[Arid_gardener] Question from Home-Hort WWW page

[Dick]

This is only my own perception with which others may agree or disagree.

I believe that potting soil must be porous enough to allow water to flow all 
the way through washing out previously deposited salts  pulling fresh air in 
behind it.  But if you set a container on concrete or hard ground, water 
will only travel as far through as gravity can take it. The attraction of 
the soil particles and pull of gravity will reach an equilibrum at some 
level determined by the soil density and the porusity of material beneath 
it. Any soil below that point of equalibrium in the container will be 
saturated without air causing feeder roots to suffocate.

If, however, the soil in the container has a direct connection with the soil 
beneath, the water table will travel all the way through the container 
pulling oxygen/air in behind it.

Personally, unless I was not in a position to rewater as a plant needs it, I 
would never use moisture control potting mix for ordinary circunstances. If 
you are using black plastic containers in open sun, you may be cooking the 
feeder roots in close provimity to the plastic. You can spray white latex 
paint on the surface or wrap burlap anchored with clothspins around the pot 
to prevent the plastic from sucking up all that mid-day 122 degree heat.

I try not to rewater until I can detect a slight wilt or loss of luster in 
foliage before soaking the root media again pulling fresh air in behind it 
as the water recedes.

You may not have adequate drainage holes in the containers. Ideally, the 
soil in a pot should have a connection with the soil beneath to get wicking 
action.

Pots are a good way to go in this climate but, without excellent drainage 
and protection as needed from direct sun, it is assisted suicide for tender 
garden plants.

Tomato fruit cannot tolerate direct son without sunburn. They can be shaded 
or sprayed with a mixture of gypsum and water. Water evaporates and the 
gypsum crystal reflects the sun.

With perfect drainage and good potting soil, you would have a hard time over 
watering.

If, however, you are using black plastic containers in direct sun, you may 
be cooking the plants.

Dick Gross, Master Gardener Volunteer
U of A Maricopa County acOOPER
----- Original Message ----- 
From: <rayt1957 at hotmail.com>
To: <arid_gardener at Ag.arizona.edu>
Sent: Sunday, April 27, 2008 2:13 PM
Subject: [Arid_gardener] Question from Home-Hort WWW page


>
> 85719
> rayt1957 at hotmail.com
>
> I have been trying to grow tomato plants in 5 gallon plastic buckets for 
> the past year, with absolutely know success(have lost about 10 plants). I 
> drilled plenty of drain holes in the bottom of the buckets and used 
> Miracle-Gro Moisture Control Potting Mix. However, I think I might be 
> overwatering them and it appears that my tomato plants might be dying from 
> pythium root rot, pith necrosis or some other disease, because of this. 
> The upper leaves start dying and move downwards and the stems become 
> hollow inside. In this respect, I think the Moisture Control Potting Mix 
> might be causing me more problems, because it retains so much moisture 
> that the roots aren't able to get enough oxygen to them. Everything I've 
> read on the internet says that you must water plants in containers more 
> often, at least several times per week, than those planted in the ground. 
> I didn't water my tomato plants for 3 weeks and that's living in Tucson, 
> Arizona, where the temperature has reached approxima!
> tely 80 degrees or more, during that period. After watering(til water 
> trickles out the bottom), within a couple of days, my tomato plants 
> starting wilting from the top, down and all but one of my plants, died. I 
> haven't watered the lone surviving plant since then(almost 3 weeks ago) 
> and it seems to be growing back, just fine. How can I possibly know how 
> much and how often, to water my tomato plants? Is the Miracle-Gro Moisture 
> Control Potting Mix the best choice for container gardening? I would 
> appreciate any advice you can give me on this matter. Thanks
>
>
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