Houstonia caerulea (Bluets) - a photographic essay

[McDonough]

This message is a photographic essay on one of my favorite plants, Houstonia caerulea (Hedyotis caerulea), common name Bluets, a member of the Rubiaceae.

While H. caerulea is not generally thought of as an alpine plant, it does grow up into the mountains, and depending on whether one considers H. caerulea var. faxonorum valid or not, the genus does get up into alpine zones in the White Mts of New Hampshire. There are choice mountain species in Western USA as well.  At any rate, H. caerulea is such a tiny bun-forming plant and blooming for such a long period, that it certainly warrants a place in the rock garden.

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!

[McDonough]

Yesterday, March 02, 2010, when some of the ice-snow pack retreated from part of the yard and garden, the buns of Houstonia caerulea become uncovered, and to my surprise, there were still vital seed pods and a few fresh flowers nestled tight to the clump.  I share this photo with you.

And in the following link we see a good blue-flowered form by SRGC member Helen Poirier, living in New Brunswick, Canada.
http://www.srgc.org.uk/smf/index.php?action=dlattach;topic=4790.0;attach=186136;image

[Hoy]

I have tried Houstonia a couple of times but they always peter out in a year or two. Maybe they don't like wet winters? I have to try once more. Should like them to self-sow!

[RickR]

Our native Minnesota species of Houstonia grows in the same areas as other alpine like plants here.  For instance, it grows in the same crevice work as Coryphantha viviparia and Opuntia fragilis.  I never thought about it growing in lawns, nor have I seen it here invading sparse turf.  I don't think ours is evergreen.

[Lori S.]

I've only ever had Houstonia caerulea come back in an acid bed, and only once at that.  Does it favour acid (or at least neutral) soil, as opposed to higher pH?  The natural conditions here are alkaline, pH 8 or higher.

[RickR]

Now I am not sure which species(s) we have in Minnesota.  I've never looked close enough to see if stamens were attached to the corona or not, or exerted, but the overall growth pattern points to H. longifolia.  I have observed them in northeastern and southern MN.  One MN flora text from the 1960's only list longifolia as extant in northern MN, not mentioning caerulea at all.  A Spring Flora of Wisconsin lists both species, with caerulea in the sounthern part of that state.  I'll have to look closer.  A trek to SW MN is on my to do list this June.  I may even catch the Coryphantha vivipara in bloom. 

At any rate, the hustonia in sw MN grow in neutral to alkaline, dry soil.  In ne MN, they are in acid dry soil.  Without anything to back up my decision except the general growth pattern,  I am guessing both are longifolia.

[McDonough]

Now I am not sure which species(s) we have in Minnesota.  I've never looked close enough to see if stamens were attached to the corona or not, or exerted, but the overall growth pattern points to H. longifolia.  I have observed them in northeastern and southern MN.  One MN flora text from the 1960's only list longifolia as extant in northern MN, not mentioning caerulea at all.  A Spring Flora of Wisconsin lists both species, with caerulea in the sounthern part of that state.  I'll have to look closer.  A trek to SW MN is on my to do list this June.  I may even catch the Coryphantha vivipara in bloom. 

At any rate, the hustonia in sw MN grow in neutral to alkaline, dry soil.  In ne MN, they are in acid dry soil.  Without anything to back up my decision except the general growth pattern,  I am guessing both are longifolia.

Rick, if you go looking for the H. aff. longifolia, would the plants still be in bloom in June?  Here, at least with caerulea, they bloom early (April-May).  If you do find what you believe to be longifolia, I would like very much to see some close-up photos, I'm not familiar with that species.  Maybe collect some seeds if any pods are available.

[McDonough]

With the diverse colony of H. caerulea shown in my photo essay, I did collect some "snippets" from those plants with a bun-like habit versus those that grew more loose and spreading.  They quickly "bunned up" in the garden, but I was surprised to see two different leaf color forms, one is red-leaved in winter and early spring, and others are green.  Here are both color forms in a side-by-side composed view, photo taken today, 03-16-2010.

[Kelaidis]

Now I have to wade through my oceans of images to extract a few to prove Houstonia caerulea tolerates the desolate wastes of mid America: We finally succeeded with by planting it in a BOG with Pitcher plants and Dactylorhize majalis! I had great luck with Houstonia serpyllifolia when I lived in Boulder: it filled a big scree with its mats and their dazzling azure blooms: I really like that plant. It grew very well with various trumpet and star gentians. Our Western Houstonias are all being called Hedyotis it seems: they are not generally as cute, except for the adorable tiny Hedyotis rubra from the high Chihuahuan desert and steppe where it can be very common: I find it impossible to grow.

Loved your photo essay, Mark: really fleshed out the images I had of Houstonia caerulea in my mind: I have seen it here and there in my Eastern spring visits, but not like your fabulous stands. Local nurseries sell it, I suspect because it is irresistible to customers! I suspect not many have it come back...

[RickR]

Yes Mark, the Housonia sp. I a speak of should be blooming in late June with the Coryphantha viviparia in SW MN.  It's normal bloom time is early to mid summer here.  I'll watch for seed, too.

[Kuchel]

Hi Mark,

I tried very unsuccessfully to post something here yesterday, but it did not work.  I wanted to show a Houstonia I had grown from seed and that is coming back again this spring.  I will have to work on using attachments.  Anyway Housonia is also growing wild here in Vermont.

Marianne
Fairlee, Vermont

[McDonough]

Hi Mark,

I tried very unsuccessfully to post something here yesterday, but it did not work.  I wanted to show a Houstonia I had grown from seed and that is coming back again this spring.  I will have to work on using attachments.  Anyway Housonia is also growing wild here in Vermont.

Marianne
Fairlee, Vermont

Marianne, try the steps I mention in your other posting where you describe some difficulties uploading images, click this link to see my response:
http://nargs.org/smf/index.php?topic=4.msg1151#msg1151

I'd very much like to see your Houstonia photo, so try the steps I describe, then report back with details about what the specific problems might be... let me know how far you get in the steps I describe.  Also, are you using a Mac or a PC?

[Hoy]

I have decided to try your Bluets once more if I find any for sale or seed. Does the Bluets come in bluer color? If I remember right those I have tried were bluer than shown in your pictures Mark, or does the pictures (or my screen) lie?

[McDonough]

I have decided to try your Bluets once more if I find any for sale or seed. Does the Bluets come in bluer color? If I remember right those I have tried were bluer than shown in your pictures Mark, or does the pictures (or my screen) lie?

Most often bluets are white lightly shaded with blue, although as you can see in the populations near me, there are pure whites, and some very pale blues too.  There are forms with much deeper blue color, but I don't have any of those yet, but I do want to get a good blue one day.  Check the link below for a good blue form.

Previously I posted the following link to a good blue-flowered form by SRGC member Helen Poirier, living in New Brunswick, Canada.
http://www.srgc.org.uk/smf/index.php?action=dlattach;topic=4790.0;attach=186136;image

[Hoy]

Yes! That is the color I remember of the plants I bought once. Thanks. I will try to get hold of different colors, maybe better chance for crossing and better viable seed.