Answer: Cherry trees prefer neutral (6.75) to slightly alkaline (7.25) soils so an acidified fertilizer is not necessary. Don't fertilize your tree for a year after planting. Then, if growth is pale or slow, you can feed with a fertilizer low in nitrogen; something like an 8-12-4 ratio (similar to what is used for roses). Too much nitrogen will result in lush, green growth at the expense of flowers. Most cherry trees are rigorous and hardy so you may not need to feed your tree at all.
Best wishes with your new weeping cherry tree.
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