The way to feed trees and get really fast growth (and great health) from them is to feed in the fall.
Using a zero based nitrogen fertilizer, you apply both phosphorus and potash to the tree.
I’m not overly strict with this. If my local farm store has a 5-30-30 or something like that, I’ll use it. As long as the first number (nitrogen) is 5 or below, it works well. Your local garden center isn’t likely to carry this – they’re too busy selling you lawn feed with high nitrogen counts. 🙂 So find a local farm supply store.
This is a short video explaining this. If you don’t want to watch the video, the main idea is that tree roots don’t go dormant most of the winter but store up energy (slowly because its cold down there) for growth in the spring. If you give them readily available food, they’ll store more and you’ll get better growth and healthier trees. We don’t give them nitrogen because we don’t want to force them into putting that out to the tree buds. Think of nitrogen as gasoline for the plant engine – too much at the wrong time and the plant engine goes into high speed. We want our tree/shrub roots idling over and tuning themselves up – not getting into spring racing mode. So very low or no nitrogen.
How Do I Do This?
There’s a scientific way to set this up but most of us aren’t ever going to go to that trouble. Here’s my practical system.
I go to the drip line of the tree and then I walk in a circle around the drip line. At step one, I take a small handfull of fertilizer and toss it in front of me in a wide arc. Then I walk to the edge of where that fertilizer fell and toss another handfull in a wide arc. Then I walk to that next edge and repeat the tossing.
When I’ve followed the outline of the drip line and I’m back to the beginning, I’m done. So it could take three handfulls or ten depending on how big your tree/shrub is.
If you want to cut this back a bit (because it does use more than you think possible), then you can skip every second tossing. In other words, toss and walk ten steps instead of 5. The tree will still get fed more than it would have otherwise (and be happier) but you’re not feeding as much.
A really small tree (newly planted) only gets two handfulls. One on each side of the tree.
Caution! Do spread it out evenly and broadly Concentrating it in small space will burn/kill tender roots.
Same for shrubs. One to each side of the bush.
The diagram above shows the extent of tree roots. If the distance from the trunk to the drip line is X, then the roots go out to 2X. And that’s the area we’re trying to cover in our feeding.
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