A.M. LEONARD 10g Fertilizer Tablets - [20-10-5] 6 Month Slow Release

Originally developed for forestry applications as a one and done fertilizer, these tablets are formulated for trees and shrubs. While native plants generally do not need fertilizer, this single application can help new plantings establish faster, particularly in low-nutrient soil (i.e.clay).
NPU recommends this for new or young plantings- mature woody species should not be given fertilizer to stimulate growth.

When using with new plantings: Apply 1 tablet for every 1 gallon plant pot. This can be done multiple ways, the important factors are to make sure the tablets sit below but near surface level, and that roots do not touch the tablet at the time of planting. 
A trusty method is: Dig the hole several inches wider than the pot, then gouge the walls of the hole with a trowel or shovel and wedge tablets into the gouges a few inches below surface level. Continue planting as normal.
Click here for a video by the Colorado Forestry Department demonstrating the usage of this product with bare root seedlings!

When using with existing plantings: Fertilizer shouldn't be necessary for established plants unless they are visibly struggling. For each 12-18in of plant spread or for each 1/2in diameter of tree trunk at the base, use 2 tablet for slow-growing plants or 4 tablets for fast-growing plants/poor soil conditions. 

Do not apply to plants that already have a slow release fertilizer applied. If in doubt of plant dosage, always underdose.

Includes 2.2% magnesium, 2.5% iron, 2% manganese, 0.18% zinc.