Shaken, Not Stirred: Pin Oaks in Spring

With the temperatures getting up into the the mid 40s, things are happening. The Willow catkins are puffing out, the Poplars are preparing to pollinate, and the Sliver Maples are beginning to bud.

But with the frost still four feet deep and lakes still frozen, some plants are finishing their winter work, such as the Pin Oak.

Pin Oaks keep their leaves through the winter and then drop them in spring. If you find a Pin Oak that is exposed to the sun and shake it this weekend, it will drop it's leaves. 

This photo of a Pin Oak was taken yesterday, April 19th, just behind our greenhouse. Pictured under it is Jeff Evander, an employee.

As you can see, after shaking the tree, 90% of its leaves are now on the ground.

Leaves give off a lot of moisture as they photosynthesize, and the ducts that channel the moisture are there even after the tree goes dormant in the fall. So shedding leaves is a way to conserve moisture through the winter. We see this in almost all deciduous trees, except for some species of Oaks and Beech trees. 

All of this begs the question: what possible strategy might the Oak have for keeping its leaves until spring?

Some have argued that Oaks evolved and have adapted to dryer soils, and that retaining leaves in the fall and dropping them in the spring provide the trees with organic matter (which provides fertilizer and retains moisture). Others suggest that the lower leaves on the tree act like a snow fence, trapping snow and thus providing more moisture into spring. Still others have argued that the leaves provide frost protection to the buds behind the leaves. A more popular theory is that the Oaks and Beeches are evolutionarily delayed, and are on their way to shedding leaves in the fall, but need a couple thousand more years of evolution to get there. 

So remember, you only have one or two more thousand years to shake (don't stir, as with a James Bond martini) a Pin Oak in spring and see the leaves drop. 

April Frost Photos

Hard to believe the morning lows for the last five or six days here in early April have been around 10 degrees. This of course postpones the ground thawing, which is the thing seasonal workers are waiting for. We can't plant trees, till the ground, or burn prairies until  "frost out." 

Even the tree budding seems to be in a holding pattern, though I'm seeing some budding on the Poplars and Red Maples now. I still have not seen my first Bluebird, though Brian Johnson, faculty member at the College of Saint Benedict/Saint John's University, reports seeing a flock. 

In the meantime, we've had some nice frosts. I took these photos Thursday morning, April 5, around 7:30 am.

Native Plants that Provide Color in Winter

I love the look of Pin Oak leaves on the trees in winter. It is as though they're saying, "What's the rush? Spring foliage won't be coming until, well, spring." So, in the process they provide us with interesting texture and color on the horizon. 

I have a tree nursery. I deliver and plant balled and burlapped trees. I must say, I rarely get a request for a Red Oak or Pin Oak, the assumption being that they are Oaks, and thereby slow growing. But this is not the case in the Red Oak family. They grow as fast as anything. The White Oaks, on the other hand, grow slowly. But they live up to 200 years and more. Their cragginess, for lack of a better word, gives them a beauty all their own. They could be regarded as an ornamental tree, justifying their existence for sheer beauty alone (and not just for their utility in providing shade).   

Of course the red of the dogwood gives a very nice color in late winter and early spring. Pruning your dogwood will generate new shoots, and it is the new shoots that are the most red (while the older ones turn and stay green). A good time to prune them, or cut them down so that they re-sprout, is in late winter or early spring.

Few plants get a worse rap than the Eastern Red cedar. I grow them in my nursery and can't tell you how many customers scoff at them, sometimes refering to them as "scrub brush." 

Their virtues are several: they attract birds like no other tree, providing dense structure and stability for nest building. They are the only plant I can think of that appears to turn from their rusty summer color to a deeper green in the winter. We used one as a Christmas tree last year and, I swear, it turned greener after we cut it down and brought it in the house. They do best in full sun but will tolerate partial shade. 

They make for a wonderful plant in a prairie, complementing the grasses and wildflowers with height and texture.