Dear Ann,

Thank you for contacting Ask Extension about your hostas. I am not sure what you mean by natural fertilizer, but perhaps you mean one that is not synthetically produced. Regardless of how they are made, all fertilizers contain some combination of the same basic elements: Macronutrients nitrogen (N), phosphorus (P), potassium (K); and micronutrients boron (B), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo), chlorine (Cl). The only difference between organic or synthetic fertilizers is the way they are produced and the form in which they are delivered.

Most plants do not need fertilizers if the soil is healthy. Too much nitrogen can produce a lot of tender new shoots that are highly vulnerable to pests. Fertilizers that are not taken up by plants will pollute groundwater and eventually lakes and rivers.

To build healthy soil, I suggest a spring and fall application of up to 1-inch of mature compost (vegetable or manures) across the soil surface of the root zone of your plants. Follow up by top-dressing with a couple of inches of organic mulch. Arborist wood chips are excellent. Purchased tree bark mulch has fewer nutrients, but is also a satisfactory mulch.

Often you will see recommendations for "balanced" fertilizers such as 10-10-10 or specialized fertilizers for roses, flowering shrubs, or other plant groups. This is largely a marketing strategy as they all contain some combination of the nutrients I mentioned earlier. The combination of compost and mulch provides all the nutrients most plants will ever need. The only plants that may require the addition of actual fertilizers are annuals, vegetables, and potted plants. 

I hope this information is useful. If you have other questions, please write again.