I have two emerald cedar trees in planters on my back deck in Toronto. I have never fertilized them before and they are starting to turn brown in patches. Is there a type of fertilizer that would be recommended for these types of trees? I have purchased some evergreen spikes but I’m not sure if they would be appropriate for a planter. Thanks for your help!
Is this the first year that the cedars are in planters? Depending on the size of the planter and whether or not it is insulated, the cedars (Thuja spp) may have a difficult time surviving a winter and I am not surprised to hear that they are browning.
If you are planning on keeping them for the summer season, I would recommend a compost top dressing and then mulching the top of the planter. Remember to keep the plants well hydrated through the summer with regular soaking until water runs out the bottom of the container. They will need regular watering until the ground starts to freeze in the fall. This additional moisture will help them overwinter another season.
For more information, see Organic Fertilizer Garden Guide.