Fertilizing newly planted shrubs
I am a Landscape Architect and I disagree with our planting spec and would like your opinion. Our planting specifications call for a balanced 20-20-20 fertilizer to be applied to newly planted shrubs (both container grown and B&B) for the entire period of warranty - usually one to two years. I have always thought that with good planting soil mix with the appropriate organic percentage mix, that the first few years after planting shoul be devoted to good root development and that encouraging vigorous stem and leaf growth at this time could be detrimental. Certainly there should be no fertilizing as a plant prepares for dormancy. Can you comment on good hort practices with regard to fertilizing thank you
Your concern and observation is legitimate. There is no one single answer that can be applied on a universal basis. Generally speaking, it's not necessary to fertilize new shrubs after planting; doing so may burn new plant roots. Soil, improved at planting time, usually will supply a plant's nutritional needs the first season. After the first year, fertilize after leaves emerge, but before mid-July. Avoid late-season fertilization; this encourages late, soft growth that is subject to winterkill.
The link below provides a more comprehensive approach to maintaining a healthy plant or shrub on a recurring basis. Section four of the article provides a detailed approach to assess fertilized need and application.