March 2016 – My Chicago Botanic Garden

Viburnum Leaf Beetle Update – Winter Scouting

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.

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.

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.

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.

Skunk Cabbage: Gross and Cool Herald of Spring in Chicago

Do you see something pushing up from the ground that looks like the claws of some creature in a zombie movie? Does it smell bad too?

Happy spring! This charmer is the first native wildflower of a Chicago spring: the skunk cabbage (Symplocarpus foetidus).

PHOTO: A skunk cabbage blooms in early March in the McDonald Woods. — A skunk cabbage blooms in early March in the McDonald Woods.

It’s a biologically intriguing, ecologically brilliant prelude to the wildflower riot about to burst forth on forest floors from the McDonald Woods at the Chicago Botanic Garden to area preserves.

It’s a welcome sight to Boyce Tankersley, the Garden’s director of living plant documentation, who pointed out skunk cabbage as we walked through the McDonald Woods, the 100-acre restored and protected natural area that is home to at least seven state-listed threatened or endangered plant species.

Skunk cabbage’s appearance means that the trilliums and bloodroot are not far behind. And spring beauties, star-flowered isopyrum, and cardamine, also called bittercress. Within a few weeks, depending on the weather, forest floors will be carpeted with wildflowers, courtesy of the sun streaming onto the earth before the trees leaf out and block it.

Skunk cabbage isn’t conventionally pretty. What you see are the claw-like pointed red-striated hoods called spathes surrounding a nub studded with blossoms. The plant creates its own heat, even amid snow and ice. The temperature inside the hood can be 95 degrees hotter than outside.

Thermogenesis is the goal for skunk cabbages, titan arums, and other “warm-blooded” plants.

The heat creates the plant’s signature smell, a cross between a skunk (hence the name) and rotting meat. This turns skunk cabbage into a paradise for flies, which seek out rotting meat where they can lay their eggs.

“It’s kind of got the rotten vegetation look going on,” Tankersley said. “It’s warm, which means there’s something decomposing, from a fly’s perspective. And then of course it smells bad. So there’s your triple play: ‘You need to come here.’”

And flies do come to skunk cabbage. They flit inside the hood looking for rotting meat, then emerge covered with pollen. Then they fly inside another skunk cabbage, and pollinate it.

Honeybees are the plant’s other major pollinator. They are attracted to skunk cabbage because it is a rare, early source of pollen, on which they feed. You can see a honeybee in pollen-coated action inside a skunk cabbage in the video below by the Illinois Natural History Survey:

Watch the Skunk cabbage video on YouTube.

Skunk cabbage is picky about where it grows. You can only find it in fens, wet woodlands, and other places where water is moving beneath the soil’s surface. At the Garden, they’re alongside the path through the McDonald Woods. Outside the Garden, a good spot is the River Trail Nature Center, a Cook County forest preserve in Northbrook.

And while you can see skunk cabbage now, the other wildflowers are still holding back. That’s because they’re smart.

“They’ve seen these warm temperatures and then had the weather snap on them,” Tankersley said. “Genetically, they know if they hope to survive, they can’t come out with the first warm weather.”

Which is why native wildflowers are almost never felled by a sudden freeze.

PHOTO: Prairie trillium (Trillium recurvatum). — The elegant—and less smelly— prairie trillium (*Trillium recurvatum*) is our next bloom to look for in the woods. Keep an eye out!

In the next weeks, the wildflower show will be on in full force. In addition to the McDonald Woods, you can catch it at forest preserves, where invasive species like buckthorn and garlic mustard are regularly removed, as they are at the McDonald Woods. Some of my Forest Preserves of Cook County favorites not far from the Garden are Harms Woods near Glenview and LaBagh Woods near Cicero and Foster Avenues on the city’s Northwest Side.

But the previews are open now. And it’s a real stinker.

Painting with Veggies

We’ve discovered a fun way to encourage the Garden’s Camp CBG campers to try a salad. Many kids turn up their noses when they hear the word, but after painting with food, our campers are eager to “dig into” their creations.

For little ones, this project is easy and fun to do with a grown-up and provides opportunities to identify colors and start learning about plant parts. Older kids can use new kitchen tools (with adult supervision) and discuss what is really a fruit or a vegetable.

Watch Painting with Veggies on YouTube.

Supply list:
Cutting board
Sharp knife
Food processor or grater
White plates

Recipe:
1 red bell pepper (see notes)
2 carrots
¾ cup chopped pineapple
½ head red cabbage
1 head broccoli (see notes)
Favorite salad dressing—we used ranch

Notes from the chef/artists:

Bell peppers don’t work well in the food processor. I recommend finely chopping them with a good knife.
Broccoli was a bit difficult to work with. Next time I’d use a bag of broccoli slaw.
Other vegetables I’d like to try are fresh corn (off the cob), chopped celery, black beans, and dried fruits or nuts.
This would be fun to do with a spiralizer, which would add a different texture. Check out this post by fourth-grade teacher Lindsay for eight great spiralizer ideas.

Prepare veggies by shredding in a food processor, and place each kind in a bowl. Use your imagination to “paint” your canvas (plate). Make sure to take a picture before digging in. Once you are done creating, top with dressing and enjoy.

Time to Prune the Apple Orchard

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.

Check This Chart Before You Start Your Seeds

Attention, fellow seed savers: as the weather warms up, it’s time to pull out all those amazing seeds you’ve been saving and start growing transplants indoors.

My “aha!” moment at the Garden’s annual Seed Swap happened when I stopped by at horticulturist Lisa Hilgenberg’s seed-starting table, and picked up a copy of her Seed Viability Chart. It’s not only a useful tool about the average “shelf life”—or viability—of veggie seeds, but also an eye-opening reminder to check the dates on seed packs before I start growing this spring. Some seeds last longer than others!

**Click here to download a PDF of the chart.** (Proper seed storage conditions are in a cool and dark place where temperature and moisture content will stay relatively stable.)

Ready to start sowing? We’ve got lots of good tips and info about how to start seeds on our blog and website: