Great way to keep soil moist for much longer periods!
I took a vacation to Florida from 5-10-12 to 5-18-12, and I had potted my dalias, as well as many tubers left over that need to be planted elsewhere, so I have about 25-30 dahlia tubers in pots.
Now obviously pots dry out much faster than the soil in the ground does, so I was worried about them drying out while I was gone, which can happen in just 2-3 days if the temps are 70 degrees F or higher, and its sunny. If the temps get into the mid 80's to 90's, then the pots can dry out in 1 day!
So I had planned on dropping 1-2" of mulch on top of the soil in the pots, but when reading the Philadelphia Dahlia Society's webpage, I read about another possible answer to the problem of keeping the soil moist.
This person on their site was talking about this absorbent polymer that is sold under 2 names(Soil Moist and another one that I dont remember). So I went to Lowes and bought a bag of Soil Moist granules.
It was a 1lb bag, and cost $12 or so. I thought that was expensive initially, but I found that a little goes a LONG way, and it can be used over and over as it lasts for years.
It starts out as white granules about the size of a large grain of sand, and it absorbs water and becomes as large as a medium-large marble! The instructions on the bag tell you to mix the dry granules into all but the top 2" of soil, and then add water. But I needed to make sure that there was enough moisture in the soil to last 10 days, so I followed the instructions from the Philly Dahlia society webpage.
I went ahead and took a bucket and added water, then poured in some Soil Moist granules to allow them to absorb the water before mixing them with the soil. You need a lot of water in a bucket, because they will absorb a lot of it, and its best to be able to see how big they will get so you can judge how much to add.
Unfortunately, I didnt add enough water, and they only grew to the size of peas, then I mixed them with soil. But that night it rained, and some of them were on my tailgate, so they fully expanded, and were larger than expected, so I might have added to much to the soil.
Anyway, after mixing them into the soil, if you add to much water or your soil gets too wet, the granules will absorb the extra water, then when the soil dries out, they will release their water back into the soil, keeping the soil moist.
So I mixed the pre-moistened granules into about 14 pots, left the other 13 pots with the same soil, but no Soil Moist granules. Then for good ,measure, I added 1-2" of mulch to all pots.
When I got back yesterday, I noticed that the pots with the Soil Moist AND mulch still had moisture in the soil, and the plants looked good, including 1 Rabitteye Blueberry plant. But the pots that ONLY had mulch on them had mostly dried out, and the other Rabbiteye Blueberry plant was badly wilting. All these pots were in the same area too. Supposedly they got 2 days of intermittent rain here during the time I was gone, but it didnt add up to much moisture.
So I ended up mixing too much Soil Moist, but I just took the extra water bloated granules and put them into 3 zip-lock baggies for later use. I used about 1/3 - 2/5 of the bag of Soil Moist to do 14, 1-3gal pots, and I still have 2/3 - 3/5 of the contents of the bag left(some dry some wet).
It can be used in those pots in that soil for years to come. It lasts for a long time supposedly. It seems to me to be a GREAT idea, well worth the effort!