‘Snowstorm’ is the first wand flower (Gaura lindheimeri) release from the Flower Breeding and Genetics program led by Dr. Neil Anderson! Wand flower is a prized garden subject because it: blooms continually throughout the summer, is a great filler plant that mixes well with other plants in garden beds and containers, and it moves in the wind adding extra ornamental appeal. Gaura lindheimeri has grown in popularity over the past decade and is among the top 25 selling perennials in the US market today. Although this Gulf Coast native (Texas and Louisiana) is reliably hardy only to zone 6, it serves as a great annual in Minnesota.

The overall goal of the University of Minnesota wand flower breeding program is to develop Minnesota hardy cultivars. Work continues towards this goal trying to generate interspecific hybrids between the highly ornamental G. lindheimeri and the hardy G. coccinea (native from Texas into Canada). Some of the G. coccinea forms in the breeding program a have wonderfully sweet fragrance and other ornamental characteristics not found in G. lindheimeri. Gaura coccinea prefers dry growing conditions and can be found in western Minnesota. Other Gaura species native to the Southern US possess diversity for foliage and color and plant habit and are being explored as parents within the breeding program as well.

Although it will take some time to continue to unlock crossing barriers between G. coccinea and G. lindheimeri, G. lindheimeri ‘Snowstorm’ is a wonderful cultivar and great addition to Minnesota gardens. ‘Snowstorm’ has proven to be a very vigorous selection with prolific flowering potential. Crowns send up multiple, wiry stems that move in the breeze and are covered with blush pink buds opening white. Plants grow to 2-3 feet tall and the airy flowering stems mix well with other neighboring plant materials. ‘Snowstorm’ is an especially nice accent mixed with other plants in medium to large-sized containers. It also works well in ground beds as a solitary accent plant, mass planting, or border.

‘Snowstorm’ and other G. lindheimeri cultivars do best in full to part sun and planted in fertile, well drained soil. They are somewhat drought tolerant and if spent flowering stems are removed they can flower even more prolifically.

There are multiple licensed Minnesota wholesale propagators of ‘Snowstorm’ and it is currently available in many area garden centers. Don’t miss out on this summer ‘Snowstorm’!!

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While this past May went down as one of the driest Mays ever, many areas around the Twin Cities have received some rain during the first part of June. That has both been very helpful for our lawn grasses and has also provided the needed moisture for many of our weed seeds, especially crabgrass to begin actively germinating. In most areas of southern Minnesota we are past the time when preemergent herbicides for crabgrass control will be effective. However, that doesn’t mean control is not possible. Those small crabgrass seedlings can effectively be controlled with postemergent herbicides. One of the newer active ingredients for crabgrass control is quinclorac. This is a very good herbicide for controlling crabgrass once it’s germinated and the seedlings are visible. However, it is usually mixed with other broadleaf control products and marketed for home use as general weed and crabgrass killers. However, it is important to note that with these combination products, you will be applying other herbicides that are not needed or even effective at controlling crabgrass. Hence, this unnecessarily introduces these other materials into the environment; something we try to minimize doing whenever possible.

Where you have a mixed stand of weeds, both broadleaf and crabgrass, a combination product like the one mentioned above, can be a good alternative to buying separate products for each category of weeds. Be careful to choose products that are safe for use on your lawn. Those containing the active ingredient glyphosate will kill all grasses and broadleaf weeds leaving the lawn scarred with unsightly brown dead spots that will need to be resodded or reseeded. Remember to always follow product label directions exactly regarding a products use. Where only a few crabgrass plants are present, they can easily be hand pulled from a moist soil thereby avoiding the use of an herbicide altogether.

Even though some rain has arrived to help out our lawns and gardens, many lawns are still showing signs of the very dry conditions encountered during the month of May. Those signs range from small brown spots intermingled with green grass to larger, completely brown areas. Future rainfall patterns and amounts for the remainder of June are, of course, not known. If we continue with our cool to mild temperatures and periodically receive some rainfall over the next couple of weeks, supplemental irrigation needs for most lawns should be minimal, if needed at all during that time. Avoiding excessive traffic and play on the lawn during those times when lawns are brown and dry will help avoid additional, often more permanent injury. Likewise, herbicide applications to lawns under drought stress can cause injury to lawn grasses that would otherwise be quite tolerant of those products.

In general, lawn grasses should be mowed at higher heights of cut from now through the remainder of the summer. Flowering of our cool season lawn grasses is winding down. As those flower heads are being mowed off, remember that those shoots ultimately die after flowering. Hence, folks will often complain about a larger amount of course, brown grass stems in their lawns making them appear thinner and even a bit unsightly. In fact, our lawns are somewhat thinner this time of year due to the dying back of those spent flower stalks. It’s really nothing to worry about. This is a natural occurrence every year. Our lawn grasses begin to regrow new rhizomes and shoots in a few weeks, which will help thicken up the lawn. This regrowth process is one of the reasons why our fall lawn fertilization is so important to the long term health of our lawns. But more on that in later article.

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Cool temperatures this spring seem to be encouraging rust fungi on roses. Several different species of Phragmidium (the rust fungus) can infect both wild and cultivated roses. Gardeners should keep an eye out for two different forms of this fungus.

Bright powdery orange spores, known as uredinia, are likely to catch a gardener’s eye. These spores form in raised pustules on the underside of infected leaves, stems, or petioles (central portion of the leaf that the individual leaflets are connected to). Yellow to brown leaf spots may be noticeable from the top surface of the leaf but may not form on all rose cultivars. Infected petioles and young green stems may actually become twisted and distorted around the site of the infection. Rust fungi can infect all plant parts except the roots and gardeners may notice bright orange pustules in unusual places!

If the bright orange uredinia are found on a rose plant, carefully inspect all stems that are one year or older for dark brown to black raised bumps forcing their way through the epidermis. These dark brown to black pustules are the same rust fungus in a different form. Dark brown to black teliospores fill these pustules and are tough enough to survive Minnesota’s harsh winter weather.

Rust fungi have a complicated lifecycle that involve 5 different unique spore stages. The two described above are those most easily seen by gardeners. The bright orange uredinia can spread on the wind to infect more leaves within the plant or on nearby roses. These spores need cool temperatures, preferably 65-70F, and 2-4 hours of continuous moisture on the plant surface in order to start a new infection. If weather conditions become hot and dry, spread of the rust fungi is dramatically reduced.

Teliospores typically do not form until late summer or early fall. They are often found in the same area as the bright orange uredinia and therefore can also occur on leaves, stems and petioles. If gardeners are seeing the dark brown to black teliospore pustules now, these were formed last year and are likely the source of this year’s infections.

The amount of damage that rust fungi can do to a rose plant varies greatly depending on several factors. Most roses are somewhat susceptible to the disease, but a few cultivars are particularly sensitive and will lose leaves in response to just a few bright orange pustules. For most roses, disease severity depends on weather conditions. If cool damp weather persists the rust fungi can grow and spread dramatically. If the summer turns hot and dry, the rust may dry up as well. A few leaf spots will not seriously affect the health of the plant but if infections on stems grow large enough to girdle the stem or otherwise restrict the flow of water and nutrients, that stem may be killed. The fungi that cause rust on roses will not infect other plants in the garden.

Managing Rust on Rose

Damage from rust on roses can be minimized by slowing the spread of the disease.

• Examine the underside of the rose leaves and young green shoots for bright orange pustules.
• Pinch off infected leaves and shoots. Collect diseased plant parts in a bag and remove them from the garden. Never remove more than 1/3rd of a plant’s foliage even if it means leaving a few leaf spots on the plant!
• Carefully inspect last year’s stems for black to dark brown raised pustules. If present, prune out and destroy all infected stems.
• If last year’s leaves are still present around the base of the plant, rake them up and remove them from the garden.
• Prune roses to promote good air movement in and around the plant.
• When planting new roses allow enough space for the mature plant. Avoid crowding plants together which increases humidity in the canopy.
• Use drip irrigation or a soaker hose instead of sprinkler irrigation to keep leaves dry.
• Several fungicides including those with the active ingredient triforine and propicanazole will protect healthy rose leaves from infection by the rust fungi. Always read and follow all label instructions when using a pesticide! In Minnesota fungicides are rarely necessary.

Remember a little bit of rose rust will not seriously affect the health of the plant. Roses will tolerate leaf spots as long as green leaf tissue remains. Stem infections should be taken more seriously as they can affect a larger portion of the plant. In both cases use of good sanitation and moisture reducing practices are often enough to successfully manage the disease.

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Waterosity, the 2009 summer exhibition at the Minnesota Landscape Arboretum, opened on June 6 and explores and celebrates the beauty and the complex interdependence of people, plants, and water. Providing homeowners with environmentally responsible ways to manage water on their property is a key theme of Waterosity. Water-wise hardscaping includes green roofs and permeable paving and both technologies help to reduce the amount of stormwater that washes over roofs and paved areas (driveways, sidewalks, and streets), carrying sediment and pollution into lakes, rivers, streams, and wetlands. Green roofs and permeable paving displays are part of the new permanent arboretum exhibit called Harvest Your Rain.

For more information on Waterosity displays and programming, please visit the Waterosity website and Waterosity Comes to the Arboretum in the May 1, 2009 Yard and Garden News.

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Permeable, or porous, paving is a type of paving that allows water to drain through to the ground below. Water can then directly infiltrate on-site rather than being diverted to a drain for off site treatment. These systems protect surface water, recharge aquifers, reduce flooding and reduce the need for traditional storm sewer systems.

There are three basic types of permeable paving:

• Porous asphalt or porous concrete mixescontain little sand or fine materials and rely on the concrete or asphalt binder to hold the stones and crushed rock together, but still leave voids for water to pass through. Both resemble a rice crispy bar.
• Permeable paver systems typically consist of highly drainable layers below a layer of concrete pavers that are designed to allow water to pass through joints between them. They resemble typical modular pavers or bricks but have corners missing or built in spacers that allow for water infiltration.
• Turf reinforcement systems offer support for vehicles and protects the grass from the traffic damage while allowing natural groundwater replenishment. These systems come as plastic grids with cells that are filled with a sandy topsoil mix and planted with grass. When properly installed, the turf grows over the height of the plastic reinforcing panels and is indistinguishable from a non-reinforced lawn.

General recommendations

Permeable paving should be considered on all projects and is a useful tool for stormwater management. It is particularly practical for projects with tight sites and strict stormwater run-off regulations.

Permeable asphalt and concrete and permeable paving blocks are designed for the heaviest use; they are meant for daily, low-speed use such as in parking lots, driveways, residential drives and similar areas. Generally, turf support structures are intended for infrequently used areas, such as event grounds, fire lanes, overflow or event parking, and other spaces where there is little regular traffic.

Environmental Context

The use of permeable paving decreases peak flow rates in area lakes, streams and rivers during a rain event because it allows water to infiltrate into the ground on site. This infiltration reduces the amount and speed of water leaving the site during a rain event. Permeable paving also reduces the urban heat island effect and can reduce the need for air conditioning.

Design and Installation

• Soil type will affect infiltration rates and must be considered when designing a permeable paver system. Subsurface drain tile may be required if clay subsoils are present.
• Subbase depth depends on the system selected, existing soils and the type of traffic the site will receive. Additional coarse, crushed rock with no fine materials may be required for temporary water storage.
• Careful installation by trained personnel will prevent settling and result in a system that will continue to function properly and be easier to maintain.

Maintenance

Porous asphalt, porous concrete and permeable pavers should be cleaned 2-3 times each year with a street sweeper to prevent sand, dirt, seeds and other materials from plugging the surface. Sand should not be applied and typically isn’t needed since water does not pool on the surface and freeze. Snow plows and snow blowers will not damage a properly installed system.

Reinforced turf may require more watering since the sand and gravel base do not hold much water in between rain showers. Slow release fertilizer will keep the grass vigorous and allow for faster recovery after vehicle or foot traffic.

Cost

The cost of permeable paving systems varies by technology and location. The estimates provided here are based on information from several sources including, the Low Impact Development Center (www.lid-stormwater.net/permpaver_costs.htm), ToolBase.org, and the Seattle Rite of Way Manual.

Paving Type	Cost/sf (installed)
Asphalt	$0.50 - $1.00
Porous Concrete	$2.00 - $6.50
Grass Reinforcing System	$1.50 - $5.75
Interlocking Concrete Paving Blocks	$5.00 - $10.00

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The dense, accelerated pace of modern urban development has affected many of the earth’s natural processes. Asphalt and concrete rooftops, roads, and parking lots cover up to seventy percent of land area in dense cities like New York, while open space in sprawling cities like Phoenix, Arizona is lost to development at a rate of 1.2 acres per hour.¹

Approximately 1.5% of the continental United States, an area roughly equivalent to the state of Ohio, was covered by impervious surfaces in 2004.² This percentage continues to grow and can be as high as 75% in urban areas. Of those impervious surfaces (not allowing the permeation of water), roofs can constitute a significant percentage. Such growth in impervious surfaces can result in a variety of environmental impacts including reduced aquifer recharging, overwhelmed storm water systems, urban heating, decreased surface water quality, and increased air ozone and particulate concentrations. These negative environmental effects impact residents and municipalities by affecting: clean water availability, storm water and sewage infrastructure costs, decreased runoff water quality, decreased employee productivity, decreased wildlife habitat, and increased operating costs of buildings through increased heating and/or cooling costs. Alternative solutions to traditional impervious building methods are being sought in order to mediate these negative environmental impacts and reestablish the green spaces desperately needed in our metropolitan spaces.

Green roofs are becoming an increasingly popular alternative to traditional roofs in metropolitan/suburban areas to reduce the environmental impact of impervious building roofs and to increase green spaces in downtown metropolitan areas. In fact, they are being used to increase green spaces across all areas of commercial development. The above illustration identifies the significant impacts of land development on a local hydrologic cycle; site development substantially increases surface runoff and the removal of tree canopy interception strips away the natural buffering capacities of green spaces- this increase in surface runoff and the removal of green space buffering has had far reaching consequences for our densely populated metropolitan spaces.

The environmental impacts and/or benefits of green roofs in this scenario can include decreased water and nutrient run-off from developed land, reduced ambient air temperature, reduced atmospheric CO2 levels, new garden areas for people and wildlife, and reduced airborne particulates and noise pollution in congested urban environments. Financial benefits can include reduced energy costs for buildings, reduced city infrastructure needs/costs, and improved psychological well-being of citizens resulting in increased productivity among employees. As roofs can account for up to 15-30% of impervious surfaces in cities, the impact of green roofs on the urban environment and citizen well-being can be high.

Green roofs can be built in a variety of contemporary styles; the most prominent distinction is between extensive and intensive systems. Intensive green roofs have been used in our country longer than extensive green roofs, but their reliance on deep soil media profiles and irrigation/fertilization to support traditional landscape plants has limited the progress and general utility of this style. By comparison, extensive systems rely on profiles generally not more than six inches in depth and have shown great merit for retrofitting existing buildings that do not have the appropriate structural support for an intensive system.

Extensive green roofs are composed of several material layers designed to protect a building and offer functionality in a metropolitan space. These layers are often composed of waterproofing membranes, a root impermeable layer, a drainage layer, extensive growing media, and vegetation. These systems have been shown in independent studies to positively impact urban/metropolitan environments by re-establishing green biological buffers that mediate storm water runoff, capture particulate pollution, reduce building energy costs for heating and cooling, provide sanctuary for urban wildlife, and improve citizen morale.

¹Community Cartography/New York City Planning Agency/Smart Growth America; F. Kaid Benfield, Matthew D. Raimi, and Donald D. T. Chen, Once There Were Greenfields: How Urban Sprawl Is Undermining America’s Environment, Economy and Social Fabric (New York: Natural Resources Defense Council, 1999).

² Elvidge, C., C. Milesi, J. Dietz, B. Tuttle, P. Sutton, R. Nemani, and J. Vogelmann. 2004. U.S.
Constructed Area Approaches Size of Ohio. Eos: 85(24): 233-240.

For more information on this topic, please see the following references:

Dunnett, N., and K. Kingsbury. 2004. Planting green roofs and living walls. Timber Press,
Portland, Oregon. USA.

Snodgrass, E., and L. Snodgrass. 2006. Green roof plants: a resource and planting guide. Timber Press, Portland, Oregon.

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Glowing, vibrant blooms bring oriental poppies (Papaver orientale) to center stage this time of year. The large (4-6”) flowers have crêpe paper-like petals and are held high above the foliage on strong, yet wiry stems. In a gentle breeze they almost appear to dance. The finely cut foliage makes a great backdrop to the flowers and the abundant, almost downy hairs that cover the foliage and stems set Oriental poppies apart from most other commonly grown poppies.

Native to central Asia where summers are warm and dry, these magnificent poppies have developed a unique adaptation method. When moisture is relatively abundant in spring, leaves emerge and plants quickly come into flower. As temperatures rise and moisture becomes less abundant, the foliage begins to die back and plants go dormant. As temperatures begin to cool in the fall and rains return, new foliage again emerges.

Although Oriental poppies are very cold hardy and survive routinely even into zone 3, care must be given to plant them in well drained soil to ensure survival. Excessive moisture, especially during summer months, can lead to their demise. In addition to having well drained soil, full sun down to half a day of sun is also important for success. In the right location they are very low maintenance. In fact, we can often find huge stands of Oriental poppies doing great on old farmsteads.

The most common flower color for Oriental poppies is orange-scarlet. Extensive breeding and selection in the late 1800’s has led to Oriental poppies that come in white, pink, peach, maroon, or purple. Many Oriental poppies have a black blotch at their base. In some forms this blotch is particularly large and ornamental. Variation is also found across different varieties for petal number as well as petal margin. There are single forms and double forms and forms that have smooth petal margins and some with frilly petal margins. There are both seed propagated varieties on the market and vegetatively propagated cultivars.

Oriental poppies do not transplant well. After suffering root injury from being transplanted, they typically have stunted growth and do not bloom well during the next flowering cycle. Typically after a couple seasons they fully recover. Elite clones are typically vegetatively propagated using root cuttings. In our climate, early spring tends to be the best time to take root cuttings. This can easily be done when moving an existing plant. Often roots left behind will sprout and lead to new plants. Sections of thicker, fleshier roots from a couple to few inches in length work well. Plant the end of the root that was closest to the crown of the parent plant closer to the soil surface, or if you lost track, plant roots horizontally just below the soil surface. When shoots form at the cut end that was closer to the crown of the plant they need to be relatively close to the soil surface to be able to emerge. It takes four to eight weeks typically for new shoots to form and emerge from a root cutting.
It can be challenging to find potted Oriental poppies in the garden center because they do not respond well to typically humid and moist greenhouse production conditions. Fortunately, they can readily be purchased as dormant plants from mail order companies or started from seed.

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There are several caterpillars that have been detected feeding on the leaves of blueberries recently. One species is the copper underwing, Amphipyra pyramidoides. This insect, also known as the pyramidal fruitworm, is bluish green with a thin yellow stripe running the length of its body along its sides and small whitish patches. It also possesses a conspicuous hump on the end of the abdomen and grows to about 1 ½ inches when fully grown. This caterpillar feeds on a wide variety of plants in addition to blueberry, such as trees (e.g. apple, basswood, maple, oak), shrubs (e.g. lilac, viburnum, and rose), and fruit including grape, raspberry, and currant.

You can also find forest tent caterpillars, Malacosoma disstria, in your blueberries. Also referred to as armyworms, these caterpillars are easily identified by their blue and black bodies, the distinctive white footprint shaped spots on their back as well as hairs that stick out along the sides of their body. These caterpillars are about two inches long when fully grown. Despite their name, they do not make conspicuous webs in trees. They commonly feed on many deciduous trees, including aspen, birch, maple, crab apple, apple, ash, oak, and elm.

Another caterpillar feeding on blueberry leaves is the linden looper, Erannis tiliaria. This caterpillar, a type of inchworm, is brown down the top of the body, has a bright yellow stripe along its sides, 10 thin black stripes, and a grayish white underside. A linden looper is over an inch when fully grown. Besides blueberries, it is commonly found on hardwood trees and shrubs, including linden, rose, elm, maple, oak, ash, serviceberry, and cherry.

These caterpillars generally do not occur on large numbers on blueberry but they are capable of minor up to severe defoliation. If management is necessary, handpick and destroy small numbers of caterpillars. If an insecticide is desired, low impact products include Bacillus thuringiensis, insecticidal soap, and spinosad are effective. Other insecticides include permethrin. Be sure that blueberries are listed on the label of any product you wish use on them.

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People have been finding click beetles lately in their yards and around their homes. They are generally between 3/8 - ½ inch long, are dark brown or black with an elongate oval and flattened body. The prothorax, the area behind head, appears ‘loose’ with the rest of the body. The back corners of the prothorax are prolonged back into sharp points.

Click beetles are found commonly on foliage and flowers as well as under bark. They are also attracted to lights. A click beetle is unique because it can right itself when it is on its back. It does this by arching the area between the prothorax and mesothorax (where it looks loose) and then snaps it back, usually producing an audible ‘click’. This action will cause it to jump up, often allowing the insect to regain its feet. If it remains on its back, it will keep trying until it succeeds.

Some residents, upon finding a click beetle, have been concerned that they have discovered an emerald ash borer, especially if they find it on a tree or under bark. Although they are similar shape, emerald ash borers are a shiny iridescent green while click beetles are a dark color. Also emerald ash borers lack the corners of their prothorax being extended back to points like click beetles possess.

Occasionally, click beetles are found inside homes. They are attracted to moisture, e.g. from water and leaves in gutters, and then can enter buildings through available cracks and spaces. It is typical to find them on the ceilings in rooms. Fortunately they are harmless and are short-lived indoors. If you find a click beetle indoors just physically remove it, no other controls are needed. They are not usually not found in homes much past June.

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Happy gardening!

David C. Zlesak, Ph.D.
Editor
Extension Educator