Fertilizing Hostas in the Spring


Good evening. I am not a fan of commercial fertilizer, but I have heard that it is best to feed your hostas as they pop out of the ground in the spring. In the US they use Milorganite. I don’t think we get that in Canada. What other organic fertilizer can I use?
Also, I have also been told that you can use Miracle Gro tomato fertilizer on the leaves in the summer because it is high in Magnesium. Is that true? What other summer time fertilizer would you recommend.

Thank you


Hello – The hostas at our house are starting to pop out of the ground!  The American Hosta Society (AHS) recommends the use of a balanced slow release fertilizer (10-10-10) applied as the hostas emerge and continued through the summer at 4-6 week intervals. The numbers 10-10-10 represent the proportion of the three main nutrients in commercial fertilizer: nitrogen, phosphorus and potassium (N-P-K). Nitrogen, the first number, promotes leafy growth, phosphorus, the second number, promotes the development of flowers and fruit and phosphorus, the third number, promotes root development. Milorganite is a slow release nitrogen fertilizer (6-4-0) not a balanced fertilizer so promotes lush foliage growth.  I couldn’t find any reference to it’s particular use as a spring application for hostas.  The AHS also suggests use of a high nitrogen foliar fertilizer with added magnesium if you’re looking for extra big hostas.

This all being said it is often a good idea to have your soil tested before adding fertilizer. Adding fertilizer regularly can cause there to be too much of any one nutrient in the soil. Once in your soil it can not be removed. The following links will help you find a place to test your soil. http://www.omafra.gov.on.ca/english/crops/resource/soillabs.htm and https://afl.uoguelph.ca/soil-testing-services

Like you, the Toronto Master Gardeners are fans of organic methods.  A Canadian hosta expert, Reggie Millette suggests that many gardeners unnecessarily fertilize their hostas. He recommends adding 4 inches of compost every two or three years. This is the process we follow at our house although we top dress with a smaller amount of compost evert year.  As well as providing small amounts of nutrients, the compost adds to the organic matter in the soil, improving the soil’s ability to retain water. Hostas do like lots of water!

The exception to this approach is the hostas we grow in containers.  As containers are so frequently watered, any nutrients are regularly leached out of the soil.  We use a granular, slow release balanced fertilizer in our pots every spring. You could also water with a balanced water-soluble fertilizer every two weeks.  Toronto Master Gardeners do not provide specific product recommendations.

Enjoy your hostas!