Unless the plant needs watering more than once a week, generally there is no need to repot.
The best time to repot a plant is in the spring so that actively growing roots will have enough time to grow into newly added potting mix. There are several signs that houseplants can exhibit when they are pot-bound. First check the frequency you are watering the houseplant.
If the plant itself makes up more than ⅔ of the height, it's time to repot. Not all plants grow taller; some grow fuller or longer (think trailing varieties). The same rule applies, though: Consider repotting whenever the plant seems to outgrow its home, Greene says.
Remove about one-third or more of the old potting mix surrounding the plant's roots. As it grew, your plant removed some or all of the nutrients in the current mix, so you'll want to give it fresh potting mix or soil. Pour a layer of fresh potting soil into the empty planter and pack it down, removing any air pockets.
Spring is the best time to repot.
In spring, the plant is coming out of its dormant period, anticipating the longer days and brighter light that tell it it's time to grow. It's ready for a fresh start in a larger pot and fresh soil.
Once you've figured out which houseplants need repotting, it's a good idea to water them well the day before you plan to upgrade their containers. A thirsty plant is a stressed plant, and already unhappy plants won't adjust well to the move. Plus, a damp root ball will be easier to work with than a dry one.
That soak you did a day or two earlier will have helped soften and loosen roots to make this whole part of the process much easier with less root damage caused. Sometimes you just have to get rough with those roots, and may break off or damage a few roots in the process. That's where step 4 (recovery) comes in.
Loosening the root ball when repotting is only essential when the plant has become completely root bound. In cases where they are not completely rootbound, you may be able to plant directly into the next pot. If the roots are not wrapped tightly around each other, there is no need to cut and disturb them.
Give Them Room to Grow
As your plant continues to grow, it may eventually get too big for its container. You can tell if a plant is ready for repotting by looking at the roots. If the roots begin to poke through drainage holes or push up through the soil, it's likely time for a new pot.
Transplant shock can be caused by incorrect planting. Frequently, plants being repotted don't have very big root systems. Damaging or disturbing these less developed root systems too much during repotting can definitely cause transplant shock.
Pot Size Is Linked to Growth
Potting up (moving a plant to a larger pot) tends to encourage it to grow faster and become larger. It's the sort of thing you do to a younger plant, sometimes more than once a year.
There could be several reasons for a plant dying after replanting, including: shock from transplantation, incorrect planting depth, not enough water or too much water, pest or disease problems, or improper lighting conditions.
For larger plants or trees, it can take months or even years for all problems caused by transplant shock to resolve. A simple case of wilting after repotting can be resolved with good care and often the plant has no residual signs of damage. A more severe case can result in dead or damaged foliage.
Make sure the plant is well watered 2-4 days in advance. You don't want to repot when it's sopping wet but being too dry will cause stress. Take the plant out of the pot. If the rootball is a bit tight, gently massage the roots to loosen them up.
Transplant Shock occurs when a plant is uprooted or placed in a new pot and shows distressed symptoms afterwards. Plant Shock is a more generalized term that happens when there is stress due to abrupt changes in environment like temperature changes, water stress, over fertilizing, or drastic changes in light.
Don't Repot Too Quickly!
Transplanting too soon will likely damage your plant's fragile roots; and if broken roots do not kill the plant, the stress placed on the roots may inhibit foliar growth.
Lack of drainage can be fatal to your plant, and it's one of the most common reasons for unhealthy and dying plants. If your plant has been overwatered due to the lack of drainage holes, you should repot your plant as soon as possible.
A common reason is that the potting mix has dried out and isn't absorbing the water. Most commercial potting mixes contain peat, which holds water well once it has been moistened, but -- as everyone who works with sphagnum peat outdoors knows -- is difficult to wet the first time.
After repotting your houseplant, avoid exposing it to direct sun for a day or two to several weeks until the roots take hold. Sunlight is healthy for plants like potted hydrangeas that thrive on it, but too much sun after repotting could harm the weakened plant as it adjusts to the new soil.
During the warm months is the best time to make the transition since the plants are actively growing. You can also wait until fall, but don't wait too long—the colder weather will stifle the growth of your houseplants and weaken their transplant success.
If you're repotting your plant because you want to give your plant room to grow, you'll want to get a pot 30% larger than the one it's currently in (blue pot in photo). However, if you're happy with how big your houseplant is, or if it's grown to its full size, you can stick with the same size pot (green pot in photo).