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Extension > Yard and Garden News > Archives > April 2014 Archives

April 2014 Archives

Ignore ash flower galls

Jeffrey Hahn, Extension Entomologist

Jeffrey Hahn, University of Minnesota

Photo 1: Ash flower gall during early spring

At this time of year, ash flower is gall particularly conspicuous.  They are black or dark brown growths found on the branches of green ash.  Because of its unsightly appearance, some people assume that it also damages trees.  The good news is that does not affect the health of ash.  Research conducted at the University of Minnesota in the 1980's showed that the presence of galls did not impact tree health. 

Control of ash flower galls is not necessary.  It is also very difficult to obtain good management of these mites.  If treatment is attempted, try an application of dormant oil when the mites become active in spring prior to bud break (which will occur soon), although this will only be partially effective.  Ultimately the best bet is to just ignore ash flower galls.  Ash has much bigger problems with emerald ash borer being present and should be considered a low maintenance tree.

M. Grabowski, UMN Extension

Photo 1: Pagoda dogwood only partially leafed out. Dead branches were killed by golden canker.

M. Grabowski, UMN Extension Educator


Golden Canker, caused by the fungus Cryptodiaporthe corni, can easily be seen on the branches of Pagoda dogwood trees (Cornus alternifolia) this time of year. Infected branches and stems turn bright yellow with raised orange blister like spots. This diseased plant tissue clearly contrasts with the purplish green bark of a healthy Pagoda dogwood. Unfortunately branches infected with golden canker are unlikely to leaf out. The disease can continue to spread through infected branches and even into main stems. It can kill all above ground parts of the tree but will not kill the roots.

M. Grabowski, UMN Extension

Photo 2: Orange bark killed by golden canker contrasts sharply to healthy reddish purple bark.


The best time to prune out branches infected with golden canker is in March or February when fungal spores are less likely to be present to infect pruning cuts. If cold weather and deep snow prevented this from happening on time, however, branches can be pruned out on dry day. Make the pruning cut at least two buds below the visible discoloration of the bark. Be aware that in some case a canker spreads irregularly and discoloration may extend several inches longer on one side of the branch than on the other. Remove infected branches from the area. They can be burned, buried or taken to a municipal compost facility.

Black Leg of Geranium

M. Grabowski, UMN Extension Educator

M. Grabowski

Photo 1: Black leg of Geranium caused by Pythium spp.

Black leg is a stem infection of Geraniums (Pelargonium spp.) that results in a distinctive black discoloration of stems. As infected stems rot, they become soft and often bend over. This disease is caused by several species of the water mold Pythium. Pythium spp. are soil dwelling organisms that thrive in wet conditions and can survive in infected plant debris and soil. Black leg symptoms often start at the soil line and move up the plant.

To avoid black leg, inspect all geraniums prior to purchase and select only healthy symptom free plants. If repotting geraniums, use new clean potting mix and new pots or pots that have been cleaned with a solution of 10% household bleach. Take care to keep tools, watering cans, and hose heads off the floor and away from dirt and plant debris. Pythium spp. can be introduced into clean potted plants by tools that have contacted contaminated dirt or plant debris. Do not over water plants.

If plants do become infected, they will not recover. Discard the plant and the potting mix. Clean the pot with a solution of 10% household bleach before reusing it.

P1220417.JPGLandscape design is always a popular subject and smart gardeners think "sustainability" when they plan a landscape project. People are eager to try new things in their gardens. Likewise, our season is so short, we have an inherent need at this time of year to get our hands dirty!

Jim Calkins and I are teaching two sessions (May, June) of our landscape design short workshop this spring through the LearningLife program here at the University of Minnesota College of Continuing Education. These are designed for home gardeners who want some good basic fundamentals on sustainable landscape design that they can apply in their own yards and gardens. These are intensive classes and are by no means meant to replace the huge benefits of securing the services and talents of a professional designer. What we have found is that after taking our workshops, people stop making - like choosing an 10x10 ft shrub for a 5x5 ft area or thinking they need to keep trying to grow turfgrass in a narrow shady side strip along their house.

Hope you can join us at one of our upcoming sessions! They are lots of fun and loaded with information. Visit the link below for more information:  U of Minnesota College of Continuing Education LearningLife Program.

Saturday mornings are a good time to grab a cup of coffee, tune tWCCO.jpghe radio to WCCO 830AM, and listen U of M Extension answer listeners' questions about everything from aphids to zinnias, from grapes to grasshoppers. Heck, we just like talking about Minnesota gardening!

Saturdays, 8-9am on WCCO radio, 830 on the AM dial. year-round
Host: Denny Long
U of M Extension Smart Garden team: Julie Weisenhorn, Sam Bauer, Mary Meyer
Extension Master Gardener volunteers: Theresa Rooney (Hennepin County), Darren Lochner (Hennepin County)
Listen for special guests like Jeff Hahn, John Loegering, Karl Foord ....!
Podcasts of previous shows here: WCCO Smart Gardens

Wasp queens active now

Jeffrey Hahn, Extension Entomologist

Jeff Hahn, University of Minnesota

Photo 1: Yellowjacket queens are occasionally found indoors during early spring

Now that spring has finally arrived, much to our relief, we may need to deal with insects that have been overwintering within our homes. This includes yellowjackets (Vespula spp. and Paravespula spp.) and paper wasps (Polistes spp.). Once freezing temperatures arrived last fall, the old queen and all the workers in nests died. The only survivors were the queens that were produced during late summer.

After these new queens mated, they left their nests and started looking for sheltered, protected sites to spend the winter, much like boxelder bugs or lady beetles. These sites include firewood, loose bark on trees and logs, brick piles, under leaves, as well as in and around buildings. The wasp queens remain inactive until it starts to warm up during late winter and early spring. When queens overwinter in homes, they can also become active when mild temperatures occur during mid-winter.

Jeff Hahn, University of Minnesota

Photo 2: Many paper wasp queen can sometimes be found in homes during early spring

Once active, wasp queens leave their overwintering sites and start to look for an appropriate place to begin a new nest. If they are in buildings, they usually become trapped. Finding wasp queens in homes and other buildings during early spring does not mean a nest is present. While only one or two yellowjacket queens at normally seen at a time, it is possible to see a larger number of paper wasp queens as they like to overwinter gregariously, i.e. in non-social groups.

Physical removal is the only necessary control for wasp queens found indoors. They are just a nuisance and do not indicate a bigger problem. Use a jar or some sort of container to remove and release them outside. If they are by a window or door, just open it up and let them fly out. Killing and removing queens is also an option. This is a temporary problem that will go away on its own.


Starting seeds = Spring

Tomato seedlings 041414.jpg

Planting seeds is a sure sign of Spring. Luckily here in Horticultural Science, there is no lack of seed starting happening. My Master Gardener friends, who work on campus, and I started seeds for the 2014 annual seed trials in the greenhouses. The trials are in their 32nd year (I think) and this year, over 100 people are participating by planting and growing out the seeds in their home garden, school gardens, community gardens, and demonstration gardens. On campus, our seed trials can be found in the Department's Display and Trial Garden located at the corner of Gortner and Folwell Avenues on the U of MN St. Paul campus. Trials this year include six herbs for tea, and six varieties of container tomatoes, bull horn peppers, spinach, yellow squash, carrots, shasta daisy, and alyssum. Seed trial results are published each year in the spring issue of Northern Gardener magazine.

I also started some seeds for the Gopher Adventures garden. GA is a day camp for kids here at the U. Kids ages 5-13 can choose to do all sorts of activities at the U from computers to rock climbing to art and dance to - yep - gardening. Master Gardeners and I plant a children's garden on the west end of the display garden. Edible plants, flowers, trees, monarch way station, plants for pollinators - even a miniature garden called "Little Goldy's Garden" complete with a very small golden gopher (it's a magnet on a stick). Last year we had straw bale gardens and pallet gardens. The seeds I started for GA are in my office on a heat mat under a grow light. I used a tray with fifty Earth plugs from Seeds of Change. I used my own seeds from home and planted a couple kinds of peppers, nasturtiums, Salvia, Echnicaea, basil, teddy bear sunflowers, and even a mystery seed that will hopefully emerge (and I can identify). This year, we'll be planting Smart Snacks - an Arboretum educational program about plants that are good snacks for people and pollinators.

Seeds are amazing. Everything needed to grow a plant (water and soil not withstanding) are encapsulated in a seed. Everyone should plant a few seeds and feel a little amazed at the result!


Surprise! It's snow mold!

Michelle Grabowski, UMN Extension Educator

M. Grabowski

Many Minnesotans have anxiously awaited snow melt this spring. The joy of seeing green grass again may be coupled with the disappointment of snow mold. Lawns affected by snow mold have round to irregular patches of matted down tan to gray turf grass. If a light drizzly rain is present or humidity is high at low temperatures, cobweb like fungal mycelia may be seen growing across the infected turf grass.

This winter's heavy wet snow layer has provided ideal conditions for the fungal pathogens that cause snow mold. These fungi thrive at temperatures just around freezing. Persistent snow or cool rainy weather provides the humidity and temperatures needed by the fungi to thrive.



M. Grabowski


Photo 2: Fluffy fungal growth on a snow mold patch on a cool rainy day


In spring the best management strategies for dealing with snow mold of a home lawn include removing heavy snow from valuable turf areas, raking up matted down turf grass to improve air circulation and drying of infected patches, and removing any leaf litter or other plant debris that may have accumulated on the lawn. Sunny weather and warming temperatures will favor growth of the turf grass and most lawns recover. In severe cases, the center of the snow mold patch may need to be reseeded.

P1230029.JPGIn 2013, our Legislature directed the Minnesota Department of Agriculture to develop BMPS - "best management practices" - for protecting insect pollinators - bees, moths, wasps, butterflies, etc. The MDA has published the Pollinator Report: Pollinator Bank, Habitat Protection and Pesticide Special Review. I am still reading it. Thought you all might like to as well.

As noted in the Executive Summary (pg. 4), the objectives of the report are: "(i) provide interpretations of the term 'pollinator bank' and propose feasibility, constraints, and uncertainties of the various interpretations; (ii) delineate past, present, and future efforts by MDA, DNR, UMN, MPCA, BWSR and MnDOT to create and enhance insect (native and commercial) pollinator nesting and foraging habitat, as well as to establish and protect pollinator reserves or refuge areas by using Best Management Practices (BMPs); (iii) discuss efforts and progress on developing BMPs to establish, enhance, protect, and restore pollinator habitat that will ultimately be incorporated into pesticide applicator and inspector training; (iv) outline the process and criteria of a special review of neonicotinoid insecticides, and provide a status update on the process, criteria, and progress of the special review of neonicotinoid pesticides registered by the Commissioner for use in this state currently and in the future."

Feel free to pass it on!

April 2nd 2014 Issue

Had enough of the Snow?

Karl Foord, Extension Educator - Horticulture

Karl Foord

Photo 1: No snow

Karl Foord

Photo 2: Snow stopped

Karl Foord

Photo 3: Snow slowed

Last Thursday March 27, 2014 I watched the largest snowflakes I had ever seen come drifting down onto our Minnesota landscapes. Did you find yourself in this type of show shower?

Snowflakes are composed of 6 sided snow crystals. When the temperature in the troposphere (the lowest layer of earth's atmosphere) is significantly below freezing, the snowflakes created under these conditions are small and termed dry snow. When the temperature in the troposphere is close to freezing, the snowflakes melt enough to create a water film enabling flakes to stick together.

Other sources have reported the Guinness Book of World Records to have the largest reported snowflake ever at 15 in. wide by 8 in. thick. This observation was made by a rancher in Fort Keogh, Montana on January 28, 1887. I tried to confirm this on the Guinness website but a search under snowflake returned zero results. However in the letters to the editor section of the periodical Nature from 1887 (vol. 35,p. 271) snowflakes up to 4 inches across were observed on January 7, 1887. This was done by catching the flakes on circular glass plates chilled for the purpose. These large flakes only fell over a 3 minute period.

Another way to measure these flakes with some form of accuracy is to create a grid on a dark piece of paper. If the grid is made up of 1 cm squares then a reference exists to reference the size when the flake falls on the paper. One would need more than an 8.5 x 11 sheet of paper to catch a Guinness record. I attempted to photograph this event. Photo 1 shows the view without snow. Photo 2 shows the view with snow, and photo 3 shows the snow captured at a shutter speed of 1/30 of a second so the length of the streaks shows you how far the snow moved in that time period. Photo 2 was taken at 1/640 of a second.

Granted this is not exactly horticulture, but I thought this might be a good if not whimsical way to usher out this year's snow as we anxiously await spring.

Karl Foord, Extension Educator - Horticulture

Karl Foord

Photo 1: Buds of Austrian Pine (Pinus nigra)

Karl Foord

Exhibit 2: Healthy buds of Swiss Stone Pine (Pinus cembra)

Karl Foord

Exhibit 3: Dead buds of Swiss Stone Pine (Pinus cembra)

Karl Foord

Exhibit 4: Buds of Korean Fir (Abies koreana)

Kathy in her article on winter burn states the following:

Wait until spring before deciding how to care for your winter burned plants. If leaves are dead but buds and stem tissue near dead foliage are still alive, new plant foliage will regrow to replace winter burned foliage.

I had significant winter burn damage on the following: all hemlocks (Tsuga canadensis), Austrian pine (Pinus nigra), and Scots pine (Pinus sylvestris), Swiss stone pine (Pinus cembra), and Korean fir (Abies koreana). I had little or no damage on the following: Mugo pine (Pinus mugo), Japanese white pine (Pinus parviflora, Glauca group), Limber pine (Pinus flexilis), Taylor's Sunburst (Pinus contorta), and Uncle Fogy pine (Pinus banksiana).

Following Kathy's lead I looked at the buds of some of these plants.

The buds on the Austrian and Scots Pines looked healthy (Photo 1 of Austrian pine buds). There were healthy and dead buds on the Swiss stone pine (Photos 2 & 3) as there were on the Korean fir (Photo 4). The bud sizes are quite different with the one on the right looking more robust.

As Kathy said we will just have to wait and see, but having a close look at the buds gives you a sense of what to expect. Frankly I hope your evergreens overwintered better than mine.

Current Insects: April

Be on the watch for these insects in April

Insects in and around Homes

• Ants

    °  carpenter

    °  cornfield, pavement, pharaoh, yellow, thief, odorous house, field, acrobat

    °  winged ants: carpenter, pavement, yellow, false honey

  Beetles

   °  carpet beetles

   °  lady beetles, multicolored Asian 

   °  larder beetles 

   °  see also stored product insects below

  (True) Bugs

   °  boxelder bugs

   °  hackberry psyllids

   °   western conifer seed bugs

  Cockroaches

   °  German, brownbanded, American, Oriental

   °  Pennsylvania wood cockroaches (found indoors or outside in wooded areas)

   Flies

    °  blow flies

    °  cluster flies

   °  fruit flies

   °  fungus gnats

   °  moth flies

   °  phorid flies (also called humpback flies)

•  Springtails

•  Stored product insects

   °  Indianmeal moths

   °  flour beetles, sawtoothed grain beetles, cigarette beetles, drugstore beetles etc.


•  Wasps (including yellowjackets)

•  Non-insect arthropods

   °  spiders  

  °  house centipedes

  °  pseudoscorpions

  °  millipedes

  °  sowbugs 

Insects in Gardens
•  Andrenid bees

•  Common asparagus beetles (first active late April to early May)

•  Iris borers (eggs hatch late April to early May)

•  Root maggots (adults first active late April to early May)

Insects in the Landscape 

•  Clover mites

•  Eastern tent caterpillars (eggs hatch late April to early May)

•  Nightcrawlers

Insects and relatives that bite or sting



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