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Archive for the Ask MG department

Choosing plants for hedges

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I would like to create a formal English garden look, where “squared-off” hedges line the garden perimeter. Can you recommend hedge plant options (other than yews) that grow at least 4 to 8 feet tall, look thick and full (like a solid wall), and grow in sun and shade?

You have several restrictions in your plant request that limit your choices. Your height requirement creates a problem for boxwood (Buxus sempervirens), a favorite of formal English hedges, because they are a rather slow grower. However, they hold the geometric pruning well, are sun and shade tolerant, and form a dense thicket of glossy leaves. Boxwoods are the choice for knot gardens, parterres and topiaries because they are evergreen and hold a crisp line when pruned.

Privet (Ligustrum amurense) grows quickly, is easily sheared to shape and can reach your desired height. It is also tolerant of light and soil variations. Unfortunately, in zones 3 to 7, it is considered deciduous, even though its dense twiggy nature is a screening element in itself.

Since the perimeter of the garden is the designated planting zone, you might consider Japanese holly (Ilex crenata), which is very shearable and has a medium growth rate. Their leaves are spiny but lustrous. They will tolerate full to part sun, but need somewhat acid (low pH) soil and good drainage with sustained moisture. The downside is that they need protection from drought and wind.

There are few if any pines or spruces that meet your criteria. However, the workhorse of the residential landscape, the columnar American arborvitae (Thuja occidentalis), may suit them all. The varieties ‘Emerald’ and ‘Techny’ both meet your height requirement of 4 to 8 feet. They hold their color in winter, and have considerable heat and light tolerance. Shearing and pruning them before spring growth will keep them full and dense. They have a natural pyramidal tendency, but can be nicely shaped to be wider at the base, to give the “squared-off” hedge look you are striving for. Keeping them slightly wider at the base allows light to reach the interior of the shrub, allowing active new growth and preventing thinning of the interior.

Growing grass under trees

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Our yard is shaded by oaks. We overseed every year with shady grass mix. But by the next spring most of the grass has died. What can we do to grow grass in this situation?

You have a couple of choices. You can continue the frustrating cycle of growing grass, or take an alternative approach to living with your oaks. Turf grass needs sun to germinate and establish a root system, even if it is the “shady grass mix.” If your oak canopy is heavy and dense, you could have the canopy judiciously thinned by a trained arborist. They will prune when the trees are dormant in winter and there is little chance for them to be infected with the oak wilt disease. This might open up the canopy enough to let the turf lawn get established.

However, you should know that oak trees can take up to 50 gallons or more of water a day. So while you are watering that lawn you’ve overseeded, the oak trees with their extensive root systems are enjoying the feast. The turf grass never gets its root system established because the oaks are not only shading it out, but also absorbing most of the water.

This is not necessarily a bad thing. Oak trees are preferable bastions of shade. The alternative is to try a different groundcover that isn’t lawn. Oak trees create dry shade. It sounds like your lawn is fairly thin underneath them, which is why you keep overseeding every year. Why not plant dry shade-loving perennials? There are a number of low maintenance plants that would not only lend interest to the landscape under the oak trees, but are low profile, will come up every year, will succeed where turf grass fails, and will provide “green coverage” that you don’t even have to mow.

Consider a mass planting of variegated hostas that would “light up” the shady area under the canopy. Another perennial often used where grass is unsuccessful is lily turf (Liriope spicata). It even looks like grass, but has the bonus of a purple-blue flower in summer, which turns to a red-brown berry in fall. At the outer edge or drip line of the canopy, you could mass plant Stella d’Oro daylilies. They tolerate a wide range of soil types and light conditions. Their yellow blooms are continuously cheerful and when finally done blooming, their foliage lasts until frost. A simple ground-hugging vine is vinca, sometimes called myrtle. It produces a lovely blue flower in spring that shows well in heavy shade. There is also the nice spotted dead nettle (Lamium maculatum) with its silver and green mottled leaves. The cultivar ‘White Nancy’ produces a lovely white flower while other varieties produce pink blossoms mid-spring.

So there are several alternatives and choices to groundcovers that aren’t turf grasses. You need to decide where to put your money: into perennials that will succeed in the shade of your mighty oaks, or continue trying to grow turf grass that will always struggle.

Planting ideas for ditches and swampy areas

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After a moderate rain, water collects in a shallow ditch at the back of my lawn. It looks swampy every year. Any design/planting ideas to improve the look of this area?

This unfortunate nuisance that often occurs in both old and new landscapes is actually a garden opportunity. Evaluate the square footage involved and consider putting in a rain garden. Very simply, a rain garden is a planted depression that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, and compacted lawn areas the opportunity to be absorbed. It reduces rain runoff by allowing storm water to soak into the ground (as opposed to flowing into drains and surface waters, which causes erosion, water pollution and flooding).

Usually, it is a small garden that is designed to withstand the extremes of moisture and concentrations of nutrients, particularly nitrogen and phosphorus often found in storm water runoff. A rain garden retards the water flow and absorption, allowing more time to infiltrate and less opportunity to gain momentum and erosive power. Because this area is in your lawn, you have the opportunity to prepare an area with select trees and shrubs as well as perennials that will enjoy absorbing and utilizing that rainwater, processing it, and creating an entire ecosystem beneficial to the greater good of the landscape.

The Wisconsin Department of Natural Resources has a 32-page online manual for the how-tos of constructing a rain garden, from measuring to digging to planting. They even include several design diagrams. The basic information is excellent, but it does focus on downspout and house foundation locations for the most part.

The key for an area like yours (away from a downspout) is to use tree and shrub species that love wet conditions. There are a number of Michigan native plants that suit the criteria well. Because you are not necessarily restricted by the proximity of a building, you can consider using trees like river birch (Betula nigra ‘Heritage’), which has the grace of a willow but none of the mess. It also has excellent winter interest in its buff pink, exfoliating bark.

Consider planting a cluster of red and yellow twig dogwood shrubs (Cornus sericea ‘Alba’ and Cornus sericea ‘Flaviramea’). These shrubs are especially suited to swampy areas and, with their colorful twigs exposed in Michigan winters, become a highlight of the snow-filled landscape. Depending on how large your ditch is, you could possibly add a smaller ornamental tree such as a native witch hazel (Hamamelis virginiana), which blooms in October and November, or a native shrub such as the common elderberry (Sambucus canadensis) whose fall fruit provides a great food source for both birds and animals.

Planting a rain garden is a very eco-friendly way to deal with standing water and provide assistance to the natural filtration process for our groundwater. You not only solve the drainage problem but also turn an eyesore into a work of beauty.

Can Easter lilies be planted outside in southern Michigan?

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The heady fragrance of traditional Easter lilies (Lilium longiflorum) or Madonna lily (Lilium candidum) is never forgotten once experienced. Both are true members of the lily family. They grow about 1-1/2 to 3-1/2 feet tall in full sun in rich, evenly moist but well-drained soil. Because you are asking about planting outside in zones 5 and 6, you’ve probably heard numerous stories of how people have a whole garden full of “Easter lilies” that they’ve planted every year and successfully had them grow and bloom repeatedly.

That being said, a few words of caution and qualification go with those success stories. The lily hybrids of Lilium longiflorum are not usually considered a garden plant, being normally hardy to only zones 7 to 9. Consequently they are grown primarily in pots here, and nurseries force them in bloom so their buds burst forth in time for the Easter celebration. Remember this observance moves on the calendar annually, from as early as mid-March to as late as mid-April. The bulb is not mysteriously intelligent; it has just been manipulated by greenhouses to bloom at the desired time.

That being said, there is a cultivar called ‘Mount Everest’ that bears fragrant white trumpets and can be grown in the ground in zones 5 to 8. If you were fortunate enough to receive or purchase a lily with an identification tag, you may know if you have that plant or another named cultivar. Or, if you in fact have a Madonna lily, it will tolerate temperatures down to 25 degrees. Unfortunately most Easter lilies rarely get tagged because they are either forced in a greenhouse or shipped in from warmer regions and are not hardy to our zones that deal with frozen soil in winter.

However, if you would like to attempt to save it in the ground, choose a sheltered, sunny spot that is well-drained. Many times we have microclimates around our homes, especially near the house foundation, that mimic a zone or two warmer than our overall region. If that warm, dry place is close to an often-used walkway, all the better to enjoy the fragrance.

Plant the bulb about 6 to 8 inches down, as you would any of the hardy summer-blooming Asiatic or Oriental lilies. Add about a tablespoon of granular bulb fertilizer to the planting hole. Evenly moist but well-drained soil at the site, especially in winter, cannot be stressed enough. You can leave the foliage intact to help feed the bulb naturally until the leaves completely brown out. Apply a heavy blanket of shredded leaf mulch to the planting area to minimize winter temperature fluctuations.

If there isn’t a place in your yard that suits these special conditions, try letting the foliage die back with the bulb in the pot. Let the soil dry out, and then lift the bulb, checking for soft spots. Make sure it is dry and soil-free. Store the bulb wrapped in a paper bag in a cool dry place until the following February. You are mimicking the winter dormancy of its native habitat. Then you can pot it up with a well-draining soil mixture, keeping the soil moist but not soggy. Put it in a warm, sunny window away from drying heat vents and watch the bulb come to life.

Selecting plants for the evening garden

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I work all day and I am home only in the evenings. What flowers can I plant that will bloom at night and maybe even have fragrance?

An evening garden relies heavily on flowers that are white or light-colored so they will be visible even on a moonless night. Moonlight really illuminates the flowers and foliage, making the garden at night a different, magical experience. Nighttime flowers are exactly that—they bloom in the evening and remain closed during the daytime. These flowers often give off beautiful, fragrant scents, and the evening dew helps intensify those scents. Even if some of the flowers do bloom during the day, it is in the evening when they give off their headiest fragrance. Scent in the evening somehow carries farther than in the daytime, and it is this scent that attracts the nighttime moth pollinators.

There are quite a few plants that are suitable for evening gardens. Dusty miller’s leaves range from gray-green to silvery white. Trumpet and oriental lilies give off a heady smell. Heliotrope, which also comes in a creamy white that will shine at night, gives off a sweet vanilla scent. Alyssum has tiny white flowers and a honey-like scent, making it good for pots and the front of borders. Impatiens also comes in white, and when planted in a pot or on a deck, it can reflect light from the moon to create a beautiful effect. Peonies, roses and hydrangeas also come in bright whites and yellows and will add much beauty to the evening garden.

A favorite flower for an evening garden would be moonflower. These are annual vines that thrive in hot weather. It is similar to the morning glory except it blooms at night. Plant it close to your seating area so you can watch its large, white blossoms unfold in minutes in the early evening—spectacular! The almost pure white blossoms are fragrant all evening and just illuminate the garden.

Pink evening primrose is another good choice. It has four satiny, heart-shaped petals that form open cups with long stamens. When they open, the blossoms are a soft, clear white that fade into pink as the flowers mature. Their scent is reminiscent of a blend of honeysuckle and lemon custard. Nicotiana is another sweet-scented flower whose blossoms close in the daytime but open in the late afternoon and fill the air with jasmine-like aroma. Make sure to include fragrant hostas like H. plantaginea, ‘Royal Standard,’ ‘Honey Bells,’ ‘Tokudama Aureonebulosa,’ ‘Sweet Standard,’ and ‘Fragrant Bouquet.’

Bright foliage is another way to create evening beauty in the garden. Lamium is a beautiful groundcover with two-toned, white-centered leaves. Lamb’s ears are another good plant for evening foliage. Other plants worth considering are white-flowering shrubs, and annuals like dame’s rocket, tuberose, petunia and dianthus.

To give your evening garden an extra dimension, add some solar or candle lights here and there, plus try a water feature. Even if it is a small fountain, the sound of water really makes the evening even more magical. The visual impact of bright whites, the scents of flowers and the sound of the evening all combine to make the evening garden a place that will calm and sooth the spirit.

Groundcover that handles foot traffic

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I would like to grow a fast-growing groundcover that is very short and can withstand being walked upon often and still look good. Are there any out there that survive in zone 4 and thrive in part sun to full shade?

First, you need to determine what “walked upon often” means in terms of frequency. Is it “light” (once or twice per day), “moderate” (about 6 times a day), or “heavy” (dozens of times per day)? The frequency of the daily traffic narrows the choices to those that can survive that impact. Second, you are limited in the number of hours of sun, and you want a fast grower. You may have to combine two or three species to satisfy all your criteria. Also remember that even though they are groundcovers, they will have tiny flowers that will call out to various insects and pollinators. An unwary bare foot could come away with an unpleasant sting.

Light traffic. Tiny creeping sedums make great groundcovers. They need little water and attention. They do grow moderately quickly if given the sunny section of your path. Sedum requieni will take the heaviest foot traffic in this group. Bugleweed (Ajuga) varieties do well in sun or shade. Ajuga “Chocolate Chip” is a small, tight groundcover whose leaves are a bronzy chocolate color. 

Moderate traffic. Try creeping Jenny (Lysimachia) varieties. They prefer moist areas with partial shade. Their leaves are the size of dimes and they spread by runners. Wherever a leaf node lands, it will root. So it can rapidly fill in any given area. It can be considered invasive if not judiciously checked. L. nummularia ‘Aurea’ has chartreuse gold foliage and is often sold as a trailing plant for containers. L. japonica ‘Minutissima’ has super tight evergreen foliage. However, it is a slow grower. So combining two varieties of Lysimachia would give visual interest as well as quick coverage. Also take a look at Kew wintercreeper (Euonymus fortunei ‘Kewensis’). It is evergreen all year, tolerates shade, harsh soil conditions, and averages 2 inches in height. This is a very durable groundcover, but coarser in texture than the lysimachias.

Heavy traffic. Thymes and Irish moss are the most durable choices. Thyme is a great survivor, tolerating being walked on many times a day. Look for creeping thyme (Thymus serpyllum) or woolly thyme (Thymus pseudolanuginosus). Both will tolerate dry soil, are present spring through summer, and can handle zone 4 conditions. They tend to do better with more sun, but will tolerate partial shade. Irish moss (Sagina subulata) will form a very dense mat and is especially effective when combined with stepping stones. It likes moisture, prefers soil low in fertility, and enjoys dense shade. Homeowners often find it in their lawns when turf becomes thin and compacted.

Ask MG: How do I grow Cleome from seeds?

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I saved the seed from my cleome plants last year. When I put the seed out this year, it grew a lot of giant weeds. What happened?

Cleome vary in height from 2 to 5 feet; some are bushy, others are stalky. The cleome you see most is spider flower (Cleome spinosa or hassleriana), or hybrids or cultivars that have the Cleome spinosa in their parentage. This plant can look beautiful in the back of the border, especially in a cottage style garden. In a more formal garden it can look out of place or weedy. Some people find the scent offensive, which is skunk-like. It produces many seeds and can spread like wildfire. To prevent this, remove flowers as soon as they have formed seed pods. The plant will make new flowers and usually keeps blooming all summer.

If your cleome from last year was not a true species but a hybrid—which are labeled with a “cross” symbol (X) in the name—the seeds will either be sterile or the plants that grow from them won’t “come true.” Instead the plants will resemble one or more of its ancestors. The only way to make sure your cleome will be the color and size that you want is to buy seed from a specific species, hybrid, or cultivar.

Ask MG: What are some suggestions for deer-resistant plants?

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My subdivision has been taken over by deer. As I plan next year’s garden, please suggest some perennial flowers or shrubs that deer will not eat.

If deer are hungry enough, they eat just about anything. This answer will include deer-resistant or rarely-damaged varieties and resources to check out more. You might first consider deterring deer from entering your garden. One suggestion is a motion-sensitive sprinkler, called the ScareCrow, which is available at many garden centers. It sprays a shocking blast of water about twenty feet, scaring away deer. Move it periodically or the deer “learn” the pattern, but it is harmless and waters your plants. Be sure to turn it off if you have guests! Also, deer do not like prickly items, many fragrant plants, and footing areas that make noise or feel unstable.

Here are some plants that deer tend to avoid. Bulbs: allium, daffodil and autumn crocus. Herbs: dill, purple coneflower, lavender, sage, tansy, thyme. Shrubs: boxwood (Buxus sempervirens), American holly (Ilex opaca), and Japanese pieris (Pieris japonica). Trees: paper birch (Betula papyrifera) and Colorado blue spruce (Picea pungens). Perennials: yarrow, columbine, bergenia, bleeding heart, oriental poppy, Russian sage, coneflower (Rudbeckia), lambs’ ears (Stachys byzantina), and yucca. Groundcovers: sweet woodruff, dead nettle (Lamium maculatum), plumbago (Ceratostigma plumbaginoides), and pachysandra.

Deer-Resistant Plants for Homeowners is a 2008 publication by Michigan State University, Bulletin E-3042. Contact your county extension office for a copy (www.msue.msu.edu). Also try the book Deerproofing Your Yard & Garden by Rhonda Massingham Hart (Storey Publishing).

What is the difference between own-root and grafted roses?

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What is the difference between own-root and grafted roses? Is one better than the other?

Own-root roses are produced by rooting and growing the cuttings of desired varieties. The types produced by this method often include Antiques, Flower Carpet, Meidiland and many Shrub varieties. Most own-root roses do not need ground level protection in winter once they are established.

Budded (or grafted) roses are produced by inserting a bud of a desired variety onto a vigorous rootstock. The types produced by budding include Hybrid Teas, Grandifloras, Floribundas, Climbing and English varieties, as well as a few from the Antique and Shrub groups. Budded roses should be planted with their swollen bud union 1 to 2 inches below the surface, plus have winter protection each year to help them survive our cold Michigan climate.

Few rose varieties are produced using both methods, so the question of one method being “better” than the other really does not apply. Since the propagation method relates to the type of rose, your choice is really determined by the rose producers and their experience of which one works best for that particular variety.

Ask MG: Why is my Purple smoke tree not smoking?

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I have a purple smoke tree that is about 9 years old. It is a large, healthy tree, but it has never “smoked.” Every spring it is full of blossoms, then when other smoke trees are beginning to smoke, the blossoms on this tree shrivel and die. I have tried watering it more, I have tried watering it less. Any ideas? J.W., Ann Arbor

Although smoke tree or smoke bush (Cotinus coggygria) requires well-drained soil and full sun, it is quite adaptable to different soil conditions. A large shrub or small multi-stemmed tree that can grow to 15 feet tall, it can work as a background plant for the mixed border or as a single specimen plant. Its claim to fame is the cloud of pinkish gray “smoke” that covers the plant in the summer. The effect is the result not of flowers, but of tiny pinkish hairs on the small fruits that occur in large clusters. There are some popular cultivars with purple leaves and darker flower clusters, such as ‘Royal Purple,’ ‘Velvet Cloak,’ and ‘Nordine Red.’

While smoke bush is relatively easy to grow, it can use some help in the early stages of development. For a new plant, avoid planting in waterlogged or poorly draining soil. For an existing plant, dig a dozen holes with a crowbar at the drip line that are a foot deep. Fill these holes with 5-10-10 fertilizer. This should be a one-time application. Early spring is best but it can be any time. It isn’t necessary to repeat this unless the smoke bush is not thriving in later years. Woody plants are going to be happier if you don’t overdo it. Annuals, tropicals and turf are heavy feeders, but over-fertilizing perennials and woody plants can force them to produce more stems and leaves than they want to, which can lead to unnecessary stress. Once established in the landscape, shrubs and trees adjust to the nutrients in the soil and often don’t want too much extra pampering. Avoid fertilizing (directly or indirectly) with high nitrogen (lawn) fertilizer; nitrogen promotes stem and leaf growth at the expense of flower production.

If your tree is planted in the lawn, remove the grass in at least a 6-foot diameter area around your tree. Mulch the area (do not pile mulch up against the trunk) and water infrequently: a good soaking once per week is much better than multiple small waterings. Smoke bush is drought-resistant and overwatering can result in few or no blooms, and makes it more susceptible to disease. Woody plants need watering less frequently than tender annuals, lawn, or herbaceous plants. Most established trees and shrubs can go weeks without supplemental watering except in very hot or windy weather.

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