| |
What
is growing media?
Growing
media helps ensure that plants
get the proper ratio of water and
oxygen - both which are critical
to healthy plant growth. Growing
media also provides support for
plant roots and it protects roots
from sunlight. You can use many
different types of media, but all
should provide the following:
- Physical support for the plant.
- Free passage of moisture (nutrient solution) to the root zone
- Proper drainage of surplus moisture.
- Adequate air circulation to roots
|
| ^ back to top |
| |
Do
I have to use growing media?
Growing
media is not entirely necessary
in hydroponics, but utilizing
a grow medium maintains a reserve
of nutrient solution in the root
zone along with a percentage of
air pore space. This can act as
a buffer and save crops from failure.
The two kinds of growing systems
which rely on grow media are Drip Systems and Ebb
& Flow Systems These systems
are most frequently used by hobby
and beginning growers as they
are more forgiving and they provide
excellent results.
There
ARE two types of systems which
require very little growing media, NFT and Aeroponics. Both of these
usually rely on a very small amout
of media in which to root a very
young plant, and the rest of the
roots are allowed to grow in the
enclosed growing chamber of the
system. In these types of systems,
watering and feeding of plants
depend solely upon the flow of
nutrient solution past the plants'
roots. If water flow is interrupted,
even for a short duration, plants
quickly die. At the other extreme,
if the root zone is continually
flooded, roots suffocate of oxygen
deprivation and plants quickly
die. A good grow medium prevents
these extremes.
Rockwool is a great growing
media, because it provides
an optimum buffering reservoir
of nutrient while maintaining
the volume of air in the root
zone. The reserve of nutrient
solution is still available even
when the irrigation system is
off for periods of time, or optimally, irrigation systems can be "pulsed"
on/off to provide plants with
that happy medium of air and water. |
| ^ back to top |
| |
What
is the best Growing Media?
Different media work
better for different growing systems
and different plant types. There
are many factors to consider such
as water and nutrient retention
capabilities, what kind of growing
system you will be using, and
whether or not you wish to reuse
the media for subsequent harvests.
Here are a few of the most
common choices :
Perlite
& Vermiculite are good media
that are often used together.
They provide excellent aeration
and water retention. This sort of
grow medium is most often used
in homemade Drip Systems. The water retention
capabilities of these sort of
mixes are closer to soil and can
even be hand-watered. Some growers
use a mixture of the two and supplement
it with natural minerals and nutrients.
We sell a great organic pre-mixed
mixture called Ready Grow .
Grow
Rocks are another
medium which provides great aeration. Grow rocks are a repellant medium,
which means that they hold little
water and nutrient. Consequently,
this medium will act only as a
support system for your plant's
roots, and provide very little
water reserves. This is a great
way to go if you're using an automated
container garden on a watering
timer. Grow rocks also work well
in the net cups used in any type
of tray system (i.e. Aeroponic/
NFT). They can be reused over
and over again for many, many
crops. In a well-maintained garden,
they would be sterilized between
each crop. The one downside to
grow rocks is that they are very
heavy (they are rocks after all!)
and they are costly to ship.
Rockwool,
a fiber spun from volcanic rock, is another
good choice. It holds a tremendous
amount of water and offers a buffer
against drying in case of electrical
outages or pump failures. Between
ninety and ninety-five percent
of the space between rockwool's
fiber is filled with air, and
it holds more nutrient solution
and air than any other grow medium.
This air space makes oxygen, water,
and nutrient solution easily accessible
to plant roots.
There
is a new rockwool product that
we love, called Grodan®
Growcubes. These little cubes can
be used in a container just like
grow rocks, but they weigh almost
nothing! They are reusable, and
when the time comes, they are
easy to dispose of. These just
might be our new favorite
grow medium.
Van
Patten, G. F. and Bust, A.F. 1997.
Gardening Indoors with Rockwool.
Van Patten Publishing, 18 pp. |
| ^ back to top |
| |
What
kind of media is best for seed
starting and/or cloning?
You
have several choices when it comes
to seed starting. Basically what
you are looking for is a medium
which will keep seeds or clones
at the right level of moisture
and which promotes strong
root growth.
Oasis®
Horticubes are specifically
engineered for optimal rooting.
They are inert with a stable pH
and need only be wet down before
being planted. When young plants
are large enough for transplanting,
the entire block can be transplanted
to the system of your choice.
Another
choice is Grodan®
Two-Inch Rockwool Blocks which
fit easily into larger Grodan® Rockwool Blocks. Great for propagation,
they stack neatly together in
nursery trays and hold young plants
upright and steady. |
| ^ back to top |
| |
Is
Rockwool Organic?
Rockwool is not considered organic, although
it does make excellent use of natural
resources: one cubic yard of rock
becomes 37 cubic feet of wool! Rockwool can be reused for many crops. When
you are finished with it, you can
break it up and add it to your outdoor
garden soil and the added aeration
will be beneficial to your outside
plants. Rockwool is inert, so it
does not add or take anything away
from plants. It can be used with
organic nutrients. |
| ^ back to top |
| |
Are
there any organic growing mediums?
We
sell a few organic growing mediums
that are proven to work. You may
also experiment on your own and
try things such as coco fiber,
wood chips, or gravel and sand.
The most successful organic substrates
are those that do not break down
readily. A coarse open structure
is better for maximum rooting.
Ready
Grow is a specialized blend
of good things to help your plants
grow, along with a nice helping
of orgainc compost. For organic
seed starting and cloning you
can try Rapid
Rooters, an organic plant starter
from General Hydroponics. |
| ^ back to top |
| |
I
heard that you need to prepare
rockwool before using it. What
is involved?
When Grodan is new it contains some
residual lime from production. Rockwool should be soaked in pH
5.0 water for about 24 hours before
use. This is done to dissolve
the lime. The lime will make the
pH value raise to 6.0. Immediately
before use, flush the rockwool
with your nutrient solution. When
you flush, you also flush out
the dissolved lime. From this
point onwards rockwool does not
change the pH in any way.
It
is important that you don't condition
your rockwool with water at a
pH lower than 5.0. If you do this,
you can damage the actual fibers
of the rockwool. If you use pH
4.0 water, you will find that
your pH jumps all the way to 7.0
. The lower the pH you use, the
higher it jumps. If the fibers
are damaged it can be difficult
to re-establish a stable pH level,
so never go below pH 5 with rockwool.
To
soak cubes, put them in a bucket
filled with water. To soak slabs,
cut a hole in the plastic bag
they come in and fill it with
water until totally saturated.
After 24 hours, cut drainage slits
in the bottom. |
| ^ back to top |
| |
I'm
using a NFT / Aeroponic growing
system. What kind of medium should
I use?
One
of the brilliant aspects of these
growing systems is that they don't need a large amount growing
medium. The only media you may need
is a small root starter cube which
can be then transplanted into a
second, larger cube or into a plastic net
cup. The roots will grow freely
down into the nutrient and oxygen
rich environment. |
| ^ back to top |
| |
How
do I sterilize my media between
crops?
After
you harvest your crop you can
wash the media to remove all the
old roots and then sterilize with
a 5% bleach and water mix (apply
one cup of bleach for each five
gallons of water. ) Some people
dislike using bleach because it
can leave a slight residue. Plants
can handle a certain amount of
chlorine, and so long as it is
very dilute, they should be fine.
Flush or soak the media with the
bleach solution for at least half
and hour (an hour is best). Then
rinse the media in clean water
and keep rinsing until the telltale
'bleach' smell is gone.
You may also choose sterilized
by using a mixture of Hydrogen
Peroxide and water (use a
glug of 35% food grade hydrogen
peroxide per gallon of water). H202 breaks down quickly to leave
only water and oxygen. For this
reason, it does not require as
much flushing. You should soak
the medium for at least an hour
and you should then r flush the
solution out of the medium with
clean water. H202 is good for
plants (it adds extra oxygen to
water) so if there is a small
amount left in the media, your
plants should be fine.
No
matter which method you use, be
careful! Both bleach and H202 will stain clothes and they should
both be handled with care. H202 is especially corrosive and you
should never let it get on your
hands. Wear gloves! |
| ^ back to top |
| |
I
have green, slimy growth appearing
on my rockwool. Should I be concerned?
Algae
flourishes in wet, well-lit locations,
and since rockwool stays moist,
it can become an excellent algae
breeding ground. Although algae
is really ugly, it doesn't directly
harm your plants because it does
not compete with the plants for
nutrients. Algae CAN become detrimental
to plants if it starts to die
and decay. (it will be black and
slimy) In this case it can attract
fungus gnats, invite bacteria
and viruses, and it can compete
with your plants for oxygen necessary
for nutrient uptake.
The
best way to handle algae is to
prevent it from occurring. Algae
needs light to grow, so cover
the rockwool with a dark plastic
to prevent light from reaching
it. The authors of the book, Gardening
Indoors with Rockwool suggest
that a thin layer of gravel or
expanded clay over the top of
rockwool will help prevent algae
growth and gnat breeding. You
should also take care to prevent
algae growth in the nutrient tank.
Shading the tanks, input and output
pipes, and other "wet"
equipment will inhibit algae growth.
Another option is to cover the
rockwool with black/white 6 ml
plastic or any other type of plastic
covering. We offer Root
Guards in our pots section. Even better are Sunleaves' Block Covers. Black on one side, white on the other, these covers do a great job of protecting plants and promoting growth.
Algaecides
are not recommended for use on
food crops. If you choose to use
a chemical product, use very little
and take great care to not expose
yourself, your pets or other people
to toxic products. |
| ^ back to top |
| |
I
have gnats breeding in my grow
media. Should I be concerned?
Those
little black critters are known
as fungus gnats. The term refers
to a large group of insects, most
of which have not been extensively
studied. They reproduce in moist,
shaded areas in decaying organic
matter like leaves and algae.
The life cycle is about four weeks,
with continuous reproduction when
warm temperatures are maintained.
Larvae not only feed on fungi
and decaying organic matter, but
on living plant tissue, particularly
root hairs and small feeder roots.
Usually, there are very few ill
effects from these flies, but
control is advised. After the
roots have been injured, root
rot may attack the plant. Entire
crops have been lost in this manner.
The plant symptoms may appear
as sudden wilting, loss of vigor,
poor growth, yellowing, and foliage
loss.
Fungus
gnats can be easily controlled
with a pyrethrin spray. They can
also be physically captured with
yellow sticky cards.
Perhaps
the most important weapon you
have against fungus gnats (and
all pests) is good grow room sanitation.
Don’t allow decaying plant
material to buildup. Always remove
fallen leaves, algae, or any sort
of organic material that collects
around the base of plants. This
material is a breeding ground
for pests and diseases.
For
more information on controlling
these pests, check our Pests
and Disease FAQ. |
| ^ back to top |