A favorite summer vegetable, and one that produces a large harvest, summer squash grows well in containers. This warm weather crop needs full sun to grow. Summer squash comes in a range of heirloom varieties; most are ready for harvest within 45 to 85 days. Small squash are more moist and flavorful than large squash, so plan to harvest when the squash average 4 to 8 inches each.
Select a 12-inch diameter (or larger) container with drainage holes in the bottom. Cut a piece of wire mesh to fit over the drainage holes; this will keep the soil from falling out. Then place the screen in the bottom of the container.
Mix one part each of peat moss, compost, potting soil and perlite in a large bucket to create a good container growing medium. Fill your container three-quarters full with this mix.
Remove your summer squash start from its container. Break apart the roots. Place the squash plant in the container at the same depth as it was planted, and cover over the roots with your soil mix.
Water the newly planted squash until the soil becomes saturated. Place your container in a full-sun location.
Check the plant's water level daily. Container plants require frequent watering, typically every day or every other day. Water as often as necessary until the soil grows saturated.
Fertilize the squash with a 20-20-20 fertilizer weekly beginning in mid-July. First, water the plants as normal. Then, mix a water-soluble 20-20-20 fertilizer with water, and follow the directions on the package, which will suggest a fertilizer amount based on the size of your squash plant.