The Dirt on Soil
Commercially available houseplant potting “soils” don’t actually contain any soil. Most are a mixture of an organic material like peat, and sand, perlite or vermiculite to help with drainage. Some contain water-retaining crystals to help minimize waterings, and may also contain slow release fertilizer to feed the plant a small amount over a few months.
There are specialized potting mixes available for certain types of plants including cacti, orchids and African violets, but most plants will grow just fine in any sterile commercial mix formulated for indoor plants.
Don’t dig up soil from your garden to grow your houseplants in. Not only is it too heavy for houseplants to grow in, it could contain pests and diseases. Container-grown houseplants don’t have a lot of room to let their roots spread, so a lightweight medium allows for best growth, air circulation, and water drainage.
Picking the Perfect Pot
Whether you opt for standard plastic or terra cotta pots, or more expensive and ornate containers, the most important requirement in containers is drainage holes. Without holes to drain out excess water, potting mixes become waterlogged and can suffocate plant roots. If you have a beautiful decorative container without holes, put your plant in a pot that does have drainage holes, then slip that one into the ornate pot.
Eventually a plant will outgrow the pot it’s growing in. Watch for signs that your plant is crowded: roots coming out through drainage holes, a plant that is top-heavy for the container it’s growing in, or little or no new growth are signs that it’s time to move to a larger container, with fresh soil.
Choose a container that is one or two sizes larger than the plant’s current pot. Resist the urge to replant in a much larger container—the soil in such containers will stay wet for longer periods of time which can lead to root rot. Repot using fresh potting mix under and around the rootball, filling the pot to the same level as previously, and positioning the plant so that its rootball is at the same level in the new pot as in the old. This way the roots can stretch down and out into their new larger home.