The Garden Professors™ – Page 138 – Advancing the science of gardening and other stuff since 2009

The Heartbreak of Plagiotropism…

…Otherwise known as “splayage”. When vegetatively propagating some species of woody plants, care should be taken when selecting where to take a cutting (piece of stem) to root. Propagation from terminal cuttings (pointy end up) usually results in orthotropism or a vertical growth habit. Cuttings from extremely lateral branches (those that grow parallel to the ground) can, in a few species, result in a spreading growth habit or plagiotropism.

This is not always undesirable – some species are purposefully propagated this way to maintain the prostrate habit that particular cultivar is known for. I’ve propagated lots of Buddleia over the years and don’t recall having this happen. Jeff, you were “Mr. Buddleia”* back in our days at UGA…please weigh in on this!

Floppulence
Buddleia davidii ‘Santana’, author’s garden.

Said plant was purchased from a little Mom & Pop greenhouse as a 4.5” pot with a 6” tall rooted cutting, and it went into our garden in May. It is now lolling all over its neighbors like a drunken sailor. What looks like a vertical piece in the back is simply propped up by the Canna. No big deal, just a good teaching moment.

‘Santana’ is a bit slower-growing than most cultivars of Buddleia, yet is in great demand due to the wacky variegated foliage. My guess? This is the result of repeated acts of propagation via lateral branches…cuttings of cuttings of cuttings. Not to mention the fact that it’s patented, so this guy may not only be floppy, but illegal (!). One of the purported upsides of the plant patenting process is to control the quantity and quality of propagation through licensing. But that’s another post topic for the future.

*Not to be mistaken for the pageant winner “Miss Buddleia”

Support your local arborist

A couple of weeks ago I was interviewed for the local paper about this year’s fall color. It’s pretty standard fare around these parts; newspapers, AAA, and so on want to know if we’re going to have good fall color, will it be early, will it last long. I mentioned to the reporter that we’re seeing a lot of early fall color in the maples around mid-Michigan, in contrast to the northern part of the state, which appears to be running a little late. The question of course, is why. I noted even though this summer was relatively cool, trees have been stressed the past several years and some pests, such as clearwing borers, that might not normally be major problems may be taking advantage of the situation. After the article appeared in the Lansing paper, it was picked up by the Chicago Tribune and USA Today (must’ve been a slow news day). Since then my volume of “What’s wrong with my tree?”calls and e-mails has skyrocketed. Depending on how busy I am I usually make an effort try to respond to homeowner calls. A few issues, such as tar spot on maple, can be diagnosed sight unseen; “My maple has little black blotches on the leaves that look like tar spots”. Most serious tree problems, however, require a site inspection in order to fully evaluate and diagnose the problem.

If callers and e-mailers really want to get to the bottom of their tree problems I usually tell them to contact a professional, certified arborist in their area. The International Society of Arboriculture (ISA) provides training and certification for professional arborists. In order to be certified, arborists must meet certification standards and take continuing training to maintain their certification. Being an arborist is a tough job. And the business of being an arborist is made tougher by the low barriers to entry. Anyone can buy a chainsaw, slap a magnetic sign on the side a pickup, and advertise himself or herself as a tree service. Quality, professional arborists have to pay for training, insurance, bonding, up to date equipment, and proper safety gear for all employees. It’s not a very level playing field. But for the client that is looking to save the oak tree that Grandpa planted when he moved into the house after the war, the knowledge and expertise of a professional is far preferable to the chainsaw of Joe’s Fly-by-night tree service.

To find a professional arborist in your area look in the Yellow pages under Tree Services and look for arborists that are ISA certified and insured. Also the ISA has a search feature on it’s website that enables homeowners to find an arborist based on their zip code.

Old Books

It’s a rainy day in the upper Midwest. My favorite time to read. Of course, I should be writing papers, grading papers, or setting up seminars for next semester. But instead I’m drawn to my bookshelves. In most professors offices that I visit the shelves are an odd mix of old and new books that focus on the particular subject which that professor works on, along with the scientific journals that relate to that discipline. It’s no different in my office, except that I tend towards older books and my tastes are just a little bit more eclectic than most. I have a particular fondness for old entomology texts and I also like books on garden remedies — whether old or new, academic or not.

In a future post, maybe next week or so, I’m going to go down a rogues gallery of books that I don’t care for, old or new. But today I’m going to do something a little different, I’m going to tell you the three books that I think are must reads for any gardener or horticulturist. But the catch is that none of these books are currently in print and so you’ll need to search for them or go to Amazon.com where you can often find dealers who have used copies. These books aren’t listed in any particular order, except the order in which they came to my mind when I put this post together.

Best Reading Book — The World was my Garden, written by David Fairchild, is one of the best horticultural reads of all time. I’ve heard Fairchild called the last of the great plant explorers as well as the father of modern plant exploration. Either title works. I wouldn’t call him the greatest plant explorer of all time (though it’s no stretch to say that he was one of the best), but he is certainly the most skilled writer (at least in my mind).

Best Informational Book(s) — The Standard Cyclopedia of Horticulture edited by L. H. Bailey is a series of three (or more depending on the edition you get) books which is basically a humongous encyclopedia of everything horticultural. The beauty of these books is the amount of information they deliver along with the appreciation that the writers (and especially the editor who many consider the father of modern horticulture) had for the art and science of horticulture. So often we, as professors, want to explain things “scientifically.” Sometimes gardeners just want to talk about horticulture as an “art”. This cyclopedia does a great job of appreciating horticulture from both sides. My favorite section is one called “horticulturists” where an overview of some of the greatest horticulturists of all time is offered, one of the saddest being E. G. Lodeman who died young, but not before writing another of my favorite books of all time, “The Spraying of Plants” — which I won’t include here because it’s a book that will only appeal to a very small audience (those who want to know about pesticides used before1900).

Best Book on Insect Control — Destructive and Useful Insects is a classic text on insect control which has seen many editions dating back to the 1920s. The best edition, at least in my mind, is the 2nd edition. The second edition of this book was out before the widespread use of DDT and so, while lead arsenate is recommended a little more than I’d like, there are lots of cultural remedies for controlling insect pests listed also.

I’d love to hear about some of your favorite out-of-print books also — anything from general horticulture to plant pathology and entomology — Let me know what your must-haves are!

Rubber mulch rubs me the wrong way

I’ve been receiving a lot of questions about rubber mulch lately. For those of you not familiar with the product, it consists of shredded tires that can be dyed and used on ornamental landscapes or under playground equipment. In fact, the Obamas had this material installed underneath their children’s play structure at the White House. It seems an ideal way to recycle the 290 million scrap tires we generate annually.

But is it?

It’s not effective: One of the main reasons we use mulch is to suppress weeds. Research has demonstrated that organic mulches such as wood chips, straw, and fiber mats control weeds better than rubber mulch.

It burns: You’ve heard stories about piles of scrap tires catching fire and burning for weeks. Well, those same flammable compounds are in rubber mulch, too. When compared to other mulch types, rubber mulch is the most difficult to extinguish once ignited. In fact, some parks and playgrounds no longer use rubber mulch or rubberized surfaces because vandals have figured out that rubber fires cause a LOT of damage.

It breaks down: Although sales literature would have you believe otherwise, rubber is broken down by microbes like any other organic product. Specialized bacterial and fungal species can use rubber as their sole food source. In the degradation process, chemicals in the tires can leach into the surrounding soil or water.

It’s toxic: Research has shown that rubber leachate from car tires can kill entire aquatic communities of algae, zooplankton, snails, and fish. While part of this toxicity may be from the heavy metals (like chromium and zinc) found in tires, it’s also from the chemicals used in making tires. These include 2-mercaptobenzothiazole and polyaromatic hydrocarbons, both known to be hazardous to human and environmental health.

It’s not fun to be around: When rubber mulch gets hot, it stinks. And it can burn your feet. Yuck.

The EPA’s website says this about scrap tires: “Illegal tire dumping pollutes ravines, woods, deserts, and empty lots. For these reasons, most states have passed scrap tire regulations requiring proper management.” So if we have legal tire dumping (in the form of rubber mulch), does that mean it doesn’t pollute anymore?

(You can read a longer discussion on rubber mulches here.)

Whoo hoo!

I promise I’ll post something more substantial today…but I had to pass this email message along that I received this morning. Way to go colleagues and commenters!

Hi Linda,

Your new weblog, the Garden Professors, is an impressive piece of work! I plugged it today in the consumer horticulture CoP blog [http://www.consumerhortcop.wordpress.com].

Regards,

Bill Hoffman
National Program Leader (Ag Homeland Security)
CSREES/USDA

More Good Stuff from the Garden Writer’s Conference in Raleigh

I should add “in absentia”… Played hooky from the convention center Thursday afternoon for a trip out to Plant Delights Nursery, Inc. with my former grad student and plant geek extraordinaire, Paul Westervelt. We followed proper Plant Delights etiquette: you make an appointment to visit at a time other than open house or tour. I teach herbaceous landscape plant i.d. as well as ornamental plant production courses, and take every opportunity to bring back images of new technology, growing systems, and great plants to my students. Since Paul is a now a grower for a large nursery, he’s also keen to learn anything he can.

We certainly didn’t go to shop [“She lies!”].

Tony amongst the yucca pups.

Even though we arrived a good hour before our appointed time (we were…excited), and even though a throng of 500+ salivating conference attendees were to besiege him and his staff the next day, owner Tony Avent very kindly made time to give Paul and me a personal tour of the back 40: where the real action is. Tony patiently answered our gazillion questions and filled our pockets with seeds. The propagation houses and trial areas have more amazing plants than you can shake a stick at. Many are one-of-kind hybrids or species. The vast Colocasia trials actually gave me goose bumps – alas, no photos were allowed. A walk through the display and trial gardens (Juniper Level Botanic Garden), resulted in several trips back through the retail houses to find that OMG! plant we just saw. We topped our visit off with the purchase of way too many yummy plants. Delightful, indeed!

The trial and breeding collection of Epimedium species and hybrids. Who knew there were that many???

North Carolina or Hawaii?? That’s Colocasia ‘Diamond Head’.

I’m in an Agave/Yucca phase and this isn’t helping a bit.

Paul demonstrates “The Joy of Plant Shopping”.

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.

A Winner!

Over the weekend Linda accepted an award from the Garden Writers Association for her book The Informed Gardener. It’s good to see that people are starting to pay attention to science based gardening, and no-one has worked more tirelessly than Linda to get the word out there!

My Favorite Class Project

Every year I teach a class called nursery management. In this class students have the opportunity to try all kinds of different growing techniques out in the nursery. They get to use a tree spade and prune and all kinds of other stuff. But something else that I have the students do is to make hydroponic systems for growing plants. No, hydroponics is not a common technique for growing plants in a nursery, but to grow plants hydroponically you need to know what you’re doing, and so this is a convenient way to make the students think about the plants they grow and what these plants need to prosper.

To start this project I give the students a water pump and an air pump (courtesy of our friendly neighborhood drug dealers — no, seriously — when the cops bust pot growing operations they give us the equipment that they’ve confiscated after they’re done using it as evidence. Much of the equipments is new, some is very high end.) Then I divide the students into a few groups, tell them what they’re growing, and give them two weeks to come up with a growing system and a nutrient solution to grow their crop (I do allow them to use our stock hydroponic solution, which will grow the plants, but won’t win anyone any prizes — most groups choose to use this as a base solution and then add to it.). The group whose plants grow the largest after twelve weeks wins a modest bonus to their grade.

So, what do we have for set-ups this year? Some very, very cool ones! First, we have a number of groups who went with a simple, non-circulating system, as seen below. Basically just an air-hose and a container filled with nutrient solution.

Another group decided to use a flood and drain system. They use a timer to trigger the water pump to fill a tray with nutrient solution for five minutes every few hours. This hydrates the containers which hold the extremely well drained ceramic beads in which the plants are held.

And finally, one group decided to use a capillary action system where the base of the container is filled with nutrient solution which is wicked up into a well drained media (a combination of rockwool, vermiculite, and perlite) into which the plants are placed. This group decided to lay their plants on their sides to encourage extra root growth.

I’ll let you know in about 12 weeks which group wins!

Eat your veggies! (But not the arsenic, or the chromium, or the lead…)

The last few years have been a perfect storm for the resurgence of home vegetable (and fruit) gardens. Grapevines are trellised along sidewalks, herbs replace the grass in parking strips, and tiny gardens of carrots and lettuce are shoehorned into any available spot. It’s all good – but we need to be particularly careful about what those plant roots might be taking up along with nutrients and water.

1) Contaminated soil. Many urban (and suburban, and even rural) soils are contaminated with heavy metals, pesticides, and/or industrial wastes. Lead is commonly found in soils near roads (from the old leaded gasoline we used to use) or from old lead-based paint chipping away from houses. Arsenic is a very real problem in North Tacoma soils, for instance, thanks to the smelter that operated there for decades. Overuse and incorrect use of home pesticides will leave residues in the soil for years.

2) Contaminated compost and soil mixes. Many of the same contaminants mentioned above can be found in unregulated composts and soil mixes. (More on this topic here.)

3) Treated lumber. The old treated lumber (CCA = copper, chromium and arsenic) is no longer being sold, but it’s out there. These timbers should not be used around vegetable gardens, as they will leach their heavy metals into the soil. Vegetables vary in their ability to take up and store these metals. (More on this topic here.) Likewise, rubber mulches may leach unwanted chemicals into the soil and should not be used around food plants. (More on this topic here.)

treated%20lumber_jpg.jpg

What can you do to avoid these problems? A few things are quick, easy and cheap:

1) Have your soils tested. I’ve mentioned this in an earlier blog on urban soils. It’s the best way to find out exactly what you have in your gardens – the good and the bad.

2) Use only certified composts and soil mixes.

3) Plant in containers if your soils aren’t safe for food. This is especially easy to do with perennial herbs, which can be kept like any other container plant on your deck or porch for years.

4) You can also replace the soil in your vegetable garden. This isn’t quick, easy, or cheap, but is a solution for some people.