When, Why, and How to Repot Your Houseplants
It’s easy to overlook the fact that your houseplant needs a new home, but eventually, every houseplant needs to be repotted. It’s best to examine your plants for signs every week. There are a number of reasons why your plants might need to be repotted. Here’s what to look out for.
- Roots growing out of the bottom drainage holes: Plants have a growth hormone in them called auxin, located in the underside of the leaves, the stem, and the roots. Ideally, you’d want the roots and the top of the plant to grow simultaneously, but if a plant becomes root-bound, you wind up stunting its growth by not repotting it. Repotting your plant in a pot one size up (once you notice those bottom roots) ensures that the plant grows evenly.
- Signs of root rot: Root rot occurs when a plant has been overwatered, or left sitting in water. You may notice sagging leaves, leaves falling off, black rot at the soil level, or even fungus gnats. There are different types of root rot and each of these calls for different root treatments but all treatments require a soil change. Your safest standard treatment is to remove the soil and examine the roots to remove whatever looks dead or rotting, spray the remaining root with neem oil, and repot into slightly damp soil. Neem oil works as a nontoxic, environmentally friendly, fairly broad-spectrum fungicide and pesticide. It’s also a good idea to propagate a new plantlet with a healthy clipping to make sure at least a portion of your plant survives.
- Lack of growth or top-heavy growth: Sure, that peace-lily looks good, but it’s been the same size since its last growth spurt when you repotted it two springs ago. This would be normal if a plant has reached its maximum size, but if it's still only a foot tall after three years and you want it to keep growing, you’d best repot. Soil becomes less nutritious over time, so an infusion of fresh soil, plus a larger pot, should create another growth spurt. Sometimes a plant will grow in a way that outpaces its roots and will become top-heavy, with stems and leaves that are bigger than what the roots in its small pot can support long-term. A move to a larger pot will help it grow more proportionally.
- A return indoors after being outside: If you set your houseplant outside in the spring and bring it back indoors in the fall, you should repot it to avoid pest infestation. Pests have up to a 90-day gestation period. That’s right— 90 days. Before repotting, it’s best to dip the plant in diluted neem oil to drown any eggs. Eggs hide on the underside of the leaves, predominantly, so be sure they are covered. When you repot, use fresh soil.
How to Repot
Once you’ve concluded that your plant needs to move to a new home, here’s how to proceed.
Supplies
- Soil: Repotting a houseplant requires a bit of matchmaking. You’ll need to know what soil is best to ensure the plant gets the right moisture and nutrition in its new home. Most houseplants do well in a standard potting mix but some have different needs. The easiest path is to take a good look at the soil your plant came in. This should tell you a little about its moisture needs. For instance, if your plant is potted in predominantly peat moss, you’ll know this plant likes more humidity and moisture retention. You can also do a little internet research. Succulents will require succulent soil, which has gritty sand, perlite, and vermiculite. Some plants need more peat moss or coir (coconut fiber) to hold water. If you don’t want to mix your own, don’t fear—most home and garden stores sell plant-specific soil that contains the right fertilizer.
- Pot: You’ll also need an appropriately sized pot. For a root-bound plant or stunted plant, it should be a step up from its current pot, but not overly large. For instance, if the plant is currently in a 3-inch pot, you’d want no larger than a 5-inch pot to replace it. This ensures even growth and minimizes the chance of root rot, which can occur when there is too much extra soil. If the plant needs a portion of its roots removed due to root rot, downsize instead.
- Drainage particles: If the pot does not have drainage holes, you’ll need to create air pockets at the bottom with a layer of river stones, broken pottery, glass, or clay marbles. This will allow those roots to get needed air and create a place for excess water to go so the roots don’t remain submerged. Allow for this drainage layer when choosing a pot. The less room you leave for drainage, the more the plant will retain water. Conversely, if there is significant drainage the plant will dry out quicker.
Method
Water your plant about a half hour before repotting. You can vary the time amount (it can be three hours before or 15 minutes), but the plant will definitely require an earlier watering to minimize the chance of plant shock.
Add the drainage layer to your pot. You’ll want to keep it less than a quarter the height of the pot itself, though that can vary based on specific plant needs.
Next, add a layer of new soil. This gives the roots some fresh nutrition as they grow downwards.
Now, carefully remove your plant from its old pot. Place one hand around the bottom of the plant (where it meets the soil) and the other hand on the base of the pot. Gently turn the plant over so that you’re mostly using gravity to push the plant out of the pot. If it’s a plastic or coir pot, you can gently squeeze until the plant pops out.
Once the plant is upside down in your hands you can loosen the soil. You want to be gentle, but definitely thorough in spreading those roots. Unless there’s a problem with the soil, it’s good to retain some of it in the new pot so the plant is encouraged to grow toward the new nutrition source. Keep in mind that a plant can easily survive losing up to one third of its roots, so don’t get too caught up in trying to preserve each and every root. Your ultimate goal is to allow the roots to spread freely through their new pot.
Place the plant in its new pot, and hold the stem upright while you add soil around it. It’s important to allow room for watering so be sure to leave half an inch to an inch on top. If there isn’t enough room to safely water it, start over and edit the drainage or pot size. Do not “dome” the soil—the plant should sit level with the soil so that all of the roots receive the same amount of water.
Moisten the soil. You should definitely water your plant a little now, but do not give it a full watering. It’s best to wait at least a day since you just watered it before you repotted it.
Place back in its previous environment. Changing location and soil simultaneously can lead to plant shock. Make these changes one at a time, unless the plant is imminent need of both. With a little love, your houseplant can thrive for many years.