Category Archives: Diseases and Insects

Winter Damage in the Landscape

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Ice Covered Stem

Those of us who live in the temperate zones i.e. those that routinely get at least one killing frost, often have to deal with injury to our landscape plants from cold temperatures. When we venture out into the garden in the early spring, we begin to see dead or damaged plants that seemed to be in good shape the previous fall. What happened?

Of course, the first thing and for some people, the only factor we think about is cold temperatures. However, there are several other weather related impacts that need to be considered.

1. Low Temperature Injury – Most gardeners are familiar with the USDA Hardiness Zone map. This divides each area of the country into units based on the typical lowest temperatures expected. For instance, if you are in USDA Zone 5, you can expect to experience winter low temperatures between -10 and -20 degrees Fahrenheit. Continue reading →

Avoiding Winter Injury in Landscape Plants

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Last week, we talked about the types of injuries and damage sustained by landscape plants in the temperate zones. We looked at the effects of temperatures, drying winds, de-icing salt, rodents, clay soils, etc. Now here are a few methods for avoiding this type of damage in your landscape.

1. Low Temperature Injury – The key to avoiding this problem is to not “stretch the zone” with your plants. This means that, for instance, if you are in USDA Hardiness Zone 6, avoid using plants that are only hardy to Zone 7 or 8. You may get away with this for several years if the winters are warmer than average. However, all that it takes is one night below the “typical” low temperature for your zone and the plant may die. That is a fallacy of people when they think that global warming automatically changes their climate zone.  You may, in fact, experience above average temperatures for 364 nights but, if that one night in the dead of winter drops below the hardiness level of the plant…it will still be dead.

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Why Leaves Turn Yellow

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Chlorophyll is that wonder molecule that magically takes the energy of the sun and uses it to combine other elements into sugars and carbohydrates. Without it, we would be a totally different world. Of course, chlorophyll also reflects the green spectrum of light which accounts for the color of most plants.

So, what is happening when an otherwise green plant suddenly develops another color? Generally, the new color is yellow since that is the underlying color of leaves which is usually overwhelmed by the green of the chlorophyll. Continue reading →

Did You Know?

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PGC-T-Sorbus-aucuparia-aka-European-Mountainash-3The mountain ash (Sorbus species) may come from the mountain but it is not really an ash tree (Fraxinus species). It is actually a close relative the apples (Malus), pears (Pyrus) and roses (Rosa) since it is a member of the Rose Family (Rosaceae). Therefore, it is susceptible to many of the same diseases of its relatives including the fungal leaf disease, apple scab and the more serious bacterial disease, fireblight. The better news is, that since it is not a true ash, it does not get attacked by the  Emerald ash borer which is in the process of killing millions and millions of ash trees throughout the Midwest.

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Crabapples for the Landscape

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Crabapples-95Crabapple trees (Malus species) can add beauty and interest to the landscape. They can also be messy, sickly and bothersome if care is not taken to select proper cultivars i.e. named varieties, to plant.

There are literally hundreds, perhaps thousands, of cultivars of crabapples currently available. Every nursery or plant store will offer many from which to choose. So, how do you make the right choice for your landscape? The following traits should be considered when purchasing one for your yard:
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Sickly Pines

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Pine-Disease-diplodia-005086Many pine (Pinus species) trees in the landscape and along the road may be looking pretty sick this time of year. Their needles are turning brown and, at times, some larger branches are dieing. In a few cases, an entire tree may suddenly turn brown and die in less than a month. What is going on?

Much of the damage is a result of winter weather. Cold, dry winter winds in combination with dry soil will cause pine and other evergreen needles to lose water but they were unable to replenish the moisture from the frozen soil. This will cause needles to turn uniformly brown from top to bottom. Severely affected needles will drop off and some twigs or branches may also die. For the most part, however, trees should survive and will green up again over the coming year or so.

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From the Pest’s Perspective

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Disease-11-0001-EditWe tend to look at moles, grubs, deer, fungal diseases and other pests from the standpoint of their impact on us and our plants. It is as if their only goal in life is to ruin our garden and they seem to do this on purpose. What do they have against us? We’ve never done anything to deserve this treatment.

From their perspective, they could not care less about us. Their goals are rather simple. They want food, water, protection from predators and a place to reproduce their own kind. If these requirements are met, they do not care whether it is in the woods or in your backyard. It makes no difference to them.

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Plant Bugs

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PGC-I-Four-Lined-Plantbug-04-EditWhat are those tiny black circular spots that mysteriously appear on the surface of leaves of mums (Chrysanthemum), mints (Mentha), Shasta Daisy (Leucanthemum), speedwell (Veronica) , black eyed Susans (Rudbeckia) and many other plants? Is the damage due to disease or insect or something else? Odds are that they are the work of a critter called plant bug.

Although we often use the term “bug” as being synonymous with insect, “plant bugs” are a specific subdivision of the insect world. They are insects of the Order Hemiptera whose mouthparts are adapted for piercing plants and sucking their juices. Several of them are common pests in the home landscape.

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Garden Home Remedies

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“Spread some lime to get rid of those grubs.” “Marigolds will keep those rabbits away.” “Plant winter squash on the third day after the full moon.” “Spray beer, molasses and ammonia on the lawn to make it healthy.”

Home remedies come in all shapes and forms. Some actually work. Others do no harm but do not work either. A few will do a lot more harm than good. After a couple of decades of answering homeowners’ phone calls, I sometimes think I have heard them all…then the phone rings again and it is something new.

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