Recognizing when
it's time to repot is the first step. Telltale signs include soil that
dries out quickly or has become degraded; roots tightly packed within a
pot or protruding from drainage holes; and water sitting on the soil
surface too long after watering. Often a plant simply looks top-heavy or
as if it might burst out of its pot. The best time to repot most plants
is when they're actively growing, in the spring or summer. However,
plants can usually handle repotting whenever the situation warrants it.
The second step is to get a plant out of its
pot. If a plant is rootbound, it helps to water the root ball thoroughly
in advance. For plants in small to medium pots, invert the pot and
support the top of the root ball with one hand. Put your other hand on
the bottom of the pot and use a downward throwing motion with an abrupt
stop. Many plants will slip out after one or two throws. If not, knock
the edge of the pot against a sturdy surface, such as a potting bench,
still holding the pot with both hands. It may take a few good whacks to
release the plant; be careful not to break the pot.
A plant ready for repotting should slide out
with the soil in one piece. If much of the soil falls free of the roots,
the plant may not need repotting. If it does, there will likely be a
solid soil-and-root mass in the shape of the just-removed pot. Roots
should be white or light-colored. Black, dark-colored, or foul-smelling
roots are usually signs of a serious problem, such as fungal disease.
Roots packed tightly in a pot don't take up
nutrients efficiently. To promote good nutrient absorption, trim the
roots and loosen up the root ball before replanting. Use a sharp knife
or pruning shears for this job, removing as much as the bottom third of
the root ball if necessary. Don't be surprised if what you cut off is a
thick tangle of root tissue. Also make three or four vertical cuts about
a third of the way up the remaining root ball.
Cut through any roots growing in a circular
pattern to help prevent the plant from strangling itself with its own
roots as it grows. If the roots are thick along the sides of the root
ball, shave or peel away the outer layer. Or gently untangle the root
ball with your fingers as if you were mussing someone's hair. Do this
along the top edge of the root ball, too.
The proper size of the new pot depends on the
plant and its potential growth rate, how well it's growing under current
conditions, and the ultimate size desired for the plant. Rely on your
own idea of what a healthy specimen of a particular species should look
like. When in doubt, go with a pot the next size up.
To keep soil from
leaking out the bottom of the pot, cover its drainage hole(s) with a
paper towel, coffee filter, mesh screen, or pot shard. If you use a pot
shard, place it convex side up to avoid sealing the hole. While it's
common practice to put gravel or charcoal in the bottom of pots, they
don't help with drainage and take up valuable space, so I don't
recommend using them.
To repot a small plant that's easy to lift, put
a few inches of moist soil in the pot and tamp it down lightly. Place
the plant in the pot, centering it. The goal is to get the top of the
root ball to sit about an inch below the rim of the pot. If the plant is
in too deep, gently raise it and add more soil. If it sits too high,
remove the plant and dig out some soil, or just dump the soil out and
start over.
Now,
fill the space around the root ball with soil. There are two approaches
to this job -- "stuffing" and "filling." Stuffers
like to press soil in around a plant. Fillers like to fill the pot to
the brim and let the soil settle in during the first few waterings.
Filling usually
works better especially with deep pots that are hard to stuff. Whether
you stuff or fill, leave some room at the top so the pot can hold enough
water with each watering to thoroughly moisten the soil.
Finally, trim the plant's foliage relative to
how much the roots were pruned. In other words, if you removed a third
of the roots, prune off a third of the top growth as well. Water the
plant thoroughly and keep it moist, shaded, cool, and misted until it is
reestablished.
Keep potted
plants well watered and fed after repotting.
