“Go for the Gold!” is a common phrase being told to the incredibly talented athletes heading to Beijing hoping to have their Olympic dreams come true. Although most of us won’t be competing in Beijing, we can bring home ‘the gold’ to brighten up spots in our landscape that beg for some extra excitement and color. Fortunately, these ‘gold medals’ are not in limited supply in garden centers; there are enough for all of us to feel like champions many times over.

Gold-foliaged shrubs can add great excitement and impact to our landscape. As more gold-foliaged variants are discovered and introduced, the choices continue to abound. Generally, the available gold-foliaged shrubs are mutations of shrubs that typically have green foliage. Without the careful propagation and preservation afforded by astute horticulturists, they would typically die out because they are less competitive than the typical green members of their species.

What makes gold-foliaged shrubs gold instead of green? Most gold or yellow-foliaged shrubs have reduced chlorophyll levels. Chlorophyll is the green pigment in plants and some algae that is essential for capturing light energy. Plants with diminished chlorophyll levels have a compromised ability to photosynthesize and generate energy. As a result, they tend to be smaller and slower growing. Periodically, seedlings or sports possess a mutation that results in decreased chlorophyll and golden foliage color. Such plants can be cloned through cuttings or grafting and perpetuated. The mutation may be directly or indirectly affecting chlorophyll. One of the more common mechanisms leading to decreased chlorophyll levels is change leading to a reduction in associated carotenoid pigments. Chlorophyll molecules have a limited lifespan, constantly being generated and dismantled. Carotenoids protect chlorophyll molecules by increasing the duration they are functional. Quicker chlorophyll turnover rates result in less chlorophyll at a given time and lighter green or golden foliage.

No matter the reason why some shrubs appear golden, they can be especially useful in the landscape, adding a bold display of brilliant color and excitement. Astute designers often pair them with plants that have dark green or purple foliage for added contrast and impact. Some gold-foliaged shrubs are more sensitive to burning in full sun than their green counterparts and need to be carefully placed in a protected location. Others do very well in full sun. Here is a partial listing of some proven gold-foliaged favorites plus some exciting recent introductions.

Time tested gold-foliaged staples

Golden-leaved spireas (Spirea japonica and its hybrid S. x bumalda) mature to a golden color and are probably the most common gold-foliaged landscape staples in the nursery trade. The two most popular cultivars are ‘Goldflame’ (S. japonica) and its offspring ‘Goldmound’ (S. x bumalda). ‘Goldmound’ is a more compact grower (~2’ tall) than ‘Goldflame’ (~3’ tall). These spirea produce clusters of small pink bloom on new and old wood on mounded, dense plants. Removal of spent blooms can encourage additional bloom production. They are tolerant of a wide range of soil conditions, but perform best in well-draining soils. They prefer full sun and tolerate light shade. Aggressive spring pruning is useful to help maintain a full, dense plant habit.

Golden-leaved barberries (Berberis thunbergii) are very commonly used gold-foliaged shrubs as well. Like other barberries, they have small thorns and should be placed and handled with care to avoid injury. The old selection B. thunbergii ‘Aurea’ is a faithful performer growing to about 3-4’ in height. The more recent cultivar, Golden Carrousel®, grows to a similar size. Many smaller, very compact cultivars have been introduced and include cultivars like Gold Nugget™ and the especially bright gold selection Bonanza Gold™. Like spirea, barberries are very adaptable which lends to their popularity. They do well in full to part sun and prefer well-draining soil.

Golden-leaved ninebarks (Physocarpus opulifolius) have been very popular over the years serving in the landscape as a larger growing, gold-foliaged shrub. ‘Dart’s Gold’ is the most common cultivar and reaches a height of about 6’. Recent introductions include the more compact selection, ‘Nugget’, selected in South Dakota and the larger growing cultivar, ‘Morning Star’, which has lime-green foliage and grows to about 8’. Compared to the spirea and barberry, most gold-foliaged ninebark tends to be less gold in foliage color, but they do fill a unique niche because of their larger plant size. Careful pruning is often necessary to maintain a full, dense plant habit and compared to some of the other green and purple-leaved ninebark cultivars. Recent research has demonstrated that these three gold-foliaged cultivars are relatively susceptible to powdery mildew compared to other ninebark cultivars with green and purple foliage.

Some recent golden treasures

One of the most popular gold-foliaged shrubs to hit the market in recent years is cutleaf staghorn sumac Tiger Eyes® (Rhus typhina). It is a mutation out of the cutleaf selection ‘Laciniata’ and was discovered as a mutation in a production field at Bailey Nurseries in Minnesota. Tiger Eyes® grows to about 6’ tall and is very versatile. It is being successfully grown in ground beds as well as serving as a very popular focal point in large containers. The golden cutleaf foliage and coarse branching and stem structure make it especially attractive and a unique addition to the landscape. Like other sumac, it is very drought tolerant and easy to grow. It is prone to suckering, especially when the soil around it is disturbed and roots are injured. Young suckers can easily be pulled. It does best in full to part sun.

A new gold-foliaged selection of bridal wreath or Vanhoutte spirea (Spiraea x vanhoutii) has just been introduced in 2008 called Firegold™. Like other bridal wreath spirea, clusters of white blooms are borne in spring on graceful arching canes on plants that reach about 6’ in height. Firegold™ was discovered in Quebec, Canada. Bridal wreath spirea are versatile, small-leaved shrubs providing a fine texture and serving as a nice backdrop in the landscape when not in flower. They are tolerant of different soil types and prefer full to partial sun. Since flowers are produced on old wood, it is important to prune carefully. Best floral displays are achieved when plants are allowed to develop into their natural vase-shaped, arching form instead of being aggressively sheared.

Garden Glow™ dogwood (Cornus hessei; closely associated with C. alba and C. sericea) is a recent release from the University of Minnesota! Relatively large, chartreuse-green leaves add a luxuriant feel to shady and semi-shady locations. The richest foliage color is achieved in bright, dappled shade. Hot, midday sun can cause the foliage to burn and should be avoided. The deeper the shade, the more green the foliage will appear. Plants are extremely cane hardy and stems turn red during winter. Plants typically grow ~5’ tall. Although very landscape worthy, it may be challenging to routinely find in garden centers because burning of foliage in full sun makes it challenging for nurseries to produce using standard, full sun field conditions.

Additional gold-leaved options

There are many other gold-foliaged options to consider as well. The following do well in full sun to partial shade. Golden mockorange (Philadelphus coronarius 'Aureus') is a medium to large shrub (up to ~6’ tall) that has a profusion of single white, fragrant flowers in late spring/early summer. Golden elderberry (Sambucus canadensis 'Aurea') has long, arching canes and plants reach 8-10’ in height. It can make a great informal backdrop in the landscape. Smoketree (Cotinus coggygria) Golden Spirit™ has bright golden foliage. It is typically crown hardy in zone 4 growing each season into a medium-sized shrub ~5’ in height by autumn. ‘Golden Victory’ privet (Ligustrum x vicaryi) makes a dense, shearable shrub that grows 3-6’ in height. Clusters of small white blooms are produced in late spring/early summer. Although listed in many resources as hardy to zone 5, ‘Golden Victory’ privet has overwintered well in many Twin Cities locations in recent years. In addition to deciduous shrubs, many evergreens are available that have golden foliage as well. Among especially junipers are a number of reliable selections with gold new growth including ‘Old Gold’ and ‘Gold Cone’.

As you cheer on your favorite Olympic athletes in the days ahead, consider celebrating the Olympic spirit by bringing home ‘the gold’ to your landscape.

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If you grow vegetables you know how it feels to pick and enjoy that first ripe tomato, green pepper, or cucumber. But after awhile, it’s hard to keep up with all the bounty and the thought of eating one more tomato just makes your tongue hurt. Giving your extra fruits and veggies to the neighbors is a fine idea. But did you know that many food shelves and churches that help people in need will also happily take your produce donations?

Marilyn Terhaar is the food surplus coordinator for the Dowling Community Garden in south Minneapolis (www.dowlingcommunitygarden.org). With more than 200 people tending plots in the 20-acre garden, it seemed like there was always some crop going to waste. So, four years ago, she spearheaded the organization of a system to harvest extra produce and deliver it to food shelves several times each week in early summer, daily by August.

Gardeners put everything they want to give in large coolers kept outside the garden’s communal shed. A calendar posted nearby shows the date of each delivery and the name of the volunteer who will be coordinating the transporation. It’s a successful system. But Terhaar hopes to improve on it in future years by encouraging gardeners to tell their friends when they go on vacation, so their crops can be arranged to be harvested for donation while they’re away.

Meeting a need

Whether you’re an individual or an organization with fresh produce to donate, it’s best to contact the place you’d like to deliver to before you actually arrive. Many places are not adequately equipped to handle perishable items. Terhaar has a list of places she works with regularly, such as Keystone Community Services in St. Paul and Sabathani Community Center and the Aliveness Project in Minneapolis.

In addition to calling ahead, Terhaar sometimes visits, too. “I want to be sure the food will get used,” she explains. “If people cook on site, like the Aliveness Project does, you know it will be used. If not, you need to make sure they can keep the food cool and give it out quickly, hopefully that same day.”

Gardening for all

Pete DeLong is one of the coordinators of the southeast Minneapolis O.W.L.S. Community Garden. The acronym stands for One World of Landscape, a company which formerly occupied the space and whose owner continues to help with the garden.

Just four years old, the garden is small with only about seven regular members. Everyone cares for the garden communally, doing everything from planning what to plant and getting things into the ground to care and harvesting. Produced is shared equally, too, and still there is far more than people can use.

So they’ve identified seniors living in the neighborhood who could use a twice-monthly donation of fresh veggies. “For us,” DeLong says, “it makes our garden not just a personal endeavor. We’re supporting the community as a whole.”

For awhile, DeLong and the other gardeners tried making deliveries themselves. But that wound up being a six-hour weekend commitment between harvesting and driving. Instead, they’ve decided to drop the produce off at nearby Pratt Community Center, which will handle the deliveries from there.

Like Terhaar, DeLong has learned that he needs to call and coordinate before dropping produce off. Last year, after making several calls, he was thrilled when he found a homeless shelter in north Minneapolis that was happy to receive the 30 pounds of green peppers he’d just harvested. He and his fellow gardeners have also set up a free food shelf on a local street near the garden. “We just put out a sign saying the food is free and people take it,” he says. “All we have to give is free vegetables. But the garden is meant to create a sense of belonging.”

Do you and your gardening friends have extra produce that is going to waste? Consider what creative ways you can help share the bounty with those in your community.

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Many commonly used woody ornamentals are plants introduced into the United States from other parts of the world. Unfortunately, some of these plants invade natural areas, displace our native species, and end up on invasive plant lists. Take a look at the Minnesota Department of Natural Resources’ invasive plant list and you will see Amur maple (native to China and Japan), common and glossy buckthorn (both European natives), honeysuckles from Japan and Asia, Japanese barberry, Norway maple and Russian olive (both native to Europe and Asia), and Siberian peashrub from Siberia and Manchuria.

With the increasing concern over exotic invasive plants, there is a renewed interest in the use of native plants in our landscapes. One underused native tree with ornamental value is Ostrya virginiana, often called American hophornbeam or ironwood.

Ironwood, native to the eastern half of the United States, was named for the hard durable quality of its wood. This wood is often used for handles of tools and mallets resulting in another common name for Ostrya virginiana: leverwood. European farmers used relatives of our native ironwood to make oxen yoke and soon two more common names were generated: yoke-elm and hornbeam. The common name hophornbeam comes from the nutlets that are born in clusters of papery sacks resembling the fruit of a hop vine. Perhaps there will be another common name for this beautiful tree in the future; today ironwood logs are used in Minnesota as a growing medium for shitake mushrooms.

Regardless of the name you give it, Ostrya virginiana has several appealing ornamental traits. It is a small- to medium-statured tree, typically 25 - 40 feet tall with a 25 - 30 foot spread to its oval or round canopy. Individual specimens may be single- or multi-stemmed and trunk diameter rarely surpasses 12 inches. The small stature of ironwood makes it a good choice for today’s smaller lots and landscapes. Branches are horizontal or slightly drooping, giving the tree a very graceful-appearing habit.

Ironwood is a member of the birch family and the dark green 2 1/2 - 5 inch doubly serrate leaves are similar to those of yellow birch. In mid-summer, the showy white or ivory fruit appear like pendants on the tree and are a beautiful contrast to the dark green foliage. Fruit are typically 1 1/2 - 3 inches long and 1 - 1 1/2 inches wide. From a distance, you might guess that you are seeing flowers on the ironwood rather than fruit.

Fall color of O. virginiana is yellow to gold, but is not considered effective because of early leaf drop. Ironwood does have winter appeal though. With its horizontal or drooping branches, the plant architecture is graceful and especially attractive on a multi-trunk specimen. The gray brown bark of mature ironwoods tends to split into narrow vertical strips that become somewhat flaky. Often these strips are a bit angled and appear to spiral around the trunk, giving the trunk a very distinctive and textured effect. Additional winter interest is added by the male flowers or catkins that are typically arranged in groups of three at the ends of branches in a pattern similar to a small bird’s foot. These catkins persist through the winter until they expand and bloom in spring.

Ironwood is reliably hardy to Zone 3b and is relatively pest free. In its native habitat ironwood is an understory tree, growing under the canopy of hardwood forests or in the tree line at a forest edge. It is found growing in many soil types, ranging from rich moist woodland soils to dry gravelly soils on slopes and ridges. In horticultural landscapes, ironwood will grow in full sun to full shade and is also tolerant of most soil types with the exception of wet soils. With its ability to grow in shade and its drought tolerance, this might be a plant to try in those difficult-to-plant dry shady sites. Ironwood can be slow to grow immediately after planting, but once established it will grow nicely. A gardener with patience will be rewarded with an attractive tree with multi-season appeal.

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It's gratifying for this old arborist and shade tree pathologist to be able to report that American elm (Ulmus americana) is once again showing up on our pallet of trees to choose from. The quest for dependable resistance/tolerance to Dutch elm disease (DED) in American elm was long and hard, and failure was a repeated occurrence. Even the best pathologists, like the late Dr. Eugene Smalley from the University of Wisconsin, could not identify dependable resistance within the species by selective breeding. Because of complicating genetic obstacles, it is very difficult to cross American elm with any other species of elm.

With the relentless selection pressure exerted by Mother Nature in the continuing epidemic of DED across the natural range of American elm, highly unlikely survivors began to appear. While it is true that the vast hulk of ‘Survivors’ have been just plain lucky and somehow escaped infections, some rarely occurring individuals seem to possess the necessary combination of genetically controlled defense strategies to have a high level of tolerance to the disease. Dr. Alden "Denny" Townsend, a geneticist with the National Arboretum, and collaborating scientists identified three such individuals by employing intensive artificial inoculation tests on some promising clones. When reporting his results, Dr. Townsend suggested that the likelihood of such tolerance in wild American elm was probably less than one in every 100,000 individuals, hence the difficulty in finding them by breeding. Of the three clones Dr. Townsend identified as highly tolerant to DED, 'Princeton' already had a name and an interesting history; its tolerance to DED was a delightful accident. 'Valley Forge' and 'New Harmony' were products of his own research at the National Arboretum. All three are available for propagation without restriction and have begun to show up in Minnesota nurseries and garden centers.

The only personal experience I have (here in Minnesota) is with 'Princeton' and 'Valley Forge.' Both are standard American elms and possess all the characteristics expected for the species. From a structural habit of growth point of view, 'Princeton' is better disciplined and easier to handle in its youth. I got 120 inches of growth out of one individual during the summer of 2006! With aggressive pruning in its formative years, 'Valley Forge' also develops into a very nice, fast growing tree.

A most exciting development I am a part of may be happening right here in Minnesota. There is an individual American elm in Afton, Minnesota that is 75 inches in diameter with a crown spread of 110 feet by 115 feet. It is between 70 and 80 feet tall and has been living in the midst of a crown fire of DED for at least 35 years without exhibiting any evidence that it has ever been infected. When DED started there, American elm was the dominant member of the woody plant community, and a DED conflagration ensued. The species is still an aggressive member of the plant community, and younger, smaller trees continue to become infected and die in the woods all around this tree. The odds of a "lucky escape" for such a large old tree under circumstances like these are incalculably low. Something else is likely at work here.

The tree was named the 'St. Croix' and first clonally propagated in August 2003. Preliminary greenhouse inoculation trials at the University of Minnesota, Department of Plant Pathology were very encouraging. A repeat of Dr. Townsend's field trials, including the 'St. Croix' and a few other clones, will be ready to begin in May 2009. The ongoing research involving ‘St. Croix’ is a collaborative effort between the Departments of Horticultural Science and Plant Pathology at the University of Minnesota and is substantively supported by the Minnesota Turf & Grounds Foundation.

While we must always be careful about becoming too enamored with any given species and never relent in our cultural struggle with DED in our communities, it is exciting that we can once again employ American elm in our landscape plans. The proposition that we may soon have a local provenance disease tolerant cultivar to add to the growing list of resistant clones is especially encouraging. The American elm is still a superlative ornamental shade tree in many circumstances. The more disease tolerant cultivars to choose from the better.

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Increases in heating costs have caused many homeowners and institutions to consider potential heating alternatives. Prior to the dramatic rise in corn prices, shelled corn was a popular biomass product that was burned to generate heat in homes. In addition to generating heat, corn burners will produce ash as a byproduct that will have to be utilized or disposed of. One question frequently asked was whether the ash could be used in gardens as a fertilizer or lime source. Most experience with applying ash to gardens has been with wood ash, which, in general, is known to have a high pH and potassium content. The chemical characteristics of any ash will depend on the material being burned and the burning conditions. Therefore, in order to determine the effects of applying ash to a garden, it needs to be characterized for a) its nutrient content b) its effect on soil pH, and c) the possibility that some elements become concentrated in the ash to levels that are potentially toxic to plants. Not knowing the characteristics of an ash product can lead to potential problems such as salt accumulation and excessive pH. This study describes some of the chemical properties of ash from a corn burner that was installed at the Central Lakes Agricultural Center near Staples. While the current high price of corn may not favor the burning of shelled corn for heat, the purpose of this report is to emphasize the importance of knowing the characteristics of any ash before you apply it to your garden.

Corn ash characterization

Ash samples were collected from a shelled corn fired boiler at the Central Lakes Agricultural Center near Staples on 15 February and 9 April, 2007. Data presented are averages of three sub-samples (replications), except for particle density of the 15 February lot of ash which had only one replication.

The ash was slightly alkaline with an average pH of 7.9 (neutral pH is 7.0). Based on its calcium carbonate equivalent (which is a measure of its liming ability), the ash had very little value as a lime source (Table 1). In contrast, the ash from burning bark and wood chips shown for comparison has a very high pH of 12.9 and a calcium carbonate equivalent of 35.7%, so if used in high amounts this ash will increase soil pH. Electrical conductivity or salt content averaged 30 mmhos/cm, which is twice the salt content of the bark/chip ash. Salinity in the corn ash was high compared to normal soil levels. Therefore, excessive applications can result in accumulation of salts in the soil. However, compared to typical fertilizer rates to supply normal amounts of plant nutrients, the salinity levels should be comparable.

Table 1. Chemical and physical properties of the ash generated by burning corn grain and comparison with ash from burning bark and wood chips.
Property	Unit	Corn grain ash	Bark & chip ash1
		average	singlesample
pH	--	7.9	12.9
EC2	mmhos/cm	29.8	14.1
CCE3	%	< 0.5	35.7
Particle density	g/cc	0.31	--
1Data from Huang et al., 1992.
2Electrical conductivity – a measure of soluble salts.
3Calcium carbonate equivalent – pure calcium carbonate has a liming capacity of 100%.

The amount of nitrogen (N) in corn ash is low, but the ash could be used to supply crops with phosphorus (P), potassium (K), and magnesium (Mg) (Table 2). The average corn ash content would be equivalent to a 1.6-21.1-13.7-4.3 fertilizer (percent by weight of N-P2O5-K2O-Mg). It is a richer source of all these nutrients than bark/chip ash. The calcium (Ca) and sulfur (S) contents of corn ash are low, but it would also supply small amounts of the plant micronutrients boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn). It is lower in Ca, S, and micronutrients than bark/chip ash. The corn ash was highly enriched with the nickel (Ni) and chromium (Cr), possibly due to contamination by the materials used to construct the boiler.

Table 2. Average elemental content of the ash generated by burning corn grain and comparison with ash from burning bark and wood chips. Dry weight basis.
Element	Unit	Corn grain ash	Bark & chip ash1
		average	singlesample
C	%	39.4	--
N	%	1.60	0.9
C:N	--	24.5	--
P	%	9.21	0.69
K	%	11.4	2.9
Ca	%	0.131	10.1
Mg	%	4.30	1.62
Mg	%	4.30	1.62
S	%	0.189	0.68
Cl	%	0.113	--
Al	ppm	77.0	13000
B	ppm	41.0	127
Ba	ppm	4.50	--
Be	ppm	<0.02	--
Cd	ppm	<0.22	3
Co	ppm	1.35	4
Cr	ppm	514	14
Cu	ppm	38.2	78
Fe	ppm	1112	3300
Li	ppm	0.337	--
Mn	ppm	195	3500
Mo	ppm	6.31	--
Na	ppm	23.7	0.16
Ni	ppm	517	12
Pb	ppm	<3.52	66
Rb	ppm	23.3	--
Si	ppm	77.1	--
Sr	ppm	2.68	--
Ti	ppm	3.22	--
V	ppm	<0.32	--
Zn	ppm	504	794
1Data from Huang et al., 1992.

The average Ni concentration of 517 ppm exceeds the EPA ceiling concentration limit of 420 ppm for land application of biosolids, so under this regulation the corn ash could not be applied to agricultural land and should not be used in vegetable or fruit gardens.

Summary and recommendations

The residual ash from burning corn grain as an energy source contains high levels of plant nutrients. It contains about 21% phosphate, 14% potash, 4% Mg, and small amounts of a number of micronutrients. The excessive levels of Ni and Cr in the ash studied were likely due contamination from the corn burner itself. It is not known if these levels in the ash will decrease over time with use of the burner. The corn ash studied had lower pH and minimal liming potential compared with wood ash. However, the salt content as well as P and K content were higher in corn ash than wood ash. Rates of corn ash application should be based on its phosphate and potash content. Based on the analysis from this study, an application of 1 to 2 lbs of corn ash per 100 square feet would provide all the P and K needed in most garden beds. Because of the high P content of corn ash, it should not be used on turf unless a soil test indicates a need for P. It would be useful to examine the ash from other situations where corn grain was used as the fuel source to see if the ash described in this study is typical or atypical of the ash derived from burning corn grain.

Reference:
Huang, H., A.G. Campbell, R. Folk, and R.L. Mahler. 1992. Wood ash as a sooil additive and liming agent for wheat: Field studies. Communications in Soil Science and Plant Analysis. 23:25-33.

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Continue to prune side stems off of indeterminate tomatoes to encourage light to penetrate the canopy and reach the fruit that is already developing. This is especially helpful for the larger fruited, later maturing varieties. Continue to supply a consistent supply of water to tomatoes as this will help prevent cracking of fruit (common after a period of drought followed by a heavy rain) and assist calcium movement in the plant and prevent blossom end rot.

Consider planting a new crop of fast maturing vegetables such as leaf lettuce, radishes, spinach and even bush beans. Many garden centers have their remaining seeds on clearance. If you cannot find seeds in your local garden center, consider mail order companies that specialize in vegetable seeds.

Deadheading annuals will help to encourage additional flowering into autumn. In addition, deadheading will remove unwanted seed and save time in the future weeding unwanted plants.

August is the height of the growing season. Enjoy the beauty and bounty of summer!

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Happy gardening!

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