Yard & Garden Line News
Volume 7 Number 1                                                               January 1, 2005
Features this issue:

Arboretum's New Visitor Center Opens in January
Salt Damage
Add a Bromeliad to your Houseplant Collection
Fungus Gnats in Homes
Editorial Notes

Arboretum's New Visitor Center Opens in January
Peter Olin, Director, Minnesota Landscape Arboretum

Roof trusses in
Great Hall.
New addition.
Photo Credits: Arboretum
On January 25, 2005 the Minnesota Landscape Arboretum will open its new 45,000 square-foot Visitor Center, which will serve as the formal entry point to the Arboretum's 1,040 acres of gardens, plant collections and natural areas. Connected to the historic Snyder Building by an enclosed skyway, the Visitor Center will provide expanded meeting and conference spaces, and will help accommodate the Arboretum's 270,000 annual visitors and 18,000 plus members.

As a centerpiece of this new facility, the soaring Great Hall will feature a web-based touch-screen information and way-finding center, a new reception desk that will incorporate the new Yard and Garden Desk, changing displays, and interactive exhibits.

The new Yard and Garden Desk augments the Yard and Garden Line with year 'round telephone service 9 a.m. - 12 Noon, Monday through Friday. Voice messages can be left and will be returned as with the present system. All phone calls will be free of charge at least for the present. A 'Walk-In Clinic' will also be available to Arboretum visitors on weekends (free for Arboretum members; $5/sample for non-members), with expanded hours during the growing season.

The Visitor Center also includes a new auditorium, which may be divided into four separate spaces for up to 375 people, two high-tech classrooms, a teaching garden and display gallery. A new cafeteria-style restaurant features views of Lake Minnewashta and one of six new terrace gardens surrounding the center. An expanded gift store will offer visitors more choices of northern-hardy gardening books, arboretum apparel, and gifts-along with a new 'Kids' Corner' that will give parents a chance to browse.

The existing Snyder Building will continue to house an expanded Andersen Horticultural Library, offices, classrooms, auditorium, fireplace room, small conservatory, and a new volunteer center, where volunteers can meet and sign up for new projects.


Come see the 36,000 spring bulbs!
Photo credit: Don Breneman
Together, the two buildings will provide up to 10 meeting spaces to accommodate an increasing number of conferences, retreats and classes-as well as weddings, bridal showers and reunions. On-site catering services and an expanded menu will also be available.

Over the past twenty years the Arboretum has grown significantly. Additional land has been acquired to protect its watershed and the Arboretum is actively pursuing purchase of the remaining watershed. The establishment of parking lot water runoff models, rain gardens, a restored wetland, and several new gardens have added to the beauty, research capacity, and learning models already established.

Please come to see the new Visitor Center through February 27, when we present our first indoor exhibit in the Great Hall - a 'live' magical miniature landscape - or early May when 36,000 bulbs come into bloom around the new Visitor Center and our next big exhibition, "Wild About Birds" is unveiled.

Salt Damage
Janna Beckerman, Extension Plant Pathologist


Salt damage on 
roadside pines. Photo credit: Plant Disease Clinic
Minnesota winters provide very little disease excitement for plant pathologists. Yes, there is the occasional ice storm, with broken limbs and branches, but for the most part, winter serves to numb our brains, and forget the problems that are developing while plants are "sleeping." One such problem is salt damage.

Most people only think of salt damage and how it affects their cars. Very few people think about salt at all, unless they've landed on their backside and wonder where the salt is! Although no estimates exist as to how much salt is placed on sidewalks (or not), in Minnesota, 200,000 -300,000 tons of de-icing salt are applied to roads each winter.

What is salt?

Salt is composed of sodium (Na) and chloride (Cl), chemically depicted as NaCl. Salt occurs in a variety forms, including the mineral halite, which is mined and used in rock salt. Sodium chloride is sold in several different particle sizes depending on its intended use. Rock salt consists of discrete crystals, where fine granules make up the typical of table salt and even finer popcorn salt. Kosher salt exists as coarser flakes, and compressed pellets are used in water softeners. Although often consisting of both salt and sand, the salt used on roads consists of mostly (98.5 percent) sodium chloride with traces of other mineral salts.

How does Salt Damage Plants?

Salt becomes toxic to plants when it dissolves in water, and the sodium and chloride ions separate. Sodium ions in the salt replace the needed nutrients phosphorus and potassium in the soil, making them unavailable to the plant. Have you ever tried to get table salt out of a wet shaker? Then you know salt absorbs water. Rock salt does the exact thing in the soil, absorbing the water that would normally be available to roots, causing root dehydration, changing root physiology, and causing additional plant stress. Meanwhile, chloride ions are absorbed by the roots, transported to the leaves, and accumulate there interfering with photosynthesis by impacting chlorophyll production.

Salt doesn't only affect the roots: When sprayed onto plants by passing vehicles, salt damages plant cells, including buds and small twigs, thereby reducing cold hardiness and leaving tissue more susceptible to freezing damage.

How to Diagnose Salt Damage

In examining plants to determine if salt is playing role in the observed damage, be sure to note which side of the plant has more severe symptoms. Damage should be more severe on side facing the road, with the plants closest to the road most severely affected. Usually, evergreen damage appears in late winter, with needle browning beginning at the tip. Keep in mind that snow covered branches will be less affected than those exposed to salt spray, and that as you move above the spray zone symptoms should abate.


Witch's brooming on dogwood caused by salt. Photo credit: Chad Behrendt
It is more difficult to diagnose spray damage on deciduous plants. Usually, leaf buds facing the road are killed or are very slow to break. Flower buds facing the road often fail, but the unaffected side of the tree or shrub flowers normally. Repeated damage by salt may result in witches brooms, or a tufted appearance.

How to Prevent Salt Damage

The easiest way to prevent salt damage is to avoid de-icing salts and use coarse sand to provide traction and make sidewalks and driveways less slick. If you must use salt, use it judiciously, and erect barriers with plastic fencing, burlap or snow fencing to protect sensitive plants and minimize contact with salt. When possible, use de-icing agents with calcium chloride, or calcium magnesium acetate (CMA), a salt-free melting agent made from limestone and acetic acid.

If an area is heavily salted, consider planting salt-tolerant plants like the ginkgo (Ginkgo biloba), winged euonymus (Euonymus alatus), or Japanese tree lilac (Syringa reticulata). Rugosa roses (Rosa rugosa) can take salt as well as the strongest margarita, and can be seen growing next to the Atlantic ocean. As an added bonus, numerous cultivars exist, with an array of color and fragrance. Perennials like Statice (Limonium spp), sea thrift (Armeria maritima ) and reed grass Calmagrostis acutifolia 'Karl Foerster' are often listed as salt tolerant. Although salt damage may not always be as manageable as you'd like, there's no reason for it to raise your blood pressure!
Please check out the new diagnostics web pages at
http://www.extension.umn.edu/projects/yardandgarden/diagnostics/


Add a Bromeliad to your Houseplant Collection
Deborah Brown, Extension Horticulturist


Photo credit:
Kent's Bromeliad Nursery, Vista, Ca.
January is a great time to treat yourself to a new houseplant or two. Flowering plants are particularly nice because they add color at a time we really need it. But if you're looking for something a bit out of the ordinary, how about a bromeliad? Think of bromeliads as a sort of cross between a foliage plant and flowering plant. Grown for their unusual flowers, they also have attractive glossy or patterned strap-like leaves.

Though very popular in Europe, many plant-lovers feel these tropical members of the pineapple family have never received the attention they deserve here in the US. It's hard to say why, though. Bromeliads are attractive, easy to care for, and relatively pest-free. Their flowers last for months on end and most have modest light requirements. Plus, they're compact and slow-growing so you needn't worry that they'll outgrow their location – or their container.

Soil dwellers versus tree dwellers

There are two major categories of bromeliads, based on where they're found in their native habitat. "Terrestrials," grow directly in the ground, no different from most plants. Pineapples (Ananus comosus) and earth stars (Cryptanthus bivittatus) are examples of terrestrial bromeliads. Cultivated as houseplants, they perform best in bright sunlight, with warm temperatures that fall no lower than 60 degrees at night. (All bromeliads like warmth, but few need as much light as these two.)

Variegated pineapple
Photo credit:
Deb Brown Vista, Ca.
Most bromeliads commonly sold for use indoors, however, are more interesting than the terrestrials. They're tree dwellers in nature, perching on branches, hanging on by means of roots that cling to the bark. Though they wrap their roots around the trees for support, these epiphytic bromeliads don't use their roots to "steal" nourishment the way parasitic plants do. Instead, most trap rainfall, insects, and plant debris in a "vase" or reservoir created by their rosette of overlapping leathery leaves. Any organic matter trapped in the water-filled reservoir gradually decomposes, providing nutrients that are directly absorbed by the leaves.

Epiphytic bromeliads often have minuscule scales on their leaves as well, enabling them to absorb moisture – not only from rainfall, but from fog and high humidity present in tropical air.

Growing them indoors

We lack the humidity and bountiful insect life that could keep epiphytic bromeliads growing as they do in nature. We can give them what they need to thrive, though. They're accustomed to only moderately bright light levels because the light they receive in the wild is often filtered through other branches higher in the tree. That means an east facing window should provide adequate light.

Proper watering will go a long way towards offsetting our dry indoor atmosphere. The soil should stay slightly moist at all times, but it's not necessary to water it directly. Instead, pour room temperature water into the plant's reservoir, letting it overflow to the soil. You'll refresh the contents of the reservoir each time you water, preventing it from becoming stagnant. Choose a porous potting soil that allows water to run right through it, rather than something spongy that holds a lot of moisture.


Bromeliad growing
outdoors in Florida. Photo credit:
Deb Brown
Bromeliads don't need a lot of nutrients. Feed the plant by adding a little dilute liquid fertilizer (½ strength or less) to water to the soil. Once a month in spring and summer should be fine if the plant receives good light; less is needed if light levels are minimal.

Flowering

Bromeliads' flower stems or spikes typically originate from within the reservoir. The flowers, and sometimes the bracts from which they arise, are often exotic looking and brilliantly colored. Some flowers develop right in the water, or barely poking out of it. In those cases, the leaves surrounding the vase often take on a brilliant color, as if to make up for the less visible blooms. (This probably attracts pollinators to the flowers, in their natural habitat.)

Bromeliads are shipped to garden centers and sold already in bloom. If possible, pick plants with flowers that are still developing rather than fully expanded. They'll last longer once you get them home. After the blooms fade, some – though not all – bromeliads may die, but by then they will have produced "pups" or offshoots from the base. These offshoots may be potted up and brought into bloom, given good growing conditions and ample time to mature.

When offshoots seem large enough, yet still don't bloom, you can trigger flowering yourself by exposing the base of the water-holding reservoir to ethylene gas. It's really quite simple. Spill out the water, place a ripe apple on the soil surface, then put the entire container – plant, apple, and all – into a clear plastic bag. Keep the bag sealed for one week. The apple naturally gives off ethylene gas which will be trapped in the bag. Your plant should bloom in about two months.

If you see no results, try it again. If the plant is in good condition, it should bloom eventually.

Fungus Gnats in Homes
Jeffrey Hahn, Assist. Extension Entomologist

Photo credit: Mike McDonough
The darkwinged fungus gnat (family Sciaridae) is a common indoor fly. Usually referred to simply as fungus gnat, this mosquito-like insect is a very small, about 1/16th inch long, slender dark-colored fly with very long legs. If you examine a specimen with a dissecting microscope, look for the tuning fork-like veins in the wing which help identify it. Adult fungus gnats are weak fliers and are usually found fairly close to where the larvae are developing.

A larva is a very small worm-like insect, growing no more than 1/4 inch long. It is a pale white almost translucent color. It has a black head but has no legs or other appendages. These larvae live in very damp conditions where they feed on decaying plant material, moist organic matter, and fungi.

When you find fungus gnats in homes or other buildings they are nearly always associated with houseplants, particularly overwatered ones, where they feed primarily on decaying or damaged roots. They are also commonly found in houseplants growing in potting soil high in organic matter such as peat.

Fungus gnats rarely feed on healthy roots. They do not typically injure houseplants and are considered to be only nuisances. These flies are known to vector some plant diseases, such as Pythium aphanidermatum, the organism that causes damping off. This is typically a problem for commercial greenhouses, although homeowners who grow bedding plants could also have issues.

In rare situations, fungus gnats may develop inside the walls of buildings where the moisture is high enough to allow fungus to grow. This is most likely in new construction where the green wood still possesses a high amount of moisture. As the wood dries, the fungus gnats go away on their own.

In two recent cases, homeowners complained about fly problems. In neither situation could they tell where the flies were coming from. One homeowner described flies buzzing around several rooms and flying into their faces, giving the impression that the flies were attacking them. A sample revealed the flies to be fungus gnats. Despite their description, fungus gnats do not attack people. When asked, the homeowner did say they had houseplants in their home giving them the likely source of the problem.

Photo credit: U of M Entomology Dept.
The other homeowner was finding a fairly large number of flies around a sliding glass door. It was difficult to identify the flies over the phone. They sounded like they may be moth flies, which would suggest a drain or a broken sewer line as the source. The homeowner believed the flies were coming from the outside (this was in November). A sample was requested and it contained fungus gnats. It is common for fungus gnats to be found around windows, but that was not the source of the problem as the homeowner believed. The homeowner was directed to look at her houseplants to discover the source of the flies.

The first step to control fungus gnats is to reduce the soil moisture. Change your watering schedule so plants receive sufficient moisture but the soil surface is allowed to dry. However, do not allow plants to wilt. You can tell when your plant needs more moisture by picking it up and feeling how heavy it is. With a little practice you can get a sense of the weight of the plant when it needs water. Also, watch the color of the leaves. When most plants are ready to be watered, they foliage will be a bit dull and less lively.

The only effective product for treating fungus gnat larvae in the soil is a bacterial insecticide, Bacillus thuringiensis var. israelensis, (e.g. Knock-Out Gnats). Also known as B.t. H-14, this insecticide is specific to fly larvae. However this product does not kill adult fungus gnats. Look for this insecticide in garden centers or mail order it from companies, such as Gardens Alive, http://www.gardensalive.com/.

You can place yellow sticky cards in the pots. This can help tell you which plants are infested with fungus gnats. These sticky cards can also help reduce the number of adults. You can not completely eliminate a problem just with these traps.

There are insecticides that are effective against adult fungus gnats, such as pyrethrins. However, they are only a short-term solution. As long as there is a favorable site for the fungus gnat larvae to develop, adult flies will continue to be present despite treating the adults repeatedly.

A home remedy that is sometimes suggested is placing a layer of sand, usually about an inch, on top of the soil. The idea is that larvae will not travel further than an inch into the soil and will not survive in the sand. It has also been suggested that an adult fungus gnat will be confused by the sand and think that the soil is too dry for her to lay eggs. While this sounds good in theory, it probably is not an effective method. Interestingly, there has not been any research conducted to prove this one way or another. However, there are no professional flower growers that use this method, nor is this a standard University recommendation. It would seem unlikely that so few people would use this method if it really was effective.

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm


Editorial Notes

Sea buckthorn. Photo credit:
Beth Jarvis
Many of us are thinking about next year's gardens. Sea buckthorn, Hippophae rhamnoides, is a plant I've been mildly interested in for some time. It's a relative of Russian olive, NOT related to the weedy buckthorn shrub and hardy to zone 3. It has few insect/disease problems. The fruit is edible and contains more vitamin C than oranges plus a host of other good things. In fact, it's of interest to scientists as a nutriceutical (food medicine). Unfortunately, the plants get 20' tall, have thorns and may be short lived. The one at left wasn't 20' tall but about a year after I took the photo, it was yanked out and replaced with the Ecology building on the St. Paul campus.

A 15-20' shrub is too large for my landscape. Male and female plants are needed to get fruit so that would mean two shrubs with a 10' spread, so I will remain sea buckthornless. (There is a dwarf cultivar but it's male only.) However, if you have lots of space, it might work for you so here are some references:

http://www.hort.purdue.edu/newcrop/proceedings1999/v4-335.html
http://www.msue.msu.edu/msue/imp/modzz/00001985.html
http://www.ag.ndsu.nodak.edu/aginfo/trees/handbook/th-3-47.pdf

Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.

Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/. Our home page has clickable links to the components of the Yard & Garden Line, such as Bell Museum of Natural History, INFO U and the Soil Testing Lab. There are new links to the Insect Journal, Plant Disease Diagnostics, Disease Watch and now the Urban Forestry Resources clinic.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. The program is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations. (Scroll down for map.)

For plant and insect questions, visit http://www.extension.umn.edu/askmg. Thousands of questions have been answered, so try the search option in the black bar at the top left of the board for the fastest answer.

If you would like to receive an e-mail reminder when the next issue of the Yard & Garden Line News is posted to the web, just send an e-mail to: listserv@lists.umn.edu (note: the second E in listserve is omitted), leave the subject line blank, then in the body of the message, type: sub yglnewslist or to unsubscribe, enter: unsub yglnewslist

Happy gardening!

Beth Jarvis
Yard & Garden Line Project Coordinator


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