Lilac Rejuvenation Project





Last year in June there was a Lilac Rejuvenation Project held at the Longfellow House – Washington’s Headquarters National Historic Site, one of the few sites that I have interring at this past year. This project was to give care to the old lilacs on the property by pruning out dead wood, and assessing them to see if they had diseases like scales and lilac borer. The scale that we were looking for was Oyster shell scale. This is a common insect that is a pest to many woody plants. ImageThis scale can kill branches and sometimes even the whole plant. The lilac borer is an insect that enters the Lilac through the main stem. This causing the plant to wilt on really hot days. Infested areas of a lilac would look swollen or cracked. While pruning the old branches out of the lilacs we were using a certain cutting method.  This method is called the three cut method. This method contains a total of three cuts. One under cut to make sure that the bark does not peel back and expose what is underneath it. A second cut the is to take the weight of the branch off  of the tree before you make your final cut, which will be removing the little branch stump left over right about the branch collar. We also planted 69 new common lilac hedges in the bare spaces in the 11 historic lilac hedges. The major reason for rejuvenating these lilacs is to restore them to the lushness they once had. Although it will take three to five years for the lilacs to return to lush shrubs that were once there during the Longfellow’s time they will eventually get big and strong. Following the Lilac rejuvenation project my mentor Mona and I have created a Lilac annual inspection report and created a new lilac inventory. The lilac annual inspection consist of: the Plants ID number, Location, Common & Scientific names, Condition assessments, work needed, date of completion and plan for replacement if needed. Our inventory is just showing the how many old plants are still there and how many new ones were planted in each bed this year.  Being able to participate in the rejuvenation project was a great experience and I can’t wait to see what the Hedges look like 5 years from now.



5 responses to “Lilac Rejuvenation Project

  1. Uriah, did you know some people who grow many old lilacs on their land will patrol the shrubs in spring with a piece of wire or paper clip with one end pulled out. They inspect each large trunk looking for lilac borer grub exit holes. Then they poke the hole to squish the borer before it comes out.

    I don’t have the patience for that since spring is so busy with new planting so I use the pheremone traps to trap the insect after it turns into a wasp. The males fly into the sticky paper . The get stuck and cannot mate with the females flying around. It helps us keep track of how many lilac hedges have the borer and it reduces the population so I do not have to spray insecticide.

    In winter I check with the American Lilac Society through their website to see what other lilac gardeners are doing with their hedges. I have not seed too many reports of rabbits nibbling the new growth on shrubs like they do at our site. Wouldn’t it be great if the rabbits would find and eat the lilac borer wasps?


  2. I’m looking forward to seeing the lilacs 5 years from now, too! Glad you were able to contribute to both the workshop and the process of documenting the condition of the lilacs at Longfellow House – Washington’s Headquarters NHS, and that you enjoyed the work, too!


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