Archives For Tom Tiddens

As we all know, good soils are the key to growing any type of plant well: annuals, perennials, turf, shrubs, and trees. The Chicago region’s soils are twofold, having positive and negative virtues. On a positive note, our soils tend to be rich in nutrients. But on a negative note, our soils are heavy and do not drain well.

The soils at the Chicago Botanic Garden are very typical urban soils, and we have the same challenges. Over the years we have tried many types of amendments to improve our soils and are about to embark on another trial…biochar.

Biochar has been used for thousands of years in the Amazon Basin of South America to greatly improve poor, unproductive soils for farming. The ancient Amazons used a simple “slash-and-char” process to create biochar. This process involved cutting and burning plant material in an incomplete “smolder” style, rather than complete burn. They worked the charred material back into the soil as a long-lasting amendment. These amended soils in the Amazon have become known as “black earth” or terra preta. Amended terra preta soils created long ago still cover 10 percent of the Amazon Basin. It is important to understand that “slash and char” is different than “slash and burn,” which has many negative environmental implications, like deforestation. “Slash and char” sequesters large amounts of carbon in a stable form, unlike “slash and burn,” which releases the carbon into the atmosphere.

PHOTO: Biochar

Biochar photo by K.salo.85 (Own work) [CC BY-SA 3.0], via Wikimedia Commons

In the past decade, the use of biochar has been investigated for modern agricultural use; more recently in arboriculture, as well as general use in ornamental landscape plantings. The Morton Arboretum and Bartlett Tree Experts have conducted several recent research trials on biochar with very positive findings. One study found the root mass of test seedlings (honeylocust) grown with biochar was significantly more compared to their control group. Another study showed improvement in plant disease resistance when biochar was used. 

So what exactly is modern-day biochar?

Biochar is similar to charcoal, except it is formulated specifically for soil enhancement. It is basically organic matter (primarily wood chips) heated in the absence of oxygen, a process called “pyrolysis.” The resulting char is carbon rich and has many long-lasting virtues. Think of it in the simplest of terms as a “sponge”: it has great capacity for holding and releasing nutrients and water.

What are the benefits? 

  • Helps hold soil moisture, and release it in drought
  • Increases soil microbial activity
  • Holds and releases soil nutrients
  • Reduces leaching of nutrients and fertilizer
  • Studies have shown increased plant growth and rooting
  • Studies have shown less plant disease when it is used. (It is thought that the increased microbial activity stimulates specific microorganisms that play a key role in eliciting plant “systemic-induced resistance,” or SIR.)
  • Benefits of one application are long lasting, and it does not take a lot
  • Biochar is made from recycled materials, such as pines killed by bark beetles or trees damaged by fire

This year the Garden has begun to use biochar in some of our more troublesome areas. We don’t look at it as a “silver bullet,” but as another tool to combat problems caused by poor soils. This new tool is being trialed and then possibly integrated into our arsenal for best practice soil management.

©2016 Chicago Botanic Garden and my.chicagobotanic.org

Last year we discovered Viburnum leaf beetle (VLB) here at the Chicago Botanic Garden for the very first time. As I said then, “I strongly suggest you begin monitoring your viburnums for this critter” as once they move in, they become a perennial pest, just like Japanese beetles.

In early March, we monitored many of the Garden’s viburnums for signs of VLB egg laying and focused on areas where we observed VLB activity last summer. I had read recommendations for pruning out these twigs (with eggs) in the winter as a management technique and wanted to give it a go. To assist with this project, I called in our Plant Health Care Volunteer Monitoring Team; the more eyes the better. The six of us (all armed with hand pruners, sample bags, and motivation) began a close inspection with a focus on last season’s new twig growth for the signs of the distinctive straight line egg-laying sites. In less than five minutes, we found our first infested twig, pruned it out, and put it in a sample bag. After about three hours, we had collected about 20 twigs with eggs.

Truly, I was expecting to find a lot more. This was somewhat disappointing, as I had created a challenge to see which volunteer would fill his or her sample bag and collect the most. This turned out to be more like a needle in a haystack search, as it was a lot more difficult than I had thought. I also feel that the egg-laying sites would have been easier to see if we had done this in early winter, as the egg-laying locations had darkened with time.

Viburnum leaf beetle

Viburnum leaf beetle

Back at our lab, I dissected some of our samples under the microscope. When I removed the cover cap (created by the female after egg laying) material of a few of the egg-laying locations, I found about six orange, gelatinous balls (the overwintering eggs). These eggs were about a month or two from hatching.

For background on this new, exotic insect pest, please see my June 5, 2015, blog on the Viburnum leaf beetle.

American cranberrybush viburnum

American cranberrybush viburnum

  • The favored viburnums are the following:
  • Arrowwood viburnum (V. dentatum)
  • European and American cranberrybush viburnum (V. opulus, formerly V. trilobum)
  • Wayfaringtree viburnum (V. lantana)
  • Sargent viburnum (V. sargentii)
  • When to monitor and for what:
  • In early summer, you would look for the distinctive larva and signs of leaf damage from the larva feeding.
  • In mid- to late summer, you would look for the adult beetle and leaf damage from the beetle feeding.
  • In the winter, you would look for signs of overwintering egg-laying sites on small twigs.
  • Life cycle, quick review:
  • In early May, eggs hatch and larva feed on viburnum leaves.
  • In mid-June, the larva migrate to the ground and pupate in the soil.
  • In early July, the adult beetles emerge and begin to feed on viburnum leaves again, and mate.
  • In late summer, the adult female beetle lays eggs on current season twig growth in a visually distinctive straight line.

viburnum leaf beetle egg laying sites

Hopefully our efforts will lessen the VLB numbers for this coming season. We will see when we monitor the shrubs for leaf damage and larva activity in late May. If nothing else, it was a great learning experience with this very new, exotic insect.

Special thanks to the Plant Health Care Volunteer Monitoring Team: Beth, Fred, Tom (x3), and Chris.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

It happens every year—like Groundhog’s Day—and I have the same déjà vu annually!

Each winter for the past 20-plus years, I have supervised and worked on the pruning of the apple orchard at the Regenstein Fruit & Vegetable Garden. Since pruning has such a great effect on an apple tree’s health, it became an annual duty of the Plant Health Care Department (that I manage) many years ago.

PHOTO: Tom Tiddens and Tom Fritz pruning the apple orchard.

Tom Tiddens and Tom Fritz pruning the apple orchard.

PHOTO: Closeup of pruning.

Cutting in the right location ensures speedy healing, and a good shape when finished.

To prune the north orchard (about 43 trees) it takes three people about two weeks. We wait until late winter/early March to begin pruning and complete the work before the buds begin to plump and open, as this is the optimal window to prune apple trees for plant health. Over the years I have been in every tree many, many times. Some are easier to prune than others, and some are downright intimidating. The one tree that is the most difficult to prune has been named “The Spirit Breaker,” and we always draw straws to see who gets to prune that one—it takes a full day! Overall, I very much enjoy this late winter pruning project, as it has become an annual rite of passage into spring for me.

Our current style of pruning strikes a balance between ornamental pruning and conventional orchard pruning, which focuses more on production (and which can be very aggressive) and less on plant health. The difference is that every cut we make is carefully made by hand back to a branch or bud, without violating the basic ornamental pruning rules. These carefully made cuts allow for healing without the dieback that can promote disease and other problems. We also work on developing proper branch angles, and thin the tree for better light penetration; another goal is to keep the height down. When pruning is complete, our orchard from a distance looks similar to conventional orchard pruning, where the older trees are kept low, but when you look closely, you can see the difference. 

PHOTO: The apple orchard before pruning.

Before pruning

PHOTO: The apple orchard after pruning.

After pruning

Why is it so important to prune an apple tree annually as we do to our apple orchard?

  • Proper annual pruning will increase harvest quality.
  • Pruning lessens diseases such as apple scab, fire blight, and leaf spot. It increases air circulation and allows the tree to dry out more quickly; moisture promotes disease. 
  • Keeping the trees thinned out (and not so tall) allows for better spray coverage for insect and disease treatments. (All treatments at the Garden are organic products, such as sulfur [mineral] for disease suppression.)  
  • Pruning regulates the height of the trees for easier harvesting.
  • Pruning allows for better light penetration for more—and higher quality—fruit.
  • Pruning allows for branch directional training that will increase production and lessen apple weight-load breakage in late summer.

PHOTO: The apple arbor in bloom, April 2012.

The apple arbor in bloom, April 2012. New whipstock was planted on half the arbor a few years ago, and the new trees should soon look this good again.

Being that the orchard is on the far north side of the Fruit & Vegetable Garden, I feel that many visitors miss out on the experience of walking through the orchard. Experiencing a walk through the orchard in the spring when the apple trees are in full bloom, with the fragrance saturating the air, is a sensory overload and a must-do! In the summer, the outer walk becomes almost tunnel-like, and you feel as if you are on another planet. It’s also fun to watch the fruit develop throughout the season, although please avoid the temptation to pick, as the fruit needs to be harvested at the proper time (which is different for each variety), and we use the harvest in many ways. Next time you are visiting the Chicago Botanic Garden, make it a point to “walk the orchard.”

As for me, I am closing this year’s book on “time to prune the orchard;” 2016’s orchard prune is complete!

Special thanks to Thomas Fritz and Chris Beiser (plant health care specialists and certified arborists) who worked diligently to get the orchard prune completed this year.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

Emerald Ash Borer has a new host: White fringetree (Update)

Emerald Ash Borer: Sad But True, Part 4

Tom Tiddens —  February 29, 2016 — 2 Comments

Emerald ash borer appears to have spread to a different host, and has now been found and confirmed at the Chicago Botanic Garden. But there’s no need for us to panic—it’s just an interesting find to document. 

As I blogged in late 2014, a college biology professor in Ohio (Don Cipollini, Ph.D., of Wright State University) discovered emerald ash (EAB) borer attacking white fringetrees (Chionanthus virginicus). Soon after his discovery in 2014, the Garden monitored its fringetree collection and found no signs of EAB activity on our fringetree collection (around 40 trees).

PHOTO: Dr. Cipollini holds the limb on which we found emerald ash borer activity.

Dr. Cipollini holds the limb on which we found emerald ash borer activity.

Two weeks ago I had the privilege of meeting Dr. Cipollini here at the Garden and scouting our fringetrees with him. Cipollini and a Ph.D. student are studying EAB on fringetrees and are scouting known populations of fringetrees in areas of EAB activity. Where better than a Garden like ours with a documented collection of fringetrees? 

We scouted nearly all of our fringetree collection very closely. Cipollini knew exactly where to look (way beyond the obvious) and carefully reviewed each of the Garden’s fringetrees. About halfway through the scouting process, a suspicious sunken area was found on one tree. With a sharp chisel, a small section of bark was scraped, revealing a borer gallery. We later removed the limb and found a D-shaped EAB exit hole not far from the gallery. Cipollini indicated that he felt the damage was about 2 years old, and this coincides with time that EAB was at its highest level at the Garden. Of all the trees we very closely monitored, we found only one that had been very slightly damaged by EAB.

PHOTO: The gallery left under the fringetree’s bark by emerald ash borer activity.

The gallery left under the fringetree’s bark by emerald ash borer activity.

We do not need to start treating our fringetrees for EAB or recommend it. The damage is old, and took place when EAB was hitting the Garden the hardest a couple of years ago; so at very high population pressure, it makes sense that they may feed on another closely related tree or shrub. Ash (Fraxinus) is in the olive family (Oleaceae), as is fringetree (Chionanthus), lilac (Syringa), Forsythia, privet (Ligustrum) and swamp privet (Forestiera). These other shrubs are being monitored as well, but it is thought that they may not be an attractive alternative host, as the EAB does not seem to go after small-diameter branches that are prominent on these other olive family shrubs.

As I mentioned in my earlier blog post, I do suggest if you have a fringetree that you look it over for signs of EAB activity.

The Garden is a member of the Sentinel Plant Network, a group that unites botanic gardens in monitoring and providing education on exotic plant pests and pathogens, and works in partnership with the National Plant Diagnostic Network (NPDN).

If you are a plant and bug person like me, please consider becoming a NPDN First Detector and help be on the lookout for these exotic plant pests and pathogens. The NPDN offers an online training course to become a First Detector at firstdetector.org. It’s free, and upon completion, you even get a printable certificate!

©2016 Chicago Botanic Garden and my.chicagobotanic.org

Unwanted wiggler discovered!

About a month ago, one of our horticulturists called me out to look at a groundcover planting that was being heavily disturbed by worms. At first look, I thought nothing of it—maybe it was increased surface worm activity from all the rain. A couple of weeks later, they were still very active, and the groundcover was actually floating on worm castings! We rolled it up to expose many worms. When I picked up a worm, it flipped out of my hand and wriggled away quickly, snake-like—not like a typical worm.

Since this activity seemed strange, I asked our senior ecologist to have a look at the crazy-acting worms. Coincidentally, he identified them as “crazy worms” (Amynthas agrestis), an invasive worm on his watch-for list that has never been found in Illinois. Samples were sent to the University of Illinois for confirmation, and the Illinois Department of Agriculture and Illinois Department of Natural Resources were informed. Our find has been confirmed—along with another find in DuPage County—and a potential find in Wilmette is being investigated. The crazy worm has been in the United States for many years in many of the southeastern states (and in the Smoky Mountains). In 2013, it was found in Wisconsin. DuPage and our find are the first confirmed for Illinois.

PHOTO: Crazy Worm (Amynthas agrestis).

Crazy worm (Amynthas agrestis)

Why is this worm bad?

  • They out-compete and push out our common European earthworms.
  • They multiply very quickly.
  • They devour soil organic matter and drastically change soil structure. This has a huge impact on forest ecosystems as well as on residential and urban ornamental plantings.

How do I identify the crazy worm?

  • They are found near the soil surface.
  • When touched, they respond immediately with a crazy flipping and jumping reaction.
  • They have a fast, snake-like movement.
  • Unlike a common European worm, they have a milky white flat band (clitellum).
  • They are 4 to 8 inches long.
  • A worm may lose its tail when handled.

What should I do if I think I have found the crazy worm?

  • Report the find to the Illinois Department of Natural Resources or Illinois Department of Agriculture.
  • To learn more about the crazy worm, just do a Google search on Amynthas agrestis (crazy worm or jumping worm).

Currently there are no treatments recommended for management of the crazy worm. Education and slowing the spread is the current course of action. The crazy worm’s primary means of spread is through the movement of plants with soil.


The Garden is a member of the Sentinel Plant Network, a group that unites botanic gardens in monitoring and providing education on exotic, invasive plant pests and pathogens, and works in partnership with the National Plant Diagnostic Network (NPDN).

If you are a plant and bug person like me, please consider becoming a NPDN First Detector and help be on the lookout for these exotic, invasive plant pests and pathogens. The NPDN offers an online training course to become a First Detector at firstdetector.org. It’s free, and upon completion, you even get a printable certificate!


©2015 Chicago Botanic Garden and my.chicagobotanic.org