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The late February weather in Chicago has been a glorious time to be outside and work in the garden. But the unseasonably warm weather has also raised questions about the long-term effect on plants and what garden tasks are appropriate.

It is best to hold off on doing any detailed clean up of garden beds as the mulch and leaves in the beds will provide some protection to any early growing perennials when the weather eventually turns cold again. Raking leaves off the lawn and cutting back perennials are all fine to do now providing your garden soil is not too wet.

Snowdrops are blooming at the Garden.

Early flowering bulbs like snowdrops that are in flower here at the Chicago Botanic Garden are very tolerant of the cold. Daffodil and tulip foliage is coming up; these might end up being damaged by a spell of cold weather, but this should not affect the spring flowers. You do not need to take any special maintenance steps to protect these plants.

If you have some perennials that are growing in a warm area of the garden with more pronounced growth, they might benefit from a light layer of mulch. For the most part, though, there is nothing special for most gardeners to do in their perennial beds.

This is great weather to prune but proceed with care. Spring flowering shrubs like viburnums, lilacs, and forsythia set their flower buds last year so pruning done at this time of year will remove flower buds and reduce the number of spring flowers. You can still prune—just be aware of the flower buds as you are pruning. Forsythia flowers along the stems while viburnums will have a flower bud at the ends of the stem.

The dormant season, and in particular late winter, is the best time of year to complete rejuvenation pruning, which is the aggressive pruning of overgrown shrubs to bring them back into scale with the garden. Shrubs like hydrangea (except oak leaf hydrangea), potentilla, and spirea that flower on new wood respond well to pruning now too. For instance, I cut my Annabelle hydrangea back to the ground each spring.

Any plants installed last summer or fall should have been mulched when they were planted. If they were not, then mulch them now to help mitigate the temperature swings in the soil and prevent frost heaving of any plants in spring. The freezing and thawing of the soil can push recently installed small plants such as 1-gallon perennials or ground covers that were grown in containers out of the soil as the weather transitions to spring.

If we receive a good covering of snow, the snow itself will not harm plants unless it builds up on them and breaks branches. It is a good idea to brush plants off during a storm if you observe them getting weighted down. Later snowstorms are more likely to come in wet and heavy. Leave the plants alone if the snow has frozen on them to avoid breaking branches during the removal process.

Enjoy the warm weather and the early blooms, both at the Chicago Botanic Garden and in your own backyard.

A couple years ago, in early spring, I got the kind of call that puts a “plant doctor” like me on edge. “Come look at the roses right away,” someone said. In my 25 years at the Chicago Botanic Garden, no one has ever called me to say, “Hey, Tom, come look at the roses; they look great today!” I’m in charge of plant healthcare at the Garden, so when I pick up the phone, there’s usually a problem.

I got the call about the Krasberg Rose Garden following a string of very damp nights that meant trouble—a white fuzz had spread over all the roses. The fuzz was a destructive pathogen that produces mycelium, or fungal spores. It can happen pretty much overnight. We ended up managing the problem, but it was scary to start off a season like that. Roses are tricky, prone to a lot of diseases and insect problems. Our friends at the Missouri Botanical Garden lost all their roses to a virus called rose rosette disease. 

I don’t just get calls about diseases or pests such as the emerald ash borer. I get called to the Butterflies & Blooms exhibition if the staff is worried about a larva or to the Elizabeth Hubert Malott Japanese Garden if there’s a raccoon problem. I like to say that I’m sort of like a CSI detective when it comes to plants. If a plant is failing, I try to find out why and what it needs. I look at the buds, the stem, the trunk, the root flare, the soil, and the plant’s history over the years.

PHOTO: Tom Tiddens poses with a cardboard coyote cutout, used to deter varmints from veg.

Tom Tiddens and a plant healthcare specialist’s best friend head out to play fetch.

I also work with the horticulturists on preventive care, including watering, pruning, weeding, and fertilizing. When I see a problem in the early stages, I’m very patient and tolerant. I like to see if Mother Nature might take care of it—maybe a hard rain will wash away any aphids or the ladybugs will get rid of the pests, for instance.

People ask me how I track the health of more than 2.6 million plants here. I have two great plant healthcare specialists who work with me, and I really rely on the horticulturists—they’re my eyes out in the field—and my volunteer team, which includes a lot of master gardeners. Every week, I give the volunteers a map and checklist marked with target plants and pests. So a typical volunteer assignment, for example, would be to check the spirea bushes in the Sensory Garden for aphids.

PHOTO: Bagworms infect a pine.

From bagworms…

PHOTO: Rust infects a fruit and leaf.

…to rust…



PHOTO: Black spot infects rose foliage.

…to black spot on roses, Tom Tiddens treats them all.

The average home gardener doesn’t have to be so methodical. Gardening shouldn’t be a chore. I like to keep things simple at home. I don’t like weeding, and I avoid using a lot of perennials or groundcovers. I like having a nice woodchip mulch bed and a mulching lawnmower. It’s the same thing with fall leaves. Everyone bags up all the leaves. Nope. I raise my mulching lawnmower, and I just grind them into the lawn.

Register now for a certificate class with Tom Tiddens, plant health care supervisor and certified arborist. From July 21 to August 28, he will teach Plant Health 2 with Kathie Hayden, the Garden’s manager of plant information service.    

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