Wood mulch can cause collar rot
Question: I planted about 12 gardenias a couple of months ago, and they appear to be dying. I checked the soil, and it’s evenly damp. They have two, 2 gallon-per-hour emitters, and they were all being watered three times a week for 20 minutes.
From the picture you sent, it looks like a lack of water. Before you say, “No, can’t be,” let me explain something.
You have a lot invested in those gardenias. From the picture, I can see you applied surface wood mulch surrounding plants, and it looks quite deep. Nice job. These gardenias will appreciate the wood mulch.
However, wood mulch can create a problem around young plants. When this wood mulch is in contact with the stems of young plants, it can keep the surrounding soil and stem too wet. This constant wetness around the stem can foster a disease called collar rot. Disease organisms attack the stem, essentially choking the plant and shutting off its water supply.
Pull the mulch away from the stems about 12 inches, and do not let it come in direct contact with the stem. The wood mulch will help the plants, but it cannot come in contact with young stems until they get quite a bit older.
Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com.