If you put something like packing peanuts in the bottom to provide drainage, you can easily plant annuals in 6 inches of soil.
Linda C

If you can find hanging baskets big enough to fit the tops of your containers, line them as you would to hang them, then plant in them. I had much better luck this way than partially filling pots with peanuts.

Thank you Lindac. I had been saving packing peanuts and now they have come in handy. I put them in heavy plastic bags which contained seeding 'soil' and they worked fine. Thanks also Handee, but I only got your note tonight after I had already prepared my pots, but yours is an excellent idea. I'll use it for my hanging planters whose hangers have broken. It may be difficult to find 18- 20 inch hanging planters. My annuals will be in tomorrow and my basement is free of packing peanuts!! Thank you both.

What a great thought: put the packing peanuts in a plastic bag before you put them in the bottom of the pot. I've always put packing peanuts in the bottom of the big pots on my deck. But when I go to change the soil, I can't add most of it to my compost pile because of the loose packing peants. D'u'oh, just put them in a bag first and they are easy to remove and reuse uunder new soil.

If you put the peanuts in a plastic bag in the bottom of the pot, there is the risk of blocking the drainage....
If you just use peanuts in the bottom of the pot, scoop the top of the pot out v e r y carefully when you want to replace the soil.
And...be careful you don't use those new biodegradable packing peanuts....or you will find your plant slowly sinking out of sight! LOL!
Linda C

Thanks for the heads-up, Lindac.I soaked each of the containers after filling them with soil, and left them to drain and the water seemed to find its way out somehow. I don't mind a little water retention because even though I use soil-moist, I find I need to water my pots just about every day. We have had temps. of over 30 degrees the last two days and everything was parched.

I like to put pinecones (plentiful in my area) in the bottoms of large pots to help with drainage and displace some of the soil to (1) save on soil, and (2) keep the containers from getting too heavy.

And they're FREE!!

I fill the bottoms of my large containers with chunks of styrofoam. The chunks are bigger than the peanuts and so when I empty the pots to freshen up the soil before planting again each spring the styrofoam is easy to pick out and reuse.

An upside down plastic flower pot is the easiest of all. They have worked very well for me.

The good thing about the plastic peanuts is that the fast growing annual root systems will USE them as growing medium. Even annuals like as much space as possible in order to develop their fast growing roots. The use of anything that blocks the infiltration into the whole container may be limiting. I often use packing peanuts in the bottom 1/3 of very large containers, and at the end of the season the root systems have completely grown in and around and through the peanuts. Limiting yourself to a very shallow root system will really put a damper on the vigor of your plants.