When Do You Repot a Plant?

When Do You Repot a Plant?

How do you know that a plant needs to be put in a new pot? Some container grown plants can be left in the same pot for years, while others need to be repotted every three or four years. Plants might need a new container because they have grown so many roots that there is no room for water and soil. Other plants can need repotting not because there are too many roots, but because the roots have dried up or rotted. Here are a few general guidelines for repotting indoor or outdoor plants.

The first thing to do is to look at your plants closely. Are the leaves all green and healthy looking? If it’s a flowering plant, like this African violet, has it been blooming normally? If your plants look vigorous and the leaves are green, chances are they are just fine and don’t need a new pot at this time. When in doubt about this, however, don’t hesitate to gently tip the plant out of the pot to look at its root system. Even picking the plant up and looking at the drainage hole might give you good information: if there are roots coming out of the drainage hole, or even clogging it, the plant probably needs a new container and fresh soil.
This is an example of a root ball that is very congested. What you see are mostly roots, no soil. This is a plant that needs a new pot and more soil. When this plant is put in a new pot, it would be helpful to loosen the roots with your fingers and pull some of them away from the root ball. Then plant this in a pot where there is a good 2 inches of soil on the sides and about three inches below. The good news about this plant is that the roots are a healthy tan and white in color…darker roots are an indication of root-rot.
Plants that have very large, fleshy roots need to be repotted more frequently. This spider plant is a good example. The roots are so thick that they have filled the pot and are no longer surrounded by soil. It’s time to loosen them a bit and place this plant in the larger, green pot with fresh potting mix. When moving to a larger pot, it’s not good to use a hugely bigger container…chose one that is the next size up, about two inches larger all around the rootball.
This is a good example of a plant that needs a new container. Not only are the roots thick, they were also growing out of the drainage hole on the bottom. By the way…when putting a plant in a new container, never put anything but soil in the bottom of the pot. Never cover the drainage hole. Just use new, good quality potting mix.
Here are two examples of plants that need a new pot not because they are so root-bound, but because there are signs of root-rot. These have either been kept too wet, or the roots (or something else) has clogged the drainage holes, not allowing excess water to flow out of the pot. Notice how there are parts of the roots in both pots that are brown and even black. Where they are black and shriveled, that is the sign of root-rot. When repotting such a plant, first use your fingers to pull the roots loose and pick off the most rotted ones. Gently pull or knock as much of the old soil off as you can. If there are many rotted roots, running a hose over the rootball to remove the old soil is a good way to deal with the situation. Once you’ve gotten the roots cleaned up and some of the old soil pulled away, you can replant in a slightly larger pot with fresh potting soil. Be sure that the pot has a drainage hole and don’t cover it. Water the newly potted plant well to settle in the new soil and roots.
This orchid wasn’t doing very well, so we popped it out of the pot to look at the roots. It needs a new pot, not because it was root bound, but because some of the roots have rotted. For orchids, pull away any moss and orchid bark that was around the roots. Rinse them so you can see which ones are black and rotted, and cut those away from the rest. Repot an orchid in a clay pot with fresh orchid bark. If you need to temporarily hold the orchid in the pot while it grows new supporting roots, do so with stakes.
Some plants can stay in the same pot for years. Succulents are a good example. They don’t have deep root systems, and as long as they’re not being overwatered, they are perfectly content to stay in the same pot.

Some other reasons that you might want to repot a plant are:

  • If a plant is growing so top-heavy that it repeatedly falls over, it’s time to transplant into a larger, heavier pot. Ceramic containers are perfect for top-heavy plants as long as they aren’t going to remain outside during the winter months.
  • If a plant is happy, but the proportions of the plant to the pot look off, you can either transplant to a slightly larger container or place the current pot inside of a larger container, propping it up to be even with the top edge.
  • If you’d like to encourage a plant to grow larger, step it up to the next sized pot so that it has more room to stretch its roots. Plants that have their roots constricted won’t grow as large.
  • Plants that have been repeatedly fertilized with synthetic fertilizers might begin to suffer because of the salt build-up in the soil. Such plants should have some of the old potting mix washed off of their roots because placing it in with new potting media. If you want to place the plant back in the same container, wash it well if it’s plastic, and soak it for a few hours in a tub of water if the pot is clay. Scrub the white signs of salt build-up off of the inside and outside of the container.
  • If you’re worried that a plant has been in a smaller pot for too long, but you don’t want to increase the pot size, you can tip the plant out, pull some old soil away from the roots, and repot it in the same container with new potting mix. Top-dressing such plants with earthworm castings (available in bags in the store) can also help keep the soil alive.
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