Gardener’s Corner

     Last week I wrote about pruning but didn’t have enough space to address all the aspects of pruning that gardeners need to know about.  This week we will finish the discussion about pruning.  Shrubs are another category of pruning that takes a little more time to write about.  There are shrubs that bloom in the spring and shrubs that bloom in the fall.  There are shrubs that we can treat like a perennial and shrubs that reach the same heights as small trees.  They all have different needs.

     The first thing I would like to discuss is renewal pruning.  Renewal pruning is a pruning that can be done to any multistemmed shrub.  An example of a multistemmed shrub would be forsythia or common lilac.  What renewal pruning entails is the removal of 2-3 of the largest heaviest tallest branches at the ground level.  Every time we make a cut on a plant we are changing the hormone level of that branch.  Let me explain.  Every branch (trees and shrubs) have a hormone at the tip of the branch called an auxzin.  This auxzin controls the growth of the branches behind that branch.  If we remove the tip of the branch we remove the auxzin and the rest of the leaves and buds behind that tip are released to grow at any rate they want, and they usually pick fast. The result is that you get a witches broom effect.  A witches broom is a growth that has many branches coming out of one point.  It can be caused by salt damage or by insect feeding or in this case pruning.  Eventually you get a plant that has very little growth at the bottom and massive amounts of growth at the top.  The shrub becomes top heavy.  It always looks like a little girl lifting her dress up to me.  When we renewal prune by removing the growth at the bottom, we have the same hormonal affect, but it happens at the bottom of the shrub.  We get a plant that maintains its natural form, stays full at the bottom, is reduced in width and height, and is healthier because we are removing the old growth which is more suseptible to diseases. Another quick way to prune multistemmed shrubs that have gotten out of control is what we call basal pruning.  You get out your chainsaw and cut the whole plant down to about 8″.  The root system is well established so the new shoots will come up thick the next spring and you’ll have a lovely shrub within 2 seasons.  Pruning of this nature can be done successfully to spirea, potentilla, dwarf lilac.  This type of pruning should be done in the fall regardless if the shrub is a spring flowering plant or a late summer/fall bloomer.

     Now let’s talk about timing of pruning.  If you have a spring flowering plant you will want to prune right after the plant is done flowering.  Spring flowering plants form their buds for the next spring right after they are done blooming.  Pruning later than spring will remove flower buds for the next year which will diminish the showyness of the plant.  Fall blooming shrubs are ok to prune while they are dormant.  Its easier to see the branch structure in the dormant season because there are no leaves on the branches.  They are also less suseptible to disease because everything is dormant.

Single stemmed shrubs like burning bush should be pruned similarly to a tree.  Always go back to a node.  Try to prune from within and not just on the tips of the branches.  This will help you avoid that witches broom affect we spoke about earlier.

My tree fruits professor at the University of Wisconsin Madison used to say,  “prune when your saw is sharp, Prune so nobody knows youv’e done any pruning, except on fruit trees which you prune until you can throw a cat through it.  But we’ll save that discussion for another day.  Happy pruning.

     In my travels through mid Michigan I talk with a lot of people.  I may be meeting with them to discuss a new landscape design or to look at a plant that is sick or dying.  No matter what I am meeting them for, we often  discuss their garden as a whole.  One of the categories of questions that seems to come up the most often is pruning.  How do I prune this plant?  When do I prune this plant?  In my first article I touched on pruning a little bit and so I thought I would go into more depth now.  

     To answer the question posed in the title of this article, its both.  Science is involved because we have to know the culture of the plant to know when to prune.  We also have to know the botany of the plant to know how it will respond to the pruning. Science also helps us to know what needs to be pruned out.  A tree or shrub may have a disease that needs to be removed and the pruner needs to know how far below the disease or injury he or she should  prune.  Art is involved, because we enjoy our landscapes aesthetically and we want our plants to be pleasing to the eye.  This may include pruning that most of us are not qualified to do for example, topiary or bonsai.

     Let’s get down to the facts of pruning.  The first rule of pruning is to remove any dead or dying branches.  How do I know its dieing?  Look for sunken areas, small leaves, areas that are soft to the touch, or a discoloration in the bark.  You may also see galls on certain shrubs or trees that need to be pruned off.  If you have any of these conditions, you will need to cut at least 1″ into healthy tissue to avoid the pest spreading to the rest of the plant.  You should also sterilize your pruners between cuts to avoid transmission of the organism to healthy tissue.  This is easily accomplished by inserting your pruners into a bath of alcohol.  It is important when you are pruning to always cut back to a node.  What’s a node?  A node is an area of the plant where a stem, bud or leaf comes out.  Pruning just above the node with out leaving any stubs on the branch will avoid further death to the branch.  After you are done removing the dead and dying branches its time to look for crossing branches.   If branches cross they will rub against each other and create a wound or could eventually grow together and create a weak area that will break in a storm.  Once we have removed the crossing branches its time to look at the overall shape and size of the plant.  For trees you may want to limb them up so you can mow under them or you may want to thin out the canopy some to let more light in.  Whatever your desires are for that tree, just remember to go slow, stand back and look often, and always prune back to a node as we discussed earlier.  The reason I say to go slow and look often, is because you can always take more off but its really hard to put it back on.  Next week we will discuss shrub pruning, timing, and how and why to perform renewal pruning on shrubs.

Let’s talk about some mistakes that can be made in the garden and lawn.  Now that its June and we are all going to be doing a lot of lawn mowing, we need to consider the height at which you cut your grass.  The healthiest height to keep your lawn during the summer 2 1/2″ to 3″ tall.  This may sound long but unless you have a golf green in your yard, in which case you would keep the blades at about 1/4″, you do not want to cut your lawn that short.  The reasons to keep it longer are the following.  The grass is able to tolerate drought much easier, it will be more competitive against weeds, it will be able to withstand foot traffic, it will be able to compete against bugs better.  Cutting the grass too short in the summer, can lead to scalping which can invite pests to gather there.  Longer grass in the summer helps to shade the grass crown so not as much water is needed.  As we move toward Fall you can shorten up the height and make it easier for the sun to get to the ground. 

Irrigation techniques are another area where homeowners make mistakes.  Many people believe that the more water the better.  Unfortunately this is not true.  Many homeowners actually overwater their plants and lawn.  Most lawns just need about an inch of water per week.  The best time to water is in the morning so the plants and lawn have all day to dry.  This is especially important for plants that suffer from black spot, like roses or powdery mildew, like lilacs.  The only time plants need more water is when they are first installed.  They have a small root capacity when they are first planted and so they dry out quickly.  Building a saucer around the plants when they are first put in helps to collect rain water or the water from irrigation and holds it in the root zone so it can soak in rather than run off.  New plants should be watered once or twice per week depending upon how much rain we get and wether or not the soil is sandy or tends toward clay.

Enjoy the summer.  Keep gardening.