Marianne's Response

The Proper Method For Applying Slow Release Fertilizer to Large Established Container Plants

I have 150 container plants (mainly resin) of varied sizes (15 each 20 gallon containers 100 each 10 gallon containers and the rest varying from 1 gallon to 5 gallons) that are perennials. There are many varieties of herbs along with “wild” flowers and camellias, tea olive, hollies, nandinas, gardenias blueberry blackberry, etc. All are recommended for my growing region (8A). My question: what is the PROPER way to feed Osmocote to these plants? I have a 2-inch mulch of shredded cedar on top of each container. Most of the plants are young (planted in Spring 2018). They were planted with new pots and fresh Miracle Gro potting soil which includes fertilizer and perlite/vermiculite mixed in.
Fall is approaching and it will have been 6 months since any fertilizer was applied. So as to not over-fertilize I depended on the existing fertilizer in the potting soil – so I have not fed Osmocote yet. My question is the specific method of application and is fall an okay time for applying the Osmocote to them? Thank you, Larry Croft. Martinez Georgia

Posted by Larry Croft on September 14, 2018

Marianne's Response

Hi Larry, I would not fertilize potted plants in the fall. Your plants look healthy but as winter approaches you want those potted plants to slip into dormancy not put on tender new growth. Osmocote is great for containers because it will not burn like some liquid plant foods but it releases nutrients slowly as the soil becomes warm. For this reason wait until spring to apply the Osmocote slipping the granules under the mulch so it is in contact with the moist soil. Osmocote needs heat and moisture to release the fertilizer. The amount to use is one scoop or 3 tablespoons per 2 gallon pot. So a 10 gallon container would need 5 scoops or 15 tablespoons. Work the granules into the top 1 to 3 inches of the soil. Water regularly and your plants will have food for the next 6 months. Then when winter returns they can go dormant again. Love your enthusiasm for gardening in containers, Keep growing, Marianne Binetti