Answer: I suspect the maples are competing with the firs for both water and nutrients. The firs have more extensive root systems and are probably winning the battle. You can feed your maples during the growing season with a complete fertilizer (amounts according to label directions), by broadcasting the recommended amount under the canopies of your maples and lightly scratching it in to the soil surface. Your firs will benefit from the fertilizer, but your maples should get their fair share, too. A few weeks after fertilizing your maples should look healthier. Hope so!
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