Ink Berry Holly

I recently talked with a Master Gardener trainee in North Alabama about her long row of Inkberry Holly that were dying one by one. She had brought a small sample of a dead stem for me to look at and I agreed it was dead. It is very hard to do a complete autopsy with a six inch sample of a large shrub. It is kind of like asking the CSI team to look at an ear and determine the cause of death of a person. I asked her to go home and dig up an entire plant so I could look at the root system.

Inkberry Holly (Ilex glabra) is native to the United States and is the only holly that spreads by underground runners. This bit of information would be helpful in the diagnosis. They are tall, multi-branched and evergreen. This holly can reach heights of 6 to 12 feet and widths of 8 to 10 feet. Inkberry holly is very adaptable to poor soils and is tolerant of extreme temperatures. It can often be found growing wild in the wetland areas of south Alabama although it is fairly drought tolerant. Inkberry holly is very pest resistant so I did not suspect an insect or disease. It is hardy in Zones 4 to 9. The leaves are a lustrous, dark green, and the fruit is typically black. This holly has many desirable features and makes a great screen plant which is the way it was being used in this case.

When she came back with a plant sample something jumped out (not literally) right away and I hope you can see it in the picture above. The plants were about 10 years old and had done fine until the year of the drought (2007). They started dying from the top of the hill and were making their way down (dying one by one). Even though the plants are fairly drought tolerant I suspected drought but I did not expect to see what I did. If you look closely you will see a layer of landscape fabric and a mass of roots above the fabric. This stolen producing plant had developed most of it's root system in the mulch layer that had increased year by year. The mulch had partially decayed creating a very good environment for roots (plenty of air and moisture) as long as moisture was plentiful. However, the extreme drought exposed the weakness of roots growing in mulch.

Mulch is great when used correctly and in moderation. If a landscape fabric is used the mulch must be removed when fresh mulch is added to avoid this problem. This same problem can develop without landscape fabric when mulch is used to excess (2-3 inches is plenty). When Dr. Jacobi at the Plant Diagnostic lab looked closely he saw few roots in the soil and almost all the roots above the fabric.

I thought this was very interesting and it may come up again after or during a dry year.