Deciduous trees that hold onto their leaves through the winter are described as marcescent (mahr-CESS-ent). Some tree species are more likely to show marcescense than others. In this region, oak species (Quercus) including pin oak, red oak, and white oak are the most noticeably marcescent trees. American hornbeam, also known as blue beech (Carpinus caroliniana), and ironwood, aka American hophornbeam (Ostrya virginiana) also tend to hold leaves. Other trees such as sugar maple are occasionally marcescent.
In autumn, the leaves of most deciduous trees develop an abscission layer where the petiole (leaf stalk) meets the branch. This allows the leaves to fall off without leaving an open wound on the stem. Dry leaves stay on marcescent trees because the leaves didn’t develop the normal abscission layer in autumn.
Marcescence is often a juvenile trait and may disappear as the tree matures. It also may not affect the entire tree; sometimes leaves persist only on scattered branches. Marcescence is typically based on a tree’s genetics, but sometimes weather plays a part. In years with early freezes tree leaves may be killed before developing an abscission layer, resulting in persistent brown leaves on many trees that aren’t usually marcescent. --Nancy Rose
Fortunately, there are many short-season tomato varieties available. Some are available as transplants but there are scores of cultivars available as seeds for starting indoors in early spring. March is a great time to get started collecting seeds and supplies as well as setting up growing lights. Start your seeds during the first two weeks of April. Click here for basic tips on seed starting.
If you spend any time perusing seed catalogs, you may see the terms “short season” tomatoes, “extra early” tomatoes, or even “ultra early” tomatoes. (Ultras are 55-66 days to maturity, according to Territorial Seed Co. which sells to folks living in the chilly western mountains as well as to us flat-landers.) These variations of “early” seem to depend on the imagination of the catalog authors and their experience with number of days to harvest, as I detected some slight differences between catalogs.
The earliest cultivars are generally determinate plants. These are the tomatoes that reach a certain height, don’t get any taller, put out a flush of fruit, then gradually cease to produce. Their vines end in a terminal flower cluster. You don’t want to pinch these plants back because you’ll lose fruit. They can be caged or staked and tied. I generally use two standard tomato or peony cages nested together for my determinate plants. I keep them from leaning when the plants are full of fruit, by using electric fence posts (metal rods about ½” thick, four feet high) to anchor the topmost ring in an upright position.
Determinate plants are often suggested for home canners who want to put up several big batches of tomato sauce. Some determinates are now available as “bush” plants, indicating short-vined plants.
Indeterminate tomatoes grow continuously, producing flowers right up to a killing frost.
Each vine ends with a growing point. I cage mine in concrete re-enforcing mesh cages, about 18 inches in diameter and almost five feet tall, with electric fence posts on the east and west sides to keep these plants from tipping in a breeze. I just keep tucking adventurous stems back inside the cages instead of pinching out suckers.
Oregon State University has been breeding tomatoes for cold climates for over 40 years. They’ve released over a dozen cultivars. Some have parthenocarpic fruits–no seeds. They will set fruit regardless of temperature as insects aren’t needed for pollination. Also, since there are no seeds, there’s no need to strain seeds out when canning.
Those of us who salivate over descriptions while shopping for seeds have occasionally been disappointed when the fruits didn’t live up to our expectations. To learn which cultivars produced best in northern Minnesota, I polled the on-line Master Gardener group for their recommendations for USDA zone 2 and 3 gardens. Here are the results:
Diane Booth, Cook County Community Center / Extension Programs Coordinator, in Grand Marais, sent the following notes. She stressed that these results express her preferences. These results were not included in the above totals.
“Our experimental gardeners trialed about 30 different varieties of tomatoes this past summer in Cook County... Since last year was exceptionally warm and dry for us we will need to trial these varieties for several more years to see how they do when we have colder, wetter weather. I grew all my tomatoes in open field conditions in fairly heavy clay soils with no pampering. I have used plastic grow tunnels in the past, but not this past summer.
“The standard tomato variety I have recommended for years has been ‘Early
Girl’. It has performed consistently regardless of weather, the flavor has
been good and production quite good. I personally have used it for the past
10 years or so to judge other tomato varieties against in our county.
“Other varieties that performed well last summer included:
‘Bloody Butcher’ - texture and flavor a little better when not overripe
‘Juliet’ - flavor was good only when fully ripe and make sure you leave on
longer so it feels a bit soft before picking
‘Cupid’ - a miniature version of Juliet that has good flavor when fully ripened before picking ‘Alaskan Fancy’ -the best looking plants, prolific, good flavor but not as good as ‘Early Girl’
‘Stupice’- had good flavor, nice meaty tomato for canning, less juice.
‘Matt's Wild Cherry’ - best tasting, won't keep, very tiny but incredible flavor. Many of the cherry tomatoes do very well for us like ‘Sweet Baby Girl’ or ‘Sweet Million’.
‘Sungold’ cherry tomato- best flavored cherry tomato this year - right up there with ‘Matt's Wild Cherry’.
“Varieties that did not perform as well for me, or I didn't like the flavor
as much, included:
‘Siberian’- low production and greatly varied flavor
‘Amish Paste’ - disease problems
‘Northern Exposure’ - very prolific, huge fruit, but I didn't like the flavor or texture
‘Anna Russian’ - huge fruit, low production, solid sweet tomato taste, but had problems with diseased plants
‘Glacier’ - just o.k. taste, not real prolific
‘First Lady II’ hybrid - similar to ‘Early Girl’ but I was not as fond of the flavor
‘Manitoba’ - nice size but the texture seemed mushy and the flavor not 'tomato-y'
‘Red October’ - really late and not ripening until the very end of August
‘Peron’ - I would try again because my one and only plant left was snapped off early by wind in spite of being caged.”
So where can tomato growers look for some of these cultivars? Garden centers are fully stocked with seeds right now that you can take home and plant. Dozens of seed catalogs also carry tomato seeds. This list of web sites, though not all-inclusive, will get you started:
(Please note that this list is just a start and inclusion does not imply endorsement by University of Minnesota Extension.)
Before you plunk your money down, check out your intended mail order source at Dave’s Garden Watchdog for experience ratings based on feedback from gardeners like you.
Like many gardening tools on the market today, pruning tools are available in a wide range of brand names, styles and prices. When purchasing pruning tools, shop for quality and durability before price but remember you usually get what you are willing to pay for in the marketplace. Reputable pruning tool manufacturers will offer warranties against faulty materials and workmanship and most provide replacement parts on request.
Most pruning tasks in the home landscape can be accomplished using very basic pruning tools: hand pruners, lopping shears, pruning saws, pole pruners or hedge shears. Hand pruners come in two basic types: (1) bypass pruners, and (2) anvil pruners. Bypass pruners have a scissor-like action where a thin, sharp blade slides closely past a thicker but equally sharp blade. Anvil pruners have a sharp blade that cuts against a broad, flattened, grooved blade. Bypass pruners usually cost more than anvil pruners but they make closer, cleaner cuts particularly on small twigs and branches up to ½ inch in diameter. Anvil pruners can make larger cuts easier for branches up to ¾ inch in diameter.
Lopping shears are similar in style to bypass hand pruners, but their long handles provide greater leverage needed to cut branches up to 1½ inches in diameter depending on species and condition (e.g., oak is tougher than linden and dead wood is tougher, until it decays, than live wood). When using lopping shears, try to make the cut in one smooth stroke to avoid further injury to the branch or stem.
A pruning saw is generally used for branches larger than 1½ inches in diameter. There are many makes and models of hand pruning saws including saws with fixed or folding blades and saws with fine teeth on one side and coarse teeth on the other. The fineness of the saw’s cutting edge is measured in points (teeth per inch). For example, an 8 point saw would be ideal for delicate, close pruning on small trees and shrubs. Most saws are somewhere between 5½ to 6 points, while 4½ point saws are designed for fairly large, heavy limbs. Saw blades can be either straight or curved. Most people prefer a curved blade that cuts on the draw stroke (pulling the blade toward you). Do not use common carpentry saws for pruning trees and shrubs!
Pole pruners can be used to remove branches from trees that cannot be reached from the ground although most people find them frustrating to use. Most pole pruners have both a lopping blade and a saw blade. The lopping blade is operated from the ground by a long rope or lanyard that is pulled downward to complete the cut. The pole can either be in sections that fit together or telescoping and can be made of several materials. Wooden poles are very heavy. Aluminum poles are lighter but because they conduct electricity they should not be used around power lines. Poles made of fiberglass or some other synthetic plastic are probably the best answer. Individuals using pole pruners should exercise caution and wear head and eye protection
Manual hedge shears have long flat blades and relatively short handles. Hedge shears also come in gasoline-powered and electric models. Hedge shears are used to shear hedges or other plants when you want a neatly trimmed or more formal appearance. While they work well for clipping new growth to maintain shape, they are not very useful for pruning trees or large shrubs.
Chain saws come in a variety of makes and sizes, both gas and electric. However, chain saws are generally not appropriate for pruning live plant material. They are best left for use during tree removal and firewood cutting.
Finally, regardless of the reason for pruning – safety, health, aesthetics – use the right tool for the job.
One of the most important aspects of pruning trees and shrubs is how the job is done. If branches are improperly cut or if care is not taken during the pruning process, the plant may be permanently damaged and plant health impaired.
Here are some basic pruning cuts that every gardener should know:
When pruning trees, make the final cut just beyond the branch collar and the branch bark ridge. The branch collar is the swollen area at the base of the branch (Figure 1). The branch bark ridge is the dark, rough bark ridge that separates the branch from the main branch or trunk (Figure 2). The primary objective is to make the smallest possible wound which will seal over in the shortest possible time.
Small branches less than ½ inch in diameter can be removed with a pruning shears. Place the blade of the bypass pruner at the branch collar and cut up (Figure 3). Leave the branch collar on the tree since it is important for the wound sealing process. Do not make the pruning cut perfectly flush with the stem, since this will result in a larger wound.
Remove larger branches greater than 1½ inches in diameter with a pruning saw using the three cut method to prevent trunk bark stripping. Make the first cut about 1 to 1½ feet from the main branch or trunk (Figure 4). Cut upward and go about one third or halfway through the branch. Make the second cut a couple of inches beyond the first (Figure 5). Cut downward completely through the branch or until the branch breaks free from the remaining branch stub (Figure 6). Make the final cut just beyond the branch collar (Figure 7).
When shortening a branch or twig, cut it back to a lateral (side) branch or make the cut at a slight angle (45º) about ¼ inch above the bud. Do not make the angle of the cut too steep nor too close or too far from the lateral bud (Figure 8).
Remember, proper pruning technique is essential in developing tree and shrubs with a strong structure and desirable form. Trees and shrubs that receive the appropriate pruning measures in the correct way while they are young will require little corrective pruning when they mature.
A wide variety of fungi and some bacteria cause cankers and galls on Minnesota’s trees and woody landscape plants.
A canker is an open wound on a branch or trunk of a tree where the bark and cambium have been killed. The bark is typically pulled back from the wound or sunken in. Sap, resin or fungal fruiting bodies may be present at the site of the canker.
A gall is an area of malformed overgrowth on a tree or branch. Galls are often a combination of plant tissue and fungal or bacterial tissue and may look like a woody tumor. Insects and mites can also cause galls to form on trees.
Both galls and cankers interrupt the natural flow of water and nutrients through a branch or stem. As the canker or gall grows, it can completely girdle and kill the branch. Fortunately for gardeners, many cankers and galls start on small branches and can easily be pruned out and destroyed.
February and March are excellent times to prune out cankers and galls in Minnesota for several reasons. First, many of the bacteria and fungi that cause cankers and galls need a wound to infect the tree. Pruning cuts create an open wound that can easily be infected by pathogenic fungi and bacteria. These pathogens and the insects that transmit them from tree to tree are not active in the cold months of February and March. Cuts made when trees are dormant are therefore healthier than those made in late spring or summer. In addition many galls and cankers produce fungal spores or bacteria in warm, wet weather. These spores and bacteria can spread the infection to other parts of the tree or to nearby trees and shrubs. By pruning out and destroying cankers and galls before temperatures warm up gardeners can prevent the spread of the pathogen to other trees in the garden. Finally, it is easy to locate cankers and galls this time of year since deciduous trees and shrubs have no leaves.
To find cankers and galls, inspect trees and woody landscape plants for areas of excessive sap or resin or unusual growth. Closely examine branches that had wilted or dead leaves during the previous growing season as this is an indication that something was stopping water from reaching the leaves. Once a canker or gall is located, it is best to cut out this branch at the point where the infected branch meets a larger branch. This will result in a cleaner cut that the tree can easily heal. If the canker or gall occurs at or near the branch axis, follow the branch into the tree, to the next branch axis and make the cut there. Once pruned out, infected branches should be burned, buried, or disposed of.
The many fungi and bacteria that cause cankers and galls have a differing capability to hurt a tree. Some galls like phomopsis gall seem to only slow the tree down, where as other galls like black knot can kill many branches on an infected tree. Trees can heal over some cankers, but others spread rapidly, killing branches and sometimes the whole tree. Some common cankers and galls in Minnesota include Black Knot, Cytospora Canker, and Fireblight.
Black Knot is a fungal disease caused by Apiosporina morbosa. Black knot infects wild, edible and ornamental species of the genus Prunus, including wild plum (P. americana) chokecherry (P. virginiana), black cherry (P. serotina) and pin cherry (P. pensylvanica). Black knot galls are rough, black, cracked, and swollen areas along the branch. These galls are a combination of plant tissue and fungal tissue growing together, with the outer layer being primarily fungal. In the spring black knot galls shoot spores into the air in response to rain. Infection is at its peak when young shoots are growing and temperatures are between 70-75°F. It is critical to prune out black knot galls before this happens and new galls are created. To remove black knot galls, cut the branch at least 4 inches below the swelling to ensure that all of the fungus is removed from the tree. Once pruned out galls must be removed from the area or destroyed because spores can be produced on pruned off branches.
Fireblight is another common disease in Minnesota that requires dormant season pruning. Fireblight is a bacterial disease that infects members of the Rosaceae family including apple (Malus sp.), rose (Rosa sp.), raspberry (Rubus sp.), serviceberry (Amelanchier sp.) and mountain ash (Sorbus sp.). The fireblight bacteria, Erwinia amylovera, infect plants through wounds and natural openings. As the infection spreads, flowers, leaves, shoots, and branches turn black and die. In woody tissue, fireblight causes cankers that look like sunken, cracked dark areas that ooze watery bacteria in warm, wet weather. These bacteria survive Minnesota’s winters in cankers on woody branches. Once temperatures are above 65°F the bacteria begin to reproduce and are carried to developing leaves and flowers by insects or rain. One canker can produce millions of bacteria and could infect an entire apple orchard! Fireblight cankers should be cut out 6 inches below the sunken dark area, and should only be removed during the dormant season. Fireblight bacteria have the potential to spread from tree to tree by clinging to pruning equipment, and all tools should be disinfected with isopropyl alcohol, 10% bleach solution, or a household disinfectant like Lysol or Listerine.
Cytospora canker is a fungal disease caused by Leucostoma kunzei. Cytospora canker can infect several kinds of evergreen trees but is most commonly seen on spruce in Minnesota. Cytospora cankers are typically sunken and completely covered in resin or sap. It may take years but the canker will eventually girdle and kill the branch. At that point the fungus colonizes the dead tissue and produces black pimple-like spore producing structures. These release spores in wet weather all year long, but most abundantly in spring. Although cankers that have not yet killed a branch can be left on the tree, dead branches should be pruned out during March or February. This will reduce the amount of new spores being released into the tree.
Pruning out cankers and galls when they first appear can save a tree or shrub from losing its ornamental value and sometimes even its life. Take the time to inspect and prune woody ornamentals now before the buds break and the fungal spores begin to spread.
Creeping through our lawns and gardens Glechoma hederacea (creeping charlie) is a pervasive weed that can be very difficult to get rid of. Growing best in semi-shaded locations with routine moisture, creeping charlie can easily find an amenable home in shaded, moist areas of lawns, under landscape shrubs, and among our herbaceous perennials.
Stems grow primarily on top of the soil and will root at nodes (where leaves come in contact with stems). Well-anchored stems hugging the soil avoid damage from lawn mowers and can be challenging to pull out. Fortunately, the unique growth habit of this weed provides us with a window of opportunity in spring where it is easier to remove. Our long, cold winters weaken roots of creeping charlie. Before plants recover by generating new roots from stem tissue laying on top of the ground and repairing some of the old roots, there is a time that the stems are poorly anchored to the ground. This is typically in March/April after the ground thaws and the soil is moist, but before temperatures have risen enough to encourage active growth. At this time one can readily lift stems with a pitch fork, a rake, or even by hand and discard them.
Manually pulling creeping charlie early in the season when it is more amenable to removal is a very useful method to get it out from between established herbaceous perennials and shrubs. Within established herbaceous perennial and shrub plantings, often physical removal is the only realistic and safe option. Creeping charlie is relatively herbicide resistant and may require repeated applications, an added challenge to removal and one that can put adjacent, herbicide-sensitive landscape plants at risk.
Removing creeping charlie manually from lawns can be especially daunting due to intermingled grass and creeping charlie stems and roots. Combinations of herbicides including 2, 4-D, MCPP, and/or triclopyr can kill creeping charlie, however, repeated applications are often necessary and applications in the early fall or in spring when the plant is flowering are often more effective than other times during the growing season.
If a standard herbicide labeled for creeping charlie or manual removal of creeping charlie are not acceptable options for eradication in lawns, a very careful application of borax (sodium tetraborate) may work. Boron is essential for plant growth, but in excess can easily kill plants. Creeping charlie has a lower boron toxicity threshold than grasses and by carefully controlling the application rate one can kill creeping charlie, but keep turf alive. The pH of the soil, soil type, and weather all influence the effectiveness of borax on killing creeping charlie. Although it can be effective, the use of borax for creeping Charlie control in turf is generally not recommended due to variable results and the risk of toxic levels of boron which will be difficult to leach from the soil. Since most broadleaf plants are relatively sensitive to boron toxicity and little is known about the boron tolerance of most broadleaf woody and herbaceous plant materials, borax should definitely not be used on non-turf areas.
Be aware of what is sold as variegated glechoma in the garden centers (variegated creeping charlie). It is often sold in spring in small pots for use as a foliage accent in hanging baskets or window boxes or for use as a colorful groundcover. It does overwinter in Minnesota and frequently more aggressive solid green sections sport from variegated plants. Timely removal of green sections or seedlings and generally keeping variegated creeping charlie in bounds will help prevent it from becoming a weed problem.
Consider saying goodbye to creeping charlie from ornamental landscape plantings by manual removal during the upcoming window of opportunity. Allowing this unwelcome guest to get a foothold early in the season will only make it more difficult to remove later. As the season progresses creeping charlie stems only become more strongly rooted and actively growing landscape plants become more difficult to navigate between.
Dave Stevenson has served as the Curator of Plant Collections at the Minnesota Landscape Arboretum in Chaska since December 1990. I recently quizzed Dave about his interest in public garden horticulture, what a plant collections curator actually does, and some of his favorite plants at the arboretum.
NR: What made you interested in being a plant curator?
DS: I became interested in working in a public garden when I worked briefly at the Garden Center of Greater Cleveland (now the Cleveland Botanic Garden) in 1983. I went back to school in 1986 with a career in public horticulture in mind. I went on to the University of Michigan to work on a master’s degree in natural resource management, focusing on arboretum management and urban forestry.
For my graduate assistantship at the University of Michigan I worked at the Nichols Arboretum in Ann Arbor, identifying and cataloging the collections dating back to the 1920s, for which there were very few records. With that experience, the curator's position at the Minnesota Landscape Arboretum seemed like a good fit.
NR: What are your major responsibilities as the curator of plant collections?
DS: I tend to view my job responsibilities on a seasonal basis. In the winter, one major task is ordering new plant material for the upcoming season. I do the majority of the plant and seed ordering for the gardens and collections. The Arboretum gardeners have the responsibility for choosing new plant material for their areas. I work with them on that selection process and also on coordinating the overall content of the gardens and collections. I also work with the gardeners to order the seeds and plants for the annual displays.
In spring and early summer I deal with all the incoming plant material and making
sure it gets in the ground as quickly as possible. Usually the gardeners
have spots in mind for that plant material that has been ordered for
their areas, but we often have new gardens being installed. In these gardens we are
typically working from designs provided by outside landscape architects and designers, and these designs need to be laid out before planting.
In summer I’m busy recording all the new plant material into our accessioning system and initiating the process of getting new plantings mapped and added to our computerized inventory. My office is also responsible for mapping other Arboretum features such as memorial benches, utilities and irrigation. Labeling plants is also a major effort. We make labels year around but the goal is to get all the plants labeled in the year that they’re planted. I also observe and evaluate plants in the collections during the summer.
In the fall we are thinking about what changes we would like to make to the gardens and collections in the following year. The arboretum gardeners are putting together plant wish lists and identifying holes in the gardens that need to be filled. All of this information ends up on my desk and has to be coordinated to make the acquisition process as efficient as possible. We are also tying up loose ends with the plant records system, making sure we have good notes and maps so that I and Jan Malysza, the curatorial assistant, can complete computer entries once the snow flies.
NR: As a total plant nut I kind of hate being asked “What’s your favorite plant?” Nonetheless, I’m going to subject you to that kind of question. I’ll start by asking if you have some favorite plant collections or gardens at the arboretum.
DS: I’d say my favorites are the Prairie, the Oak Collection, and the Pine Collection.
NR: Any favorite individual plant specimens at the arb?
DS: There is a large white oak (Quercus alba) just south of the Wilson Rose Garden that has a very picturesque form. I’m also fond of the female Kentucky coffeetree (Gymnocladus dioica) on the Morgan Terrace, identifiable at this time of year by the large brown seedpods dangling from its branches. And I like the 'Acrocona' Norway spruce (Picea abies 'Acrocona') that sits in a prominent spot in the Dwarf Conifer Collection.
NR: What would you love to grow that's not quite hardy enough here?
DS: Spike winterhazel (Corylopsis spicata), a large shrub from Japan. In early spring it’s loaded with short racemes of fragrant yellow flowers. I’d also like to be able to grow lacebark pine (Pinus bungeana), which has really interesting multi-colored, patchwork-like bark. We do have a young lacebark pine at the arboretum, planted in 1998. Time will tell whether it survives.
NR: What would you tell a first-time visitor to be sure to see?
DS: The Pillsbury Shade Tree Exhibit. It has interpretive signboards and lots of specimens for people who are looking for good trees for their yards. There are also a number of unusual or marginally hardy trees, dating back to when this space was the Southern Trees collection.
NR: Thanks, Dave.
For more information on the Minnesota Landscape Arboretum see:
Vegetables and flowers that need an 8 to 10 week head start can be sown indoors now. This includes peppers, eggplants, parsley, blue salvia, impatiens, alyssum, and edging lobelia.
When starting seeds indoors avoid damping-off (a fungal disease that can cause seedlings to collapse at the soil line) by using sterile potting mix and clean pots and trays. Provide seedlings with adequate warmth and light for quick and healthy growth. Always water with room temperature water (68-77°F). Keep seedlings moist but not soggy. Circulating the air around seedlings with a small fan may also help.
Cut branches of early spring flowering shrubs and trees like forsythia, pussy willow, red maple, plums, and cherries to force into flower inside and enjoy an early taste of spring.
Longer days in March trigger renewed growth in houseplants. Potbound houseplants should be moved to new pots that are a few inches wider than the old pot. Use fresh potting medium and thoroughly water newly potted plants. If you haven’t fertilized houseplants all winter, start providing water-soluble fertilizer at about half strength.
March is prime time for pruning most deciduous trees and shrubs. You can prune spring-flowering shrubs now if you only need to do a little thinning or shaping, but if you need to do extensive pruning wait until just after they’ve finished flowering so you don’t lose this year’s floral show.
For larger views of newsletter photos just click on the image.
Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/.
Deb Brown will be answering a few gardening questions with Cathy Wurzer on MPR, the first Friday of the month during the fall and winter, between 8:30 and 9:00 a.m. Then in spring, she'll be back at her regular schedule, 10 a.m. the first Friday of each month. The program is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations.
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.
Receive an e-mail reminder when the next issue of the Yard and Garden News is posted to the web:
Regional Extension Educator - Horticulture