The Biggest Katsuratree I've Ever Seen!

This rambling specimen of a tree is another one from Dumbarton Oaks.  I saw this from across the large green near the house -- the wall behind it lines R Street in Georgetown. Naturally, I was drawn to its spindly habit, which reminded me of Louise Bourgeois's spider sculptures. 

 

Closer inspection of the bark made me think this was Cercidiphyllum japonicum, or katsuratree, though the tree seemed far too big for this to be so.  In its native habitat of China, the trees can reach up to 100', but in cultivation they rarely get much larger than 35 or 40' -- and that's an impressive size.

But indeed, a few persistent leaves and subopposite buds indicate that this is katsura.  Without a doubt, the biggest one I've seen!  Most people think of the beech tree when they recall their trip to Dumbarton (and more on that beech another time), but this katsura is worth a visit, too.

Pseudocydonia sinensis

Last week, when I was visiting Dumbarton Oaks, I noticed some deep red leaves on the ground.  At first glance, I wondered (irritably) if Dumbarton Oaks used a tree as plebeian as the dreaded Bradford pear.  Those can, despite their other problems, exhibit some lovely rose petal-like fall color.  But rounding the corner, I happily realized this was a different tree.

 

As you can see, the fluted bark is exfoliated and quite different from Pyrus.   Instead, the bark was more similar to Pinus bungeana, or lacebark pine.  The mottling isn't just white, silver, peach and gray, like Platanus, Stewartia or Lagerstroemia, but has an army green color in the bark as well.  It's quite striking.

 

The plant was also a mystery to me; I had no idea what it was.  My best bet was that it was still a relative to Pyrus or at the very least, a member of the Rosaceae family.  Looking up at the canopy, I got another clue.

At the time, a glimpse of these large fruit furthered my belief that this may have been a pear.  Though they are awfully lemon-yellow for a pear, it seemed possible.  I determined I'd have to do a bit more research when I got home to pin down exactly what this was.  

In any case, I was wowed by the contrast between the deep red foliage with the bright yellow fruit. 

It turns out that this was Pseudocydonia sinensis, or Chinese quince.  It's a very rare specimen tree, native to China, that is indeed in the Rosaceae family.  The fall color, fruit and beautiful bark are all characteristic of the species.  For a long time, it was classified in the Cydonia (quince) genus, but the absence of spines ultimately led to its classification in its own genus (P. sinensis is the only species in the genus). Cydonia is not to be confused with the shrub with the same common name, Chaenomeles.

Dumbarton Oaks Paving Patterns

Last weekend I was able to spend quite a bit of time in Georgetown.  I was housesitting at a property almost directly across the street from Dumbarton Oaks, which of course, as a landscape architect and horticulturist, is a dream location.

On Friday I spent a few hours at the gardens to get some extra images for my library. (It's embarassing to admit, but most of my other Dumbarton Oaks photos were taken with a non-digital camera.  That's how long it's been since I've had a lengthy visit.  Shameful.)

There are obviously a wealth of photos that I'd like to share, but today, I'm just going to post photos of some of the different paving patterns.  Enjoy!

 

Gravel and Belgian Block at the Drive.

Random rectangular motor court. 

Diagonal running bond with stone steps and band.

Interrupted curving running bond with header edges.

Basket weave with soldier edges.

Diamond detail.

Tile with stone banding.

I wish I knew for sure what kind of stone this is! Anyone know?

Running bond with circle and diamond details. 

Stone pavers with gravel.

Stone pavers and aggregate with brick edging beyond.

 Knot detail.

PJM Rhododendron

Here's another iPhone shot of a Central Park plant taken on a run this week: Rhododendron 'PJM' group.   I say "group" because the specimen below is a PJM type of cultivar, but I can't fathom which specific cultivar it is.  PJMs are crosses between R. carolinianum and R. dauricum var. sempervirens.  They are named for Peter J. Mezitt, founder of Weston Nurseries in Massachussetts.

 

PJM Rhodis have much smaller leaves than R. maximum or R. catawbiense, two other popular species.  The flowers are a bit smaller, too and don't bloom in umbels.  Some cultivars, like this one, turn a bronzy purple in winter. 

The plant typically blooms in spring but many of these group will bloom again in late fall.  I've seen cultivars of PJMs bloom almost all winter, though in less profusion.  Overall, the plant may remind you more of an Azalea-type Rhododendron, but if you count the stamens on this flower, you will see there are ten; Azaleas have five stamens.

Sycamore Maple and Incestuous Nomenclature

First of all, apologies.  It's already after 5 on a Tuesday and I've yet to update this site.  I'm in New York until tomorrow and have been a bit overrun with meetings and catching up with some good friends.  But I still managed to get in a run in Central Park yesterday and today.  

 

I stopped to take these shots of sycamore maple, or Acer pseudoplatanus, since we've been covering trees with fall color quite a bit lately and this tree is probably at its peak. As you can see, while the leaves are not as fiery as its cousin, Acer saccharum, they are a fairly clear, bright yellow.  The leaves are also serrated, unlike sugar maple, Norway maple, or even hedge maple.  Acer rubrum, or red maple, also has serrated leaves, as do other species in the genus, but I've yet to post on them.  But, if you're familiar with red maple leaves, you may notice that the leaf below is a broader shape, with five distinct lobes, whereas A. rubrum often has trident-like leaves.  The lobes on sycamore maple also are a touch fatter or wider at the mid-point; red maple lobes consistently taper in size and are widest near the middle of the leaf, narrowing to the points.  Finally, and perhaps obviously, red maple leaves this time of year are usually, well, red.

Sycamore maple is called thus because the bark has a thick, scaly bark similar to sycamore (Platanus occidentalis).  And here's a good example where nomenclature can get a touch confusing:

London plane tree is Platanus x. acerifolia and the species name is indicating the leaves look like Acer, or maple.

Norway maple is called Acer platanoides because the leaves look like london plane tree, or Platanus x. acerifolia.

Sycamore maple is called Acer pseudoplatanus because the bark (below) looks like sycamore (and probably because platanoides was already taken!).

The whole thing gets a bit cyclical, like a flawed math formula, doesn't it?

The tree is not native and while it is not as outrageously invasive as Norway maple, it can conquer over natives due to its high tolerance to salt, drought and wind.  It's just that resilience which lead to the plant being brought here from Europe and Southwest Asia, sometime in the late 19th century.

White Oak

Since we're on the topic of oaks, what with Tuesday's post on red oak, it seemed appropriate to follow up with another oak species, the white oak, or Quercus alba. 

Quercus alba is a native forest tree found in the United States from Maine to Florida and west toward Minnesota and Texas.  It's a slow-growing tree and its high sensitivity to compaction makes it a little-used tree for ornamental applications.  It's also a tell-tale pH indicator.  Chance are, your soil is acidic in the presence of this (and other) oaks. 

And, as you can see, the fall color is excellent.  I think this, along with scarlet oak (Q. coccinea) are among the best of the genus for fall color.  Unlike the red oak, white oaks have rounded lobes, though the depth of the sinuses is quite similar. 

The bark is much shaggier-looking than red oak, and has a silvery gray sheen to it.  The common name, white oak, is referring to this light-colored bark.  Like the red oak, it is fairly easy to identify in the winter.  In addition to the tree's beauty, the white oak is very important in a manufacturing capacity.  The wood is used for furniture, flooring, boat building and for wine and whiskey casks.

Dirr writes, "Difficult to pen my emotional ties to this species," and I'm sure that sentiment resonates well with many people in the eastern states where this tree is ubiquitous.   He comments on the tree's beauty near Biltmore Estate, as well as along the Blue Ridge Parkway in Virginia, which is not too far from where this specimen was growing (this is at my parents' place in northern Virginia).  After looking at this gorgeous display of fall color, contrasted against such a perfect November sky, I'm hard-pressed to disagree with him.   ...I may just have to revise my list.

Northern Red Oak

Below, to the right, is a shot of Lewisohn Hall, at Columbia University's campus.  I usually meet my students for the first time outside the doorway - our first class begins here.  (Obviously, this was taken last spring.)  It's a great place to introduce students to the subtle differences among trees.  Immediately flanking the portico are two small specimens of Acer palmatum.  This gives me a chance to talk about leaf orientation and explain that, among trees at least, an opposite leaf orientation is the first clue in identifying a species. 

 

After this, I have them study the two large shade trees in front of the building.  In the foreground we have Quercus rubra or northern red oak and in the background, Q. palustris, or pin oak.  Whereas most people would simply catalog them both as 'trees', some would know they are oaks.  A few would understand they are different species of oaks.  Finally, fewer still would know they are different species when there are no leaves on the trees to aide them.  But look closely, even in this photo, and it's clear the texture of the bark is different.

To me, red oaks are one of the easier trees to identify, sans leaves.  The bark consists of smooth, shiny furrows and rough raised ridges.  I describe it to students by saying it looks like someone has taken a butter knife or their thumbnail and gently carved the furrows in the bark.  The smooth shiny quality can reflect the sun brilliantly, too.  

Despite the common appellation, I think the fall color on red oak is fairly ho-hum.  You use this tree when you want a magestic, long-living shade tree, but not if brilliant fall color is your priority.

The leaves are (I hope) universally recognized as oak leaves, but differ from the popular leaf of the white oak (Quercus alba) because the lobes of these leaves are pointed.  The sinuses (the spaces between the lobes) are relatively shallow and the leaf itself is quite large, which means it can pose more of a litter problem than the aforementioned Q. palustris which has smaller leaves with deeper sinuses.

Teddy bear (cactus)..and bunnies!

Not that I particularly need an excuse to post pictures of cute rabbits (or hares - what's the difference anyway?), but it is Friday and that makes this post a bit more festive anyway.  Why not throw in a few pics of this desert cottontail.  Which, by the way, is a true rabbit.
 

 

I saw this in a small park next to what looked like unmanaged desert on the way back to Phoenix, right off of I-17.   There were literally dozens of them when we drove into the park, scampering to safety before we could even hop out of the jeep.  Luckily, I found this one hidden in a mess of cholla, or Cylindropuntia.

That genus name should be vaguely familiar.  Cylindropuntia literally means cylindrical Opuntia.  Indeed, for some time chollas (pronounced CHOH-ya) were considered members of the Opuntia genus, but the absence of paddle-like stems has finally merited its own genus.   

Above, a small cholla, no more than 24" high.  I am stumped about which species of Cylindropuntia this is.  It looks quite a bit like C. tunicata, but that's native to Chile and I doubt this plant is an invader, they were ubiquitous in Arizona.  If it was an invasive non-native, I'm sure I'd have figured this out via books or websites.  C. spinosior is the most common cholla in Arizona, but this looks too hairy or spiny to be considered a member of that species.  Frankly, to go along with the thematic 'cuteness' of bunnies, I'm hoping this is C. bigelovii, or teddy bear cholla. 

There are 22 species of Cylindropuntia in the United States, so chances are this specimen is none of the above.  Though seeing a common name like teddy bear cholla (called that because from afar the plant looks more fuzzy than spiny).

 Happy Friday!

Agave

So today, we are going to go back to Arizona for a bit.  I still haven't blogged about one of my favorite desert plants, the Agave.  This one below is most likely Agave deserti.  A common name for all Agave is century plant.  It's called this because the plant lives a very long time before it blooms.  It doesn't take 100 years, however, it's more like 30. 

The flower stalk grows from the center of this basal rosette of thick, fleshy, spiny leaves.  The stalk reaches anywhere from five to fifteen feet in height, growing as rapidly as 2.5 inches a day.   The flowers are yellow and can set as many as 65,000 seeds.  This is important since creating such a fast-growing blossom depletes all the plant's resources and after seeds are set, the entire thing dies. 

Agave is an important resource in the desert habitat.  Carpenter ants can live in the leaves and in times of drought (which is often) bighorn sheep chew on the leaves for their only available source of water.  Skipper butterfly larvae also rely solely on these plants for sustenance.

Below, in Central Park Zoo, there's a relative to A. deserti, A. americana. Native to Mexico, this Agave  is most often hybridized and grown as an ornamental. 

Chances are, if you like a good margarita now and then, you know that Agave is what is used to make tequila.  However, don't go harvesting either of the plants showcased in this post.  The plant you're looking for is Agave tequilana.

Mahonia, again

Last week, I blogged about Berberis haematocarpa and it's resemblance to Mahonia.    I illustrated this by posting some photos of Oregon grapeholly, or M. aquifolium, but another common Mahonia species is M. bealei or the leatherleaf mahonia.  Here's a shot of one growing in northern Virginia.

 

Leatherleaf mahonia has, as the common name implies, thicker, larger leaves with sharp spines.  It's stiffer plant than M. aquifolium though is also far hardier. You're more likely to encounter this performing well in zone 6, which makes sense when one considers this species is native to China. 

 You can see the small yellow flower buds have already taken shape on this plant.  Mahonia bealei does bloom much sooner than M. aquifolium, and will display yellow, slightly fragrant flowers as soon as January.  After they bloom, the plant sets large blue berries which tend to languish on the plant, since its non-native status means local wildlife generally avoid the fruit.  (Read: deer-resistant.)

Though it's tempting to use a broadleaved evergreen - especially one that deer avoid and has showy flowers and fruit - I'd pass on Mahonia bealei.  The plant is invasive and threatens to become a management problem in forests where it's begun to appear.