Archive for the Ask MG department

Preferred growing conditions for redbuds

February 24, 2020 • Leave a Comment

I bought a 4-foot tall redbud and it has not grown at all. It leafs out, blooms for spring, then it looks dead by mid-August. Maybe it has verticillium wilt? Does this come back every year? If so, how do I prevent it?

Eastern redbud (Cercis canadensis) is highly valued in the urban landscape for its pink spring flowers and its smaller, manageable size. As an understory tree, it prefers moist, well-drained, deep soils. It tolerates various soil types, except those that are permanently wet, and adapts to full sun or light shade. Regular watering and fertilizing are keys to keeping it vigorous. Unfortunately, it suffers dramatically from lack of water, too much water, or mechanical injury.

Since your redbud does bloom and leaf out in spring, but looks dead by mid-August, your tree may be responding to inconsistent water patterns. There is plenty of moisture available in spring, from snowmelt and rain. By the apex of summer heat, the redbud may be packing all its energy into saving moisture for survival by dropping leaves and going dormant. This is not the typical pattern of a tree suffering from the soil-borne fungus verticillium wilt, which is incurable and progresses over time until the tree is dead.

Before assuming your redbud has this disease, consider the soil conditions where you planted it and your maintenance practices. Is the tree in the middle of lawn, competing with turf up to its trunk for moisture and nutrients? Is it subject to potential mowing damage? Has it ever received a slow-release granular fertilizer beyond its nursery container? Does it get regular deep watering during periods of no rain? With conscientious adjustments to maintenance and amendments, you strengthen your redbud’s ability to withstand such diseases as verticillium wilt, canker, and even insect pests.

With the new growing season upon us, re-examine your plant maintenance routine and strategize a consistent watering program as well as a spring and fall granular fertilizer application. If your tree is sited in lawn, remove the turf away from the trunk out to the tree’s drip line so the root zone has an equal chance for water. The redbud likes moist (not soggy) soil that is well-drained and rich, medium sunlight, and fertilizer to replenish what was used from its original container. Be observant about the tree’s progress through the season, and you may get to enjoy your redbud’s lovely yellow fall display.

Can vegetable gardens be planted near or over septic fields?

July 27, 2019 • Leave a Comment

Our vegetable garden is over part of our septic field. This is the only part of our yard that gets enough sun. Can there be a problem with possible contamination?

There can be a problem with contamination. Unless your septic tank is completely self-contained and does not permeate into the soil, there are health concerns. Most governmental units have mandated households to convert to self-contained systems to protect Michigan’s groundwater from contamination.

Septic effluent contains chemicals and pathogens potentially harmful to people, animals or plants. Soil types affect how a septic system behaves. Clay soils release cleared effluent in a few inches. However clay does not percolate or drain well and is not a good choice for a septic site in general. Sandy soils permit greater travel of effluent and pathogens, because they drain so quickly. In that case, contaminants can travel greater distances.

Root crops such as carrots or potatoes, which grow in the soil, are likely to pick up pathogens from effluent in the soil over, next to, or downhill from drain field trenches. Leafy crops like lettuce or broccoli that develop above ground may be contaminated by pathogens that splash up from the soil surface during watering or a rainfall. Above ground crops like those that vine (cucumbers, tomatoes, peppers), are less likely to be affected by splash up since they grow vertically out of the way. Homes where water is “hard” and which use a salt-based water softener system are more apt to be passing high levels of brine into the septic drain field. These salts can damage plants that grow nearby.

As septic effluent drains out into the lines, it is filtered slowly through the soil. Beneficial soil microbes digest harmful bacteria and viruses. While septic systems are designed to prevent disease-causing soil contamination, there is no easy way to know if your system is functioning properly. In addition to bacteria, consider all the household chemicals that go down your drains every day. Plants are by nature absorbing and processing “factories,” cleaning up the environment. All of this can end up in those vegetables you planted in the only sunny part of your yard.

What is causing purple leaf color on vines?

July 22, 2019 • Leave a Comment

I recently planted several vines in containers in full sun as directed. Now I’ve noticed the leaves appear to have a purple cast to them. What might be wrong?

Signs of stress caused by improper pot size, insufficient nutrients, soil, water, weather conditions, site incompatibilities or drainage can by themselves, or in combination, cause color change in plant leaves. Some plants with dark green leaves that are prone to leaf burn can develop color changes in their leaves if they are receiving too much light. The opposite is also true if they do not receive adequate light. Then again there are plants that have naturally occurring color changes in their leaves and the color is not indicative of a plant problem. With the wide selection of hybrids available, it is not a surprise that we find it difficult to figure out if the coloring is genetic or not.

Annual and perennial vines are easy-to-grow plants if you have a basic knowledge of their cultural needs. Some key facts pertaining to raising vines in your garden: Select varieties that will thrive, not just survive, in the garden. Site conditions to consider include light, water, weather and soil. Most vines like well-drained, organic-rich soil that will support their fast growth rate. Once the vine develops a good root system, stress will be kept to a minimum. Container-grown plants should be watered and fed regularly with a balanced fertilizer. Don’t postpone installing the vine’s support system; they love to hold on. Mulch helps to keep in moisture and cool the root system. Pruning should include removal of diseased or damaged stems. A perennial vine requires removal of dense, tangled growth to allow air flow for healthy growth, while annual vines require little pruning except for shaping.

False indigo growing tips

June 27, 2019 • Leave a Comment

I have 4 false indigos (Baptisia) by my house that were doing great some years ago, but now are very leggy and die off by midsummer. I have 4 other ones near a large pine tree that look magnificent. The ones by my house used to look this way. These plants have been here since we moved into our house 15 years ago. Is there anything I can do to get them back to their full size?

There are two clues in your Baptisia predicament. The first hint is the four plants “near a large pine tree” are magnificent. The second hint is the plants by the house “have been there since you moved in 15 years ago.”

False indigo wants full sun for best performance. Although they like rich soils, they are very tolerant of poor soil and arid conditions, which is what they have around the large pine tree. Since the ones by your house used to look that way, it’s possible a matured tree canopy now diminishes access to full sun. In shade, false indigo gets leggy and needs to be staked. They also spread by rhizomes out from the main base and can consume considerable garden space. Your false indigos have that elbow room out at the pine. The false indigo next to your house may have used up all the space they had available in 15 years, particularly if they are confined by a house foundation and a nearby concrete walk or driveway. There’s no place for them to go.

Since we are moving into the heat of summer, wait until fall to cut back and dig up the false indigos along your house and divide them. Replenish and amend the soil in the area and transplant a limited number of small divisions back to this area. If examining the overhead tree canopy reveals access to full sun is compromised, you can plan to stake the transplanted divisions or simply add them to the great crop you have growing out by the pine.

Choosing plants for hedges

June 22, 2019 • Leave a Comment

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

June 18, 2019 • Leave a Comment

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

April 15, 2019 • Leave a Comment

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?

April 1, 2019 • Leave a Comment

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

February 21, 2019 • Leave a Comment

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

January 28, 2019 • Leave a Comment

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.

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