Top dressing for raised beds with a vegetable garden

Asked March 28, 2019, 9:23 AM EDT

This is my third year of raised beds for my veggie garden. My husband purchased Peatland's Pride Mushroom Compost Soil and Peat Humus locally at Baroda City Mills (55 bags), so we now have 2-3 inches of it on top of our beds. I have read conflicting details regarding whether you can get seeds to germinate in mushroom compost soil, and whether transplanted seedling can do well. Will the combination with peat humus be OK? Marge

Berrien County Michigan raised bed gardening

1 Response

It would be difficult to determine whether this composition would be a problem. Mushroom compost alone can be a problem with your plants and seedings primarily due to high salt content and how well it has aged. We also don't know the pH and nutrient content of the material. You could to a soil test (https://homesoiltest.msu.edu/ ). You can call or email the manufacturer for details of this mix. Check the package for usage instructions. One would hope the manufacturer would have considered someone using this material in this manner. If you are transplanting in you should notice quickly if it is a problem. If you are seeding it may take some time. You could try a sample of seeds in in a pot (or flat) to check the results prior to seeding in the garden. Check out the following links:

https://extension.psu.edu/spent-mushroom-substrate

https://extension.oregonstate.edu/news/what-mushroom-compost

I hope this helps,