Archive for the Ask MG department

How do I care for transplanted roses in spring?

March 31, 2022 • Leave a Comment

Last October, I transplanted two climbing roses and a standard rose bush. What should I be doing for them this spring?

There are four basic tasks for transplanted roses. First, carefully remove winter protection about the time you see crocus and tulips emerging from the ground. That indicates the ground temperature is warming slowly and your roses will be taking up moisture soon. If any of your roses were grafted, expose the graft union and check for growth buds on the rootstock (below the graft). You do not want to encourage these rootstock sprouts—remove them. On your climbers, if you have laid the canes down on the soil and covered them up, now is the time to uncover and gently lift the canes up and attach them again to their support structure.
The second task is pruning in April, when you start to see bud swell on the canes and branches, or around the time forsythias bloom. Remove dead branches and prune for air circulation, crossing branches and aesthetic cane length based on the supports.
The third step is their first feeding, which can be done at pruning time. A general slow-release fertilizer blended for roses is great. Spread it at the dripline and gently scratch it into the soil. Roses are heavy feeders. Many rose growers use organic supplements, such as fish emulsion or additional slow-release granular fertilizer, once a month until August to keep them healthy against disease and insect attack.
Lastly, as the roses start to push out leaves and new growth, apply a preventative spray for fungal diseases like black spot. A horticultural oil spray later in May into June can help with insect problems.

What are good plants to give as a wedding party favor?

March 14, 2022 • Leave a Comment

At our upcoming wedding, we want to give a seedling or plant as a wedding party favor. We need suggestions as to what tree or plants can be planted in Michigan in September. Since there will be about 500 guests, the price of each plant must be relatively low.

Congratulations on using a plant as a wedding party favor! One of the best choices for fall planting, and a Michigan native, would be a white spruce (Picea glauca) seedling. These strong conifers transplant easily, and tolerate a wide variety of soil types and sun conditions. They are used for windbreaks, lumber, and sometimes Christmas trees. They have a strong conical form and hold their limbs out horizontally. The dense branching provides shelter and food for birds and other wildlife. What a fitting long-term remembrance of your wedding.

Understanding the large quantity, you want to deal with a local wholesaler/retailer that can offer a practical price. Consider Cold Stream Farm in northwest Michigan (www.coldstreamfarm.net). Please remember that 500 seedlings will likely be prepared in bulk. You will have to separate them and individually wrap their roots in a moisture-retaining mulch and secure in a waterproof sleeve. Therefore, timing your order is important so that the seedlings are not stored indefinitely. Once received, you have approximately one week to separate, rewrap and distribute. Prepare a tag for each tree that tells guests to plant as soon as possible and the optimum soil and light conditions.

Scientists estimate there are about 9,200 undiscovered tree species

March 1, 2022 • Leave a Comment

**Coniferous mixed forest, Val Saisera, Italian Julian Alps, Italy. (Photo: Dario Di Gallo, Regional Forest Service of Friuli Venezia Giulia, Italy)**

University of Michigan: A new study involving more than 100 scientists from across the globe and the largest forest database yet assembled estimates that there are about 73,000 tree species on Earth, including about 9,200 species yet to be discovered.

The global estimate is about 14% higher than the current number of known tree species. Most of the undiscovered species are likely to be rare, with very low populations and limited spatial distribution, the study shows.

That makes the undiscovered species especially vulnerable to human-caused disruptions such as deforestation and climate change, according to the study authors, who say the new findings will help prioritize forest conservation efforts.

“These results highlight the vulnerability of global forest biodiversity to anthropogenic changes, particularly land use and climate, because the survival of rare taxa is disproportionately threatened by these pressures,” said University of Michigan forest ecologist Peter Reich, one of two senior authors of a paper scheduled for publication Jan. 31 in Proceedings of the National Academy of Sciences.

“By establishing a quantitative benchmark, this study could contribute to tree and forest conservation efforts and the future discovery of new trees and associated species in certain parts of the world,” said Reich, director of the Institute for Global Change Biology at U-M’s School for Environment and Sustainability.

For the study, the researchers combined tree abundance and occurrence data from two global datasets—one from the Global Forest Biodiversity Initiative and the other from TREECHANGE—that use ground-sourced forest-plot data. The combined databases yielded a total of 64,100 documented tree species worldwide, a total similar to a previous study that found about 60,000 tree species on the planet.

Read more from U-M…

How and when do I train and prune thornless blackberries?

February 19, 2022 • Leave a Comment

How do I trellis thornless blackberries? I have several 2- to 3-foot-tall plants that have many hard-to-tame shoots pointing in every direction. I planted them last spring and none had fruit last year. I wound the longest ones around the wire between the metal fence stakes, which are about 3 feet high. How and when do I prune?

Thornless blackberry primo canes tend to grow along the ground like a vine for the first two years after planting. They also do not produce a large crop the first season. Proper pruning and strong wire support are needed. For thornless blackberries, you need two wires at heights of 3 feet and 5 feet from the ground between posts 20 feet apart. Because of the vine-like nature of this bramble fruit, individual plants should be 10 feet apart.

Now for pruning. Cut back the main trailing canes at the top by several inches in late winter to 4 to 6 feet. That would be roughly March, before bud swell. This pruning forces development of sturdier, more fruitful canes. Keep them tied to the upper wire. For wild lateral shoots, select only those parallel to the wires, trimming them back to about 12 inches. Guide and tie them to the lower wire. Remove cane shoots that go out perpendicular from the wire trellis. This forces the plant to concentrate its energy on the remaining canes for healthy growth and better fruit production. Make sure you prune out any damaged or weak, spindly canes. Proper pruning and trellising will bring your thornless blackberries to an enjoyable production level.

Can I grow ivy groundcover under trees?

February 16, 2022 • Leave a Comment

We have a beautiful 32-year-old maple tree in our backyard and a city locust tree on the boulevard in the front yard. It is difficult to grow grass under both trees. If we planted ivy as a groundcover, would it hurt the trees if it climbed up them? My neighbor had some voracious vine grow up his mountain ash and the tree died.

The age of your maple tree suggests a large trunk and root flare with heavy shade. Turf grass needs sun and water, both of which the maple tree takes first with its mature canopy and characteristic surface root system. Give up on growing grass under it. Apply two inches of composted mulch between the root flares out to the canopy drip line. Keep the compost and mulch away from the trunk and off the root flares. You can then “pocket plant” shade-tolerant perennials like hosta and liriope, which will grow comfortably in those conditions, offer seasonal bloom, and give you an interesting, low maintenance groundcover.

One can grow grass under a locust although they too are shallow-rooted. If you thin out the canopy to allow more sunlight to reach the ground, a shade turf seed mix can work if the area is properly prepared. However, a boulevard takes heavy abuse from vehicles and weather. You may be better off applying the mulch method to the locust as well. The liriope is both sun- and shade-tolerant and will handle some road salt applied in winter. There are also creeping junipers that hug the ground and give you conifer presence all year. The key is to plant away from the tree trunk.

Any kind of climbing ivy is difficult to control. Their accelerated rise within a tree’s canopy crowds out the tree leaves. The tree loses its food production source that feeds its roots, which in turn feed the branch scaffold. The tree literally starves and dies, as witnessed in your neighbor’s yard.

Why doesn’t our garden have earthworms in the soil?

February 11, 2022 • Leave a Comment

Our several-year-old vegetable garden is high in organic matter but has no earthworms — none at all. What are possible reasons and potential solutions? If the soil is not healthy for worms, is it lacking something important? Our lawn adjacent to the garden has plenty of worms.

A productive garden thoroughly depletes the organic matter to produce those prize-winning squash and tomatoes. So we correctly add organic matter annually. The problem may lie in the method.

There are also different kinds of earthworms. Some live closer to the surface as evidenced by those living in your lawn. Epigeic species live in or near the surfaceplant litter. They are typically small and are highly adaptable to variable water and temperature conditions associated with lawn culture. Endogeic species are more mobile, making temporary tunnels, and live in the upper soil layers feeding on soil and organic matter. Then there are the deep-burrowing anecic species, which we often call “nightcrawlers.”These guys drag surface litter down into their burrows which can be several feet down below the soil surface.

The nightcrawlers are much more common in the north and east where there are clay and loam soils. Something that gardeners do not realize is that continuous tillage or disturbance of the soil will cause most earthworms to vacate the premises. Remember your lawn soil is rarely disturbed. If you mechanically rototill organic matter into your garden every year or vigorously deep dig your soil before planting, you may be chasing the worms away. They don’t get the chance to do their job. You keep destroying their optimum working conditions.

Examine your garden prep and add compost into the top 6 inches instead of deep tilling. The vegetables will still take all that they need. Cultivate it in by hand rather than mechanical means. Continue to practice good crop rotation.

How do I care for my damaged kousa dogwood tree?

January 28, 2022 • Leave a Comment

I planted a kousa dogwood last summer, and it looked to be doing well, with nice autumn foliage. Last fall it looks as if a fat raccoon has tried to sit in the fork, and two of the largest boughs have been torn off. The damaged dogwood height is about 5 feet, the largest branch left is 3/4-inch diameter, and there is a huge scar where a branch got torn off. What should I do this spring to the wound?

Do not paint or bandage the wound left by the torn branch. This only provides hiding places for insect pests and traps moisture which can lead to mold issues. Trees have an amazing ability to heal over injuries. When the wound occurred, the cambium reacted chemically to seal off that area to prevent moisture loss. Eventually an exterior bark layer will form over that spot, much like a person’s skin heals from a cut.

Make sure the dogwood is sited for optimum light and water preferences. Water the roots deeply when day temperatures are high and rainfall is absent. The tree has endured stress with this injury and used additional resources to repair itself. You can apply a granular tree and shrub fertilizer around the root zone before mulching to help the plant rebuild its energies.

Provide two inches of composted mulch over the root zone, avoiding contact with the tree trunk. Watch the tree’s growth during the season. You may notice stunted leaf and branch development and even lack of bloom buds on the side of the tree with the wound. To prevent inquisitive critters from chewing on the bark, place a narrow cage of wire mesh around the trunk from the ground to about 2 feet up, being careful not to wrap the trunk with wire.

After spring bloom, you may prune the dogwood to re-establish shape and form. In early fall, you can apply another light dose of granular fertilizer per the container label to help the tree’s nutrient storage for winter.

Elsewhere: Flowering Dogwood Problems

Will adding mulch increase the soil depth of a bed?

January 25, 2022 • Leave a Comment

If I keep adding mulch to my garden beds, will it not eventually increase the soil depth in that bed? And if it does, what happens to all the surface roots if I remove the mulch (soil)?

Adding about 2 inches of mulch to our garden beds prevents moisture loss, improves the soil condition, and prevents weeds from germinating. Natural wood mulch, composed of fine wood chips, ground up leaves and twigs, encourages worms and microorganisms to break down the material into nutrients which plants can absorb through their roots. This relationship between the soil organisms, decomposing organic material and plants creates a self-sufficient ecosystem if we, as the caregivers, don’t ruin it.

When you clean your garden beds in spring, lightly cultivate the surface material into the soil bed. How much light and water a particular bed gets can speed up or slow down the composting of the mulch. Some beds may need an inch of new mulch each year around mid-June or when temperatures heat up. Other beds may be slower and may only need additional material every other year. Application is not an auto-pilot garden chore.

Do not apply more than what is recommended. More is not better for preventing moisture loss or weeds. Thriving plants have deep roots in the soil rather than roots close to the surface. Overloading on mulch gives the plant a false sense of where the real soil is and can keep the hair-like roots away from microorganism activity.

Can I use a rusting antique urn for planting?

January 12, 2022 • Leave a Comment

I have an antique iron urn that is sitting outside and has begun to rust. Is there any danger to plants if I use it for a container/planter? Does it matter if I use annuals or perennials? I am also considering planting a yucca in it; how do you think it would do?

Your container will work well with no adverse reactions to rust by your plants. However you must drill several large holes in the bottom of the container to allow for drainage. To stop the soil from plugging the holes and restricting drainage, put a piece of screen or weed cloth over the holes. You may have a problem with the existing rust on the bottom—if you place your container on concrete or wood, the rust and water that drains out may stain the surface below. Annuals are always a good choice for planters; they do well in the summer and are not a concern when it comes time to put things away for the winter. Perennials (or the yucca) will require protection from the winter elements (such as putting the container in the garage). The same would be true for an evergreen or shrub. Perennials will also require repotting and division due to the restricted environment in the metal urn.

How do I overwinter cannas?

November 1, 2021 • Leave a Comment

Canna lilies are vigorous growers, spreading and creating large clumps of fleshy rhizomes that can be dug, lifted, and stored over the winter so they may be planted again next season. (Eric Hofley / *Michigan Gardener*)

I have been unsuccessful in overwintering cannas; they get mushy or just don’t survive. What’s the trick?

Canna lilies are vigorous growers, spreading and creating large clumps of fleshy rhizomes. Whether in the ground or container, their vibrant colors and reblooming ability make them desirable additions to a garden. Keeping our favorites from year to year is also cost effective.

Using a fork, gently lift the shallow-rooted clumps from the soil and lay them out on trays with newspaper. Separate the rhizomes with your hands, being careful but not paranoid if some of them break. Sort and trim out any damaged rhizomes. If they have been in ground or container soil, do not wash them off. Let the soil dry naturally and brush it off later. If they have been in a pond situation, then clean that debris off. Let them dry for a couple days.

Trim the stalks to about two inches above the rhizomes with a clean knife or pruners. Remember all naked rhizomes look identical. To keep varieties identified, put a label with each group and keep them separate. Once dry, wrap them in dry newspaper or paper lunch bags, and place in open cardboard boxes. Shoeboxes are great for large numbers of multiple varieties.

The key is keeping them dry and cool while you wait to replant them. Cool, dry basements and fruit cellars that don’t freeze are ideal. Do not place near furnace vents where heat can make them sprout prematurely. Check once or twice over winter for soft or shriveled rhizomes and discard. If more than a few are rotting, then move them to a drier location.

Related: Planting cannas in containers

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