Use an artificial soil composed mostly of peat moss
Good soils such as Fafard or Pro-Mix use perlite, peat, and other ingredients to produce a soil that will not compact over the summer. Real garden soil compacts and turns into concrete under the pressure of regular watering. When it does, plant roots stop growing because they require good open spaces to move into and absorb nutrients.
Hard, compacted soils do not grow good plants so do not use real soil in your containers. I re-use my artificial potting soil from year to year. I dump it out of the pot. Chew it up with a shovel to cut up all last year’s roots and add approximately 10 % by volume of compost. The compost increases air spaces and gives plants a boost in healthy nutrition.
Feed your plants weekly
Nitrogen, the engine of plant growth, is water-soluble and as you water your containers from the top the dissolved nitrogen is leaving from the bottom. I use a fish-emulsion liquid feed with seaweed to provide all the trace nutrients my plants require and recommend it highly. You can use any liquid plant food (like Miracle Grow or Shultz) to promote growth. Compost tea is the Cadillac of liquid plant food and if you make your compost tea, your plants will respond with bigger and better blooms as well as increased vigor.
Soak it to the bottom at each watering
Continue watering until water emerges from the pot bottom. This ensures the roots can reach all parts of the container and grow properly.