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Archive for the Ask MG department

Dividing ornamental grasses

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We have 3 zebra grasses and all are growing nicely from the outside of the circle that each forms. The center of each plant is brown and has no new growth. We have heard that you are supposed to burn the grass but that sounds a little drastic. Is there any way we can get rid of the brown centers and yet preserve the healthy parts of the plants? C.T., Farmington Hills

You might have confused “burning grasses” with the prescribed burn method used to rejuvenate a planted prairie situation. With ornamental grasses, such as Miscanthus, feather reed grasses (Calamagrostis x acutiflora), or switch grasses (Panicum), the appropriate method is to cut them down to the ground in late winter (late March here in Michigan). This allows the gradually longer daylight hours to reach the root crown and stimulate new growth.

Your zebra grass (Miscanthus sinensis ‘Strictus’) is considered a “warm season” grass, which means it needs the warmer temperatures of May to kick into gear. The feather reed grasses are “cool season” grasses and will show new shoots as early as mid-April. This is why it is very important to cut down your winter interest grasses by the end of March to take advantage of the increasing daylight.

Because yours are showing “melting out” in the center, this is a sure sign they need to be divided. This should be done shortly after cutting them back, before active growth begins, and as soon as the soil is workable. You will need strong shovels, spading forks and possibly a pickaxe and a handsaw. Dig out the entire root ball of each grass and lay it on its side on a tarp. You may be lucky and be able to break the root ball apart with a sharp shovel. However, it often takes two spading forks placed back to back into the root ball and two people prying back on them with plenty of determination to make a dent in separating out chunks of the root zone. If you don’t mind sacrificing a hand saw to dirt and plant roots, that works very well also, especially if you are the only one working on the job.

Once you have broken the root ball, it is not difficult to separate the viable roots from the dead center into transplantable pieces. You not only have more plant material for free but have also revitalized the grass as a whole. The transplanted sections will welcome having more space to grow.

 

Repairing soil visited by cats

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What can I do to repair soil in a yard that is occupied/visited by several neighborhood cats (to help eliminate the smell and to make the soil better for plant growth)?

Cats are territorial and often use urine as a way to mark their properties. Cat urine contains pheromones, which is a substance that cats and other animals use for communicating. Pheromones are much like fingerprints with humans, as they are used to identify the cat to other animals. When a cat sprays, it is his way of letting other cats know that this is his territory.

If you can identify the areas most frequented, you can repair the soil by removing the compromised material and adding new soil appropriate for the plants you are growing. Cat urine is highly acidic. Some resources suggest neutralizing any remaining acidity still in the soil with hydrated lime and thoroughly mixing it into the soil.

Once you remove the urine-marked soil, the cats will return and want to refresh their territory. Therefore, you need a multi-pronged approach to keep them away. Go for odor repellant and the element of surprise. Purchase a commercial product to spray on your plants and soil surfaces that will repel them from re-staking their claim to your garden. A product that contains the scent of a predator such as coyote or fox, effective against rabbits and squirrels, is also effective with cats. They will go someplace else rather than take the chance of encountering a predator. Secondly, a motion-activated water sprayer has demonstrated that its unexpected “attack” can keep the more persistent offenders away. Using other motion-activated devices that emit unexpected noises, like a dog barking, can also be effective when used in combination. Cats are quick learners despite their often aloof attitude. Once you have established your gardens are no longer a feline restroom, they will seek out less threatening facilities.

 

Problems with coneflower blooms

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I have six coneflowers in my butterfly garden. As the older blossoms are turning brown and starting to fall off (I assume going to seed), there are small worms under the buds. Are those worms invading my flowers or are they simply helping the garden out? A majority of the blossoms falling off have these worms under the them. If they are invading the flowers, how do I get rid of them without poisoning the plants, which would affect the caterpillars? C.H., Wayland

The sunflower moth is one of the most damaging pests of sunflowers and coneflowers, and we have seen its presence in our area. Adult sunflower moths are nocturnal, gray to tan in color, about 2/3 inch long, and rest with wings clasped tightly to the body. Flowers in the early stages of bloom are favored for egg laying at the base of the florets. The moths can complete a generation every 30 days, so several overlapping hatchings can occur. From hatching to full maturity is about 15 to 19 days. The half-inch caterpillar has light brown and white stripes along its length. They begin feeding on the pollen and florets, later boring into the head. The first indicator of trouble is a tangled mat of webbing and caterpillar frass that looks like fine sawdust. The top of the seed head looks deformed and bumpy, with the individual seeds pushed up and away from the flower base. The injury caused by the larval feeding provides infection sites for rhizopus head rot, which is what causes the blossoms to deform, turn brown and fall off.

Remove a coneflower head and cut into it to see if larvae are or were present. Take the sample to a knowledgeable nursery or the MSU Extension for positive identification. Begin with removal and disposal of infected flower heads and daily monitor newly emerging buds for fresh larvae activity. Handpick the newly hatched larvae from the coneflower heads. Many of the larvae pupate within the flower heads. However, others descend to the ground on silken threads to pupate in crevices or under leaf litter and ground debris. The key here is to remove any compromised seed heads before the larvae can pupate. You interrupt the repetition of the life cycle.

Secondly, cultivate and clean the area at the base of your coneflowers to a depth of 2 to 3 inches to prevent any overwintering. Sunflower moths do not attack coneflowers until the first flowers open since they are attracted to pollen and scent. So there is no point in scouting for moths until the flowers begin to open. Then it must be done frequently because migratory moths can appear in large numbers virtually overnight. Scouting should be conducted about an hour after sunset when moth activity begins to peak by using a flashlight. There are also pheromone traps that attract and capture male moths.

A preventive insecticide that contains organophosphate materials is best applied as blooms begin to open and has a somewhat greater residual activity than pyrethroids. The insecticide must be applied to the flower face to be effective. Controlling the moth larvae raises concerns about impacting pollinators such as bees. Applications should be made in early morning or late evening when pollinators are not flying. Evening is preferable if you have healthy bee activity, as this will allow some dissipation of material overnight before the bees are active again. Pyrethroids tend to be safer for bees because of their repellency. Dust and wettable powders tend to be more toxic formulations for bees than solutions or emulsions.

In short, it is preferable to trap the moths, handpick the larvae and sanitize the soil base before using an insecticide that could potentially harm an already stressed population of pollinators such as bees.

 

How to transplant poppies

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My father planted some poppy plants back in the 50’s and they have thrived very well in his yard. Every year I would take one to him. He passed away in 1979. I now have my own home, and I have tried to transplant them to my garden in the spring, fall, and summer, but with no luck. The problem is I only have one plant left. They are a very pretty orange. When is the best time and what is the best way? J.J.F., Dearborn

The Oriental poppy is the most conspicuous of all the poppies and a popular garden plant. Poppies are easy to grow and care for, and are relatively maintenance-free and deer-resistant because many parts of the plants are poisonous if eaten. There are no special cultural requirements for Oriental poppies; they perform well under average garden conditions. However, because they have a large, fleshy taproot they are very difficult to transplant except when they are dormant. After the June blooming period is over, the plants die down entirely to the ground and remain practically dormant for a month or more, leaving large, bare spaces in the garden. About the middle of August new growth begins and a little tuft of green leaves appears.

The plants should be lifted and divided while they are dormant or just after the new growth begins. Root cuttings may also be made at this time and are very easily handled. The roots should be cut into small pieces 1 to 2 inches long, each piece containing at least one joint. These should be placed on a bed of soil, either in a flat or in a cold frame, being laid in a horizontal position. A light covering of sand or sandy loam should be spread over them to a depth of about 1/2 inch and the bed should be kept well-watered and partially shaded until active growth has started. If conditions are favorable, roots will develop from each joint and in a short time the leaves will begin to appear.

Oriental poppies will reseed and often revert to the brilliant flame of the old-fashioned type. Harvest the seedpods when the poppies go dormant, split them open, and gather the seeds to plant the following year. After they have sprouted and you have thinned the seedlings, you may consider mulching the bed to help retain water. In the heat of summer when the plants are dormant, there is no need to water them unless you are experiencing a period of drought. Poppies do best in full sun, although a few varieties can handle light shade. They rarely need fertilization. In the early winter after the first frost, apply a protective layer of mulch over the bed; remove it as the weather warms in the spring.

Healthy-looking rose bushes fail to bloom

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I have 6 rose bushes that get morning sun. The foliage looks great but I get no roses. I inherited these plants when I bought the house and I don’t know anything about them. I have good drainage and have given them rose fertilizer. C.M., Allenton

Your roses with no blooms are more than likely not receiving enough direct sunlight. In order to produce flowers, roses must have full sun, which is usually defined as a minimum of 6 to 8 hours of direct sunshine. Morning sun doesn’t sound like it fulfills that requirement. Perhaps the rose bushes have become shaded as the surrounding landscape has matured and trees and shrubs have grown larger, creating shade where there was once full sun. If that is the case you have two options.

First, it may be possible to prune back the offending trees or plants that are creating the afternoon shade, thereby allowing more sunshine to the roses. In a mature landscape that can be difficult due to the probable destruction of the aesthetics provided by the larger plants. A second and more viable option is to simply transplant the roses to a new space with the full sun they need. The best time to transplant roses is in the very early spring, while they are still dormant, before any new leaves have sprouted. You can get a jump on the process by digging and preparing the new rose bed this growing season in anticipation of the big move. Then, next spring, dig each bush with the largest root ball you can handle and move them into the light.

Maintaining tree peonies

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My tree peony is almost 3 feet high and about 7 years old. It is healthy and gets about 7 huge fuchsia blooms. Two years ago it sent up a couple of what I assumed were suckers from the root system. I cut them off at ground level. Last year it sent up about a half dozen and I cut all but one off just to see what it amounted to. It did have one tiny pale pink blossom and the leaves appeared to look more like a bush type peony. I’m afraid to let these mature, as it’s taking away from the tree appearance. What exactly are they and how do I deal with them?

Tree peonies are flowering shrubs which grow from 1 to 6 feet tall. The reproduction of tree peonies is mainly done by two methods of vegetative propagation: tuft division and grafting. In the division method, a large plant is simply divided into small plants, each bearing its own roots. In the grafting method, a regular herbaceous peony’s rootstock is used to nourish a tree peony scion until the tree peony produces its own sustaining roots.

The process of planting a tree peony is similar to planting an herbaceous peony, except for two major differences: Allow 4 to 5 feet for the spacing of tree peony plants and plant the tree peony deeply to permit its own roots to form more rapidly and abundantly. The union of the scion and the rootstock should be at least 5 to 6 inches below ground level. If planted too shallow the herbaceous rootstock will send up shoots of its own, called “suckers.”

You can tell the difference between a new tree peony shoot and one from the rootstock by the way they look. The foliage is quite different from that of the grafted tree peony. Wait until you are sure these suckers are from the rootstock before removing them as your tree peony will also produce basal shoots and these are what you want. Carefully cut the suckers off, as close to the root as you can.

To really solve the problem, however, as soon as you can tell your tree peony has grown some of its own roots, dig it up in the fall and cut off all the root below the original graft. Keep cutting back suckers, until you can dig the plant. If sucker roots are left to grow for any length of time, they will diminish your tree peony or worse.

Tree peonies are heavy feeders but dislike large doses of fast-acting nitrogen fertilizers. They respond well to a generous, early autumn top dressing of a slow-release organic fertilizer. Its high potash content encourages flowers to develop. A light sprinkling of a general fertilizer can be applied in the spring.

Tree peonies respond well to pruning. You should aim for a broad, multi-stemmed shrub of up to 5 feet in height which will not need staking. Chinese and American types have a naturally branching habit and will need less regular pruning than the Japanese and French types.

In February, just as the growth buds are swelling, trim off all the dead wood. You will often find that the new shoots are coming from lower down the stem, leaving a small dead spur. Whole branches will sometimes die. These should be pruned back to a live bud, or to just above ground level.

With a young plant, only remove dead wood during the first two years to help get the plant established. Don’t be tempted to prune further. After this, if your plant forms a good shape, no regular pruning is needed. However, if your plant has few stems and is poorly shaped, then prune hard. You may see buds at the base of the stem or shoots coming from below the soil. Prune back to these or down to 5 inches or less from the ground. Even if you can’t see any basal buds, adventitious ones will form. The best time to prune is early spring, although this may mean that you sacrifice some flowers in the coming year. You can prune directly after flowering but regrowth is slower.

If you have, or inherit, an older tree peony which has never been pruned, it can be transformed and rejuvenated by applying this same technique. It is best to prune just one main stem each year, cutting it down to about 5 inches. It takes courage to do this, but is usually successful. There’s no need to be concerned about moving even a large, mature tree peony. Just move it during early autumn as you would any other woody deciduous shrub.

Pruning lavender plants

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How much do you trim lavender bushes? Mine are getting rather leggy and sprawling. When is the best time to prune them?

Let’s assume these are English lavender plants (Lavendula angustifolia), since these are hardy and the most popular in our area. There are many varieties of English lavender, but all have the same basic care. There may be several reasons why your lavender plants are getting leggy and sprawling, including pruning, water, light, and soil.

Pruning is essential for lavender. Pruning is not the same as harvesting. When flowers are harvested, typically not much of the plant is removed. Growers prune plants twice a year: very early spring (April) and after they bloom. Lavender will become leggy and flower production will decrease significantly if it isn’t pruned quite hard. Prune down to three nodes on the new growth above the old wood, which looks gray and isn’t flexible. The plant is usually trimmed to a dome shape to let in lots of light and to help the air circulate. April is a good time to do this. Then do another trim in late summer to early fall. If you happen to prune at the wrong time, don’t worry, the blooms will be back even stronger next year.

Another factor that contributes to a leggy, sprawling plant is overhead watering, or too much water. Lavenders are very drought tolerant, especially after they are established. Watering should only occur as a supplement for hot, dry weather and they should not be placed where sprinklers water daily. In a typical Michigan summer (no droughts or periods of high temperatures), no watering at all may be needed. Light, as in full sun, is essential. Picture the open fields of lavender in Provence, France. Lavender doesn’t need a special soil, so long as it is very well-drained, even sandy. Very rich, clay or damp soil is not recommended.

Steps for healthy blooming hydrangeas

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How can I get ‘Nikko Blue’ hydrangeas that
have not flowered in years to bloom?

Hydrangeas are colorful flowering shrubs that aren’t bothered by pests or diseases, and can bloom for weeks at a time. The reason the flowers go on for so long is that the showy parts aren’t flower petals at all. They are colorful sepals that are sterile, but showy so that they attract pollinating insects. The fertile flowers, usually found in the center of the cluster, are quite small and inconspicuous. The sepals can’t be pollinated, which means they don’t go to seed, and that’s what prolongs the “flower” show.

Hydrangeas thrive in part-shade and prefer a moist, woodsy soil enriched with peat moss and leaf mold. For best success, water them well throughout the growing season.

Two words to remember when it comes to hydrangeas that refuse to flower is “too much.” Although hydrangeas grow well in some shade, too much shade can result in gorgeous leaves and no flowers. Another problem could be too much fertilizer, specifically high nitrogen fertilizer. This again will give beautiful leaves but few, if any, blooms. Use a balanced fertilizer such as 16-16-16 at the time they start to bloom. Too much water or too much dryness can also result in lack of flowers.

Most big leaf hydrangeas (H. macrophylla, also called “mopheads”) bloom on the previous season’s growth (old wood) and are reliably hardy to hardiness zone 6. In Michigan it is advisable to protect mophead hydrangeas to ensure bloom. The old wood of the hydrangea must survive in order to get blooms the following summer. ‘Nikko Blue’ is a mophead type that for many years was one of the few relatively hardy big-leafed types available. However, many gardeners protect it in early winter by stuffing fallen tree leaves around the shrub and covering it with an upturned bushel basket or burlap.

The choice of location is very important: place them close to the house, on the north or east side. The south or west side would expose them to afternoon sun, which is too hot in the summer and increases the chance of bud damage in the winter. In addition, unseasonably low temperatures after a mild winter also cause a lack of blooming on big leaf hydrangeas. If the plant is actively growing and hit by a late spring or early winter frost, the buds freeze and the hydrangea won’t bloom.

Another common reason why macrophylla hydrangeas don’t bloom is improper pruning. Again, most hydrangeas bloom on old growth (last year’s wood). If you prune too much old wood or you cut that wood too late, you won’t get blooms. These varieties set their buds after bloom in late summer, so spring pruning would remove that year’s flowers. The proper time to prune the flowering stems is soon after bloom, in late summer, back to a healthy pair of buds or shoots. The only pruning necessary in the spring is removing dead wood as new growth emerges.

What is a plant volunteer?

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What do people mean when they say a particular plant is a “volunteer?”

A plant is called a volunteer when it grows in an area it wasn’t planted. These can either be desirable or undesirable plants. If you like the way it looks, it’s a desirable plant; if you don’t, of course it becomes undesirable. Another word for a volunteer plant is “weed.” The definition of a weed is any plant that grows where it’s not wanted. A beautiful sunflower is a weed/volunteer when it appears in a bean field. There are several ways these plants can get to your flower bed or garden. They may come from roots or seeds you planted the previous year, animals may deposit them in their feces, birds can drop the seeds, or the wind may blow them in. If you like the plant… leave it; if not…remove it!

What are the bugs on my nicotiana and how can I control them?

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I grew Nicotiana sylvestris for the first time this year and I have three questions. First, as the plants started to blossom this spring, tiny white and brown bugs appeared all over both the flowers and the foliage, especially the undersides. Near the end of the season, there must have been thousands of these bugs all over the plants! The foliage and flowers were healthy and bloomed wonderfully all season. I tried insecticidal soap in the early summer, but that didn’t seem to faze them. Should I be worried about these bugs overwintering, and what, if anything, should I do differently next year?

Second, at season’s end, I noticed that each seed head had dozens of tiny, brown particles. Are these all seeds? If not, is there just one seed per each “head”? It seems difficult to determine what exactly the seed is. Does this plant self-seed? Third, should this plant be deadheaded throughout the season? As each white bloom faded to brown, I plucked it out, but should I also have cut off the oval seed heads?

What you probably had on your Nicotiana were aphids. They attack the tender new growth and buds of fleshy plants, including Nicotiana. When these insects shed their exo-skeleton they fall on the foliage and give the appearance of thousands. Aphids reproduce rapidly, especially in hot weather, therefore it is difficult to get rid of them quickly. Insecticidal soap will work, but must be applied every 6 to 8 days to kill any eggs that might hatch. For another natural way of getting rid if these pests, try ladybugs. They can be purchased at your local garden center and can take care of a large population of aphids in a matter of days.

The seed pod on Nicotiana is the green, oval shaped part at the base of the flower. These should be removed for flower longevity. In mild winters, Nicotiana can self-seed if the seed pods are left on the plant.

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