Hat Racking Hollies

At the Scott Arboretum we have many mature hollies. Over time these majestic plants develop a broadly pyramidal habit which often spreads out at the base and can encroach on pathways, buildings, etc. Fortunately, most species of Ilex respond well to a severe type of pruning called ‘hat racking’ which rejuvenates large and overgrown hollies. We have successfully applied this type of pruning to Ilex aquifolium, Ilex opaca, and most recently to a hybrid holly, Ilex ‘Doctor Kassab’.


This practice is best completed in March. I like to step back from the plant and draw an imaginary outline of where I want to prune the tree. On a pyramidal American holly, Ilex opaca I will reduce many of the branches so the remaining habit reflects a very tight pyramid.
On March 14, we pruned our Kassab holly in front of the Arboretum offices. The overall habit of this plant is somewhat rounded so the approach was to reduce all branches by 2/3rds thus leaving a much reduced, but still rounded tree.

The term ‘hat racking’ was coined because virtually all the branches with leaves are removed leaving a skeletal network of branches which looks like a hat rack. In spring these naked branches will be covered with leaves which will emerge from latent buds on all the stems. The first growing season the tree will still be fairly open, but by the end of the next year’s growing season the tree will show very little sign of having been severely pruned.

Categorized as Garden Practices

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  1. I have what I believe is a type of holly shrub. It’s only about 2 feet tall but it spreads out like a canopy around a lamp post. It is at least 20 years old. It used to be pruned regularly, but has been, inadvertently, ignored for the last few years and has become rangy with about a two foot wide bare spot where it appears it has died. The outermost leaves (very small) look great, but it’s thick woody stems are long and bare. I think it needs a good pruning, but I’m afraid to prune it back as far as it appears to need to fill in again. Any ideas? I can post a picture, if any one can tell me how and help me identify the shrub and it’s needs. Thanks, Laura

  2. Laura,

    If you can send me an email image to abuntin1@swarthmore.edu I can probably better address your pruning question.

    Andrew Bunting, Curator

  3. I linked this blog entry to my reply t a query about getting a holly away from the sidewalk of a newly-purchased house in Florida. I added a disclaimer to the effect that doing the same thing to crape myrtles amounts to plant abuse.

    I suppose that a regional guide to landscape plants’ toleration of severe pruning (or outright coppicing/cutting back to the ground) could be of some use.

    I’d been introduced to hatracking as a legitimate, if drastic, technique by (I think) a paperback pruning handbook from the Brooklyn Botanic Garden, which is currently in hiding.

  4. I live nearby in Media and have two American (I believe) Hollies on opposite sides of the steps leading up to our front door. They are about 30 years and they are intruding on the entrance to our house. I have had some local landscapers comment that they should be cut down and removed since they are the wrong type of tree for the locations. Can you recommend some local arborists that could hat rack our hollies?

  5. Frank,

    I would try to find an arborist who can do this type of pruning. You might even want to show them this blog. For this type of work on campus we would use Bartlett Tree Care. Our local rep is John Studdy.

    Andrew Bunting, Curator

  6. Bartlett Tree Expert Co. also offers a 10% discount on all services to Scott Arboretum members. Follow this link for details http://www.scottarboretum.org/membership/discountprogram.html

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