Houstonia caerulea - photographic essay

[TheOnionMan]

I'd like to share with SRGC Forum members a photographic essay on one of my favorite plants, Houstonia caerulea (Hedyotis caerulea), common name Bluets, a member of the Rubiaceae.

Ubiquitous in Eastern USA and here in Massachusetts (Northeastern USA), it is extremely variable, always charming, yet perhaps because it is so common, the plant is largely underappreciated. Nor has the great range of variability been explored, documented, and enacted upon.  Typically seen growing on sunny to partially shaded highway embankments in areas with poor soil that support only sparse grass and mosses, it is a familiar sight in its most insignificant manifestation, a mere wisp of a plant making filmy sprays of tiny white or faintly bluish flowers.

But I have seen specimens that dazzle the eye and spark the imagination, a rock gardener's dream to be sure. Typically such spectacular plants, as I have spotted them, are growing in moist locations in neighborhood lawns amongst lush, deep green spring grass, where trespasser's shall not venture, but the eye strains for glimpses of 6" round domed mounds of pristine white, as if imitating Aretian Androsace, at least from afar, but merely growing in someone's lawn! The prospect so close, yet unreachable. I imagine knocking on someone's door with what would surely seem a bizarre and suspect request to gain access to these magnificent domes of white, for a petite snippet, when they are mere "weeds" in someone's un-mown spring lawn.

Occasionally serendipity happens. On an unusually hot Sunday afternoon late April 2009, I ran a local 10k road race in Groton, Massachusetts. After the race, I walked back to a large business where runners were allowed to park. I crossed the multi-acre lawn in front of the business, approaching a partly sunny hollow at the edge of a grove of mature trees, and there before me was a fantastic colony of Houstonia caerulea. These were in a somewhat drier site without the luxuriant hemispherical domes mentioned previously, but nonetheless an exciting colony of variable Bluets.

Let me share some photos exploring the diversity of this colony. Most were pure white, but some light blues were present too. In western Massachusetts, I have seen some very deep blue forms indeed, but none of such color were to be found here, however the range of flower size, impressive floriferousness ratio on some plants, and forms with tight foliage masses, more than compensated. What this colony revealed to me was, the superior forms with extraordinary flower count were not necessarily a factor of soil and moisture, but were indeed genetically separate individual plants where one could select superior forms.  I hope to have some of these growing in my lawn soon!

Tangential detour:  somehow when I see massed bluets, I think of Androsace and Dionysia, but here they grow in the lawn instead of on the undersides of sheer cliffs and caves, how convenient :-)
http://www.dionysia4u.com/index.htm

[Paddy Tobin]

A very pleasant looking plant, Mark. Certainly worth a place in the garden. Many thanks for the series of photographs which show the plant perfectly.

Paddy

[maggiepie]

Mark, the bluet colony is fantastic. I love bluets, they are one of my absolute favourite plants.
They flower their hearts out and always cheer me up.
I haven't seen white ones. It's not easy to find seeds and I have yet to see it in any of the seed exchanges.
Here's one of my little clumps.

[ranunculus]

Superb images folks ... many thanks for posting.

[Maggi Young]

I have only ever seen Houstonia growing in a rock garden or trough, where it is certainly very charming but I have never seen such a sight as these swathes of the gorgeous plants, looking ffrom a distance for all the world like a snowdrop wood..... quite lovely.

Very neat growing patches, too....giving the "flavour" Mark suggests of some of the primulaceae..... I see what you mean, Mark

[Lesley Cox]

The form I have, I bought as 'Millard's Variety' and it is a good blue, though much looser in growth than what I have as H. c. alba. I love them both. I've also had seed of HH. acerosa and rubra but neither has germinated, alas.

[Lesley Cox]

Helen, your blue looks very good and compact. Mine is so sprawling (in quite a lot of shade though) that is has scrambled through and more than half killed a decent sized plant of Rhodo. keleticum.

It's quite possible to transport Houstonia because I sent the white one to Sweden a couple of years ago, I believe successfully. Maybe when your weather warms up again...?

[maggiepie]

Lesley, all mine grow in lovely little round clumps, I've never seen a sprawling one.
I keep finding little babies and sticking them them here and there, am so scared of losing them.
I just remembered I had bought some rubra seeds a couple of years ago, not one germination from them. They are supposed to be fragrant I think.
Will look forward to the warm weather 

[Lvandelft]

Wonderful to see these plants in their habitat Mark.
We grew the Millard's var. by the 1000's for the trade for many years, but the H caerulea we always lost.
Maybe the soil too calcareous for them? and planted on the wrong place too.
The Millard's var. was (and is still) a very good seller in spring, but I never found seeds, so probably sterile?

[TheOnionMan]

Mark, the bluet colony is fantastic. I love bluets, they are one of my absolute favourite plants.
They flower their hearts out and always cheer me up.
I haven't seen white ones. It's not easy to find seeds and I have yet to see it in any of the seed exchanges.
Here's one of my little clumps.

Helen, that's a fine blue-flowered one you have.  These do make seeds, just that the capsules and seeds are so small to make any sort of seed collecting tedious indeed, it is no wonder these rarely show up in seed exchanges.

[TheOnionMan]

The form I have, I bought as 'Millard's Variety' and it is a good blue, though much looser in growth than what I have as H. c. alba. I love them both. I've also had seed of HH. acerosa and rubra but neither has germinated, alas.

I haven't heard of 'Millard's Variety' (seems like a nice blue), nor even "alba" appended to H. caerulea. 

I think when you see such colonies in a variety of shapes, growth forms and colors, I wouldn't put much stock in an epithet like 'alba', as plants I've seen in New England typically range from white to light blue.  In western Massachusetts, in the gardens of the late Geoffrey Charlesworth and Normal Singer (South Sandersfield, Massachusetts), the natural color spectrum of wild Bluets on their large property went from white, through many shades of blue, to some really standout strong blue ones, just part of the color variability.

By the way, I referred to the plant habit so often seen as being mere wisps of a plant making filmy sprays of tiny flowers.  To see it in open half-shaded wooded areas, you might not give this plant a second look, it is so thin, wispy, and inconspicuous.  You can see in some of the photos I uploaded, even is this excellent colony of plants, some are much looser in flower, with flowers more spaced than others.  I selected a couple tight growing ones, and the foliage actually started to "dome up", it shall be interesting to see what they do this year.  They're also starting to seed around already.

[Rodger Whitlock]

Mention of bluets takes me back a long time. When I was in elementary school in the early 1950s, in the suburbs of Washington DC, there were school-sponsored Saturday morning nature walks; we'd bus to some site of interest and there be exposed to Ma Nature.

At I was introduced to bluets, growing in the grass. That would have been no later than 1955. Never saw them again until some time after 1975 I found a pot in a local garden center here.

Unfortunately, they are only an annual for me. Can't handle our infernal dry summers. But when I see them in the spring, as happens quite often, I will buy a pot for old time's sake and a walk down memory lane. Truly a sentimental journey!

[Lesley Cox]

I think they are one of those species which like lots of moisture but in a very sunny spot, not always easy to achieve. Many water loving irises are the same. So if they have these conditions they grow really well but tight and if they need shade to achieve the cool soil, they tend to be looser.

I guess the "alba" is just another way to say it's a white form, not necessarily a variety. And I suppose the 'Millard's Variety' was simply a selection of a decent blue. Helen's blue looks almost lavender bluwe whereas my Millard's is just about a sky blue, the colour when you look straight up in the air on a beautiful sunny day, (whatever that is ) And who was the Millard I wonder. This form has been around for many years. I think I first had it perhaps 40 years ago. I've not had self sown seedlings on either of mine and if there's been any seed it's been too small to notice. I'll have a better look shortly. They're both in bloom now.

[TheOnionMan]

I think they are one of those species which like lots of moisture but in a very sunny spot, not always easy to achieve. Many water loving irises are the same. So if they have these conditions they grow really well but tight and if they need shade to achieve the cool soil, they tend to be looser.

Yes, but that is the point of my posting.  Some of the overhead shots I posted, looking straight down on numerous clumps of H. caerulea, all growing inches apart from each other and getting the same degree of moisture and same amount of light, show dramatically different growth forms, so there are GENETIC differences in the various forms, not just different environmental and edaphic reactions affecting their growth in general.  So, in this population, it should be possible to select a tight clumping, super floriferous, non-meandering form of Houstonia caerulea versus the run-of-the-mill nondescipt form of the species.  My seedlings from a few selected forms of this colony already this past fall started mounding up into tight mounds versus the insignificant filmy wisps of plants that grow just a few hundred feet away naturally in a clearing in the woods behind me.  But I agree, this plant need the right balence of sun and shade, half day of sun is best.

[Paul T]

Nice looking carpet, Mark.    I don't think I've heard of them before.  Very pretty.  I am guessing they wouldn't like our summers though?