screen and can quickly cover up an unsightly fence, shed, or family member.  Now that’s a useful plant!


I spent so much time writing this I ran out of time to hunt for plant photos. So here you go: My traveling T.Rex enjoys a nice, hoppy Virgin Islands Pale Ale on a lovely beach in St. John.

Carrot-top syndrome in white pine

I know a few folks out there are starting to believe that I’m just an apologist for the nursery industry.  While it’s true most of the nursery people with whom I work are hard-working folks trying to do their best to run a successful business and produce a quality crop, there are certainly some issues out there and I’ve got my share of pet peeves.  One of the things really that chafes my heiney is what I refer to as “Carrot-top” syndrome in eastern white pine (Pinus strobus).  White pine is one of the most commonly planted conifers in this part of the world.  White pine is native throughout much of the eastern US and is an extremely fast growing tree that makes a good ornamental when planted on the right place with room to grow.  It is also widely grown as a Christmas tree in the Upper Midwest as well and therein lies the rub.  Many nursery producers also grow Christmas trees and many Christmas tree growers also dig nursery stock.  The result?  White pines that have been heavily sheared as Christmas trees end up planted as landscape trees.  Once in the landscape, the upper portions of the trees will quickly resume rapid growth, with some shoots growing 2’ to 3’ or more per year; while the side shoots that had been repeatedly sheared barely grow at all.   After a couple of years the net result is neatly trimmed Christmas tree with a wooly beast growing out of its top.   What’s the solution?  Ideally producers should identify which portion of their trees will be sold as Christmas trees and which are destined for the landscape trade.  Christmas trees can be sheared to meet demands of that market while landscape trees can be pruned much more lightly to maintain a single leader and conical form but keep obvious layers of whorls.  The dilemma, of course, is that growers don’t always know which trees will end up and the Christmas tree lot and which will be dug for the nursery trade.  The other, more challenging problem is that, given a choice, 99 out of 100 garden consumers will choose the neat-looking Christmas tree for the landscape, unaware of the wooly mess that’s about to be unleashed in their yard.  The solution?  Education on both sides; making growers aware of the issue and making consumers realize that the only way to have a natural-looking white pine in your yard is to start with a natural-looking white pine.


Heavily sheared pines will retain the outline from from shearing for years while the top rages out of control.

How on Earth Did I Land This Gig?!

Linda referred to my recent absence from the blog – but it was in the name of education, I swear!

Cocos nucifera, the iconic coconut palm.  My office for the past two weeks. Or a Corona advertisement. You pick.

This study abroad to the Dominican Republic sent Virginia Tech students (mostly biology and natural resources majors) to the Punta Cana Ecological Foundation for the entire semester, with faculty rotating in for two-week stints on topics from ornithology to geography. My topic was “tropical horticulture”.  The professor previous to my session had to cancel his trip; by the time I arrived, the un-chaperoned students had basically gone feral.  Corralling them with promises of beer and French fries, I coaxed them out onto plant i.d. walks.  By the time our field trip to the national botanical garden rolled around, they were blurting out plant names left and right.  Made me proud!

Identification walk featuring salt-tolerant plants. That’s red mangrove, Rhizophore mangle, on the right. Feral students on left.

The ecological foundation’s shade houses, orchard, and organic veg gardens grow some of the produce for the resort and made for a great learning experience (unusual greenhouse pest problem: tarantulas).  I’ll post more tropical plant pics and factoids in January – when we’ll really, really need to see them.

Morinda citrifolia, better known as Noni.  Though chock full of vitamins and all manner of secondary metabolites of medicinal interest, the smell of ripe Noni is comparable to Limburger cheese left in the sun for several days.  Shrieks of “NONI!!!” meant someone was about to get pelted with over-ripe fruit.

 

Graft and corruption

It’s election season – but that’s not why I’m doing a blog on “graft and corruption.”  Instead, let me back up and explain that today I gave a seminar on diagnosing urban tree death.  One of my points to the group was the importance of knowing the history of a site – what species were selected, how trees were planted, whether there had been any major construction activity, etc.  I thought I’d continue the importance of site history into today’s posting.

Here’s a photo of a street tree – a Prunus spp.  (Disclaimer: I am not endorsing a candidate for Mayor of Seattle despite the appearance of a campaign sign in the photo.)  It’s a healthy enough specimen, though possibly a bit large for this narrow planting strip:

Several years ago you would have seen a different tree in this same spot:

Now did this weeping cultivar somehow transform into an upright form?  Let’s look at this second photo in its entirety:

This reminds me of my favorite childhood book on Greek mythology, which had a great drawing of Athena springing from the head of her father, Zeus.  Yes indeed, we are seeing the scion of a grafted tree lose the battle to the rootstock.  Rootstocks, by their very nature, are vigorous.  If we revisit the first photograph again, this time a little closer, we can see all that remains of the poor scion:

Lesson:  if you are using a grafted tree in the landscape, you need to keep the rootstock under control.  Grafted trees are probably not good choices for low-maintenance landscapes.