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Best medium for moisture retention in hanging baskets and pots

Posted by piper101 Z9 So.Calif (My Page) on
Sat, Mar 29, 08 at 12:36

Hi, After taking a class from a local nursery about soils etc. I'm contemplating replacing my soil on most of my container perennials and hanging baskets etc. Now that I know the potting soil I used, bagged, was mostly junk, I'd like to get more life out of my perennials and this might be the way. I was thinking that it might help to have an agent in the soil that would hold moisture in my pots and hanging baskets since there are times when I am away from home and hire a young girl down the street to water etc. I usually end up losing a few for lack of water, I'm assuming.
So....when I do this, would perlite or vermiculite be the better water holder? Or something else someone knows about? I know about pumice for drainage and airation. I do the organic thing so I don't want to use those funky water crystal things. Thanks for your help.


Follow-Up Postings:

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RE: Best medium for moisture retention in hanging baskets and pot

The problem is with containers they are exposed to the heat and sun nothing will stay moist for long but I believe compost would be the best medium to plant in versus perlite or vermiculite.

Here is a link that might be useful: Propagating Perennials


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RE: Best medium for moisture retention in hanging baskets and pot

  • Posted by tapla z5b-6a MI (My Page) on
    Sun, Mar 30, 08 at 12:26

The problem with compost and vermiculite is that they lose their loft and compact "after about .... ohh, .... say 10 minutes." Credit to Rhizo for first using that line In soils, perlite promotes drainage and improves porosity. It's also effective for starting seeds & cuttings. Actually, perlite holds quite a bit of water @ about 3/4 quart per gallon of perlite. The dry weight of perlite is about 7 lbs/cu ft. Wet, it weighs about 18 lbs for the same volume, so it holds more than 2-1/2 times it's weight in water, but since it's soo light, that's not much. It also gives its water up quickly, so has a steep water retention gradient.

Vermiculite is about the same density, and has an even higher capacity for holding water and a very high cation exchange capacity. It also contains some magnesium and potassium that are available for plant uptake, but it is not very durable and will compress if handled when wet. It also has a slightly higher pH than perlite.

Turface is a baked clay granule and the Schultz Corp bags it and labels it as their "Soil Conditioner". This product has more than 13 acres of surface area per lb, which translates to very good water/nutrient retention.

My suggestion for a soil that will hold very good volumes of water and still drain well is:

6 parts Turface or Schultz Soil Conditioner (same thing)
3 parts fine pine bark
1 part sphagnum peat
1 part vermiculite
1 tbsp garden lime (dolomite) per gallon soil
a micronutrient source or use a fertilizer that has all the minor elements.

The compaction factor that makes vermiculite a suspect choice at any notable volume in container soils is a minor issue when the total volume is kept somewhere near 10%, so it's no accident that the volume of vermiculite suggested works out to around 9% in the above mix.

Al


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RE: Best medium for moisture retention in hanging baskets and pot

Thx Al !!!!!


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RE: Best medium for moisture retention in hanging baskets and pot

A problem frequently encountered with hanging baskets is how often they need to be watered. For many it can be downright difficult to keep up.

While the potting mix is important may I suggest that it might be a secondary concern (in terms of water retention) to the type of container used?

When I see hanging baskets in stores I generally see plastic containers with a million holes in them or wire baskets intended to be used with fiber linings.

In both cases water loss is going to occur at an elevated rate due to evaporation because of how much air the pot itself allows to touch and dry the mix.

For the life of me I can't understand why 99% of containers intended to be set on a solid surface have impermeable walls (or nearly so) and a single drainage hole on the bottom, but 99% of containers intended to be suspended in the air are incredibly perforated.

Perhaps try lining the hanging basket container with plastic sheeting (like the kind sold in the painting section of the hardware store) and punch a single drainage hole in it. This should slow down the water loss due to evaporation.


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RE: Best medium for moisture retention in hanging baskets and pot

Does the Schultz soil conditioner you are recommending say "Clay Soil Conditioner" on the bag?


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RE: Best medium for moisture retention in hanging baskets and pot

On a visit to Victoria, BC fifty years ago I was fascinated by the hanging baskets of flowers on the lampposts throughout the business district. When my inquiries found they required a daily watering I was put off the idea of creating my own. Today I do have some hanging baskets on an automatic drip system that waters every other day during the summer. I use my regular container soil with plants tolerant of some abuse. Al


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RE: Best medium for moisture retention in hanging baskets and pot

  • Posted by tapla z5b-6a MI (My Page) on
    Wed, Apr 2, 08 at 10:51

Yes, Gigi.

Al


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RE: Best medium for moisture retention in hanging baskets and pot

  • Posted by tapla z5b-6a MI (My Page) on
    Wed, Apr 2, 08 at 12:38

BTW, Piper. JaG made a good catch when he noticed you said "hanging baskets". For some reason, when I read that, I was just thinking of suspended pots and hadn't taken into consideration the fact that there would be so much more evaporative loss from the baskets. My bad! ;o)

His observation that the soil make-up is secondary to the cultural effect of the basket is true. You really should prolly consider lining your baskets with something that will eliminate or at least reduce the surface area exposed to the drying effects of the wind. The soil is still a good choice, but it probably won't go as far toward solving the problem as you'd like w/o incorporating JaG's suggestion or something similar.

Take good care.

Al


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