At Christmas time the 20-foot-high Foster’s holly at the back of my lot looked beautiful. Therefore, I was astonished when, three weeks ago, I looked at the tree and noticed that almost half the crown was dead. I am trying to determine the cause of the damage, prospects for recovery and, if the tree needs to be replaced, whether I can replant the same species. Upon inspection, I noticed small black specks on leaf undersides and clusters of short horizontal grooves. I don’t think either of these are the cause. We also had this bed landscaped with a pre-emergent herbicide (but we’ve done that before and it never hurt the tree).

You are right in assuming the black spots and horizontal grooves are not the cause of the holly dieback. The black spots are a normal morphological characteristic of Foster’s holly. At first, I thought the horizontal grooves might have been left over seven-year cicada damage but then remembered the cicada’s egg-laying resulted in vertical chevron patterns. So I am stumped by the horizontal grooves. The bottom line though is the injury to your Foster’s holly is most likely due to winter damage. This year was very difficult for all broad-leaved evergreens and Delaware is at the northern range of that holly’s hardiness. You can prune out the damaged branches. If the tree is misshapen you might just want to remove it and start again with a new holly. Depending on the remaining structure, it may be possible to train a new leader to take over for the damaged portion. There is no reason not to plant another Foster’s holly. This winter was unusual and we could go 20-30 years without seeing the kind of damage to hollies we experienced this year. You could also replant with a hardier holly, like Ilex opaca (American holly).

I have read a lot about using native plants in the paper lately. I would like to use more native plants, but I don’t want my garden to look unkempt. What do you suggest?

I am glad you asked. The idea that native plants are sloppier than exotic species is really a misunderstanding. There are many native plants that have neat, clean shapes. It is a matter of how they are used in the landscape and how the garden is designed. A garden comprised of many perennials will have a blowsy, English cottage-garden look. Some people like that, and others find it sloppy. If you want a neater landscape, use a few perennials mixed with masses of shrubs that provide structure and order. Use larger masses of fewer species. Aromatic aster (Aster oblongifolius ‘October Skies’ or ‘Raydon’s Favorite’) is an example of a native plant with a great neat habit. The plant forms a mound of self-facing foliage, so it is a good edge or border plant. It has neat, clean foliage for most of the year and is covered with blue/purple flowers in mid- to late fall.
Send your gardening questions to the Delaware Gardener, University of Delaware, New Castle County Extension, 461 Wyoming Road, Newark, DE 19716-1303.

source : www.delawareonline.com