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Archive for the Ask MG department

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.

Ask MG: Growing apples in Michigan

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What are the causes of apples dropping from trees prematurely while still very small? Is malathion a safe, readily available treatment for apple trees after the petals fall? Can you recommend a book for growing apples in Michigan? D.E.

Premature fruit drop can be natural, environmental, or pest-related and it takes some careful observation to determine which category yours falls into. An early apple drop before the fruit has matured may be the result of an overproduction of fruit by the tree. The plant simply cannot support the continued nourishment for such a vast number. Profuse flowering and extensive pollination can cause this overproduction beyond what the tree can sustain. Subsequently, it “sheds” a few pounds of excess fruit to conserve energy in a natural thinning process. Some fruit tree growers will even manually thin a tree to increase the quality and size of the final product, beating the tree to the punch.

Premature fruit drop can be environmentally stimulated by unfavorable conditions like frost, excessive heat or cold, or drastic changes in humidity. Living in Michigan, any of those conditions are quite possible in the flower to fruit cycle. Since symptoms can also be soil-related, it is important to check your regularity of watering and that the proper nutrition is offered the tree at the root zone. A soil test geared toward fruit tree production would zero in on those nutrients and their correct proportions. You can obtain a soil test kit from your county’s MSU Extension.

Another environmental occurrence is herbicide drift. Never apply herbicides in windy or dead calm conditions. Dead calm is often associated with a phenomenon known as temperature inversion. Contrary to popular belief, spraying under such conditions can actually increase drift distance. The culprit spray may be several yards away, making it difficult to pinpoint the source.

Pest-related fruit drop occurs much later in the season, when the fruit is very near maturity. So insect pests are probably not the reason for your premature drop.

As for the application of malathion, a readily available insecticide for homeowner use, proceed with caution. Make certain you correctly identify the pest, that the insect pest exists on your apple trees and that it is doing damage before arbitrarily applying any insecticide. Malathion is particularly effective against leafrollers and codling moths, which can damage apples, and must be applied at specific intervals. All label instructions and cautions should be followed to the letter if applying it yourself. A better choice would be to contact a certified arborist for an accurate diagnosis and treatment. Oftentimes beneficial insects can be eliminated from nature’s cycle in the homeowner’s fury to protect their plants.

For Michigan apple growing information, contact the your county’s MSU Extension and obtain how-to bulletins on tree fruit. For a nominal cost, you will get targeted, science-based information on Michigan climate, the best apple varieties, and proper techniques to successfully grow apples in Michigan.

Ask MG: Does fertilizer have the potential to repel deer?

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I am looking for a deer repellent and found out some people have used Milorganite fertilizer to repel deer. Have you heard of that, and what would be the advantages and disadvantages?

According to Milorganite, “There is information in the common press and on web sites that state Milorganite is a deer repellent. Milorganite is not registered with the EPA as a deer repellent yet.” Additionally, a customer service representative for Milorganite said, “We do not use this statement in our marketing, since it has not yet been proven scientifically.”

Milorganite received its name in a contest in 1925, derived from MIL-waukee ORGA-nic NIT-rogen, named by McIver and Son of Charleston, South Carolina. It is the solid microbes produced from a water treatment facility in Milwaukee, Wisconsin. It is described by Cornell Waste Management Institute (Fact Sheet 2006, by Ellen Z. Harrison, Director) as “treated sewage sludge or biosolids.” They claim it ends up as a heat-dried pellet (thus killing viral and bacterial pathogens) and not compost. Milorganite literature assures it is tested daily and is safe for use as a fertilizer around children and pets. They also claim it is organic, however according to Cornell Waste Management Institute, “Sewage sludge products are not allowed for use in certified organic agricultural production according to the U.S. Department of Agriculture regulations.”

Cornell also conducted testing for the product as a deer repellent. Their 2005 preliminary findings indicated it reduced deer damage in summer when alternate foods were available, but not in winter or spring.

The benefit of Milorganite is its use as a slow-release nitrogen fertilizer containing 6 percent nitrogen, 2 percent phosphorus and 4 percent iron. It won’t burn plants if too much is applied because it has virtually no salt content like other fertilizers. It is recommended you keep the product away from children and pets and to wash hands immediately after handling.

Transplanting hydrangeas

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I realized that my 3-year-old ‘Nikko Blue’ hydrangeas are planted in full sun and need to be moved. Can I transplant them to another location and, if so, when should that be done? J.K., Canton

Don’t panic and brandish a shovel at your ‘Nikko Blues’ just yet! Your “full sun” could have some ameliorating conditions that dilute the intensity of the light. Although hydrangeas are natural woodland plants, they can handle full sun if moisture is consistent and they are protected from midday sun, the real scorcher of the day. That said, their preference is dappled shade. That can be achieved even with a high tree canopy. Greater consideration should be given to desiccating wind patterns and protection from those.

If you still feel you need to transplant your shrubs, fear not. A hydrangea’s root ball in most cases is quite compact and generally comes out of the ground with a good quantity of soil adhering to its roots. This enables transplanting with a minimum slow down in growth. At three years old, yours should still be a size that you can handle easily. Late spring is the best time to plant or transplant your hydrangeas. Keep as much soil around the root balls as possible. The top of the root ball should be just below ground level in its new home. Make sure you put a little leaf compost in the bottom of the hole and spread out the roots into the new space.

Avoiding downy mildew in the vegetable garden

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I believe my most recent cucumber crop fell victim to downy mildew. My zucchini ended up with what looked to be the same stuff and the vines turned to mush. I have sandy loam soil in 8 x 8 raised beds. In fall, the beds are amended with shredded leaves and in the winter they get all our coffee grounds. I also have oyster shells sprinkled here and there for the tomato plants. Is there anything else I can do this spring to improve or pre-treat my garden soil in hopes of preventing this problem?

Downy mildew spores do not winter over in Michigan. Each year the spores blow north from southern areas, accounting for the late season appearance of downy mildew. When any plant falls victim to downy mildew, it is generally a combination of excess moisture, humidity, and not enough air circulation. Although your sandy loam soil drains nicely, it may drain too well, which increases your need to water. Besides rotating the placement of your crops every year in your raised bed, your cucumbers would benefit from a pyramid or A-frame trellis. This would raise them above the soil surface, allowing air to circulate and giving you cleaner, straighter cukes. Secondly, avoid watering overhead. Invest in a drip line that targets each plant’s root zone instead of spraying the entire bed. The best solution to a downy mildew problem is to choose and grow only genetically resistant plant varieties.

If your mildew problem is powdery mildew, which does winter over in the soil, combine the cultural practices above with the use of an organic fungicide made from bicarbonate of soda and summer horticultural oil. Too much of either one can be very damaging, so use an organic commercial product that has a proper formulation and is labeled for the particular plant you are going to treat.

Zucchini and cucumbers are nutrient hogs. Your application of organic compost and amendments is on the right track so long as it is cultivated well into the soil. The use of finely pulverized oyster shells adds lime and will increase the alkalinity of the soil, which in Michigan is normally not recommended (shells not finely ground have no effect). Keeping the moisture even is also very important, which is why a drip line is so effective. However, the best way to check your soil for the vegetables you want to grow is to get a soil test. The MSU Extension Service has soil testing kits available.

Hostas have new growth with different leaves

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I planted a variety of hostas 4 to 5 years ago. A couple have new side growth that is different from the parent plant. Would these plants be a cross from two different hostas or are they reverting back to the original plants that they were hybridized from?

Hostas are hardy, easy-to-grow, shade-tolerant perennials known primarily for their beautiful foliage. Their leaf color can be affected by the amount of sun the leaves receive: a variegated variety planted in full shade tends to turn to solid green during the summer and come back up variegated the next spring.

They can sometimes backmutate: new shoots revert back to one of the parents. Well over half the varieties were found as “sports” or mutations on existing cultivars. A sport occurs when a plant mutates into a different color leaf pattern. For example, a gold hosta may sport to a gold with a green edge, or any other number of color pattern changes. The reason that so many sports are found is that they are genetically fairly unstable. A new term has been coined for folks who intentionally indulge in this new and popular pastime of looking through nurseries for these mutations: “sport fishermen.”

Hostas can also be grown from seed. Just like people, their offspring will not look exactly like their parents, but they will share a few of the same characteristics. The leaf color of the seedling will be derived from the color in the center of the leaf of the parent plant (grandparents are included here also). Green varieties will usually produce green offspring, blue varieties will produce some blue, some green, and some gold offspring. Gold hostas will produce some of each also. Edged variegated hostas will not produce variegated offspring. Only cultivars that have white streaks (streaky) in the center of the leaf will produce variegated offspring. White-centered cultivars will produce all white hostas which usually die due to a lack of chlorophyll.

Related: Hostas: sun vs. shade

Roadtrip: Check out the Hosta Hillside at Hidden Lake Gardens

How to make your own soilless potting mix

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What is a good formula for making soilless potting mix?

Years ago Cornell University published a simple and effective recipe for a soilless potting mix that works well for most plants. It is 1 bushel of peat moss, 1 bushel of perlite or vermiculite, 1/2 pound of dolomitic limestone, 1 pound of 5-10-5 fertilizer, and 1-1/2 ounces of 20 percent superphosphate fertilizer. Most commercial mixes now on the market began with this recipe and have since been amended to create a plethora of combinations suited to specific plants. There are special commercial combinations available for seed starting, houseplants, cactus, violets, orchids, and many many more for general container plantings.

You can create your own soilless potting mix using the basic recipe as a start, depending on your particular needs. For instance, using perlite allows for needed air pockets, along with quicker drainage and drying, but probably will require more frequent watering. Using vermiculite, on the other hand, creates air pockets, but holds moisture longer for those plants that do not like to dry so much between waterings.

Another option is to use composted woody fines or ground bark in place of some of the peat moss. The woody fines and bark absorb water more readily than peat moss. Coir (coconut husk) is also an excellent ingredient in place of or in addition to peat moss. Dry peat moss resists wetting and you will find that commercial mixes include a wetting agent to facilitate the wetting of the peat moss. You should always wet peat moss well before use, and if it ever dries completely be sure to water the container several times until you know the water is being absorbed and not just running off the top and down the insides of the container, as dry peat moss will shrink inward and pull away from the edges of the container, allowing too much runoff.

The addition of builder’s sand will create a mix that drains very quickly for cactus or succulents, and also add weight to the container if you have a tall plant that is prone to tipping over in a lightweight mix. In terms of fertilization, if you are less inclined to do it regularly, try substituting a slow-release fertilizer that will last for several months. If you are an erratic waterer, try adding some of the new crystals made of polymers that hold water and release it gradually. A way to help yourself decide what ingredients a particular mix should have might begin with reading the ingredient labels of the commercial products. You will get some good ideas for amendments that suit your special needs.

As you concoct your own version of soilless mix, keep a few things in mind. Your goal will be to have water move through the media quickly, leaving water absorbed by the media and at the same time leaving air pockets in the media to supply oxygen for the roots. The one big “don’t” is don’t use real soil from your yard or garden in the mix. It is heavy, doesn’t drain well in containers, and brings in pathogens and possible chemical residuals. You may also want to compare the cost of your chosen ingredients to the cost of commercial mixes. Making your own may or may not save money.

Is peat moss green-friendly?

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My husband and I put a lot of effort into making gardening decisions that are best for both our immediate environment and the global environment. We have heard that the manufacturing of peat moss is stripping rainforests of essential nutrients. We don’t know if this applies to Canadian peat, sphagnum peat and/or Michigan peat. Can you help us sort this out so we can make informed decisions? 

Like other natural resource sectors, the harvesting of peat moss around the world has attracted the interest of concerned environmental groups, governments and the public. Rainforests and peat swamps in South America, Southeast Asia, the Pacific and Africa are clear-cut and burned. This is not for the purpose of harvesting peat, but to make way for soy and palm oil plantations. In Ireland and Great Britain, peat bogs are in danger of disappearing. The problem there is exacerbated by the relatively small acreage of peatlands, and by development, agricultural use, and the commercial harvesting of peat for fuel. Many conservationists, gardeners, and wetlands scientists in these countries have recommended a boycott of horticultural peat.

In the United States, peat moss is harvested in Indiana, Florida, Illinois, Michigan, and Minnesota, but most of the peat Americans use (about 98 percent) comes from Canada, which boasts 270 million acres of peatlands. Canada harvests some 40,000 acres of sphagnum and exports 90 percent of it to the United States for lawn and garden use. Canadian peat is mainly partially decomposed remains of sphagnum moss, but may also include other marshland vegetation: trees, grasses, sedges, etc. As it grows, the lower parts of sphagnum die and are buried beneath the new growth; eventually, the dead moss is compacted and deprived of oxygen by the weight above it and forms peat, a dense vegetable mud. This mat of dead and living sphagnum literally supports the plant life of the bog. If sphagnum moss is not cut out completely, it will slowly grow back. This process can take at least 5 to 25 years.

The majority of companies involved in this industry, through their association with the Canadian Sphagnum Peat Moss Association, have articulated a policy for the preservation of environmentally sensitive peatlands and for site restoration or reclamation of harvested sites. The policy urges peat producers to manage peatland after their use, including restoration of harvested bogs to a functioning peatland when harvesting is finished.

Peat produced in the United States is mainly reed-sedge peat. Although Michigan has an abundance of peatlands, it is not widely harvested. We have very strict laws and regulations to protect wetlands and the flora and fauna they sustain. Michigan peat is really a decomposed sedge grass. Canadian peat is acidic. Often, Michigan peat is not. Most Michigan peat comes from dredging or digging in areas that were once wet. Canadian peat is fibrous while Michigan peat is made of very small particles that can compact. Michigan peat is difficult to get wet initially and is difficult to get dry when it does get wet. If used on the top of a soil surface, it erodes with rains and blows away when dry. If you are trying to acidify soil for the planting of rhododendrons, azaleas, blueberries, holly, pieris or other plants that need a low pH, use Canadian.

Can gardeners use Canadian peat without feeling guilty? A Cornell University Web site recommends conservative use, relying on compost and manure as sources of organic matter for garden soil. Although it’s better at holding water and doesn’t compact, peat moss is nutrient poor and lacks compost’s beneficial microorganisms. Compost is incredibly important because of the nutrients jam-packed into it. When you combine both peat moss and compost you get an excellent mix. Peat moss restructures the soil and compost provides the nutrients. By blending the two together you’ll reduce the use of peat and the compost’s tendency to compact the soil and thus allow more air, water and nutrients to reach plant roots.

Encouraging grapevines to produce fruit

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When is the best time to trim back my grapevines? And how far can I prune them back? They are on an arbor and have grown very thick. They did not produce much fruit last year.

The best time to trim back any grapevine is roughly March to early April. The object is to minimize sap bleeding from pruning cuts. Sap is what feeds the new growth that will produce your fruit. Grapes are borne on new growth that arises from last year’s wood. Once the sap begins to run, the bleeding from pruning cuts is difficult to stop.
It appears your vines need thinning, as evidenced by their thick growth and lack of fruit. Grapevines are very long-lived. The permanent stems, or “rods,” can become very thick and aesthetically gnarled. However, they can still produce strong new fruit-bearing shoots. The key is to restrict the vegetative growth so that fewer but finer bunches of grapes are produced.

Depending on the number of permanent stems on your arbor, remove much of the extended vine growth to leave two or three strong stems per permanent rod. Then cut those stems down to one or two strong outward-facing bud nodes. From these swollen bud nodes will come the strong shoots that will produce fruit. When cutting to buds, always cut beyond the swollen node to prevent structural damage to the stem. Once new growth begins, watch for excessively long young shoots. Prune these green vegetative shoots away to just above their node.

An ongoing exercise throughout the growing season, this pruning will concentrate sap into the main fruiting stems and allow air to circulate and more sunlight to reach the fruiting vines. Without vigilance, you get the indiscriminate tangle currently occupying your arbor.

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