Asked April 23, 2019, 9:49 AM EDT
Is it safe to use 12-12-12 fertilizer on Rhubarb? Also want to know if cow manure is okay to use.
Charlevoix County Michigan
We don't suggest using a fertilizer with all 3 nutrients, especially one containing phosphorus, unless you have gotten a soil test, and it shows that your soil is lacking in phosphorus. Many of Michigan soils already have enough phosphorus, so if we simply keep applying more, the excess isn't used but is carried away and ends up in waterways, i.e. creates algae blooms.
Rhubarb likes organic matter, so composted manure or other compost applied annually, is a good practice. Here is an MSU Extension resource that provides more information on growing rhubarb.