Water, the universal
solvent, is critical to plant growth. Nutrients are transported by
water. Diseases are also transported in water. Managing water
properly will give you bigger yields.
Summertime and early fall
is when Pythium usually appears. "Pythium" is a generic
name for several different root and stem rot fungal species –
Pythium, Verticillium, Phytophthora, and Fusarium. For example,
"damping-off" in seeds, seedlings and clones is caused by
Damage from Pythium
includes infection, reduced yields, and ultimately crop failure.
Pythium can spread like wildfire in water-based hydroponic systems.
Recirculating hydroponic systems provide ideal conditions to rapidly
spread Pythium throughout the garden.
In hydroponics Pythium
flourishes in anaerobic, oxygen-poor, warm (24-33C), and poorly
circulated nutrient solutions. Poor draining heavy clay soils also
Pythium is spread by
un-sterilized tools, tainted water and rotting roots from past crops.
It can also be introduced into the grow room by infected plants.
The key to preventing
Pythium is keeping plenty of oxygen available to roots. Water
temperature dictates the amount of dissolved oxygen in the nutrient
The amount of dissolved
oxygen in a nutrient solution depends on the water temperature. Cold
water can 'hold' more dissolved oxygen. A fully aerated solution at:
Amount of dissolved oxygen
water can hold at different temperatures
10C is 13 ppm
20C is 9 – 10 ppm
30C is 7 ppm
Roots require twice as
much oxygen for each 10-degree C. increase in root system
temperature. But the oxygen carrying capacity of the nutrient
solution will drop by more than 25 percent! There will not be enough
dissolved oxygen to supply the root's oxygen needs. This leads to
sustained oxygen starvation. Slow growth, nutrient deficiencies,
root die-back and low yields result. This stress also makes plants
susceptible to disease and pest attacks.
Fotos of healthy and
Yellow, limp, wilting
leaves, often with nutrient deficiencies
The pH slowly becomes more
Root tips brown – could
also be from over-fertilization
Low water consumption
Darker roots, not bright
white – Note: organic fertilizers also discolor roots
Roots turn brown and slimy
and could smell bad. Often plants look healthy.
Root collar swells and
becomes reddish and later darkens.
Outer portion of the root
is easy to pull off, exposing a thin strand of hair-like tissue.
Damaged roots will not
grow back. Slightly infected roots may turn white again if treated
promptly. Dead roots are a breeding ground for Pythium.
Keep plants healthy,
vigorous and stress-free to prevent Pythium. Pythium is virtually
impossible to eradicate from an infected system. It is best to clean
and sterilize everything with bleach and start over with new clean
Maintain a clean system
with healthy plants
Do not over-fill reservoir
use a device to meter out or shut off water when filling.
Use tank additives to keep
tank clean and healthy
Change and sterilize
temperatures between 19 and 22 degrees C.
Constant aeration. Use
venturis, air stones, and daily h2o2 usage to increase dissolved
oxygen. Allow nutrients to fall back into the reservoir to create
Keep ph below 6.2.
Reduce chances of
root rot by using good sterilized soil. Add amendments to improve
drainage and aeration.
Avoid over watering.
Saturated soil promotes anaerobic conditions.
Inspect roots for
browning. Stressed plants are attacked first, so it is important to
inspect crop and remove unhealthy plants.
Keep ph stable, between
5.5 and 6.0
Keep reservoir / root zone
temps low: 15 and 21 degrees C. Submerged pumps will increase water
Remove and destroy roots
and surrounding soil near infected plants. Provide good drainage and
avoid overcrowding plants.
1. Dip roots in Hydrogen
Remove each plant from
hydroponic system and cut off diseased roots. Dip in H2O2 for a
minute or longer.
2. Sterilize equipment
with 5 percent bleach solution
3. Apply anti-pythium
additives, Vitamin B1, and fresh nutrients to a sterilized reservoir
strength, at cooler temps. Reduce light levels until roots start to
provide vitamins, hormones and nutrients to the plant to encourage
beneficial bacteria to colonize the root system, out-reproducing root
disease organisms, and may "feed" on decayed roots.
Additives should be added during every tank change, except for H2o2.
You can still plant
seeds and clones outdoors. Plant seeds indoors and transplant
for best results.
Prepare soil before
transplanting by adding amendments. Use water-absorbent polymer
crystals to hold water in remote gorilla gardens.
and clones. Move transplants outdoors for an hour the first day and
increase the time by an hour every day. In 7-10 days, transplants
will be acclimated.
seedlings and clones outdoors. Remove lower leaves on leggy plants
and bury up to first set of leaves.
caterpillars, rabbits, mice and deer are the main pests now. Set
out bait for mollusks and caterpillars. Discourage rodents and deer
Mulch plants weekly to
conserve and attract water.
Water plants regularly.
A healthy female clone in a 30-liter container can easily use 5
liters of water a day.
Fertilize if necessary
with a complete mix with more N than P and K. Be careful to not
over-fertilize. Apply a soluble fertilizer if able to water plants
Prune and bend plants
to avoid detection. Prune top of plants to control growth.
Protect roots from
cooking in pots by shading pots.
Keep humidity at
less than 60 percent in the grow room to avoid problems. High
humidity promotes mold and pest attacks. Keep oscillating and
extraction fans on 24 hours a day if necessary.
below 30 degrees will keep your garden growing strong and
Water plants daily if
necessary. Water usage goes up to more than a liter a day for strong
healthy plants. But, be careful not to over-water.
Lower fertilizer dosage if
leaves show signs of tip burn or are excessively green.
Flush plants with a
mild nutrient solution at least once a month.
Take clones so
they are ready to transplant the day you harvest.
at leaf undersides closely for spider mites and eggs. Spray
mites with pyrethrum or neem as needed.
Replace harvested plants with clones the same day of harvest.
and disinfect room before moving in clones.
Remove odors from
flowering plants with ozone or charcoal filter.