Question
I have 4 techny arborvitae planted 2 years ago.all are 5' tall..
all of them are not dense;  it is full of bud. some of leaves are yellow in color.  can you pls tell me what is the reason.. how can i make it green and dense??

Answer
Hello Oswin

Thank you for your question.

Arborvtae are very disease resistant and have few pests, but they have a very shallow root system and as they need a lot of water to grow well, the spacing between them and other large shrubs or trees is vital.  

Also you don't say which state you are in, but these shrubs should not be planted where there long hot summers!  Elsewhere they need to be planted at least 9' to 10' apart and well away (14' to 16') from other trees and large shrubs so that they are not competing for moisture and nutrients.

I think lack of moisture may be the problem here, unless the conditions mentioned above were fully satisfied.

I think that at 5' tall, digging up and replanting your arborvitae might be impractical, even with the shallow root system, but you might try giving your plants extra water and mulching around them with about 3" of shredded bark to keep the moisture in.

I can't guarantee that this will work, but it's worth a try.