Is the soil causing my plants to die?

Asked September 25, 2015, 8:48 AM EDT

The last two years we have planted impatiens, petunias, and vinca, and all have succumbed to some sort of wilt. Currently out of 36 plants that have been planted this year one remains. This year for example we started with white vinca and petunias. The petunias died off fairly quickly. Lose leaves, stems turn soft, and then harden up like wood. I replaced the petunias with other vincas; they too have now died off. We have two areas that are split with a sidewalk. One side of the sidewalk the vincas have survived. The petunias did not and last year all the impatiens died on both sides. I was wondering if there was a way to get the soil tested for possible disease or any other suggestions.

Baltimore County Maryland

6 Responses

It could certainly be a soil issue that is causing your plants to fail, especially since the plants are of different species. The first thing to do would be to actually smell the mulch and the soil. If there is a sour odor or a chemical odor, there could be some contamination. Actually, submitting the soil to a soil laboratory and requesting identification of an unknown contaminant, is probably prohibitively expensive. If you can find a lab to perform such a test, you usually have to tell them what contaminant you want them to test for.
The impatiens may have succumbed to downy mildew, a disease that has prompted us to recommend not planting impatiens until a suitable control can be developed.
It is highly unlikely that the disease crossed over to the other species, which prompts us to recommend that you rake away the current mulch next spring and add a good amount of compost, LeafGro, or other good quality organic soil amendment to the planting bed. The microbes in the compost should help to neutralize any chemical contamination.
It is a good idea to have your soil tested, however, for pH, available nutrients and Cation Ecxhange Capaci ty (CEC). The following page from our website should be helpful:

Thank you for that information. Fro your recommendation on removing mulch would you suggest I remove the top layers of soil and replace as well? Would planting flowers next spring in the new bed be a smart idea or should we skip a season?

Personally, I am reluctant to recommend that soil be removed unless there is firm evidence of a chemical contaminant involved. If you are using a dyed mulch, there is the possibility that the wood used is still 'raw' and not well decomposed. Such a condition would damage the plants by robbing them and the soil of the necessary nitrogen for plant growth. It may suffice to remove the mulch and add the organic amendments before planting next spring. Be sure and check the soil for any odors and make sure that the bed drains well. Sometimes you can overcome poor drainage in a bed by simply elevating the bed, i.e. adding a couple of inches of soil and organics so that the roots are not in soggy soil.
Avoid planting impatiens, and you may want to try some different plant species.

Thank you once again. I will follow these tips and then use more of an organic mulch as opposed to the Scott's mulch I have been using next year. Possibly try begonias or something else. Tired of wasting $$ on flowers!!

Quick question...would it more beneficial to strip the mulch & replace before winter then doing so in the spring?

No. You can leave it. The mulch can age in place.