Green Giant Arborvitaes Dying!?
Hi, I had13 green giant arborvitaes planted around the 3rd week in May (would have been much sooner, but Covid happened). The plant in the pictures looks like it is dying!? It has discoloration; like a golden or manilla folder color on some foliage & some bronzing too. It also has little brown spots on most of the foliage regardless of the color of foliage.
They were planted in clay soil with larger holes than the bulb with topsoil & a little fertilizer. The bulbs were left in the burlap (all bindings removed tho) & the tops of the bulbs were above ground somewhat-with the burlap open. I try to water each day, with a hose that has an extension on it that makes the water spread out like a sprinkler (fan) & I put it at the base of the trunk for approx 4 minutes on each plant. The plants of most concern like in the photo, receive sunlight all day. I had an arborist come out & look at them, but he said these plants can take a lot. He sprayed with a fungicide & an insecticide. They seemed to have stopped the deterioration, along with me cutting away dead foliage, but they are still on the decline again already!? I don't know what to do!? Are they stressed? Diseased? Receiving too much or too little water? Infected? Have root rot? Plz help! Let me know if u need more pics or anything too...thx u!
Oakland County Michigan
This is certainly a disappointment to have your Green Giant Arborvitae in trouble so soon after planting.
A plant that is failing that quickly after planting is usually due to poorly draining soil which may be the case with you shrubs in clay soil. Arborvitae are raised in fields of well-drained soil and do not develop the same types of roots as those that are grown in heavier, wet soil. When they are moved to clay soil, the roots do not adapt to the wetter conditions and die. You could dig out one of the shrubs and look at its roots—are they black or white and plump. In this way, you could assess how well the soil is draining. Is it muddy?
In clay soil, you could be watering too much. Most plants need 1 inch of water a week—perhaps more when they are just planted. Stick your finger, up to the knuckle, into the soil near the root ball. If the soil is moist and cool, you don’t need to water; wait until the next day. You can measure the amount of water the trees get by putting a tuna can in the garden and measuring the amount of water/rain it receives. You may not need to water on a rainy day.
If the bed is too wet/doesn’t drain well, you may have to move them to a better location. Before you plant, you can do a percolation test of the soil. To learn how to do one, go to: https://www.canr.msu.edu/news/determining_soil_infiltration_rate
I hope this helps you with your plants.
Thank you for contacting Ask An Expert.