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Showing posts from April, 2014

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 ma…

Pagoda Dogwood Branches Infected with Golden Canker Are Unlikely to Leaf Out

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…

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 o…

The Smart Garden: Landscape Design Basics Workshop

Landscape 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 narro…

Extension on WCCO radio "Smart Gardens", Saturdays 8-9am

Saturday mornings are a good time to grab a cup of coffee, tune the 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 …

Starting seeds = Spring

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 …

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…

A good read: MDA Pollinator Report

By Julie Weisenhorn

In 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 establis…

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 s…

Follow-up on Kathy's article on Winter Burn

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 p…