Wonderful wood chips

I’m in love…with arborist wood chips.  These are not your beauty barks or other packaged mulches, but the chipped branches and leaves fresh from the tree crews. It’s a great way to keep this resource out of the landfill – and don’t even get me started about using this great mulch material for a “biofuel!”

I’ve written about wood chip mulches a lot, but thought today I would post some photos to show you how well they work in suppressing weeds and promoting growth in restoration sites.  We published a paper on this in 2005, though we’ve been using them in ornamental and restoration landscapes for about 10 years.

Here’s a recent project: a wetland buffer enhancement was being installed in an area that was covered in Scot’s broom (Cytisus scoparius) and blackberry (Rubus discolor):

Heron's Glen-6

We had a brush cutter mow it to the ground, then put a foot of wood chips down.  Later, we planted poplar, ash, willow and alder on the site:

We had to keep records, both written and photographic, for the county who monitors wetland projects.  So we took photos every year at the same points for comparative purposes.  Here’s what part of the site looked like immediately after planting and then after 5 years:

That’s not to say that we haven’t had to battle resurgent blackberries.  They migrate over from the wetland itself (which we can’t touch) and tip root.  But the increasing shade and competition from the trees has weakened their ability to take over, and the Scot’s broom has been gone for years.

So that’s one reason I love wood chips.  I’ll do a follow up some week showing how they can be used in the home landscape.

The joys of arborizing!

It’s Holly’s day…but she’s off playing in a tropical paradise.  So because she seems to be of a sunnier disposition than I am, I’ll post happy thoughts today.

One of my favorite pruning techniques, especially for small urban landscapes, is arborizing.  This is a way of creating small trees out of large shrubs – and often, a large shrub is as much as a small landscape can handle.  Rhododendrons are common landscape plants here in Seattle, and the larger ones lend themselves beautifully to this practice:

  

As you’ll notice in this example, arborizing not only creates an aesthetically pleasing tree form, but also moves the crown away from vehicular and pedestrian traffic.  This protects the plant from damage and enhances access.

This also works wonderfully in landscapes where you would like to have layers of shrubs, rather than one massive plant.  Look at this Ceanothus:

Arborizing this shrub not only allows planting additional plants underneath, but also allows some light into the house (note the window in the background).

Fall is generally a good time to prune (after the crowns have gone dormant).  It’s easier to see trunk and branch architecture in deciduous trees, and generally places less stress on the plant.

If you’ve arborized shrubs before, which species work well for you?  Which ones not so well?

See?  I can be a happy blogger!

Where the Buffalo Roam

Just kidding. We have no buffalo on the campus of Virginia Tech, just lots and lots of students with the flu. Yuck.  But this is much more interesting:

Bouteloua dactyloides (bless you!), better known as buffalo grass:

We’ve recently added a 1-acre meadow to our on-campus teaching and display garden (the Hahn Horticulture Garden at Virginia Tech).

Native trees, shrubs, perennials,and grasses surround a central lawn of buffalo grass. As one of the components of tall- and short-grass prairie, it is a popular forage in the west and midwest. Toughness and no-mow-ability makes buffalo grass a candidate for the low-maintenance lawn. We chose the cultivar ‘Bowie’, which has been reported as a good choice for the Mid-Atlantic…more cold and moisture tolerant.  But it’s not cheap – ran us $15/lb with a seeding rate of 3lbs/1000 sq ft. We ordered 1/4 acre’s worth. Our horticulturist Paul calibrated the spreader not once but three times, and was still nervous.

We’re pretty happy with the progress – it’s filling in nicely after 18 months. Once established, buffalo grass will pretty much choke everything else out, but until then, broadleaf weeds and crabgrass are a bit of a pain. Extremely drought resistant, it also handled this year’s surplus rainfall with no problems.

The best way I can describe it is, er, cute!  It’s so fluffy, and forms pet-able 6″ tall tussocks with little seed heads dancing about. One just might, after a hard day of academia-induced anxiety, want to lay down in it and make a “grass angel”.

We’ve already had a light frost, hence the tawny color. This presents a teaching opportunity:  most of the turf around here is tall fescue or blue grass – fairly evergreen, cool-season grasses. Buffalo grass WILL turn golden-brown in winter, and we’ll get lots of questions as to whether or not our meadow is “dead”.  No, it’s just resting!

If you’re thinking of trying buffalo grass or something other than run-of-the-mill turf for your lawn (or even ripping it out altogether), check out ideas from Susan Harris and friends at www.lawnreform.org

Moo... So there's a weed or two...

RAWRRR!

Posted in honor of Garden Rant’s Halloween-related garden photo contest.

Pick me, Amy, pick me!!!



Now For The Scary Part

This little dude is the Florida Semaphore Cactus, native only to hardwood hammocks in the middle and lower Keys. According to the Center for Plant Conservation, Opuntia corallicola may very well be the most endangered plant in the United States.”  Only one wild population remains (eight individuals), plus a few sites of re-introduction. Loss of habit and an exotic cactus moth have contributed to the demise of this most personable of cacti.

Arbitrary travel tip: I snapped this photo during a recent visit to the fabulous Key West Tropical Forest & Botanical Garden. Please pay them a visit if you’re ever in the vicinity – they are doing so many great things, with so little $$$, as is the case for many small public gardens. And then head straight to Kelly’s on Whitehead Street for outstanding $3 margaritas…served in a pint glass!

Alternatively:  "Aieeeee!

Baring it all, again.

Earlier in this blog we had a rather robust discussion about the merits of transplanting trees bare-root.  Bare-root transplanting has had a renaissance in arboricultural circles, based in large part on the work of Dr. Nina Bassuk and her colleagues at the Urban Horticulture Institute at Cornell.

As our bloggers noted, transplanting trees bare-root has advantages over balled and burlap trees (larger portion of the root system stays with the tree) and over container-grown trees (more natural root system development).   One disadvantage of bare-root trees is the need to protect roots from desiccation during storage and handling.  Also, some trees respond better to bare-root treatment than others.  Nevertheless, I think we will continue to see increased interest in bare-root planting.  One notable trend is planting relatively large-caliper (4” and larger) trees bare-root.  This phenomenon has coincided with the development of the air spade, a tool which produces powerful a jet of air that allows arborists or nursery workers to carefully excavate an entire root system with minimal disturbance.  Unlike digging a tree with a traditional tree spade, the air spade allows nursery workers to maintain virtually the entire root system when lifting a tree.  Last week,  my esteemed colleague, Dr. Tom Fernandez, and his Nursery Management class at MSU worked with Paul Swartz, MSU campus arborist, to lift a 10” caliper weeping white pine from our campus nursery.  Members of the class took turns using the air spade to excavate the entire root system of the pine.  Since the class is divided into lab sections that meet throughout the week the process was spread over several days.  After each lab period exposed roots were covered with wet burlap to prevent drying.  By the end of the week the tree was ready for lifting and was transported via flatbed truck to its new home at the front entrance to the MSU Horticulture Teaching and Research Center.   Paul Swartz reports that he has successfully used the air spade to move several large specimens on campus and the technique is especially useful for moving trees from tight spots that can’t be reached with a mechanical spade.  As more and more arborists acquire air spades look for this technique to become more common.

NOTE: Photos courtesey of Dr. Tom Fernandez.


The air spade uses a stream of compressed air to excavate roots.


Note the extent of the root system.  A 90″ mechanical spade would have missed at least half the roots of the tree.

Once the roots are excavated the tree is ready for lifting.


The pine resting comfortably at its new home.

Take it all off (cue bow-chicka-bow-bow music)

OK, I know there are skeptics out there including many of my dear colleagues.  Though it seems that at least some of my photos are making an impression.  So here is another little photo tour through bare-rooting – this time with a bigger tree.

This demonstration was given at the 2006 ISA conference in Washington.  This is a good sized tree…

…that we plopped into a Rubbermaid watering trough after removing the burlap…

…and washed off all the clay.  It is deceptively easy to do.

Oh!  I almost forgot!  We put some duct tape around the trunk just above the burlap before we started this procedure.  Look where the tape ended up:

So there is another really compelling reason to bare root trees.  Had we not, this tree would have been planted 10 inches below grade.  But I do have to say the burlap made pretty patterns on the tree:

Another plus – with the clay gone, these trees are really easy to pick up and move around!

And it didn’t need staking once it was mudded in…

 

And it looked great seven months later with little to no maintenance and lives happily ever after.  The end.

Health care reform (of trees)

Nothing is more frustrating to a gardener than watching a newly installed tree or shrub slowly die.  In performing “post mortem” analyses on failed landscape plantings, I’ve identified four common errors that can be easily avoided:

  • inadequate root preparation
  • improper soil preparation
  • planting below grade
  • inadequate aftercare

This blog entry will be dedicated to the first point – but before I do so, we need to understand how nursery plant production has changed over the last several decades.

A brief history of propagation
Many years ago the only way to obtain young trees and shrubs was as bare-root plants.  Plants were field grown, then dug up during dormancy for storage and shipping.  Bare-root trees and shrubs are usually only available during a narrow window of time, but in general these plants are healthy and structurally sound.  Most importantly for our discussion, growers can see the woody root system of bare-root plants and cull those that are not well formed.

The development of containerized production methods meant that plants could be grown and sold year around.  When plants are grown in a production greenhouse, they are generally started in small liner pots and gradually moved through a succession of increasingly larger pots.  Ideally this is done before roots become potbound, or the roots are corrected when “potted up” (moved to a larger container).  What we found, unfortunately, in a study of nursery plant quality, is that root systems are often ignored in an effort to produce large quantities of plants quickly and cheaply.  It is not considered to be cost effective to examine and correct root flaws during potting up, so the entire root mass is moved into the new container.  Structural root flaws are not self-correcting and will become more severe the longer they are ignored.

Based on our study, as well as evidence collected by numerous researchers and arborists, it is apparent that poor root quality is a significant problem in containerized and balled-and-burlapped trees and shrubs, at least in this part of the country.  Therefore, we need to correct root flaws before installing woody plants into the landscape.

A quick intro to correcting poor root systems
Balled-and-burlapped plants have a clay rootball; despite its appearance, it is fairly easy to remove the clay simply by removing the burlap and twine and soaking the entire rootball in water.  You can facilitate the process using your fingers to work out the clay, or use a gentle stream of water (Figure 1).

Figure%201.jpg
Figure 1.

Once the clay is removed the root system can be evaluated.  If you find woody roots that are circling, girdling, or in general not growing horizontally and away from the trunk (Figure 2), they should be pruned (Figure 3).  You want to develop an evenly distributed structural root system.

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Figures 2 and 3 – before and after

The pictures in this post are from my own Cercis tree, which I planted in April of 2004.  This is not a great time for planting, since Seattle has notoriously dry summers.  Nevertheless, that’s when I planted and as you can see from Figure 3, I had to remove close to 70% of the root system.  I mudded it in well (which eliminated the need for staking), mulched, and kept the root zone well rooted.  It sat for about 3 months and did nothing (Figure 4), except of course the flowers died quickly!.  In July it leafed out (Figure 5), and 3 years later had doubled in size (Figure 6).  It is now close to 15 feet tall and is in excellent health.  Given its initial root system, it’s doubtful it would have done this well without intervention.

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Figure 4 – April 04              Figure 5 – July 04               Figure 6 – July 07

(I have performed radical surgery on hundreds of tree and shrub root systems and have only lost one small shrub, whose root system is in Figures 7-8.  Kind of tough to prune something as fatally flawed as this.)

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Figures 7 and 8 say so much more than I can.