Occasional repotting is a crucial part of maintaining happy, healthy houseplants. If you look up through the hole in the bottom of the pot and can see the roots-- or worse, if the roots are growing out through the hole-- it probably needs more room. (Note that there are a few exceptions, because some plants prefer to be slightly potbound. It always helps to read up on your particular plant.)
How often should you repot? It depends on the plant's growth rate, but most gardeners will tell you to repot your plants every spring. They'll like the extra room to wiggle their roots around a little, and you'll be changing out the old, depleted soil. This is important because indoor plants don't get that layer of rotting organic matter like the ones in your garden.
You'll need a container to put your plant in. You can use any empty container with a hole in the bottom, from the expensive terra-cotta pots (these are good for their breathability and moisture retention) to an old yogurt container. Just make sure it has holes in the bottom. Sometimes you can get away with using a closed container if you put down a layer of gravel first, but holes are best.
Be gentle! Plants are easy to damage. Then again, if you didn't already know that, you might want to consider a nice goldfish instead. Better yet, go with a plastic plant.
If you've just brought the plant home, leave it alone for a few days. Plants don't like big, sudden changes. Let it get used to its new surroundings before you do anything drastic.
Likewise, don't try to repot an ailing or dormant plant. Make sure the plant is healthy, green, and growing first.
Now you're ready!
- Wash everything. Wash your hands. Wash any utensils you plan to use. Wash the pot, especially if you're reusing an old one. Plant diseases spread easily. I learned this the hard way last summer when I used pots someone else had thrown out-- I lost nearly all my plants to a nasty damping-off fungus in a single afternoon. Use hot, soapy water and rinse well, or better yet, run them through the dishwasher.
- Put down some newspapers or be outdoors. This is going to be messy.
- Get your potting mix ready. You can buy it in big bags at the store, but you may need to tinker with it to fit your plant's needs. Remember when you learned about the three types of soil in third grade science class? Sand doesn't hold moisture, so adding it to the soil will give it better drainage. Succulents, herbs (especially lavender, sage, and rosemary), African Violets, and any plant that doesn't like to be watered frequently will prefer soil with a higher sand content.
You can also improve drainage by putting a layer of gravel in the bottom of the pot. It's not necessary, but it will prevent the plant's roots from sitting in a pool of stagnant water if you overdo it. This might be a good idea for people who tend to be over-enthusiastic with the watering.
- Put down a layer of potting mix about one or two inches deep. Keep in mind that you'll want to leave some room between the soil and the top of the pot once you put the plant in.
- Hold the plant firmly, turn it upside down, and tap the bottom of the pot to remove the plant. If it's really stuck, carefully run a butterknife around the inside of the pot to loosen it.
- Loosen the root ball. Roots need lots of air pockets, and your potbound plant probably has its roots compacted together in a hard knot. Once again, be gentle; it takes a long time for a plant to recover from serious root damage-- if it survives at all.
- Place the plant on top of the soil. Hold it upright while you fill in the gap between the root ball and the sides of of the pot. Don't pack the soil too tightly; remember how roots like air pockets?
- Spread a little soil on top and firm it down a little, just enough so that the plant won't wiggle around. There should be about a half-inch to an inch of space between the soil and the top of the pot.
- Water your little friend and he's done! Remember that it might be a little traumatized, so put it in a sunny spot and leave it be. He'll get over it.