Geraniums will grow indoors, outdoors, in the garden or in pots as long as they have the proper soil mixture. Gardeners prize the geranium for its bright cheery blossoms and use it to brighten up window boxes and flower beds. Since the flower is a heavy bloomer, it needs rich soil to provide the plant with enough nutrients to continue flowering for months at a time.
Compile a potting mixture by adding the most basic ingredient, garden soil. Use the sterilised loam sold in garden centres instead of soil from your garden to avoid any soil-borne diseases, bugs or problems that might thrive in a container. Pour the loam into a wheelbarrow for mixing with the other ingredients.
Add an equal amount of perlite to the loam in the wheelbarrow as it will improve the aeration of the soil, according to Linda Neeve, from the University of Iowa.
Dampen peat moss in a bucket, stirring and adding more water as necessary until there are no dry spots left. Add the dampened moss to the wheelbarrow and work it into the mixture to improve the amount of organic material and moisture available to the geranium plants. Do not allow the peat moss to dry out before filling the geranium pots or you will have a hard time getting the moss to absorb water instead of repelling it.
Adding fertiliser is key with geraniums grown in pots, even though they start out with a nutrient-rich soil. Work a balanced slow-release fertiliser into the soil to provide the plant with a steady supply of nitrogen during the growing season in addition to the monthly feedings you will provide. Follow the directions on the packaging of the fertiliser for the amount to add for your amount of soil. Mix it into the potting mixture in the wheelbarrow.