Answer: Sweet gum or liquidamber leaves make great compost materials and even putting them whole into the soil should not harm the soil. Especially if you buried them, watered them and turned them a few times as they were decomposing. So I don't think the leaves are the cause of the problems with your cucumbers. There can be some weather related issues, or it could be that your seedlings or your transplants just are not healthy. (Cucumber plants are subject to many fungal related diseases.)It's still early in the season so you can replace your plants with nursery grown transplants and still get cucumbers this season. As for the garden, I would continue to add compost, grass clippings and shredded leaves to the soil. As they break down they will turn your garden soil into rich garden loam. Best wishes with your cucumbers.
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