Movin' On Up

How can you tell when your houseplant needs repotting? It is not wise to repot into larger containers before the plant is ready. For instance, foliage plant nurseries try to ship plants out as soon as they are viable in the pot, and thus there is no immediate need for potting up in size once they reach the retailer or the customer. Indoor plants can suffer in a situation where a small root system has to contend with a large amount of wet soil.
A pot of soil serves two purposes for plants: it offers a place to hang out, where the roots anchor the plant in place, and it retains moisture and nutrients for the root system. Sometimes a plant grows top heavy, and may need a larger, or perhaps only heavier, pot to balance the size. Most plants can be kept in the same pot for a very long time, providing adequate water and nutrient is supplied. We pot the plant up one size to cope with increased water needs.
The most obvious symptom of a pot-bound plant is the soil drying faster over time. Or, if the soil doesn’t drain as well as it had been, it may need new medium. While a few roots coming out of the drainage holes at the bottom of the pot is not a sure indicator of the need for more space, lots of roots coming out can be a sign that there is no more space inside!
I recommend moving a plant to a larger pot (an increase of only one or two inches in diameter) at the beginning of the growing season, usually late-March into April. Even plants inside the house generally grow slower during the winter months and faster in the summer. They take their cue from the increased amount of light they receive when days are longer in late spring and summer. This means that roots are growing as well, and may need more room. Potting up a size will give a plant the additional moisture retaining soil it needs to handle the new growth. If you wait until the end of the growing season, the roots will begin to slow down, and may take a long time filling out the new larger pot.
It is always better to use a container with drainage holes in order to avoid root rot. Plastic, glazed ceramic, or other non-porous pots tend to retain more moisture in the soil, while unglazed pots such as terra-cotta, allow for drying from the sides of the container as well as the top of the root ball. Most plants will do fine in either type, although moisture retaining succulents generally appreciate the faster drying terra-cotta.
In most cases, a single piece of broken pottery or a flat stone covering the drainage hole is sufficient to keep the soil in and let the water out of the pot. Window screen patch is another great way to cover drainage holes without inhibiting drainage. Placing a lot of gravel in the bottom of the pot usually only serves to make the pot heavy. If you are anticipating a lot of water build up in the drainage saucer, put the gravel in there so that the pot always sits above the water.
Use a commercial potting mix—never yard soil—that is appropriate to the type of plant. Succulents, for example, prefer a mix that has a lot of drainage material (coarse sand, fine gravel, perlite, etc.) so that the plant can dry quickly between waterings. Plain soil particles are flat, and tend to pack down, leaving little space for water of oxygen. Potting mixes contain amendments to prevent this compaction. Plants that like even moisture will do well in a peaty mixture. Potting medium often comes labeled in such a way as to make it easy for us…”cactus mix”, “African violet soil”, and so on.
Place a layer of potting mix in the bottom of the new pot. The amount you put in will be determined by the height of the plant’s root ball, as you want the existing top of the root ball to sit just below the top of the new pot. This will leave room to water without overflowing onto windowsill or floor. Never add potting medium to the top of the root ball. Damp medium around the stems or trunk of a plant can cause it to rot. .
With most plants, you can gently loosen the roots at the bottom of the root ball before placing it in the new pot. Some plants, however, do not like their root balls “messed with”—palm trees, for instance. And then there are plants that have thick, heavy, practically indestructible roots (spider plants, Clivias, asparagus fern, etc.) that need to be attacked with a knife or pruning shears in order to loosen them up.
Once situated in the new pot, fill in around the sides of the root ball, firming as you go, until the surrounding soil reaches the top of the root ball. Water the root ball in, and if this causes a drop in the fresh potting mix, add a little more medium to bring it up to level. As you will probably have torn or cut some roots in the transplanting process, a newly potted plant needs to rest and recover from the “operation”. Place the plant in a bright spot, out of direct sun for a few days until it recovers. 
Be sure to check the original root ball for water needs rather than feeling the newly added outer ring of soil. When watering, make sure the water is taken up by the original root ball, as well. Do not fertilize until you see new growth, your sign that the plant is happy in its new home. 
Posted: 5/9/2013 by Margot | with 0 comment(s)
Filed under: MargotGunn, TheGreatIndoors
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