Emerald Ash Borer (EAB) is an exotic insect that is destroying ash trees throughout the eastern part of North America.  This pest is slowly getting closer to North Dakota, with the closest known infestation in the Minneapolis/St. Paul metro area (March 2012).  The insect’s major mode of movement is people – especially when it is transported by campers and others who bring along infested firewood. 

This video discusses the Emerald Ash Borer (EAB) and its potential impact on North Dakota.  The impacts are likely severe, as green ash makes up the vast majority of the native forests, shelterbelts and urban forests throughout the state.  “Burn it where you buy it” is a recurring message directed towards campers and other recreational visitors.

More information on EAB can be found at www.emeraldashborer.info; a map with the most up-to-date locations for EAB is at http://www.emeraldashborer.info/files/MultiState_EABpos.pdf.  The ND Department of Agriculture’s EAB page is at http://www.nd.gov/ndda/pest/emerald-ash-borer-eab.

Joseph Zeleznik, Ph.D.
Extension Forester

The Perennial Plant Association (PPA) has named Brunner macrophylla ‘Jack Frost’ the 2012 Perennial plant of the year. Known by many common names – Siberian bugloss, brunnera, heartleaf brunnera, and false forget-me-not – this hardy beauty for North Dakota and surrounding prairies will be put to good use in many shade gardens this upcoming growing season. While this perennial will thrive in shady locations, it can be used in eastern exposures – morning sun - providing the soil can be kept moist.  With that qualification of consistent moisture, the soil ‘Jack Frost’ will be planted in should be high in organic matter and dressed with a generous covering of peat or compost.

Growing to a height of 12 to 15 inches with a spread of 20 inches, this hardy perennial will give multi-season character to the garden and landscape setting. The forget-me-not flowers show up in mid-to –late spring, and are held in clusters several inches above the frosty silver foliage. Because of the rough texture of the foliage, it will be less palatable to browsing deer.

This handsome, mound-forming plant will mix/blend well with other shade garden favorites like hosta, bleeding heart, and ferns. Propagated mostly by tissue culture, ‘Jack Frost’ is a sport of Brunnera macrophylla ‘Langtrees’ and was discovered in a flat of ‘Langtrees’ at Walters Gardens, Inc.in Zeeland, Michigan. From a practical standpoint, the expanding foliage does a pretty good job of hiding ripening bulb foliage.

Ron Smith, Ph.D.

Photo Credit: Walters Gardens, Zeeland, Michigan

With the mild and dry winter we have had thus far in North Dakota, I’m betting that we will not see a -25 F temperature between now and April  1^st. My colleague and friend, NDSU’s Climatologist, Adnan Akyuz, Ph.D., says to not let our guard down. The last time we had a -25 day in February was in 2008; in March it was in 1917 – occurring as late as March 15^th.

While I contend that we are 97% “out of the woods” for getting this cold hit, we both want to issue a “be on guard” statement, and encourage keeping a wary eye on the changes in our weather patterns. Europe and Russia are getting a brutal blast of cold and snow, Alaska is having its share of unceasing snow and cold, and parts of the eastern US are experiencing wide swings in temperature extremes. Will Baltimore, New York City, and St Louis all have more snow and cold than we will here in ND? Time will tell!

Should the unlikely happen to show up in a forecast, try to protect your recently planted trees and shrubs with anything possible you have on hand. Snow, if it is still on the surrounding turf, is an excellent insulator, and can be piled around and up over the crown and lower stems or branches. Even though our newly revised Plant Hardiness Zone Map indicates a mild climate emerging, we still have the potential to get hit with a wipe-out temperature nose-dive. Keep up the vigilance with your eyes on the daily forecasts! 

Ron Smith, Ph.D.

Wrapping trees for winter protection is not an attempt to keep them ‘warm’ but has the objective to prevent or minimize three sources of winter damage: from desiccating winds, sunscald, and gnawing rodents. Even if the trees in the landscape have survived previous winters unscathed, a wise horticulturist would not try to stretch this luck too far. Winters in ND, SD, and MN are so unpredicatble and variable that even well-established plantings can get hit hard when least expected.

 Protection from Desiccating Winds:

Don’t wrap evergreen trees like a Christmas present with burlap. That has the potential to create more problems than it solves by eliminating too much light and packing the branches too closely together, which often breeds disease problems before the covering gets taken off in the spring. Instead opt for a buffer against the wind and direct sunshine on newly planted or smaller evergreens in this fashion:

This burlap barrier would be oriented to buffer the winds and direct sunshine from the west or southwest, yet still allow the top to get sufficient sunlight and air. Using anti-desiccants have not proven to be effective in this, in spite of the fact they are still promoted and used by homeowners and professionals alike. The anti-desiccants simply do not have the staying power needed to see them through the long winter months.

Protection from Sunscald:

This is really an incorrect term as the sun doesn’t actually ‘scald’ the trunk or bark of the tree. Common on newly or recently planted trees, it shows up on the west or southwest side of the thin-barked trees the spring following the winter months. On cold winter days, the sun can heat up bark to the point where cambial activity is stimulated. When the sun is blocked by a cloud, hill, or building, bark temperature drops rapidly, killing the active tissue. The result is something like this:

The sketch on the left shows the damage caused which will heal slowly if at all, while the sketch on the right shows the wound cleaned up by cutting the loosened and damaged bark back to where it is attached to the trunk cylinder. From there, normal healing will begin taking place at the start of the growing season.

Rodent Damage:

Rabbits and voles are the major perpetrators of this damage. Rabbits can walk across the top of snow cover and nibble branches and girdle the trunk. Voles will work on the trunks of trees under the snow. The tree should be wrapped with either Kraft paper or hardware cloth up to the first branch, and from that point up, the branches sprayed with a repellant like Liquid Fence or Plantskydd. Both will also protect against deer damage in rural areas. Wrapping in this manner will also protect the trees from sunscald.

By being a little proactive in care for your woody plants, ND’s severe winters need not be a major concern. Little things can make a difference from one season to another, such as microclimate. If a particular tree or shrub just doesn’t come through the winter in a particular location no matter what care is provided, consider a relocation on your property where slight climatic conditions may make a difference.

Ron Smith, Ph.D.   
Horticulturist and Turfgrass Specialist
ISA Certified Arborist

We all know that it is normal for deciduous tree leaves to change color and drop at this time of year. What doesn’t seem to be understood by many people is that “evergreens” drop their needles at this time as well. Not as colorfully, but they are dropped none-the-less.

Here is a photo, courtesy of the US Forest Service – showing what is considered a “normal” needle drop at this time of year on a pine.

Note that the yellowing of the needles is confined to the older material; the current season’s growth is normal and healthy appearing. Consequently, evergreens have a “needle life-span” that is roughly unique to each species. Leaf life-span is the age when leaves are shed from a plant. In conifers this includes leaves with acicular (needle-like), awl-like, and scale-like forms. Two extreme examples of leaf life-span differences are larches and bristle cone pine. Larches are deciduous conifers that retain needles for 5 to 6 months (a growing season) and shed them annually. In contrast, needles exceeding 40-years old have been documented on bristlecone pine. Typically, bristle cone pine trees retain needles for approximately 15 years, rather than the maximum 40 year plus extreme. Other examples between these extremes include spruce (5-7 years), Douglas-fi r (4-8 years), and white pine (2-3 years). Leaf lifespan varies between conifer genera (i.e., spruces, pines, firs, larches, etc.) and species within a genera.

Needle drop will vary from year to year with the same evergreen: extremely dry weather will cause the drop to occur a little ahead of schedule and in a grand fashion (all at once, or so it appears) while in normal growing seasons, the needle drop may be very little or held off until the following spring.

I encourage homeowners to make a ‘sport’ of this; start with this year recording the date that needle drop is observed and whether or not it is heavy, normal, or minimal, and see how this data varies from year to year.

- Ron Smith, NDSU Horticulturist and Turfgrass Specialist, ISA Certified Arborist

With fall ‘officially’ here, questions have been coming in concerning dividing perennials. As a sweeping generalization, they should be divided in the season opposite their flowering time. This means spring flowering plants should be divided in the fall and fall bearing plants in the spring. Many summer blooming plants can be divided in either the fall or spring. This allows for maximum energy utilization for foliage and root production, with the result being healthier and showier flowers the following season.

Here is a short list of some herbaceous perennials that can be divided at this time of year:

Achillea x ‘Coronation Gold’ – now or in the early spring

Ajuga reptans

Cersastium tomentosum

Dicentra spectabilis

Hemerocallis species

Hosta species

Paeonia lactiflora

Phlox paniculata

Of course, if the need arises to move or divide any herbaceous perennial, then do it irregardless of the season of bloom. Gardeners would rather attempt to save a favorite plant than to know doing nothing will spell its doom.

- Ron Smith, NDSU Horticulturist and Turfgrass Specialist, ISA Certified Arborist

(Pictured: "Hosta", Ian BC North,available under a Creative Commons Attribution-NonCommericial 2.0 license)

NDSU Extension has posted a new video on caring for your lawn and tress after floodwaters have receded. Extension Forester Joe Zeleznik and NDSU Extension Horticulture Specialist Tom Kalb inspect a park that had been flooded in Minot, ND and give advice on what to do next.

Watch it now.

Apples being eaten by birds and squirrels; melons, pumpkins, and squash being ravaged by rodents –rabbits, voles, raccoons, whatever!! They in essence, are getting to your garden crop before you do!

Stop waiting for a hard or killing frost to harvest your apples and other produce from the garden It is September 21,  and 90% of the edible stuff in your garden is at, or close to its peak of ripeness. Better to get everything harvested rather than lose a significant amount to the wildlife roaming around your property.

Apples and melons are climacteric fruits and will continue to ripen after harvest. If you place them in a bag with a ripe peach or banana where ethylene is generated, the ripening will be accelerated. It is better to get something out of your garden a little under-ripe than to lose it all to nature’s interlopers!!

(Photo courtesy Flickr user chedder)

- Ron Smith, NDSU Horticulturist and Turfgrass Specialist, ISA Certified Arborist