A Comparison of Weed Control Strategies in Christmas Tree Plantations Using Mechanical and Chemical Methods or Shropshire Sheep

Year 1

Because the summer of 2024 was our third summer working with conventional weed control in the Christmas trees, we had less of a learning curve for our controls, Patches A and B.

In Patches A and B, our procedures were generally as we had expected. Mulch was spread by hand around each tree very early in the spring.  Herbicide application at the base of each tree occurred at three planned times: late spring, mid summer and early fall.  Occasional spot treatments with a hand sprayer occurred throughout the patches as needed.  Mowing occurred when vegetation height approached 6 inches, or about halfway to the base of the tree foliage. 

However, early in the season, vigorous grass growth under cool, wet conditions required more mowing per week than anticipated. Growth predictably slowed later in the season as drought conditions developed, minimizing necessity of cutting.  

For grazing sheep in Christmas trees, there were few parameters available. We needed to develop guidelines for stocking rate, length of grazing in each paddock, and work flow.

We based our stocking rate on the amount of grass we would have in the middle of the summer when grass growth slowed. The five ewes went in the first paddock in early April. However, because of an exceptionally rainy spring, the forage grew faster than the sheep could eat it. The forage overgrew the trees, requiring sporadic mowing.

Our labor rate in early season was high due to limited available fencing while we waited on our netting order to arrive. We would place the netting to enclose the sheep, then move the entire set-up to form a new paddock a couple of days later. This process took extensive time and choreography to prevent the sheep from becoming loose.

Once all of our netting arrived, our efforts decreased considerably. We set up rectangles so that the sheep could be more easily moved in a rotational grazing system. Labor hours with setting up netting decreased considerably.

Each week, the water wagon needed to be moved across the farm to be refilled from a hydrant.  This was also a difficulty prior to receiving the additional fencing; later in the season the wagon could be more easily rolled into the aisle between the tree patches.  However, we feel the entire watering process could still be improved and will experiment with other options going forward. 

The majority of our labor costs were at the beginning of the season, and our costs went down as we streamlined our work flow.

Labor Hours and Costs (based on a $25/hour salary):

For patches C and D, equipment costs should significantly decrease going forward, just as the labor costs will.  The two major expenses this year were for fencing and components to provide water for the animals (wagon, tank, hoses, etc.).  These are one-time purchases and should last  indefinitely. The water wagon provides additional value as it also serves as a shade structure. 

The Shropshire ewes that grazed in the Christmas trees were already on the farm, so the expense of acquiring sheep was not included in our calculations. Purchasing sheep would have required a line item of $3,000 added to the budget. 

For patches A and B, costs are more fixed.  Several seasons of experience have shown the time commitment and fuel consumption for each mowing session is predictable.  Applying herbicide and laying mulch are also known quantities.  All of these expenditures are recurring year after year.  

A zero-turn mower was already being used from prior seasons. Like the sheep, this expense was not included in the budget.  A mower purchase would have added a line item of approximately $7500 to the budget.  

While the cost for grazing sheep in Christmas trees was higher than weed control methods of mowing, spraying, and mulching, we found that nearly all (97%) of sheep expenses were for items that can be reused. Only 66% of Christmas tree expenses could be used long-term.

Year 2

Our hypothesis was that tree damage and overgrowth would not occur in Patches A and B, due to the older age of the trees and heights of two feet or more. There was room for error, too, in case we needed to experiment with stocking rate and pace of rotation.

Within the first two weeks, we found that when the sheep rose from their shade under the water wagon, they ran into the trees in the row next to the aisle and broke branches. Since these were bigger trees, they would snap more easily than the younger trees. Because of this, we moved the water wagon to an outside aisle along Patch A.

With more animals available in year two, we were able to match the stocking rate to the vegetation growth, leading to a consistent rotation schedule. We were able to move the sheep to a new paddock every two days, which helped us work much more efficiently each day. The grass was eaten down evenly and stayed clear of the tree branches, not overgrowing them.

Also, with the right stocking rate, sheep did better than traditional methods at keeping weeds away from trunk of tree. Mulch didn’t always prevent all weeds from growing up during the growing season, so in C& D, weeds growing through the branches sometimes had to be pulled. But the sheep grazed around the trunks closely and kept that vegetation down.

In early May, the ewes began to lamb. These lambs were crossbred Shetland/Shropshires. The lambs helped us confirm that breed matters when grazing sheep in trees. While their mothers did not eat the fir needles, the lambs did. We surmise that their Shetland heritage, not their Shropshire heritage, led them to do this.

That tree species matters was also confirmed.  There were a few eastern white pine (Pinus strobus) in Patch B.  The ewes were fenced among these pines after weaning their lambs.  The pine needles were intact prior to putting the sheep in; afterwards they were all consumed.    

In July, we started to notice more missing branches. Even though we had moved the water wagon to the aisle outside Patch A, fir branches were still being broken off.

We then witnessed the ewes rubbing their heads against the trunks of the trees, which caused the breakage. It seemed the trees were the most convenient option when they needed to scratch their heads against something. Some of the damage included broken leaders, and marketability for the future became uncertain.

To mitigate sheep scratching against the tree trunks, we installed a scratch brush to the water wagon. Tufts of wool on the stiff plastic showed that the scratch brush was being used. However, the sheep continued to rub their heads against the trees, as well. More observation is needed to see how far they will walk to access a scratch brush.

To prioritize tree health, we removed the sheep from Patches A and B and began grazing them in a tree-free paddock.

Results from the traditional weed control methods in Patches C and D showed more hours of mowing mowing in Year 2 than in Year 1. Rain was more consistent and came at the right times in June and July 2025 than in the summer of 2024, when we experienced drought. Mulch application in early spring and herbicide application as needed remained the same in method.

Labor costs for Year 2 and comparison with Year 1 were as follows: 

Labor Hours and Costs (based on a $25/hour salary):

The sharp increase in hours of mowing is shown in this graph of labor hours in Years 1 and 2:

The trend line for tree labor hours shows a sharp increase from Year 1 to Year 2 due to the increase in precipitation in Year 2:

While sheep showed a higher number of hours for the first six months of the project, the sheep trend line showed a more gradual increase in labor hours. The sheep are in the tree patch in all types of weather, so labor hours stayed more even. 

Sheep costs, excluding new livestock, were $510. Long-term purchases included modifications to the water wagon and a mineral feeder at $352. Fly predators and mineral, recurring yearly costs, were $158. These numbers show that once infrastructure is established, sheep can be a low-cost way of controlling weeds. The budget for new livestock was $2,250, and each sheep can produce several lambs in their lifetime, returning our investment in the cost of the sheep.

Christmas tree costs for Year 2 included mulch and mowing fuel. We continued to use glyphosate purchased in Year 1. 

Similar to Year 1, items related to the sheep enterprise (modifications to the water wagon, mineral feeder, and new sheep) can be used for multiple years. Mineral and fly predators are costs that would have been borne by the livestock operation no matter where the sheep grazed.

Mulch and fuel costs will be recurring, yearly costs for the Christmas tree operation. These recurring costs are added to increased costs for labor during periods of increased precipitation.