why do you think it is a drainage problem causing the poor health?

You really can't add anything at this point without disturbing the roots and the watermellon will *not* appreciate it at all at this stage.

You can add a wick by simply poking an absorbant material up into the drainage holes with a pencil or some other long, thin object and letting a portion hang out.

You may simply have a clogged drainage hole though. If you can tip the container a bit and poke your finger into the holes this will fix the problem, at least temporarily.

Still, why do you think it is a drainage problem? I am not saying it isn't, but I didn't read anything in your post that indicated a drainage problem, just that the plant was in poor health. Trying to be thorough, not just a pain in the butt ;-)

The soil isn't drying out. We've had 80+ weather the last several days. The watermelon & the pumpkin get the same amount of sun. The pumpkin is dry several inches down whereas, for the watermelon, you barely brush the soil aside and it looks as if it was watered only that morning. The plants are actually not that big, only about 6". They were transplanted three weeks ago and have just been going downhill ever since. Before I got them transplanted, they got little water, were sheltered, and they were thriving. These plants were actually my second set. My first set died before I could ever get them transplanted. They started wilting and I kept giving them more water, but didn't realize that they weren't draining properly so I drowned them. My new set is wilted and going crunchy like my first set, which is why the only thing I could figure was that it wasn't draining properly this time either. Is there something else that could be wrong with them?

- Is there something else that could be wrong with them? -

Unfortunately, yes.

Watermellons (and other vine crops) are very susceptible to fungal and insect attacks. A vine that looks good one day and is wilted the next day and goes downhill uncontrollably stands a good chance of being diseased or injured.

I am *not* saying that is the case with yours, I can't know that.

If you wish to focus on the drainage (a potential problem as well) then go ahead and use the wick. If the current plants die I suggest you replace the potting soil entirely (in case of disease) and focus on a mix with larger particles, but do be prepared to water the heck out of it once the plants do get growing as they will use all the water you can give them. I, personally, would be hard pressed to use a fast draining mix with watermellons, but I find daily watering a chore, not a pleasure as some do.

In the mean time perhaps try only spot watering around the small plants (once it dries out a bit) instead of getting the entire pot wet. Not much you can do about the rain though.

I agree. Stick a wick as far into one of the drainage holes as possible and then watch to see if water drips out along the wick. Roots rot if they are surrounded by water but the plant usually suffocates before then.

If you read the (Long) thread below, you'll benefit greatly from understanding what a perched water table is and how it can ruin your plants, the need for aeration in the soil, and how that's accomplished, etc.

Here is a link that might be useful: Container Soils and Water in Containers