Vegetable Garden and Cedar Hedge*


A cedar hedge frames my neighbor’s back yard, and my vegetable garden runs down the property line, in full sun. My garden is 20+ years old and the cedar was planted three seasons ago. I have read that cedar will stunt the growth of many plants. And this has been the case. For instance, five cucumber plants have resulted in one cucumber, yet many flowers, just no cucumbers. Most tomatoes will be harvested green. Four ghost pepper plants resulted in no peppers, and not even one flower. Is there something that can be done to the soil to counter the effect of cedar hedge?


Allelopathy is the term used to describe the ability of some plants to produce chemicals that inhibit the growth of other plants, bacteria and insects.  While there is evidence that some species of cedar (Thuja) may have allelopathic qualities, there is no clear evidence that these species affect plant tissue.  Similarly, there is a common belief that conifers will increase the acidity of soil.  However, research has shown this process takes a long time, and the impact on soil pH is transitory and minimal. From your question, it appears that the new hedge has not created any additional shade on your garden, and given the symptoms you are describing, it doesn’t appear that the cedar hedge is the cause of your issues.

Cucumber plants produce both male and female flowers, but only the female flowers will produce fruit.  Cooler weather in the spring can inhibit the activity of pollinators like bees, resulting in fewer flowers being pollinated and thus fewer cucumbers.   Tomatoes typically take between 40 to 60 days to ripen after pollination.  A cooler spring will lengthen the time it takes for tomatoes to ripen.  Hot weather in the later summer or early fall will also slow the ripening process.  Similarly, cool spring weather can inhibit the production of flowers in peppers, and hot weather can cause blossoms to drop.  It’s also possible that the nitrogen levels in your soil are too high, which encourages lush foliage at the expense of flower production. 

If your area experienced a cool spring, or period of excessively hot temperatures, this may explain the issues you are having with your vegetables. You may also want to have your soil tested to confirm the levels of nutrients in your soil.  If you live in Ontario, the Ontario Ministry of Agriculture and Farming has a list of accredited soil testing labs here, or you can ask a local reputable garden centre about soil testing services in your area.

You might be interested in the information below:

Cornell Vegetable Program

The Myth of Allelopathic Wood Chips