When plants are happy and thriving the foliage grows above the soil while the roots grow below. If left in the same container for an extended period of time the roots can grow out of the bottom of the pot or start circling the inside of the container; they can become root bound. Eventually all thriving houseplants need to be repotted or transplanted to avoid being root bound. To check if a plant is root bound, spread your fingers over the top of soil, tip the plant upside down, and lift the container off to examine the roots. If the roots form a white mass circling the container it’s time to repot the plant. Houseplants typically respond best to transplanting in the springtime when they are starting active growth.
The first step in repotting your houseplant is to choose a new container. Whether you purchase a new container or reuse one, choose a pot that is only one to two inches larger in diameter than the current one. When reusing a pot, it's important to clean it thoroughly to avoid transferring pathogens and insects. A solution of twenty percent bleach mixed with water works well for disinfecting containers. Rinse well with plain water after scrubbing.
Next select a potting mix. Choose a good quality potting mix. Soil from the garden is not a good option as it does not provide enough drainage and has weed seeds and pathogens in it. Potting mixes are typically soilless blends with peat for moisture retention and perlite to improve drainage along with compost and fertilizer. If repotting orchids or cacti, choose a mix specifically designed for those types of plants.
Start by placing a small amount of slightly moistened potting mix in the bottom of the new container. If the drainage hole is large, place a small piece of porous landscape fabric, a coffee filter, or a small shard from a broken container over the hole to reduce the loss of potting mix through the hole while still allowing drainage.
Inspect the roots of the plant. Healthy roots are white and firm. Any that are black and mushy should be cut out and discarded. If the plant is root bound, tease the roots apart to encourage new growth. If the roots are too tightly bound, score them in a couple of places with a sharp knife. Place the plant in the new pot on top of the layer of potting mix. The plant and the top of the soil ball should be slightly below the lip of the pot, at the same level it was in the old pot. Add more potting mix to fill around the sides of the soil ball. Gently tap the pot on the potting bench to settle the soil in around the roots. Water thoroughly. If the new soil mix settles too much along the edge of the pot, add enough more to bring it level with the top of the root ball.
Keep the soil moist but don’t overwater.
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Updated Monday, February 01, 2016