Thuja trees can benefit from fertilizer, but the timing and type of fertilizer you use can depend on the specific needs of your tree and the growing conditions in your area. Here are some general guidelines:
Fertilize in spring: Apply a slow-release, balanced fertilizer (such as 10-10-10) in early spring, just as the new growth begins to emerge.
Repeat as needed: If your tree is growing slowly or showing signs of stress, you can repeat the application of fertilizer in mid-summer.
Consider soil conditions: If your soil is rich in nutrients, you may not need to fertilize your Thuja tree as often or at all. Have a soil test done to determine the nutrient levels in your soil and adjust your fertilizing accordingly.
It's important to follow the manufacturer's instructions when applying fertilizer and to avoid over-fertilizing, which can cause excessive growth and other problems. If you're not sure about the best fertilizer for your Thuja tree, consult a local nursery or gardening expert for advice.