However, even greater benefits await if, from time to time, a water soluble fertilizer is applied. Even though I know I should fertilize several times during the growing season (some say every two weeks), I actually only get around to it a couple of times in the summer.
If you go to the nursery or gardening section of your local big box store, you'll see all kinds of specialty fertilizers. The reason is because the percentages of the basic components, nitrogen, phosphate and potash are specific to the intended plant. Well, I can't buy one for my roses, one for my Japanese maple, one for my bell pepper plants, etc. What I need and what is most economical is a one-size-fits most product. So I buy the basic all purpose Miracle Gro water soluble fertilizer. I use one tablespoon per gallon of water and mix it into my watering can. It can be a lengthy process since I have about 30 pots which explains why I don't do it very often.
A few things to remember:
1) It's best not to fertilize during the hottest part of the day.
2) Don't apply to dry soil. Moisten the soil a bit first, then apply.
3) Keep fertilizer away from leaves. The salt in the granules will draw the water out from the leaves making them look burnt.
4) If you don't want to fuss with the granules, it also comes in a liquid version that can be added to the water.
5) Your plants will appreciate your efforts and will reward you accordingly.
Bookshelf: Container Gardening Books