Answer: New plants do not need to be fertilized. If you want to give it a little boost, you could top dress with compost -- spread a very thin layer of compost on the soil surface all around the tree, over its roots.
Also be sure to use a shallow layer of organic mulch year round. Place the mulch two to three inches thick over the root area. Do not allow it to touch the bark of the tree, keep it a few inches away from the trunk.
The most important thing you can do for a new tree is to water correctly. Your goal in watering is to keep the soil evenly moist like a wrung out sponge, not sopping wet and not dried out. To know if you need to water, dig into the soil with your finger. If it is still damp, do not water yet. When you do water, apply it to the soil surface and water thoroughly and slowly so it soaks down to the deeper roots. After watering, wait a few hours and then dig down to see how far the water soaked in; it can be surprising.
There is no set schedule for watering, it depends on your soil type and on the weather. Using an organic mulch several inches thick over the root area will help reduce watering needs as well as feed the soil gradually as it breaks down over time.
If you want to fertilize, do it next spring. Next spring you can top dress with compost again and if you wish, use a complete general purpose granular or slow release granular fertilizer such as 10-10-10 per the label directions.
Good luck with your new tree!
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