Hues of hydrangeas

Hydrangeas are in full bloom this time of year.  I snapped these photos yesterday of several hydrangeas, all planted along the same strip of land.  Just look at the different colors:

Why so many colors? Most of you probably know that genetics play a role, as does soil pH.  But there’s much more to it than simple soil chemistry and genes.

1. pH:  Strongly acidic soils produce blue hydrangeas, while slightly acid to slightly alkaline soils favor pink or red flowers.  Soil pH can be modified by adding lime to raise soil pH or ammonium sulfate to acidify the soil.

2. Aluminum: Aluminum, a toxic heavy metal, is required for blue hydrangeas. Like other metallic elements, aluminum binds tightly to clay particles under alkaline conditions. As the pH becomes more acidic, aluminum becomes soluble and can be taken up by plant roots.

3. Nutrients: Relative concentrations of phosphate, nitrogen, and potassium have significant impacts on the uptake and activity of aluminum.

4. Pigments: Blue hydrangea flowers depend on the formation of a complex among three partners: an anthocyanin called delphinidin with a sugar attachment, a phenolic acid co-pigment, and aluminum. Co-pigment differences among species and cultivars will influence flower color.

And here’s an interesting factoid about hydrangeas: ever notice that they are rarely bothered by insects or other animals? Accumulation of a toxin like aluminum in their tissues may be the reason.

GP Hit List: Ligustrum sinense (Chinese Privet)

[And I don’t mean “greatest hits”, I mean “Mafia hit”]

Gardeners, yardeners, and designers are on a perpetual lookout for a good hedge species. Hedges are useful in so many ways: providing backdrop for a border, making good neighbors, containing football players, etc.  In reference to the latter, the field at Sanford Stadium at the University of Georgia (cue woofing!) is known as “Between the Hedges”.  In the extensive lore of UGA football, everyone makes like it’s some sacred plant, but (gasp!) it’s just plain ol’ privet. Aside to Jeff, my fellow UGA alum: CNN just reported the dubious distinction that Georgia is the #1 party school in the country (again).  Maybe this is why I can’t remember the Krebs Cycle.

Variegated Chinese Privet in all its shrubby glory; photo from University of Arkansas Cooperative Extension.

Back to privet. Designers of D.O.T. landscapes such as medians and interchanges seem especially enamored. Clouds of variegated privet (L. sinense ‘Variegatum’) dot interstates throughout the South.  Yes, it’s tough, useful, variegated, and touted as “wildlife friendly” by some leading gardening resources. The berries are indeed good bird food; therein lies the problem. Seeds pooped out by birds results in the green, non-variegated version – much more vigorous and deposited everywhere. For the record, the variegated form also reverts like crazy.

My family’s farm in northeast Georgia is bordered by the North Fork of the Broad River. Over the years, the river bottom, and then the fence lines at all elevations, have filled with privet. It is, pardon my language, a total bitch to remove and almost impossible to eradicate.  The State Botanical Garden of Georgia in Athens has an entire squad dedicated to eliminating it from acres of river bottom; ironically, only a few miles from Sanford Stadium. Thought of mostly as a Zone 7-9 plant; we have lots of it in the woods here in the mountains – an entire zone cooler.

Distribution of L. sinense; USDA PLANTS Database

Ligustrum sinense is on at least two official Invasive and Noxious Weeds lists by the Southeast Exotic Pest Plant Council and Florida Exotic Pest Plant Council as well as several international lists.  Nursery growers and landscapers across the South know these things. So why, why, why, do they continue to produce and spec it?  “Variegated foliage sells. People see it, like it, and then ask for it. It’s a bread-and-butter item.”  This comment came from the owner of a fairly large nursery that sells to independent garden centers.

Our industry yelps whenever a state or federal mandate threatens to impose restrictions on a best-seller (Hedera helix, for recent example).  There are LOTS of terrific woody plants out there, people.  The Dirr book is now up to 1250 pages – thumb through and pick a few alternatives. Cease and desist with the Chinese privet.