Sandra's Garden: proof not all Phlox are created equal

Species name: Phlox subulata

Common name: moss pink, moss phlox

Location: Sandra's garden

Last year I posted a blog about moss phlox, a native species we have in our garden that gets a little out of control in really sunny areas. It's a species native to North America, and one that occurs relatively commonly throughout its native range in bright and sunny, damp areas (despite also being drought-tolerant). It is much more common in the United States than in Canada. I knew this species was a popular garden plant based on what I've read about it, but I had never seen any of the cultivars created in greenhouses aside from the "normal" light purple type. Well, here's a spectacular demonstration of the "hidden" morphological variation that some plants contain. This variety of moss phlox was not created in the lab, but is a product of controlled breeding. Despite this, you would never find this variety of phlox in the wild unless it escaped from someone's garden.

So how do we "create" morphological variation in plants that is not typically seen in the wild? The secret is some patience, and a lot of time on your hands (it helps to have a greenhouse because it speeds things up a bit). Natural mutations in the wild create different alleles, or copies of a gene, that can show different morphologies if they have a chance to be expressed. Most of these mutations are what we call "recessive", which means you have to have two copies of the gene in order to be able to see the effect. This is good for the plant if the mutation is detrimental, but bad for gardeners if the mutation is something we want to see. In order to increase the number of recessive mutations in a population you back-cross the plants (breeding a daughter plant with a parent plant), or force inbreeding (forcing a plant with the gene to pollinate itself; sometimes this isn't possible in plants). After enough generations, which can be anywhere from 10 to over 1000 generations to get a pure line, you have a plant that shows only the allele you want expressed. Most garden plants are created this way; you back-cross over a certain number of generations until you get the desired effect in nearly all seeds grown. A huge downside of this type of selective breeding and back-crossing is that you're decreasing the genetic diversity in a population by selecting the alleles you want expressed and eliminating all others. For most plants this isn't a big deal; the ones grown in gardens are hardly reflective of the population as a whole in most cases, and if a virus or fungus or bacterium evolved that could eliminate an entire population of ornamental plant because of the inbreeding and a lack of resistance it wouldn't matter much. You would replant the next year with a different variety and hopefully the problem is solved. The big problem occurs when we start doing this with crop species, as we have been doing for over 12,000 years. Corn, for example, is so susceptible to disease that it is completely unable to survive without human intervention (not to mention we have eliminated the corn plant's ability to disperse its seeds; this is a slight problem if you're a corn plant but a major benefit if you're a human wanting to eat corn seeds). Soybeans in North America right now are on the verge of a massive population collapse due to the fungal disease called the soybean rust. It has recently shown up in the southern United States and is attacking soybean crops that have all shown to be susceptible to the disease. We grow the same variety in Canada (bred to have an increased seed size with an increased oil store in the seed), but are only saved from the attack of the pathogen due to our much colder winters that the fungus can't survive. It's only a matter of time before an entire year's crop is wiped out which could be absolutely devastating to the North American economy.

The previous blog post I did about this plant (which you can read about HERE) mentioned the smell of marijuana that this plant supposedly has, and the drug busts that have occurred as a result of people innocently growing moss phlox and having the smell waft in the wind. I did pick some leaves and crush them up; if you use your imagination I guess it smells like marijuana. I have a hard time believing that it would produce enough of a scent to convince someone there's a drug op in their neighbour's back yard, and I also have a hard time believing that someone would mistake the smell of phlox for the smell of marijuana!

The Scottish bluebell, but not the British or American bluebell

Species name: Campanula x hybrida

Common name: Bellflower, bluebell (although not truly a bluebell at all!)

Location: Ontario

You'll notice this plant has no species status diagram! Since I have no idea what species went into making this hybrid (I have some guesses, but I'm not positive on any of them), I can't say for sure where in the world the genetic base of this hybrid is from, so I'm not going to tarnish its reputation. Many ornamental species of bellflower are from North America, and many of them are from Europe and western Asia. A few are even from temperate Africa. There are a couple species in the genus Campanula that are invasives in North America (some declared invasive more recently than others), while others are critically endangered. I'm sure that a more thorough genetic exploration of this group will reveal that it's actually not one genus at all but many, since the morphological variation in the group is quite drastic. If you're really observant, you'll notice that the bellflowers and the moss phlox are competing for space in this particular location in the garden!

One of the most impressive features of this plant is the morphological variation that occurs on the same plant. While this is not unique by any means in the plant world, this is one of the most common garden plants that displays drastic morphological variation of plant features all on the same individual. The leaves at the base of the stem, sometimes arranged in a basal rosette but more often extending vertically up the stem are broad, sometimes heart shaped and sometimes arrow-head shaped, with a wavy margin (but sometimes smooth). As you get further up the stem, the leaves become more grass-like: long and very, very thin. Once the individual plant is in flower, the large leaves at the base of the plant wither and die, leaving only the small needle-like leaves along the stem. I'm not entirely sure why a plant would do this; it seems counterintuitive since the largest leaves at the bottom would be best able to make fuel for seed production.

While working on an identification for this plant, I stumbled on a fascinating website of flower photography. A man named Brian Johnston has taken a series of photos of many different species of plants in flower, and documented their flowering cycle from the first appearance of a flower bud all the way through to seed set. If you're interested in browsing through the photos, please click HERE and then click on "Flowers" at the top of the page in the grey toolbar (2 links to the right of the yellow "Share" link) and then choose your flower. The photos are absolutely stunning!

Not all Phlox are created equal!

Species name: Phlox subulata

Common name: Moss Phlox, Mountain Phlox

Location: Ontario

The Moss Phlox is a ground cover plant native to North America, with its natural range extending from Quebec to British Columbia and south towards Colorado and Tennessee. I would argue that now in certain habitats (like my back yard) it has become invasive, perhaps because of a decrease of natural competitors in the areas which it now grows. Almost all species of Phlox are native to North America (a few species, or only one depending on your definition of species, are native to Siberia) in some capacity, with overlapping ranges extending from East coast to West coast and from Alaska south to Florida. The variation in this genus of plants is a great example of "niche theory", which states that plants and animals evolved to specialize to a specific niche, and so "microhabitat" can be a leading contributor to the evolution of new species. This theory has been all but abandoned in recent literature in favour of other theories since it could never explain all the variation seen in an area by itself, but it's still a good theory used in conjunction with others to explain species distribution. The genus Phlox contains more than 65 species, being distinguished by their size at maturity (ranging from only a few centimeters tall to over a meter) and their flower colour. Horticulturalists have hybridized various species to produce new and unusual flower colours that would not have been present in large numbers in natural populations.

Other than a popular ornamental plant, Phlox species in general are not used for a whole lot. There are no species with any medicinal value (either historical or current) with the exception of Garden Phlox which is a powerful laxative. This should also suggest that it's a poisonous plant, and shouldn't be consumed! The analysis of the essential oils in the plant done by a lab in Denmark didn't show the plant to have any promise as one containing chemicals previously documented to fight cancer, slow the progress of AIDS or diabetes, etc.

One humorous side-note to this plant is that it supposedly (I've never noticed this phenomenon, but maybe it is not uniform across all species) has a very similar smell to that of marijuana and has caused the "backyard bust" of a few homes in England and the United States after neighbours reported the smell. I doubt the plant itself would be mistaken for marijuana since they differ drastically in appearance!