|
Home
>
Virtual Greenhouse
>
Potting
Repotting,
Potting Mixes, and Pots
By Brad Thompson
Correct potting
is a very important part of begonia growing
culture. The size and type of pot will
determine to a large extent whether your
plant will thrive.
Regular repotting
is very essential to the well being of your
begonias especially in their first few years
as they are growing and maturing. Later,
after the plants are mature and have already
reached the maximum size that you want them
to be you can let them go for a couple of
years without repotting. Yearly repotting
will still be beneficial.
Even with plants that you intend to
keep in the same sized pot you need to
change the mix regularly to keep the plant
growing vigorously. The elements of your
potting mix do break down over time and the
mix will lose its draining qualities and
airspaces to hold oxygen. You have
certainly noticed when repotting plants the
old mix, especially in the bottom of the
pot, has turned to fine mud. The following
is a list of tips and procedures for
repotting.
When to Repot
You should wait until a plant has
filled its pot with roots before repotting.
If you gently remove the plant from its pot
you will be able to tell if it’s ready. If
the plant roots hold all of the potting mix
together then it’s ready to be moved up. If
there is still loose mix that stays in the
pot after you pull the plant out it needs
more time. (Pulling the plant out of the
pot will not hurt it if done carefully.)
If you have waited too long and the plant
is really root bound you should gently
loosen the roots before repotting.
Sometimes if you have a plant that
doesn’t grow like it should, you may need to
repot it. Even if it hasn’t filled the pot
with roots, repotting back into the same pot
with fresh mix may give it a burst.
Selecting the pot
Don't repot a begonia into a much larger
pot.
Generally, move up one pot size at a
time. It’s better for the plant to
be repotted more frequently in smaller jumps
than to make one big jump.
If too large a pot is used, the soil mix stays too
wet, then the soil sours, and the roots die.
For small plants only move them up in
1 inch increments until you get to about 6
inch size. After that you can make 2 inch
jumps in size, such as a 6 inch pot up to an
8, then an 8 up to a 10 etc. Also note,
when moving up the smaller plants you need
to remember that moving from a 3 inch round
pot (for example) to a 4 inch square pot is
a much larger jump than moving up to a 4
inch round pot. Don't move up to the square
that way unless your plant is very well
rooted and has pretty good size and even
then be careful with the watering.
What
potting mix to use
Mixes for outdoors
Many of you have your own potting
mixes. If what you are using is giving you
good results then keep using it. Mixes work
differently depending on the growing
conditions and your watering practices.
I have experimented with various mixes
over the years and have found a mix
that works perfectly for me. The reason it works well for me
is that it’s very porous and allows water to
drain well. It has enough organic matter to
counteract my alkaline water as it breaks
down, and my plants like it and grow strong
healthy roots.
I have tried other mixes based on
Supersoil™, Unigrow™, Bandini™ and some
other commercial mixes but none of them
really worked satisfactorily for me. I do
know that growers in other parts of the
country have their favorite mixes. It will
take experimenting to find out what works
for your locale. Consulting other begonia
growers in your area will give you a good
place to start in determining a good mix for
your area.
Some commercial mixes contain sawdust,
which binds up the nitrogen in the potting
mix so your fertilizer doesn't work
properly. Some stay either too wet or too
dry to work well for begonias. Even when
mixed with other amendments such as perlite,
oak leaf mold, etc., they just didn't seem
to work as well for me as the mix I use now.
One important note is whatever mix you
use it shouldn’t contain garden soil. You
should only use mixes that are soil-less.
This means they are composed of organic
components but don’t actually contain soil.
Garden soil contains soil born pests and
diseases. Some growers also use peat or
peat based mixes, which may work well where
you have to water frequently because of
extreme heat in the summer. They can be
very hard to keep wet if they ever dry out
completely if composed of mainly peat
though. Nearly all growers use a potting
mix that is at least partially peat based.
If you ever buy a plant that is
planted in peat or a mix that is very
different from the one you use, remove as
much of the original potting mix as you
can. Then repot it in your own mix. If you
leave the old mix, especially peat moss, it
can dry out later in the middle of your pot
and not rewet with normal watering. You
won't even know until the plant starts to
suffer.
I've had plants that I left the
original potting mix on and planted in
baskets. They always seemed to be wilted
looking even though they had just been
watered. When removed from the pot I found
that the couple of inches of fresh potting
mix were fine but that I had a large brick
of dried peat moss in the middle. The peat
was as hard as a rock. What was happening
was when I watered the water just ran around
the dry middle and out the bottom of the pot
so the center never got wet. You can see
that it’s important that whatever mix you
use that your plants always be in that same
mix. If you change to another mix remove
all of the old potting mix first.
This is the mix that I use for
Southern California. LGM may not be
available in other parts of the country.
You may be able to make a comparable mix
using other brands.
1 part LGM planter mix
1 part LGM leaf mold
1 part small (1/8 in to 1/4 in) size
orchid bark
1 part small #2 perlite
I know growers who use various
prepackaged mixes and combinations based on
Sunshine™, Fafard™, Miracle-Gro™, and
Supersoil™ and other brand mixes with
excellent results. You may need to
experiment to find what works for your area.
Mixes for indoors
For plants grown indoors you should
always use a soil-less mix. Most of these
are peat moss based. Most of the
prepackaged mixes will do fine for begonias
grown indoors. You may need to add perlite
so some of them. You shouldn’t add things
like oak leaf mold to mixes for indoors.
Basically mixes for indoors are to hold
moisture and food, and to give the roots
something to hold on to.
How to
Repot
Knowing how deep to plant.
When repotting, except for
rhizomatous, rexes and some tuberous, try to
plant the begonia deeper than it was planted
before. This is especially important if you
have old stumps at the base of your plant
from previous year’s pruning. This will
give your plant a fresh new look and also
cause new bottom growth and new roots to
form. If necessary, especially if you want
to keep it in the same size pot, remove
enough potting mix from the bottom of the
plant so it can set low enough to cover up
those stumps. Make sure to allow for at
least a thin layer of new potting mix in the
bottom of the new pot.
Filling with mix
There are differing opinions on this
point, but I'll give you mine of course. I
like to firmly pack the new potting mix
around the plant. The reasons I do this is;
to remove large air pockets which will fill
with water, to make sure the plant is in
good contact with the new potting mix, and
so the new mix will stay the same wetness as
the old mix. My feeling is that if you only
fill around the root ball loosely, when you
water later, the water will flow too easily
through the looser outside mix. So, it may
not wet the root ball evenly. Some feel
that if you pack the potting mix down you
damage the roots too much…I haven't found
that to be the case in the thousands of
plants that I have repotted that way. More
coarse mixes may need more packing down than
light mixes like peat.
Fertilizing when repotting
When I repot my plants I always give
them a fresh dose of Nutricote™. Nutricote™
is a time release fertilizer product. It is
water release so gives a small amount of
fertilizer every time I water. This makes up
for any times that I miss my regular
fertilizing regimen. There are many similar
products such as Dynamo™ and Osmocote™.
Different products may have different names
or different availability in various parts
of the country. Repotting is the easiest
time to apply the Nutricote™ because you
know they need it then so if you
consistently use the Nutricote™ for every
plant you repot then you won't miss any.
Follow the directions on the Nutricote™ for
amounts and how to apply.
Types of
pots
I'm only going
to cover the four major types of pots that
are commonly used. They are clay, plastic
and wooden pots, and wire baskets. Each has
its merits.
Unglazed clay
pots allow the roots to
breathe because they are porous and allow
air and water transfer. Glazed pots are
similar to plastic in how they work. Many
types of begonias grow well in clay pots,
such as rhizomatous begonias which resent
wet potting mix. The mix in clay pots dries
out faster so clay will especially help
growers who are chronic over-waterers. Many
growers exclusively use clay pots and have
found them to be the best pots to use.
Nearly all begonias can be grown well in
clay pots. The drawbacks to clay pots are
that they are heavy and they cost more. But
they look nice and last a long time. Trying
to lift a 15 inch clay pot might be a
challenge for most people. Once the plants
get to a certain size sometimes clay pots
aren't practical. Clay pots do come in every
size and shape for nearly every purpose.
Make sure to only use pots with drainage
holes.
Plastic pots
are the most commonly used pots. They are
lightweight, relatively inexpensive, long
lasting and work well for nearly all
begonias. Watering and sizing correctly are
the main problems with plastic pots. Unlike
the other three pot types which are porous,
plastic pots are not and hold water much
longer. This usually isn't a problem and
growers can usually find the correct size
pot and potting mix to grow their plants in
properly. Again, only use pots with drainage
holes. Plastic pots have few bad qualities
and they can also be found in any size and
shape needed. White and light colored pots
should be avoided because they deteriorate
quickly in sunlight so aren't very long
lasting. And they are frowned upon at
begonia shows.
Wooden pots
are still used but aren't as common. They
work very well and most begonias can be
grown easily in them. They aren't as easy
to find, they don't have a good range of
sizes, and they are expensive. They can be
long lasting though and some can last for 10
years or more. Unless you have a specific
design in mind you probably won't be using
very many wooden pots. You should make sure
to buy redwood pots if you want them to
last. You can find pots of other woods that
are only redwood stained and not actually
made of redwood. They should have drainage
holes but since they aren't water tight it
isn't as essential as with the clay and
plastic.
Moss baskets
are still commonly used for their aesthetic
value and also because begonias grow
extremely well in them. They are expensive
but do last a long time. Well, actually the
baskets are cheap, it’s the sphagnum moss
that can be expensive. They consist of a
wire frame wrapped and lined with long
fibered sphagnum moss. If you decide to
make one use the green moss and not the
brown floral type. After lining they are
filled with mix and the begonia is planted
as usual. They are usually hung up as
hanging baskets.
The moss allows
for perfect air and water exchange and is
nearly fool proof to grow in. They are a
lot of trouble to make and wouldn't be
practical for large collections but are nice
for larger specimen baskets because they are
lighter than any other pot would be of that
size. Rhizomatous begonias can even make
wonderful hanging baskets using this type of
pot. They can be trained to grow completely
around the pot to make a begonia ball.
Also, even with the other types of begonias,
they can be planted through the bottom of
the pot also to make a ball.
There are also
various liners for the moss basket wire
frames. Some are coconut fiber mats that
are cut to fit the pot. These should be
treated just like the moss covered baskets.
There are other liners, which are plastic.
Wire baskets lined with plastic liners
should be treated as plastic pots.
You can also make
your own wall pocket type moss pots for
growing begonias on walls for
semi-epiphytically. Attach chicken wire
over a section of wood, line with sphagnum
moss, and fill with a small amount of mix.
Begonias, especially rhizomatous and
trailing, will quickly cover the board.
This method works well with all begonias
considered epiphytic. I have a B. lymann-smithii that has been growing on such a
board for over eight years.
|
