Spring Mulch Cautions from Purdue's Rosie Lerner

Although the benefits of mulching garden plants are many, wood mulch that has been improperly stockpiled can lead to plant injury or even death. Young herbaceous plants are the most susceptible to such injury, which becomes obvious shortly after applying a hardwood bark mulch. Plants may look like they have been burned with fertilizer or pesticides, or possibly, are under severe water stress. All of the above could potentially be a problem, but apparently, we must now add "sour mulch" to the list of suspects.

When hardwood bark mulch is stacked in tall piles and allowed to stand for long periods, the material

Photo credits: Rosie Lerner/Purdue Extension

in the center of the pile begins to compost anaerobically (without air) and may sour. The term "sour" refers to the extreme acidity that occurs under such conditions (reported to be pH of 1.8-3.6, while that of "normal" mulch is generally close to 7.0). Some reports indicate that pine bark does not sour.
The mulch tends to heat as it breaks down, and steam may be seen escaping from the pile when it is finally disturbed. This heat can directly injure plants, if the mulch is not allowed to cool first. However, the more serious problem is that anaerobic composting of hardwood leads to the production of several plant-damaging components; methane, alcohol, ammonia and hydrogen sulfide are possibilities.

Injury to young, tender plants is swift, usually within one day of applying mulch. Symptoms include yellowing or blackening of foliage and leaf drop. Depending on the extent of the injury, plants often are able to recover. Thorough watering, especially during hot, dry weather, will help prevent further stress. Do not apply fertilizer to plants injured by sour mulch; such materials can cause further injury. However, if plants recover yet seem to be lacking in vigor, a side dressing of nitrogen may be helpful in mid-summer if weather conditions warrant. Avoid fertilizing during hot, dry weather.
The best course of action is to prevent sour mulch injury in the first place. Stockpiles should be no higher than 4 feet, if possible; if it’s necessary to stack taller, turn them periodically to allow some aeration. Alternatively, sour mulch can be made fit for use by spreading in shallow layers and allowing it to air out for a few days, preferably a week, before using around young, tender plants. If no rainfall has occurred, watering the mulch also may help wash away toxic accumulations.

Purdue University Offers Four Plant Doctor Apps for Plant Problem Diagnosis

I would like to encourage you to take a look at the Purdue Plant Doctor suite of smart phone apps. These handy tools will help you diagnose and find recommendations to manage the most common insect, disease and environmental problems on the most common trees, annuals, perennials, and tomatoes in home gardens. The apps are a pocket encyclopedia that uses over 2,000 photos to identify and fix more than 200 problems on over 200 kinds of plants. 

Screenshots from Tree Doctor App

Imagine you are in your home garden and you notice a problem on the leaves of with your favorite shade tree. These apps will help you diagnose plant problems with an app in three easy steps. First identify the kind of plant that has the problem. So, for example, if you are using the Purdue Tree Doctor, choose the kind of tree (eg. oak, maple, or pine) to narrow your search. Second, you choose the part of the plant that looks bad (leaves, flowers, branches, trunk or roots) to narrow your search even further. Third, you match the problem on the plant with our photos by swiping through our collection of high resolution photos. To save you time, the app arranges the photos for each of the plants so that the most common problems show up first! You can confirm your diagnosis by reading details linked to the photo.

If you already know the problem you have, just skip the diagnostic process and look it up from a list. Then you can get detailed information about the damage the problem can cause, its life cycle and how to control it with some combination of cultural practices and, if needed, a pesticide or fungicide.

You may purchase all of the above mentioned apps by clicking on this link to buy from the iTunes or Android store.

Excerpts taken from Turftips Article by Cliff Sadof, Department of Entomology and Janna Beckerman, Department of Plant Pathology Purdue University

Goldenrod - A Native Treasure to any Garden

Be careful to not confuse one of the many native varieties of fall blooming goldenrods as the cause of your hay fever this time of year. Your sneezing is likely caused by giant ragweed, which also blooms around the same time. In Indiana, we predominantly find Canada, Missouri, and Giant goldenrod growing naturally in ditches, along roadsides, and in meadows. As the name suggests, goldenrods are often recognized by the showy yellow inflorescence. Click this link below to read more about the value of goldenrod to insects in this article written by Tom Turpin, Professor of Entomology, Purdue University. On Six Legs - Goldenrod