Tuesday, February 2, 2016

Plant of the day is: Oxydendrum arboreum or sourwood tree

Plant of the day is: Oxydendrum arboreum or sourwood tree

Caught my eye as a large tree for the Ericaceae family.  I'm used to seeing lots of alpine Ericaceae species so this one gave me a little bit of a double take, and then I was quite taken by it's for and color.  That color.  Oh my.

Oxys - Greek for sour
dendron - Greek for tree (references the sour tasting leaves)
arboreus - Latin for 'of a tree'

Photo Credit: Msact (CC BY-SA 3.0)

Taxonomy, etc.:  Well, as I mentioned, it is in the Ericaceae or heath/heather family.  Most members of this family fare found in acidic and/or infertile growing conditions.  It's a pretty large family with about 151 genera and 3,554 species.  Pretty large.  You'll likely be familiar with other members of the family: cranberry, blueberry, huckleberry, rhododendron, azalea...etc. etc.  Many species also have evergreen foliage and strong mycorrhizal associations.  Oxydendrum arboreum is actually a monotypic genus, just the one species.  Located in the Vaccinioideae subfamily (closely related to Vaccinium (the tasty genus :)).

Description:  For once I don't have to scour the corners of the internet for good information.  Plenty to find out there.  A small deciduous tree up to about 20 m tall or so.  Leaves are alternate, simple, elliptical to lanceolate and 4 to 7 inches long.  Very finely serrated leaf, a good photo of leaf, twig, flowers, and form can be found via the great people at Virginia Tech (they also have an app which is great for tree ID...recommendable).  Has a small petiole.  Flowers are hermaphroditic, white, borne on on loose panicle stems.  Flowering occurs about mid summer.  Fruit is a 5 parted capsules with loculicidal dehiscence :) that releases two very tiny two winged seeds.  Good twig ID with almost non existent buds appressed to the stem.  The leaf scar is elevated with one leaf bundle (see VT site for good photo).  Fall color is knock your socks off red.  A show stopper.    


Culture/habitat:  Found throughout a good chunk of the Appalachian mountain range.  Makes it down to the coast in Mississippi and Alabama as well as to the coast of North Carolina/Virginia.  Prefers a slightly acidic to neutral pH.  MUST have well-drained soils.  It is a must.  Near some of it's out limits it actually grows in very sandy, almost dune like soils. Hardy to Zone 5, so it can definitely take the cold but languishing in humid weather in poorly drained soils is sure to upset it.  In the Appalachian Mountains, sourwood is most abundant on subxeric open slopes and ridges with chestnut oak, white oak, and scarlet oak up to about 5,000 feet in elevation (rarely over).  

Propagation:  Found some good info on this.  USFS says they don't root well from cuttings and wildflower.org says they should root fine with hormone.  Gotta love conflicting information.  The seeds supposedly don't need pretreatment for germination BUT I found a study earlier today that mentioned a 1 month cold stratification decreased the amount of light needed to prompt germination and also decreased the time to germinate.  I will be giving these a brief cold period for this reason.  


Fun facts:  Plant it next to Nyssa sylvatica for some amazing fall color.  The lumber has been used for hand tools and used to be used to make wagon sled runners.  They are VERY popular with the bees and sourwood honey is a thing down South (it granulates slowly...neat).  The largest known sourwood is in Robbinsville, N.C. coming in at a whopping 36 m!!  It is a really great and probably under appreciated species.  In normal landscapes probably only going to reach 10 m or so and is a slow grower and a slightly more difficult tree to grow/find in nursery trade.  Still a great tree, worth going out of your way for if you got a nice well drained soil (if you don't have clay backfill for a yard...which is hard to come by...).

Anyways, enjoy folks!

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