This summer, when you stop by for ice cream at the Rose Terrace Café, be sure to look UP—and marvel at the incredible trees above you. These 28 GREENSPIRE™ linden trees (Tilia cordata ‘PNI 6025’), a cultivar of littleleaf linden, are actually pruned into a 270-foot-long hedge!
Littleleaf lindens are native to Europe, central Russia, and western Asia. They are relatively disease-resistant and low-maintenance trees. Their dense canopy provides ample shade for a hot summer day, and the heart-shaped leaves turn an outstanding gold color in the fall. They have a very symmetrical conical shape, strong central leader, and can reach a height of over 50 feet when mature—a great landscape tree for the Chicagoland region!
Twice a year, working carefully, twig by twig, a crew of four to five staff members from the Grounds Department prunes all 28 trees in the Linden Allée to precise measurements—once in the winter for shaping, and once in the summer for detail grooming. The design is very uniform and creates a formal allée of trees. The sides are pruned at a slight, almost imperceptible angle, and are 4 inches narrower at the top than at the bottom. This allows sunlight to reach all of the leaves, while still visually appearing to be straight, not slanted. The undersides of the trees are pruned level, and even the tops of the trees are pruned into a perfectly flat hedge shape.
Guillermo Patino, who has been with the Garden for more than 20 years, is the crew leader for this project. He is an expert at maneuvering the large aerial lift in and around all of the trees, as even the back sides of each tree must be pruned. And then, once every hour, he hears over the radio, “The tram is coming!” He moves his giant machine out of the way, allows the tram and visitors to pass, and then at the blazing speed of 2 miles per hour, drives back down to his work area to continue his pruning.
An interesting and unique characteristic of linden trees is that they are very tolerant of heavy pruning, making them the perfect candidate for hedging, espalier, and bonsai.
This work takes the staff more than 500 hours to complete over a period of two full weeks. A big project at the Chicago Botanic Garden, but the finished product is well worth the effort!
Gardeners are facing bigger challenges than usual this spring due to a “perfect storm” of weather conditions that scorched evergreens, protected plant predators, elicited heavy use of road salts, and encouraged snow molds. The scorch or burn that has left patches of brown on arborvitae (Thuja), yews (Taxus), boxwoods (Buxus), and other evergreens is the worst and most widespread I’ve seen in my 29 years at the Chicago Botanic Garden. Branch damage from voles and rabbits is also particularly bad this year, and heavy and prolonged snow cover also promoted snow molds, creating bleached-out patches of lawn. Road salts put additional environmental stress on our landscaping.
The bad news is that more plant damage is likely to appear once the weather is consistently warm, though many plants will recover from the long, hard winter. While plants may have to be severely pruned or removed altogether, the polar vortex has given us a few important reminders about growing in the Chicago area and could ultimately make us all better gardeners.
During the cold winter months, evergreens continue to lose water vapor through their leaves or needles. The leaves must replace the water by pulling it up from the roots. But when the ground is frozen, the plants’ roots cannot absorb water to resupply the leaves.
If the weather turns warm and sunny while the ground is frozen, evaporation from the leaves increases and the water cannot be replaced. The resulting symptoms, discolored or “burned” foliage, tend to show up quickly in spring, when days are sunny and warm.
Bright winter sun and strong winds can accelerate evaporation, and it’s typical to see the worst burning on the west- and south-facing sides of a bush or tree. Signs of winter burn include needles or leaves that have turned golden or brown. Sometimes a plant has an overall yellowish or off-green color. Leaves may appear bleached. Salt sprayed up by passing traffic can exacerbate the problem and accentuate damage on the road-facing side of the plant.
Many evergreens—particularly fast-growing varieties such as yews—will be fine after a light pruning. Deeply scorched plants will require heavy pruning, leaving unsightly “holes.” Slower growing evergreens may take years to recover from a severe winter burn, and gardeners must decide on a case-by-case basis whether it’s best to remove the specimen.
Unfortunately, some evergreens will be a total loss. This is especially true for plants grown at the edge of the hardiness zone. To determine whether a bush is going to make it, look for new buds or lightly scratch a branch to look for signs of green wood. Patience is often a virtue in gardening, so if you have any doubt about a plant’s viability, give it some time.
The deep drifts of snow and prolonged snow cover were a boon to such plant predators as voles and rabbits. The blanket of snow shielded voles, mouse-sized creatures that travel under the snow, from hawks and other predators, leaving the creatures free to gnaw on branches and trunks. The drifts also provided a stepladder for rabbits, which feed on top of the snow, allowing them to reach higher into bushes. Signs of rabbit damage include a 45-degree cut in branches. Severe rabbit damage often looks like a bad pruning job, but gardeners can improve the situation by evening out the bush. Branches that have been girdled—or chewed all the way around—are likely to die and should be pruned back.
The sparkling white drifts also promoted snow molds, which can leave large patches of dead-looking lawn. Typically, lawns will bounce back after raking and light fertilizer. Lawns damaged by salt spray might not recover as quickly, and strips growing along roads might need to be replaced altogether.
It’s never good to lose a plant or shrub to the elements, but the polar vortex did provide the type of reality check that can lead to best gardening practices. In a relatively mild winter, Chicago-area gardeners may have success with plants growing at the edge of their hardiness, but these plants can be killed or severely damaged in typical USDA Zone 5 conditions. Perhaps you’ll think twice in the future before putting something less-than-hardy in the garden. Good mulching and watering habits, and planting in the spring to give plants an entire growing season to become established, will increase the vigor of your plants and may help minimize winter burn.
Another virtue of gardening is that it forces you to look forward. So keep last winter’s lessons in mind as you clean, prune, maintain, and perhaps replant this spring.
Historically, fruit trees, shrubs, and berries were grown at home out of necessity. Colonialists were entirely dependent on what they could produce themselves, and in time, a fruitful garden became a common symbol of independence from foreign imports—highlighting a new American pride in agriculture.
The farm-to-table movement of today epitomizes the fruit-growing traditions of the past by “growing as close to the plate as possible.” Sweet, juicy fruit can be easily grown in gardens of all sizes: on small urban lots, in containers on terraces, or in large suburban gardens. Harvesting homegrown fruit continues to be a gardener’s most satisfying pleasure, and with a bit of advance planning, choosing suitable varieties to plant this spring is possible. Here are a few ideas to get you started creating, and/or caring for, your edible landscape.
Plan to plant strawberries
No grocery store strawberry ever tastes as good as one grown in your own yard. An easy starter crop, strawberries are self-fertile, so you can start small if you like—plant just one variety or only one plant—and still reap a reward. Choose strawberry varieties carefully, however—they vary greatly in flavor, disease-resistance, tolerance of different climates, and harvest time.
Good choices for Illinois gardens are larger June-bearing strawberries such as ‘Earliglow’ and ‘Allstar’. Day-neutral or everbearing strawberries were developed to produce flowers and fruit continuously throughout summer and fall, ignoring the seasonal effects of day length on fruit production. Of the many day-neutral and everbearing varieties to choose from, ‘Tristar’ is a reliable berry for our zone. At the Garden, we grow everbearing strawberries ‘Mara de Bois’ and ‘Seascape’ in hanging baskets and vertical plantings, because they are among the first to fruit in the spring, but also produce a June crop followed by a final fall crop.
Planting several varieties together in your garden extends your harvest time, ensuring there are plenty of strawberries for eating out of hand and enough fresh berries left over to make strawberry jam.
Choose healthy plants for a healthy harvest
Start with quality, virus-free, and disease-resistant plants. Mail order nurseries and garden centers have bundles of bare-root plants available. Lesser quality plants are prone to fruit rot, mold, and fungal diseases like Verticillium wilt.
Select a planting location in full sun; avoid low-lying spots or crop beds that have grown tomatoes, potatoes, or cane fruit in prior years. These crops can harbor soil pathogens like Verticillium and Phytophthora which can affect new plantings. While strawberries prefer to grow in soil with a bit of acidity, a pH of 6.2 is ideal; the varieties mentioned above perform well in Chicago.
Aim for early spring planting, as soon as the soil can be worked, and its temperature is above 40 degrees Fahrenheit. Mid-April to mid-May is ideal. Space plants 12 inches apart, leaving 3 feet between rows. Fifty plants produce enough fresh home-grown fruit for four people all summer long.
Plant with midpoint of crown at soil level. Roots should be planted straight down. Strawberries are shallow-rooted, and mother plants spread by runners—which can be removed if desired, to develop stronger plants and to promote bigger fruit.
Water your plants well, particularly when they are fruiting. Mulching with straw helps keep fruit clean and dry, and up off the soil.
Spring tasks: Prune Raspberries
Red, yellow, black, or purple raspberries are easy to grow in hedgerows as natural barriers along lot lines or on post-and-wire trellises. Cane fruit is best managed with proper spring pruning, which prevents a tangled mess and makes your late-summer harvest far easier. Regular pruning keeps brambles in line while allowing air flow through the plant—lessening the risk of fungal diseases like Botrytis and rust, and increasing both yield and berry quality. Both types of raspberries—summer-bearing and everbearing (or fall raspberry)—benefit from a good March pruning.
Summer-bearing raspberries produce a single crop in the summer on canes which have overwintered. It is important to confine them to a 1- to 2-foot-wide hedgerow to encourage air flow and sunlight. Begin your pruning by removing dead, diseased, or damaged canes first. Then, head back (prune) the spindly top 6 inches of cane tips. Removing the thinnest wood which produces the smallest berries forces the growth into the more vigorous lower part of the plant. Finally, remove less vigorous canes—in an established plant, those canes with less than a pencil’s diameter thickness—leaving 6 inches between canes (enough room to easily pass your hand between canes).
Fall-bearing red and yellow raspberries can produce fruit on both the current season canes (called primocanes) and second-season growth (floricanes). Thus, they can be pruned to bear one or two crops with a method called, “double cropping.” (We demonstrated both methods last year on our brambles in the Regenstein Fruit & Vegetable Garden.)
To produce one heavy fall crop, cut all autumn raspberry canes back to ground level in the spring. Canes should be cut as close to the ground as possible to encourage new buds to break just below the surface. All new canes will grow from this radical pruning and produce a single crop of berries.
A second method of pruning produces a small crop on the previous year’s growth and later, a second crop on the current season’s canes. When a double crop is desired, remove dead, diseased, or damaged canes in March, leaving the vigorous canes to fruit. Tip-prune those back by one-third of the total length of the cane, or to trellis height. The new shoots or primacies will produce the second larger crop. After the second fruiting, the canes will die and should be removed.
Pruning for blackberries is similar to raspberries. They are also pruned in March by heading back the “leaders”—the main canes—by one-third (or about 36 inches). This tip-pruning helps to stimulate the growth of lateral branches, which is where blackberry sets fruit. The lateral branches should be pruned back to 12 inches, or where the branches’ thickness is about the diameter of a pencil.
Who doesn’t love a warm winter blanket? With unseasonably cold temperatures continuing into early April, that blanket has been especially welcome this year. If you are like me, though, you just can’t wait for that first day when you lose the covers and open the windows. It is that breath of fresh air that tells us summer is just around the corner.
Our Krasberg Rose Garden is ready for its breath of fresh air, too. All winter, many of our roses have been under their warm blanket of composted horse manure. Compost protects roses from the harsh winter winds and freeze and thaw cycles that can be deadly to many cultivars.
As the hours of sunlight increase and daytime temperatures get warmer, however, we need to start inspecting our roses for signs that it is time to remove the compost and prepare the roses for the beauty yet to come.
The process is fairly straightforward. In late March, or whenever we have had several warm days with limited risk of a killing frost, we use our hands to carefully remove the thawed compost from around a rose bush. We need to inspect several bushes because some areas of our Garden thaw and start actively growing earlier than others.
We look for yellow, bright green or reddish growth around the base of the plant — these are new rose canes. If we do not see any new growth or if new growth is still very small, we may cover the roses for a few more days. The warm compost encourages rose bushes to break dormancy.
However, if we see new growth and it is an inch or longer, then is it time to completely remove the compost and let the canes grow freely. The sooner this new growth begins to photosynthesize in the sun, the healthier and stronger your plant will be the rest of season. Remember that this new growth is very fragile, so we use gentle care when removing the compost.
Once we remove the compost, our team then prunes the canes for optimum health. We first remove any cane that is black or brown — these are dead or dying — and anything that looks diseased.
From there, we prune the shrub until it has five or six healthy, large canes that are at least the diameter of a pencil. The pruning should result in an open center, with the top bud on each remaining cane facing away from the center of the plant. The open center maximizes the amount of sunshine and air circulation within the plant — important components to plant growth and disease prevention.
We also take time to frequently disinfect our pruning tools as we work through this late-winter chore. Tools can easily transfer diseases from one rose shrub to another, so sanitation is very important. Mix a solution of 10 percent rubbing alcohol or bleach and 90 percent water in a spray bottle to spray on your tools.
By taking a few simple steps like these right now, the rose bushes will be on their way to beautiful blooms in June. Now that’s a breath of fresh air.
That’s why Ivan Watters, the Chicago Botanic Garden’s curator of bonsai, travels to Japan every year to attend Kokufu — the Japan National Bonsai Exhibition and most important bonsai show in the world.
“It’s a true learning experience,” he says. “You pick up technical ideas, artistic ideas, and learn a few bonsai tricks.” For example? “The first branch of an informal upright bonsai should come out of the midline across the front of the trunk. But the unconventional branch on one entry started at the back of the trunk and wrapped around to the side, with a secondary branch positioned to hide the manipulation.” It’s a vivid description, sure to be shared with his bonsai volunteers.
Watters is a long-time member of the Nippon Bonsai Association, the venerable group that sponsors the exhibit. Held this year (for the 87th time) at the recently renovated Tokyo Metropolitan Art Museum, Kokufu brought together 204 of the most outstanding trees in the country, culled from 500 entries. As always, requirements for entry are firm. Trees must reside in Japan (quarantine issues prohibit the Garden from competing) and, if selected, entrants must wait three years to compete again in the show.
This year marked Watters’ 20th year attending the show. What caught his eye this year? One large bonsai that combined nine separate Japanese white pines, each more than 100 years old. “It was the majesty of it,” he remarks, “so beautifully placed in their container.” Also large in scale were several bonsai from the Imperial Palace Collection, holding pride of place at the entrance to the show. Displayed on burgundy velvet cloths, the imperial bonsai befit the proportions of the Imperial Palace — many imperial trees are more than 500 years old and have been in the collection for more than 300 years.
Watters took a side trip to the Omiya Bonsai Art Museum in Saitama, and to a small exhibit (just eight trees) at a temple celebrating ume season, the flowering of Japan’s plum or apricot trees.
The trip wasn’t allbusiness. Watters also hosted an 81st birthday party for bonsai master Susumu Nakamura at the latter’s favorite eel restaurant, Izuei. Nakamura, the former vice chairman of Kokufu, donated 19 of his trees to the Garden’s collection in 2000. (Only one other donated tree has come to America, at the United States Botanic Garden.) On this latest trip to Japan, Watters gifted Nakamura with a copy of the Garden’s newest publication, Bonsai: A Patient Art. The beautifully photographed book illuminates the intricacies of bonsai in both art and history. Most of the trees that came from Nakamura are included in its pages, including an extremely fine example of a formal upright bonsai, the white pine shown here, which has been trained for at least 100 years.
This spring, Watters and his volunteers are busy repotting more than 100 bonsai trees in preparation for the reopening of the bonsai courtyards on April 29. Watters is also teaching bonsai workshops. Bonsai Basics on June 1 is a good first class to begin your learning.
Curious about the Japanese trees at the heart of the Garden’s bonsai collection? Bonsai: A Patient Art is available to purchase. This stunning volume presents more than sixty living masterpieces from the Garden’s collection. Board member and bonsai enthusiast Robert H. Malott supported publication of this beautiful book.