Sunday, November 27, 2011

Parking Lot Oaks

Plants that can live (and thrive) in adverse conditions like parking lots and roadway medians are special indeed.  Those that do so are prized by landscape designers and their use often is repeated.    These same trees might show up on lists of urban (also known as “street”) trees.  While maples are often used in these conditions, here are five oak trees that I have seen recently that fit this bill; four are native and one is exotic.

Nuttall oak (Quercus texana)
Pin oak (Quercus palustris)

Pin oak (Quercus palustris) has been a parking lot staple for many years around North Atlanta.  The trees planted some 30 years ago are now trees of considerable size – in places where they were allowed to remain.  Unfortunately in some urban areas, trees are considered expendable when it comes time to expand further.  Don’t let the common name fool you – the pin oak does not have slender “pin” shaped leaves.  The leaves are broad and usually have 5-7 lobes.  Q. palustris tends to retain it’s dried leaves over the winter, allowing for some measure of privacy when planted in a residential area.  That characteristic plus slightly drooping lower limbs are key identifiers for me.  The acorns are rather small and striped.  Like many urban tolerant trees, this species is naturally at home in poorly drained soils with high clay content.  I have never noticed this species having any remarkable fall color. 

Pin oak (Quercus palustris)


Willow oak (Quercus phellos) is another parking lot staple and continues to be used even in new developments.  Perhaps the narrow, linear leaves are more friendly to clean up crews in the fall than other oaks.  This is the tree that people think of when you mention “pin oak”.    The rapid growth rate and pleasing shape of the mature tree are probably two of the reasons it is still used in design.  Again the acorns are rather small (perhaps a plus for high traffic areas) and faintly striped.  Again this tree is naturally found in poorly drained areas, making it ideal for use in urban areas.  The fall color is yellow and rather unremarkable.  I found this example in a church parking lot along with the pin oak above.

Willow oak (Quercus phellos)


Shumard oak (Quercus shumardii) is a moderately fast growing tree with handsome lobed leaves.  It became popular as an alternative for the overused Pin oak some years ago.  The leaves of the two species are very similar in appearance but Shumard oak has better fall color and the dead leaves do not persist.  The acorns are much larger and resemble those of Northern red oak (Quercus rubra).   I found this example planted as a median tree along an office park throughway, but the trees were not doing very well.  My research shows that while this species can do well, it does prefer more moisture than others.

Shumard oak (Quercus shumardii)



Nuttall oak (formerly Quercus nuttallii or Quercus shumardii var. texana, now Quercus texana)  is perhaps the most recent favorite in parking lot design when it comes to choosing an oak.  This species is the best looking of the group: the leaves are handsome and lobed and have superb fall color.  Couple those looks with a fast growth rate and you have a winner as far as the landscape design folks are concerned.  The acorn is similar in looks to Shumard oak, except smaller in size and with a “goblet” shaped cap.   I found this example in a supermarket parking lot where the acorns on the ground were numerous.  Southern Living magazine's garden editor recently featured this tree in his blog.

Nuttall oak (Quercus texana)



With so many native oaks to choose from, you would think designers have no reason to pick any non-native oak.  Occasionally though you will find someone using Sawtooth oak (Quercus acutissima).   This oak is notable for its fringed acorn caps.  Some folks think it is our native bur oak (Quercus macrocarpa) when they find the acorns and search the Internet based on the acorn cap’s appearance.  The leaves are quite different between the two, however, and bur oak is not naturally found in Georgia.  The leaves of Sawtooth oak are long and narrow, not lobed, with bristly teeth on the margins.  It has no remarkable fall color except perhaps a very brief transition from green to yellow before turning brown on the tree.  Although once promoted as a “good wildlife” tree, there are plenty of native oaks that can fill this role. I found this one in a gas station parking lot.

Sawtooth oak (Quercus acutissima)


So if you’re looking for a good street tree, the four native choices listed above are ones to consider.

If you are interested in what the acorns of other native oaks look like, you can look at my other posts: New Acorns for Me and Nuts about Nuts.





Sunday, November 20, 2011

Witchhazel - the original fringeflower

Despite the wide-spread distribution of American witchhazel (Hamamelis virginiana) in Georgia, I have not had an opportunity to see it in flower until this past week when we found it on a GNPS rescue site.  What a beautiful and delicate flower it is!  The four-petal yellow flowers appear after the leaves have already fallen, creating an almost sculptural arrangement on the bare branches. The flowers are considered lightly fragrant.

American witchhazel (Hamamelis virginiana)


Witchhazel is a large shrub or small tree that is found throughout the eastern United States as an understory plant in upland mixed hardwood forests.  It is usually found with oaks (Quercus spp.) and our site was no exception – the oaks found on this site included Scarlet oak (Quercus coccinea), Northern red oak (Quercus rubra), Chestnut oak (Quercus prinus), Black oak (Quercus velutina), Southern red oak (Quercus falcata), and White oak (Quercus alba).

Witchhazel leaves are alternate, simple, lobed, and deciduous.

Leaves of Hamamelis virginiana
I think the winter twig is rather distinctive with it's naked terminal bud (that is, it has no special bud scales - those are the actual leaves that will unfold in spring).

Winter twig of Hamamelis virginiana

As I mentioned earlier, the distribution in Georgia is quite remarkable – it is found from the Blue Ridge down through the Piedmont to the Coastal Plain.  If it were not such a modest looking plant most of the year, I’m sure more people would be familiar with it.  It is a member of the Hamamelidaceae family.  It’s physical resemblance to Fothergilla (commonly called witchalder), another member of the same family, is to be expected, but I was surprised to find that it is also in the same family as Sweetgum (Liquidambar).

Distribution of (H. virginiana), courtesy of USDA Plants Database

In addition to the unusual late-fall flowering time (November in North Georgia), the development of the seeds is also quite unusual.  Although pollination occurs in the autumn, fertilization does not occur until later, so the fruits develop during the summer of the next year, becoming ripe almost at the same time the new blooms appear. When the fruits are ripe, they burst open, forcibly ejecting two shiny black seeds some distance away.   Supposedly the sound of the event is loud enough to be heard if you are nearby.

The top of a 10 foot plant, held down for a picture

There are a few cultivars of the native eastern witchhazel available.  Look for H. virginiana 'Harvest Moon' and ‘Little Suzie’.  H. vernalis is the late winter/early spring blooming Ozark witchhazel, native to the southwest; you may find forms of that also.  The blooms are yellow with reddish/purplish accent and are known for good fragrance.   

Beware of accidentally getting the Chinese species, H. mollis – cultivars and hybrids of it are quite common, including H. x intermedia 'Arnold Promise'.

Sunday, November 13, 2011

Score! New Acorns for Me

Last year I wrote about how I am crazy about native tree nuts, acorns in particular.  Well, fall is the perfect time to go crazy.  In my previous blog entry I showed pictures of some of the acorns I had gathered in my area.  This year I was able to add to my “collection” in a significant way.  By the way, I don’t keep my collection in seed form – I plant them around the property so that I can “grow” my collection in every sense of the word!

Quercus prinus, Chestnut oak

The first addition to my collection is Quercus prinus (synonym Quercus montana) which is known as Chestnut oak.  One of the areas where we rescue plants has many Chestnut oaks.  I happened to be there when the crop hit the forest floor this year so I gathered a bunch.  As a member of the white oak group, these acorns sprout quickly and many of them had already sprouted when I collected them.  The plump, shiny acorns are 2-3 times bigger than the more common Quercus alba (White oak).


 
The second addition qualifies as one of my “significant” findings because I have wanted it for so long.  There is a Scarlet oak (Quercus coccinea) across the street from me, and I have checked the area around it every year for fallen acorns.  This year it finally produced some!  Based on the leaf shape and bright color, I have always considered it to be a Scarlet oak rather than a Northern red oak (Quercus rubra).  The acorns I gathered this year confirmed that my identification was correct – there are distinctive concentric rings around the base.

Scarlet oak across the street

Quercus coccinea acorns















The third addition is also a Scarlet oak.  This one is outside of my neighborhood but along my usual walking route.  The tree itself is too tall to see the leaves on the tree, but I have seen the leaves on the ground and the shape of them is quite atypical (in my opinion) for a Scarlet oak.  In fact the first time that I saw them, I thought it was Mapleleaf oak (Quercus acerifolia), but that species is not naturally found around here.  I know that oaks can hybridize in the wild and suspect this individual has both red and scarlet oak ancestors.  This year I finally found the acorns on the ground, and they are Scarlet oak acorns.

Fancy Scarlet oak leaves!

I also got some Georgia oak (Quercus georgiana) acorns; I didn't collect them myself - someone brought them to a meeting.  I have a few small Georgia oaks in my yard (leftovers from an Arbor Day project at the school), but it will be nice to grow a few more from seed.  The acorns are small and remind me of Southern red oak - they have an orange-ish top and faint stripes as well but a bit more gloss.  The picture below includes a leaf from one of my oaks.

Georgia oak, Quercus georgiana

I have water oak in my yard (Quercus nigra) but have never seen any acorns associated with my population.  I did find some acorns while working on a restoration site in Smyrna for GNPS.  The acorns are remarkably similar to both Georgia oak and Southern red oak in size, shape, and even right down to the faint stripes.  I don't know if this is typical, but I also noticed a band of orange/tan around the top of the acorn.

Water oak, Quercus nigra


So those are my acquisitions this year.  I’d also like to publish an update to my notes in the previous blog entry for two species.  The first is Southern red oak, Quercus falcata.  As the acorns in my yard pile up on the ground, many of them half-eaten by the local squirrels, I am reminded of the distinctive color of the nut meat - a bright orange.  Sometimes the color even affects the top of the acorn (visible after it separates from the cap).  Also, the outside of the acorn is often distinctively striped.  Here are some new pictures from acorns gathered this year.

Southern red oak, Quercus falcata

Here are some pictures of Northern red oak, Quercus rubra. These acorns are considerably larger than the ones I photographed last year and I think represent the species a little better than my previous picture. In addition, I like to include some leaves with my pictures going forward.

Northern red oak, Quercus rubra.

Sunday, November 6, 2011

Don't Cut Back

Leaves are falling down all around us, late season perennials are producing seeds, and acorns have turned areas of ground under oak trees into what appears to be a game of marbles.  It is a time for plants in the temperate areas of the United States (like Georgia) to shed the leaves that they no longer need and for seeds to disperse. Even pine trees drop some of their needles.

Rudbeckia hirta seedhead - waiting for a bird

This is also the time of year that gardeners feel compelled to “tidy up” the garden and “put it to bed”.  What a ridiculous idea!  Does Mother Nature do that? No!  She has many good reasons for not doing so, and I’d like you to consider some of them as you ponder the list of “garden chores” that you have created for yourself.


Leaves enrich the soil as they break down and as critters like worms and beetles eat them and poop out free fertilizer.  Omnivorous birds like Brown thrashers sort through leaf litter to find and eat these creatures - so you are feeding the birds as well when you have a good layer of organic material.

Leaves feed earthworms and beetles - and feed your plants
Rake the leaves off the lawn (or chop them up with your mower) but don't let them leave your property! Giving away leaves is like giving away money.

As perennials die back, their dried stalks hold the remains of their flowers and their ripening seeds. Fluffy seed heads attract the attention of small birds like Gold finches to come feast on them.

Seedheads of Eurybia spectabilis

Plants continue to support insects even in this phase.  Larger insects and birds happily keep these insect populations in check – Mother Nature expertly uses the food chain to keep the local ecosystem balanced. Healthy populations of birds rely on these small insects being there for them.

Bugs on Eupatorium will feed others


So resist the urge to "tidy up" and let Mother Nature finish what she started.  The rest of the critters we share this place with will certainly thank you.