20-20-20 is Miracle Grow. It is really strong stuff. It's formulated for indoor potted plants that are over-watered. If you water your plants no more than once a week indoors or have plants outside, you can get by much better with a timed-release fertilizer like Osmacote or better yet an organic blend. You can vary the formula to meet the needs of your plants. Organic and inorganic fertilizer materials are available at your local feed mill or nursery and fertilizer receipes are available in the gardening section of your local library. You can also call the county agent's office for assistance.

Thanks for the information.
You've been very helpful.

I agree with brhgm. I use the cheapest slow release pellets I can find or an organic granular fertilizer. I use just a teaspoon in a small pot or a small handful in a very large pot. I would fertilize in March in your zone and probably again when plants need a boost like July because their growing season is so long. Most fertilizers are 10-10-10 but organic would be much lower but better utilized by the plant. If you have compost that is just fine for fertilizer instead. Each number is supposed to be for foliage, roots, flowers or something like that, but you'll find fertilizer for roses labeled with the same numbers as fertilizer for tomatoes. So don't sweat that. The organic and the compost have more in them as far as trace minerals and not just the nitrogen-phosphorous-potassium (NPK) that the 3 number ferts have. Hope this helps.