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Replacement options for a dying ash tree

September 30, 2020 • Leave a Comment

Ginkgos in the fall can be spectacular, the fan-shaped leaves glowing gold. Sometimes the color is a less showy yellow-green, but whatever the fall color, the leaves drop quickly soon after and all at once, a leaf raker’s dream.

Part 2 of 2 – Trees for root spaces greater than 10 feet wide

When an ash tree is the friendly cover above your patio or picnic table, and it is doomed to fall to the plague of emerald ash borer, its loss is a personal one. Here’s some consolation: in that location, with park-like room for roots to spread, many species can be expected to grow well and quickly.

Choose from this list and score one for diversity. By planting one of these excellent but underused species, you’ll help diminish the chance of whole-neighborhood defoliation during some future insect or disease attack.

Trees for root spaces at least 10 feet wide

These trees need larger boulevards and islands, where roots have at least 10 feet to spread in all directions:

Ginkgo (Ginkgo biloba, fruitless male varieties such as ‘Autumn Gold’ and ‘Santa Cruz’) 50 to 80’ tall with a variable spread (‘Santa Cruz’ is very wide, ‘Autumn Gold’ just a bit more than half as wide as tall). Grows 12” or more per year in its youth, slower as it matures. Flowers are inconspicuous. Fall color can be a superb gold. Female trees are not desirable as the fallen fruit is malodorous. Full sun. Prefers deep, moist, sandy soil but will tolerate almost any situation.

Hackberry (Celtis occidentalis) 40 to 60’ tall and wide, may be larger. Grows 1 to 2’ per year. Grows in almost any soil and moisture condition, in full sun. Makes no show of flower or fall color. Hard-seeded, berry-like fruit loved by birds and small mammals. This is another of many native trees that are just being discovered for use in the landscape. Like the ash, it’s a tree that rarely stars, yet always fills a supporting role. Some selections have been made, such as ‘Prairie Pride’ with especially lustrous leaves and a broad crown or ‘Windy City’ for a fast growth rate and especially wide spread reminiscent of its relative, the American elm.

Hardy rubber tree (Eucommia ulmoides) 40 to 60’ tall and wide. Grows 12 to 18” per year. Lustrous dark green foliage that’s pest free (and so it’s wonderful to sit under!). Inconspicuous bloom. No fall color. Full sun and almost any type and condition of soil. This tree fits the bill for people who want a non-fussy, relatively fast-growing, pest-free shade tree that does not drop fruit or seeds.

Turkish filbert (Corylus colurna) 40 to 50’ tall and about half as wide. Grows 12-18” per year. Nothing worth seeing in its tiny flowers or fall color. Nuts ripen in fall. Dark green foliage is pest free. In full sun and well-drained soil can tolerate almost any other adverse condition, including the droughty soils that cause scorch on maples.

**Yellowwood is a little known native that’s nearly pest free, a true showstopper in bloom or fall color, and excellent for shade on small properties by virtue of its wide spread.**

Yellowwood (Cladrastis kentukea) 30 to 50’ tall. Wider than tall. Grows about 12” per year. Fragrant white flowers in large pendant clusters in June. Smooth gray bark. Full sun and well-drained soil.

Trees that should not have any restriction to their roots

These are trees that belong in back yards, parks and wide open spaces.

**Bald cypress strikes many people as an evergreen, then surprises them in fall by dropping its needles.**

American linden (Tilia americana) 60 to 80’ tall and 2/3 as wide. Grows 12 to 18” per year. Small white flowers in June are fragrant enough to carry across a yard and very attractive to bees—thus this is called “bee tree.” Fall color sometimes yellow. Full sun to half sun. Almost any soil.

LEFT: American linden is a stately, dependable shade tree—pyramidal in its youth, showy in bloom, and comfortably rounded in old age. RIGHT: Bur oak has no showy flowers and its fall color is dull yellow. But it is rich in character with deeply ridged, corky bark—an outline to admire while you lie in its shade.

Bald cypress (Taxodium distichum) 50 to 70’ tall and half as wide. Pyramidal. Grows 1 to 2’ per year. Fern-like foliage emerges yellow green and fades to yellow or orange-brown before dropping in fall. Shaggy red-brown bark and buttressed trunk base are attractive. Full sun. Moist to wet soil.

Black gum is all you could want in a shade tree—high branched, not messy, and great fall color. However, it is not tolerant of compacted, dry or highly alkaline soils, so plant it to replace a back yard tree, not one by the street or sidewalk!

Black gum (Nyssa sylvatica) 30 to 50’ tall and 2/3 as wide. Grows 12” per year. Its bloom is inconspicuous but fall color is stupendous, from yellow orange to deepest scarlet. Small fruits ripen in early fall and are eaten by birds. Full sun or part shade. Deep, moist, well-drained soil. Don’t site it in harsh winds.

Bur oak (Quercus macrocarpa) 70 to 80’ tall and wide. Can be larger. 8 to 12” growth per year. Nothing to note in terms of flower or fall color. Full sun. Most any soil. More tolerant of city conditions than almost any other oak.

Dawn redwood (Metasequoia glyptostroboides) 70 to 100’ tall, 25’ wide. The tree is an impressive pyramidal form. Grows 3’ a year. Inconspicuous flower. Foliage is ferny, very attractive and sometimes red-orange in fall. Bark is shaggy red-brown, easy to like. Full sun. Prefers moist, well-drained soil but is very tolerant of wet soil. Pest problems are very rare.

LEFT: Dawn redwood may keep its lowest branches into old age and sweep the ground, or branches can be pruned to accommodate traffic. The author was not a believer until she saw dawn redwood as a magnificent street tree in Manhattan. RIGHT: Kentucky coffeetree in winter is a stately form indeed.

Kentucky coffeetree (Gymnocladus dioicus) 60 to 75’ tall, not as wide as tall. Can be larger. Grows about 12” per year. Flower is insignificant. Female trees can bear large, hard pods; if this is unacceptable, hold out for the male variety ‘Prairie Titan’ or ‘Stately Manor.’ Fall color may be a good yellow. It can aggravate fastidious rakers since in the fall the leaves, the ribs that connect the leaflets, and the seed pods drop at different times. Full sun. Deep, moist soils are best, but the tree will tolerate almost any city condition. This tree got its name when early American settlers used the seeds as a coffee substitute, but we are now told its seeds are toxic.

Lacebark elm is a dependable, fast-growing, wide-spreading shade tree with gorgeous bark. It has an additional common name, Chinese elm, that causes some people to confuse it with an inferior tree, Siberian elm.

Lacebark elm (Ulmus parvifolia) 40 to 50’ tall and wide. Grows 1 to 2’ per year. Inconspicuous flower. Fall color may be yellow or red-purple. Mottled, peeling bark is a plus in winter. Full sun. Moist, well-drained soil is best but it tolerates many soil conditions.

**Swamp white oaks are faster-growing than most people realize, so we can enjoy them in their youth as well as leave them to our grandchildren.**

Sawtooth oak (Quercus acutissima) 40 to 60’ tall and wide. Grows 2’ per year during its first twenty years. Golden catkin flowers in spring can be attractive. Foliage is very clean, deep green in summer, often a good yellow in fall. Acorns drop early in fall. An impressive, high-branched shade tree. Full sun. Well-drained soil.

**Shingle oaks can frustrate some gardeners by holding onto leaves through winter. Others see the leaves as winter interest. Isn’t diversity grand!**

Shingle oak (Quercus imbricaria) 50 to 60’ tall and wide. Can be larger. Grows 12 to 18” per year. Leaves unfurl red, are lustrous dark green in summer and become yellow to red-brown in fall. Full sun. Moist, well-drained soil.

Swamp white oak (Quercus bicolor) 50 to 60’ tall and wide. Can be larger. Grows about 12″ per year. With age, develops an impressive, stout trunk and deeply furrowed bark. Fall color can range from yellow to maroon. Full sun. Moist to wet soil.

Article by Janet Macunovich and photos by Steven Nikkila, www.gardenatoz.com.

Replacement options for a dying ash tree

September 1, 2020 • Leave a Comment

Part 1 of 2 – Ash replacement trees for root spaces less than 10 feet wide

Chinese fringetree is a workhorse that also blooms once a year and supplies fruit for the birds. Remember, the ash trees we’re replacing offered no flower and only brief yellow fall color. Their greatest quality was dependable growth even in tough places.

Emerald ash borer has erased millions of native ash trees from our landscapes and forests. It’s hard to believe that similar devastation happened just decades ago, when millions of American elms fell to Dutch elm disease, or that America has also experienced the loss of certain poplars, black locusts and virtually all of its millions of acres of American chestnuts since 1850.

Perhaps we can stop history from repeating itself. After every previous loss, we planted as America always has—in a big way, in masses. As a result, our urban forest is dominated by just a few species, notably various maples, honeylocusts and littleleaf lindens. To protect ourselves from future widespread loss we have to break that pattern and plant a greater diversity of trees around our homes and on our waysides.

Even before the onset of emerald ash borer, concerned arborists had put a moratorium on ash and maple planting and begun planting less common trees. Tree planting became a matter of mixing species within a city block, rather than planting lines of hundreds of the same species, even the same clone of a species. They are making sure that trees won’t in the future be exposed and lost in blocks of hundreds and thousands, as they are now being lost.

For that next epidemic will occur. In this age where materials are whisked from one side of the world to another, complete plant quarantine and protection from new pests is impossible. You can take the same smart step and plant one of many wonderful tree species that are not in the “big three” when you replace that lost ash.

Choose from the following line-up. It’s a catalog sorted by the amount of root space the tree will have to grow in. After looking into all of them, I have an interest in so many that where my family removed 20 dying ashes from a relative’s property, we’ll probably replant with 20 different species from this list!

Trees for spaces where roots can spread just 5 feet wide

These trees can tolerate the restricted root space of small islands and the narrowest strips between sidewalk and street. Some may need pruning to remove lower branches as they grow, creating clearance for traffic below the main branches.

Chinese fringetree (Chionanthus retusus). 15-25’ tall, may be taller. Slow to grow, less than 12” per year. Often shrubby in habit, to attain tree form must have lower limbs removed as it grows. Hardy within the Detroit Metro area but may not be hardy in the colder parts of zone 5 in suburbs. Bright white confetti flowers in June. Blue-black fruit in fall is relished by birds but borne only on female trees, if a male fringetree is nearby. Fall color may be yellow. Grows in full sun or part shade. Prefers deep, moist soil but is very tolerant of a wide range of soil conditions.

Crabapples such as ‘Sugar Tyme’ are most often listed with ornamental trees, but those between two and three stories tall serve well as shade trees. It may be necessary to remove lower limbs while the tree is young to provide clearance for pedestrians and other traffic.

Crabapples (Malus varieties with known disease resistance such as ‘Adams,’ ‘Prairifire,’ ‘Red Jewel,’ and ‘Sugar Tyme’). 15’ (‘Red Jewel’), 18’ (‘Sugar Tyme’), 20’ (‘Prairifire’), 24’ (‘Adams’), rounded or slightly narrower than tall. Grows about 12” per year. Flowers white (‘Red Jewel’), pale pink (‘Adams’, ‘Sugar Tyme’) or dark red-purple (‘Prairifire’). Fruit small, red and persisting prettily into and even through winter. Birds eat the fruit in late winter. Full sun, well-drained soil.

Hawthorns are game for drier, windier places than many trees and their fruit is a favorite for songbirds. For safety’s sake around your home, choose a thornless variety such as ‘Crusader’ or the nearly-thornless ‘Princeton Sentry.’

Hawthorns (thornless types such as Crataegus phaenopyrum ‘Princeton Sentry,’ Washington hawthorn, and C. crusgalli var. inermis, Crusader hawthorn). 20 to 25’ tall and wide. 12-15” growth per year. White flowers (with unpleasant odor—Crusader) come later than crabapples but help these trees masquerade as crabs. Fall color orange to red or purple. Crusader keeps its small reddish fruit into early winter, ‘Princeton Sentry’ until spring; birds are attracted to both. Full sun and any type of soil so long as it is well-drained.

**Japanese tree lilacs are most often single-trunked, like this young one that will thus be very good one day as a small shade tree.**

Japanese tree lilac (Syringa reticulata). 20 to 30’ tall and not quite as wide. Grows 12 to 18” per year. Creamy white, fragrant flowers open in June, weeks after common lilac. No significant fall color but the polished red brown bark brightens a winter day. Full sun. Well-drained soil.

Kousa dogwood has a reputation as “the dogwood for the sun” but this is misleading. Although more tolerant of full sun than its cousin, the earlier blooming flowering dogwood (*Cornus florida*), it prefers some shade. In the sun, it’s known for developing drooping leaves and failing to attain the much-sought horizontal branching.

Kousa dogwood (Cornus kousa). About 20’ tall and wide, can be larger. Grows about 12” per year. Often sold as a multi-stemmed or very low-branched specimen, but single trunk kousa dogwoods make excellent small shade trees if lower limbs are discouraged or removed. White flowers in June that persist into July. Varieties with pink flowers, larger or later blooms are available. Large rosy fruits favored by birds in late summer. Bark develops polished tricolor effect as the tree ages, very attractive in winter. Fall color may be good maroon. Part shade is best but will tolerate full sun. Moist, well-drained soil.

Redbud. Who would have thought that the romantic woodland tree that blooms in early May as if flocked with thousands of red-violet flowers would be such a winner in parkstrips along roads and driveways. Needs pruning while young to remove lower limbs for pedestrian and vehicular traffic.

Redbud (Cercis canadensis). 20 to 30’ tall and wide. Very fast growth when young, slowing to 12 to 18” per year. Flowers are tiny but numerous, red-violet nubs all along the branches in May. Fall color can be a clear yellow. Bark is near-black with crevices revealing orange beneath. Some people object to the shaggy winter look in a year when many seed pods form. Best in half sun or full sun in moist, well-drained soil but is very tolerant of almost all light and soil conditions except soggy soils.

Serviceberry is a native with international appeal. You can buy named varieties such as ‘Autumn Brilliance,’ ‘Cumulus,’ ‘Prince Charles’ and ‘Snowcloud,’ which have been selected by growers in Europe and the U.S. for traits such as tight upright form, larger flowers, more consistent fall color or resistance to the few leaf diseases that may harry this tree.

Serviceberry (Amelanchier species). 25’ tall, may be taller; 15-20’ wide. Grows 1-2’ per year. Fragrant white flowers in early May. Edible, sweet, blueberry-sized fruit in midsummer loved by birds. Fall color variable each year, yellow to deep red-orange. Smooth gray bark. Best in sun or half-sun in moist, well-drained soil.

Trees for root spaces between 5 and 10 feet wide:

**Amur cork tree assumes such an interesting broad shape and open crown that it invites you to come into its shade.**

Amur cork tree (Phellodendron amurense, fruitless varieties such as ‘Shademaster’ and ‘His Majesty’). 30 to 45’ tall, often broader than tall. Grows 12 to 18” per year. No showy bloom. Brief yellow fall color. Very open crown provides light shade and beauty of line in winter. Handsome corky bark develops in its old age. Full sun. Most soils are okay.

**Golden rain tree provides welcome showy bloom in mid- or even late summer but is not well-known, so it has not been widely planted.**

Golden rain tree (Koelreuteria paniculata). 30 to 40’ tall and wide. Grows 1 to 2’ per year to form a round crown of widely spaced branches for light shade. Flowers are large yellow conical clusters in late June, but bloom time is variable from plant to plant; some don’t flower until August. Seed pods are showy, like yellow-green Chinese lanterns draping the tree in bunches. No fall color. Full sun to part sun. Any well-drained soil. Tolerates high alkaline soils, drought and heat.

Hophornbeam or ironwood (Ostrya virginiana). 25 to 40’ tall and wide. Grows 8 to 12” per year. No significant flower or fall color, just a dependable small shade tree. Full sun to half shade. Well-drained soil.

**Hornbeams have lustrous foliage and sensuous bark. They also tend to hold their foliage long into the winter and so are often planted to serve as tall hedges.**

Hornbeam (Carpinus betulus, European; C. caroliniana, American). 40-60’ tall, 30-40’ wide. 8 to 12” growth per year. American hornbeam or musclewood smaller by half and slower to grow than European. Inconspicuous flower. Fall color late, yellow, variable by year. Smooth steel gray bark more or less fluted like a well-muscled, flexed biceps. Best in full sun and well-drained soil.

**Katsura foliage is captivating for its rich color in summer, lack of insect and disease damage, and the sound it makes in a wind.**

Katsura (Cercidiphyllum japonicum). 40’ tall, may be taller; variable in width. Blue-green foliage is purple while leafing out, yellow in fall. Grows 1-2’ per year. No significant flower or fruit. Best in rich, moist, well-drained soil in full sun.

**Mountain silverbell tends to be low-branched, so it may need pruning of lower limbs while young to obtain clearance for traffic in its shade.**

Mountain silverbell (Halesia monticola). 60’ tall by about 40’ wide, upright or conical in form. Grows 12-18” per year. White or pale pink bell flowers hang from the branches in May. Fall color is not usually notable. Part sun is best. Moist, well-drained soil.

Article and illustrations by Janet Macunovich and photos by Steven Nikkila, www.gardenatoz.com.

Plant Focus: Crocus

September 1, 2020 • Leave a Comment

For a gardener, there are few sights as welcome as the first crocus of the year, peeking its flowers through the freshly melted snow of late winter. Crocus is a very hardy perennial and one of the few plants that can bloom as early as February or March. By being hidden deep in the soil, crocus corms are naturally insulated from severe temperature changes, ice and wind. Flowering is initiated by just a few consecutive days of temperatures above freezing. Once the first few inches of soil can thaw, flowers emerge and will last for several weeks despite more wintry weather. Crocus flowers can protect themselves by closing up in the evening and also whenever they experience severe weather.

**‘Yellow Mammoth’ (Photo: Dutch Gardens)**

Crocus have long been popular with gardeners for several reasons. Their durable flowers are available in many colors including yellow, white, purple, blue, and pink. One plant will usually return year after year and develop offspring that can produce additional flowers in beautiful drifts. The two-inch flowers are made up of 6 oval petals that surround 3 prominent yellow to orange stamens. Crocus grow from one-inch corms rather than actual “bulbs.” Both are just compressed stems: bulbs consisting of fleshy scales and corms being more solid. Gladiolus is another example of a corm.

**‘Whitewell Purple’ (Photo: John Scheepers, Inc.)**

Crocus are native to the rocky slopes of the Mediterranean countries and southwest Asia. They adapt to cold winters, full or partial sun, and well-drained soil. Most Michigan gardeners have the first two, but well-drained soil may have to be created if clay is prevalent. Drainage can be improved by adding aged pine bark or compost to your soil. Since crocus corms are planted 3 to 4 inches deep, only about 4 inches of soil below them needs to be well-cultivated. Corms should be at least 3 inches apart. However, this is the type of bulb that looks great planted in more natural and random masses.

Most crocus have only one serious threat to their perennial existence. Hungry bunnies seem especially tempted by the leaves, flowers and corms of several species. Corms can be protected by several methods. Gravel worked into the soil above the corms will make digging them up difficult. Liquid or powder deterrents can be used to treat corms before planting. Keep in mind that freshly planted bulbs and corms are most likely to create curiosity amongst browsers. Once established, they are rarely disturbed. If all else fails, you can plant in below-grade, wire mesh cages that are impenetrable. To protect leaves and flowers, apply a granular deterrent or a spray.

**‘Ruby Giant’ (Photo: John Scheepers, Inc.)**

There are many varieties of spring-blooming crocus but most of the hardy ones fall into four species. Crocus ancyrensis is golden bunch crocus. The selection ‘Golden Bunch’ produces up to five deep orange-yellow flowers in a “bunch” per corm. Of the four species, this is one of the earliest to bloom; late February is not unusual if Mother Nature is cooperating. This is also one of the more vulnerable to attack from the bunnies.

**‘Jeanne d’Arc’ (Photo: John Scheepers, Inc.)**

Crocus chrysanthus is available in several varieties, all of which are referred to as snow crocus or golden crocus. ‘Cream Beauty’ is a strong grower that is primarily white with a white center. ‘Ladykiller’ is also white but with purple on the outside of the petals. ‘Advance’ is yellow inside but the outside is unique because the petals alternate creamy yellow and purple. Corms produce 1 to 4 flowers each in late February or early March. Like C. ancyrensis above, rabbits admire this species.

Crocus tommasinianus is a wonderful choice for several reasons. This species is the most pest-resistant crocus available. If you have lost crocus to rabbits or squirrels, this may be the choice for you. C. tommasinianus is also the most prolific grower. It will quickly naturalize to form masses of flowers. The most readily available variety is ‘Barr’s Purple.’ Its deep violet petals fade to a bright white center that is highlighted by bright orange stamens. It blooms almost as early as the above two species, usually in early March.

The most popular species is Crocus vernus or Dutch crocus. Unlike the previous species, one large flower with large gold stamens is produced from each corm. It is available in several colors ranging from white to stripes to purples. ‘Jeanne d’Arc’ is a bright white with large flowers. ‘Pickwick’ has large white flowers with dark lavender stripes inside and out. ‘Remembrance’ and ‘Flower Record’ are deep lavender and pale lavender respectively. Dutch crocus usually bloom from March to early April.

Fall is a perfect season for planting. Cooler weather means less heat stress for both plants and people. Plants are naturally becoming dormant and are far less susceptible to drying out and experiencing transplant shock. Fall is also the only season for planting spring-blooming bulbs and corms. Once the ground freezes, the opportunity is lost and you’ll regret not having these heralds of spring glowing in your early season garden. Crocus are relatively inexpensive and are available almost anywhere bulbs are sold. With minimal effort this fall, you can enhance your existing landscape and welcome spring with the bright blossoms of crocus.

**‘Blue Pearl’ (Photo: Van Bourgondien)**

Crocus CRO-kus
Plant type: Corm (commonly referred to as a “bulb”)
Plant size: 3-5 inches tall
Habit: Clump-forming
Flower colors: Purple, violet, reddish- purple, lilac, yellow, cream, white
Flower size: 2 inches wide
Bloom period: Late winter to early spring
Light: Full to partial sun
Soil: Well-drained
Uses: Plant in natural drifts in the perennial border, lawn or rock garden
Remarks: The corms develop offspring that can produce additional flowers to create a naturalized look

George Papadelis is the owner of Telly’s Greenhouse in Troy and Shelby Township, MI.

RELATED: Colchicum and Fall Crocus

ELSEWHERE: More on Crocus at Chicago Botanic Garden

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