Knecht’s

Leif’s article in this week’s Northfield News discusses thoughts on spring pruning of trees.

Property owners who are eager to be working on their yards and gardens need to be careful this time of year to choose tasks that help prepare for another successful gardening season, but won’t damage soils, plants or property. We often hear that pruning trees is best done in the winter time, but most of us lack enthusiasm for pruning during cold weather.

Now that temperatures have warmed to comfortable levels, and we are in the transition from winter to spring, there is a short window of opportunity to do pruning of trees and shrubs before the early season growth flush is fully under way, and before oak wilt, Dutch elm disease and canker are active. Try to complete your pruning projects on oaks and elms and honeylocust in the next ten days and on the other plants before they leaf out.

Pruning before woody plants leaf out is easier because leaves do not obscure your view of the structure of the tree or shrub that is being shaped. This allows for better decisions on which branches to remove, and results in a better plant architecture that stands up to storms, ice, snow and is more visually appealing.

A common pruning mistake on shade trees is waiting too long to remove lower level branches. The longer you wait, the thicker their lower branches become. It is not unusual to see shade trees in people’s yards with branches 3″ to 6″ thick just 3 to 6 feet above the ground. When finally removed, the pruning cuts leave wounds 3″ to 6″ wide or larger. Wounds of this size usually take from 4 to 10 years to have bark grow over and seal the wound. This is not only unsightly for a long period of time, but also a long time during which decay may start.

It is far better to prune shade and ornamental trees early and often. During the first 10-15 years in the landscape, these valuable parts of your landscape should be pruned every 1-2 years, and after that every 3-5 years. My rule of thumb is that any branch which needs to be removed should be trimmed out before it is any thicker than your thumb. This means that pruning wounds are generally ½” to 1″ in diameter and heal over in just one to two growing seasons, greatly reducing the risks of decay, and also giving a much more pleasing look.

Another way to prevent decay when pruning trees is to make cuts just outside the branch collar, rather than cutting flush with the trunk. The branch collar is the slightly wider area of the branch right where it joins the main stem. On branches the size of human fingers, I usually leave about 1/8″ to ¼” inch of the branch collar in place. This makes for a slightly smaller diameter wound, but avoids the appearance of leaving a protruding stub.

(This picture shows the protruding stub which needs to be taken back a little further, but not flush with the trunk)

The branch collar tissue which remains after the cut secretes phenols which wash over the cut. These phenols help prevent decay from beginning, but are only produced by the collar tissue, and not the regular bark. If you cut away all the collar tissue by cutting perfectly flush with the trunk, you remove part of the trees natural decay prevention systems.

If you fail to prune your tree for many years, the results can be far worse than the limited perils of going ahead with pruning. Branches that are too low on a large tree will block out sunlight penetration to the soil surface, causing grass to die out and creating an unsightly yard where little else will grow well.

Failure to prune also increases the risks of catastrophic damage during wind, ice and snow storms. This typically happens when weakly attached branches grow to large size, and then catch lots of wind or ice. The very weak attachment then splits out under the heavy load, leaving a huge gap in the canopy of the tree.

By constantly removing very steeply angled branches and leaving branches that are from horizontal to about 45 to 55 degree angles to the trunk, strong attachments are likely to form, giving decades of resistance to storm damage.

Over a period of 10 to 20 years, you can gradually remove lower branches until the canopy of the tree begins at 10 to 20 feet above ground. Careful thinning of the crown will let a little filtered light through to keep grass growing, and the high canopy also allows early and late day sunlight to reach grass and other landscape plants from the sides. This will create both a beautiful tree and vibrant grass and gardens.

Labels: Spring Yard Work, Yard and Garden Notes by Leif

The Minnesota Nursery and Landscape Association has a set of 21 gardening tip sheets that we have available on our website. These are located in our Library, on the right side under the MNLA heading.

Just click on the topic that you’re interested in and it’ll pop up! Topics include Annuals, Azaleas, Feeding Wild Birds, Perennials, Shrubs, Water Gardening and so on. If you have questions that you need answered - please Contact Us and we’ll get you the answers you need!

Labels: Resources

Last October, Jordan and Grandpa collected acorns from the woods where we live south of Northfield. Grandpa taught Jordan how to know what acorns were good and which ones would not grow into trees. He helped get the acorns ready for their winter dormancy period. Grandpa explained to Jordan that he would be able to help us grow some of these acorns on into trees that he and his brothers would be able to plant the trees in an area on our farm that we will be calling “The Grandson’s Grove”.

Today, Jordan and his little brother, Tyger, came and helped plant not only the acorns, but also native sugar maple (hard maple) seed. They could see how the acorns had sprouted and Grandpa showed them how they should be planted.

The sugar maples were next and they had to be planted just a certain way as well. Tyger’s attention span was just long enough to get the seeds in the trays and he wanted to be one to something else.

This summer they will come to the nursery and check on their trees and see how much they have grown and help to take care of them. Next spring, they’ll be able to take them out to the woods and plant them in the ground.

A job well done - the acorns and seeds are planted - and watered and ready to grow into trees!

Labels: Forests of the Future

One of the first signs of spring in the landscape is the “blossoming” of the pussy willow shrubs. We have a few large pussy willows in our meadow and the late afternoon sun yesterday was brilliant shining through the branches.

The pussy willow will grow into a large, multi-stem shrub - 15′ to 20′ in height and between 12′ and 15′ wide. The catkins appear in the spring ahead of the leaves. Preferring full sun the fast growing pussy willow can grow in partial sun, and will tolerate moist soils.

The pussy willows are great in wind breaks, along the edges of the woods, wet areas, for visual screens, etc. The show the pussy willow offers is in the spring with the catkins. Once these are gone, the leaves come out a shiny, glossy green and it is just a large shrub the rest of the year. The fall color of the leaves is a yellow.

In the spring we cut the branches of the pussy willow and use in a variety of ways. I have a large pottery vase that we fill with the branches and branches from the red-twigged dogwoods and it sets in the corner of the family room. They’re also wonderful in dried arrangements such as swags - just use your imagination. You can put a smaller pieces of the branch in cut flower arrangements. If you do not put them in water, the life on pussy willow branches can be many months.

Labels: Spring Plants

Finally - it’s Spring! Leif’s article in the Northfield News this week discusses spring yard work - be cautious not to rush into the yard or your flower beds too soon!

The arrival of spring in Minnesota brings not only a great sigh of relief from the inhabitants of this great state, but also eagerness and excitement. This excitement extends not only to those who love to whack a baseball or softball, or to those who cast a favorite lure into a fishy spot rather than lower it through a hole in the ice, but also to the huge number of people who love to play in the dirt.

Toddlers, housewives, grandpas, professors, farmers, corporate executives, truck drivers and shop keepers are but a few examples of the legions of people who love to tend their gardens, landscape beds and fields. When snow banks finally disappear, these members of the gardening fraternity are impatiently waiting for their chance to play in the dirt, plant new varieties and nurture beauty for the eye and bounty for the table.

My cautionary message is to wait a bit longer before turning those first shovelfuls of dirt. Allow the soil to dry enough so that when it is worked it will not compact. Working soil when it is wet can cause compaction as the microscopic air spaces between soil particles get squeezed out, and the soil subsequently dries into a hard lump with poor capacity to accept moisture and inability to allow rapid extension of root hairs through the soil profile.

Wet soil that is walked on, driven on or tilled when wet, will suffer different degrees of compaction depending on the amount of disturbance, and the type of soil. Generally speaking, sandy/gravely soils can recover from compaction more easily and quickly than finer silt or clay soils. Its best to leave the soil alone until it is dry enough to crumble when worked. If you work the soil and it comes up lumpy and sticky, back off for a few days and try again.

Soil that has already suffered from compaction can be rehabilitated over time. When conditions are fairly dry, dig through the compacted layers of soil to physically break up the slabs and layers of extremely dense soil that usually has poor drainage and low oxygen levels. If spring and summer are the time you have to work on the compaction problems at your site, you will only be able to get partial results. Digging, tilling, plowing, and deep ripping make a huge difference, but Mother Nature has to be allowed to do the rest of the job of reducing soil compaction at the microscopic level.

Just as freezing and thawing breaks up our streets, the compacted lumps and hunks of soil get broken up at a microscopic level by repeated freeze/thaw cycles. Water expanding and draining away from within compacted soil gradually re-creates the tiny air spaces between soil particles. Also aiding in this process are myriads of insects, rodents, worms and micro-organisms. They are Mother Nature’s roto-tillers.

An additional way soil regains a healthy structure is the growth, death and decay of plant roots. Roots expand as they grow, and when they die and decay pathways remain for moisture, oxygen and nutrients to enter the soil profile.

Unfortunately, soil compaction can sometimes be so severe that only partial rehabilitation can be achieved, so try your best to avoid activities that could cause compaction. In these situations progress can be very slow, but each additional winter with its many freeze/thaw cycles will help a bit.

The best time of year to work on soil compaction is fall. By mechanically breaking compacted ground into chunks that are left exposed to a winter’s cycles, fall tillage/digging takes advantage of an assist from nature. Don’t let this stop you from doing some work on your compaction problems in the spring. You will just have to wait for the winter to get the additional help from the freeze/thaw cycle.

As you work compacted ground in the spring, you can choose to work in some soil amendments that will be helpful in the long run. Peat, compost, sand, manure, wood chips, bark, perlite, vermiculite, high quality topsoil and fertilizers all can help the situation, when worked into compacted soils.

Just remember to temper your spring fever with patience to allow the soil to dry enough before you work it. If you see mud balls and lumps back off, and if you see the soil crumble as you work keep going on your way to another day of happy gardening.

Labels: Spring Yard Work

‘Walker’s Low’ - Nepata is the 2007 Perennial of the Year awarded by the Perennial Plant Association. This plant is hardy to Zone 3 - though not low in stature as the name implies, it will grow to 30 to 36 inches tall. It prefers full sun but can handle some shade. We have this plant here in our display gardens and it performs all summer long. We can cut it back and in a blink of an eye - it is back in full bloom - looking stunning. It’s low maintenance and disease free.

You can combine this with pink or yellow perennials such as Elfin Pink Penstemmon, Goldsturm Rudbekia, many of the yellow and pink daylilies, coreopsis, and the list goes on. We’ll have this perennial available along with the companion plants. Try this plant in your perennial bed - you won’t be disappointed.

• Service your lawn mower - clean it off thoroughly, sharpen or replace the blades, install a new air filter and spark plugs.
• Gardening tools - clean them if you didn’t get a chance to do it last fall, sharpen them, replace blades, tighten screws, etc.
• Purchase your garden seeds, fertilizer, grass seed, etc. and be ready to go when the time is right.
• Prepare your lists or double check them on the plants you’re going to use for your annual beds and containers.

Perennial Beds

• If you didn’t mulch your perennial beds last fall - check them if you can now or as soon as the snow melts enough to get a look at them. If you see frost heaving of the perennials - try your best to get them back in the ground and apply some mulch to them until the soils warm up uniformly to prevent the frost heaving.
• Late in March, pull back the mulch and keep it handy in case of a April cold snap and
• Remove stems and seed pods that you kept for winter interest and
• On your ornamental grasses - clip them down to a few inches above the ground.

Pruning Trees and Shrubs

March is definitely the time to complete pruning your trees. Make sure you get your oaks, honeylocusts, and elms pruned before the weather warms up. The fruits trees and maple trees can be safely pruned now without a problem. The sap that will run isn’t going to harm the trees now- it’s just a little messy is all. Pruning trees when the leaves are off makes it so easy to see the true architecture of the tree and will enable you to make the best decisions as to what to prune out and what to leave.

Shrubs - - - - be careful what you’re pruning. If you have spring blooming shrubs - Forsythias, Lilacs, some Spireas, Azaleas, Rhododendrons, etc. do not prune now until after they have flowered. If you prune now, you will be removing the flower buds and you will have the spring show that you waited all winter for. Flowering shrubs should be pruned after they have flowered. For shrubs that you have that don’t flower - they can be pruned anytime with the except of the pine shrubs. Pine shrubs - such as the Mugho Pine - should only be pruned from mid-May to Mid-June.