Grower convenience, mostly.

As Al says, the plants growing in media that requires more frequent watering are usually
the healthier plants.

Josh

What purpose do containers with built-in reservoirs serve?

Matt

Seriously?

Grower convenience = grower doesn't water as often.
Sorry if that wasn't clear.

Josh

Provide a mosquito breeding area.

...and a place for frogs to hang out ;)

Josh

Is watering container plants from the bottom bad practice?

Matt

I usually leave a question that is specifically addressed to one person to that individual but in lew of the answers you received above I decided to give my take and leave Al (tapla) to answers your question also.

Watering from a bottom reservoir in conjunction with a fertilizer strip on top and cover ( ie Earthbox design or Josh's homemade version) is a very different concept than top watering containers. It is a patented idea utilizing what they call the gradient dispersal of nutrients at a very stable rate.

For growing certain vegetables and annuals each method (top watering vs self-watering containers watered solely from the bottom) has it advantages and disadvantages though I consider SWCs almost bullet proof if you follow instructions. In theory you can't over fertilize and you can't overwater or underwater (WITH THE PROPER MIX). That may be true of top watering containers as well but you must stay on top of fertilization constantly as well as monitoring your water applications.
Of course, once you know what top watered containers require and have a system down , they too, work great. They have certain advantages as well.

I am watering self-watering containers every single day in the height of the season. For me, they are not anymore convenient as regards to watering. They are much more convenient as to fertilizing as you use a fertilizer strip applied only once compared to constant liquid feed over the season in a top watered container. Time release fertilizer approachs the ease of a SWC but that has it drawbacks (and a learning curve as well).

Having said this, I have many, many regular top watering containers as well as SW ones. I enjoy both ways of container gardening. You must try self-watering containers to fully appreciate their attributes and understand any possible drawbacks. You can't compare the two systems without that experience.

Well said, Farkee - and the upper case emphasis you placed on the key point for SWCs is worth everyone's time to scroll up to your post and review.

Al

Yes, well said, indeed!

...Only one problem, I don't have any self-watering containers (if I'm the Josh in reference).

Josh

Thanks for kind comments. I have always been interested in the premise behind SWC and have purchased all the different commercially- available types over the years to compare to one another. Plus, of course, made a few home made versions. Some of my Earthboxes are going on 15 years or possibly older.

And Josh, I meant this Josh.

http://www.josho.com/gardening.htm

Here is a link that might be useful: Josho's home made SWC

Farkee, in my question about SWCs, I was speaking in reference to hanging baskets that have built-in reservoirs, and watering top-watered containers from the tray. I have never used an earthbox, nor do I have any knowledge of using a fertilizer strip. What is a fertilizer strip? I guess I'm dumb when it comes to that way of planting...lol!

Al, you said that when watering container plants, they should be watered enough to saturate the soil good and enough water should come through the bottom of the container to flush the soil of any salt build-ups. My question in the subject of SWCs is how are the salt build-ups in the soil removed if SWCs are used, there's no flushing process with SWCs.
Is it OK to water top-watered containers from the tray sometimes?

Plant lover,

Do you mean something like this:

http://www.gardeners.com/Self-Watering-Hanging-Planter/PotsPlanters_HangingPlanters,34-368,default,cp.html

With something like this --the premise is if you just keep the reservoir full you can't over or underwater. You would still have to water frequently. You also would need to avoid a dense mix otherwise the roots would suffer. Again though I have never used small versions of SWCs.

As far as flushing out fertilizer salts in a hanging basket I would think that if you water enough until quite a bit of water is coming out of the drain then salts would be leached out too.

Fertilizing from the top (ie liquid fert.?) and then later filling from the tray? Trying to think of the scenario you are asking about--if you only filled from the bottom and when you did fertilize you didn't let any extra water come out the bottom then I would think excess salts could be built up but I will let other comments.

For info. about a fert. strip in relationwhip to Self-watering containers go to earthbox site.

Here is how it is set up:
http://www.earthbox.com/resources/about/

Good luck with your gardening.