I added 15 bulk bags of Mushroom manure(2yr old) from Gardenworks in my new rose bed on August for fall planting, as suggested by their staff. Now I found both online bare root rose sellers warned to not use Mushroom Manure since many roses don't like it. What can I do now? Thanks
Spent mushroom substrate (SMS) tends to be alkaline because of the soluble salts. Dig in sphagnum peat moss to offset that. It may be that because of the age of the SMS it may not be all that bad. You can fertilize with 16-20-0 which contains sulfate. It is a turf fertilizer but works very well for roses. If you can find it on sale, it's a lot cheaper than the advertized "rose" fertilizers. Good luck.
Thanks for your advice. I'll add peat moss to my bed. Since I'm new on this, would you tell me more about what does the fertilizer do and how to use it? Can I but it on local garden center? How about sprinkle a lot water(no rose yet), does it help to release the soluble salts? Thank you, Eric
My suggestion of 16-20-0 was for our prairie soils which generally have sufficient potassium. Depending on your soil you may want to look for an inexpensive fertilizer with potassium and sulfur along with nitrogen and phosphorus. The best thing would be to consult with rose growers in your area about fertilizer practices. Join the local rose society. If you don't plant until spring, won't the winter rains have washed out any dangerous amounts of the salts? For general fertilizer information there are many places on the internet that will help educate you. Here is a place to start.
