You can build your own from wood and insect screen. You can go to the dollar store & buy plastic containers (rectangular or round - colanders) that have hundreds of perforations in them for $____ (guess how much). Or you can spend the big bucks & use any one of a number of sizes of containers designed for holding pond plants.

Here is a link that might be useful: C'mon. Let's go look at those pond baskets he told you about!

I've never used air root pruning containers, but I am familiar with the work of Dr. Carl Whitcomb who has led the research and development of these containers for the nursery industry. Dr. Whitcomb's book Plant Production in Containers is very informative--so much so that I'm thinking about shelling out 70 bucks for the revised edition. It has lots of information on air root pruning, as well as other facets of container growing.

It's my feeling that air root pruning containers might be unnecessary for the home gardener. If you're only growing a few plants, it might be possible to achieve the same effect by manually pruning the roots and potting up in a timely fashion. (What do you think Al?) This would be impossible for a nursery growing thousands of plants because of the labor required.

So now Rudy--you have to include manual pruning as part of your research and let me know the results. That way I don't have to spend money on those containers myself if they are not helpful. I'll include a link to Dr. Whitcomb's own company that sells the air root pruning containers (only in bulk unfortunately).

Jason

Here is a link that might be useful: rootmaker containers wholesale

As a hobby grower who's interested in woody material for bonsai, I think of them more as an intensive care unit for sick trees or trees and shrubs collected from the wild. Often these plants have left behind 95% of their roots and a root-friendly environment goes a long way toward getting them re-established in a container. Because the added aeration promotes lots of fine roots, o/a plant development is much quicker in these containers.

Like all containers, they work best with an open, well-aerated soil. The down side of using them, for some, is the extra effort required to keep plants watered and fertilized. Root-pruning or, at a minimum, potting-up is still required, but not as frequently. They do help to reduce the occurrence of encircling, girdling, and malformed roots.

Al

If you are starting out with seeds you might want to try a soil block maker. They are labor intensive, messy until you get the hang of it and expensive but they work. You can make your own blocks without the expensive tool by making a frame of thin wood. The slats should be 2 1/4 to 3 inches wide and the length can be what you think you need so long as each can be cut to the middle at 2 1/4 to 3 inches. I put mine in trays that are 12x16 inches so the slats are cut to fit in that. The long slats are cut half way through starting the measurement in the middle of the length. You will adjust according to the size of your tray. The short slats are cut the same way and the slats fitted together to form a frame like the dividers in a tray of tomatoes or oranges. Fill the spaces with the block making soil and let them set up. Remove the slats carefully and you have soil blocks. You can always make a frame outside of the tray and just put the finished blocks in the trays if that is more convenient. I like to use capillary cloth for watering. The blocks don't get knocked around that way. As germination takes place the good blocks can be separated out to save space. I think I typed all the info correctly. This is the first time I have needed to do it. If I messed up let me know.
This is a typical recipe for the soil blend.
Henry's Recipe for Making Soil Blocs
For decades, some gardeners have been making soil blocs as an alternative to buying sterile mix and those plastic 6-packs. Although the planting mixture is not sterile, it provides better nutrition than the sterile soil mixes and hence stronger, healthier plants.
Soil blocs are made with a simple hand press available from Fedco Seeds or Johnny's Select Seeds. Following the recipe below, you can make 2-inch cubes that will support balanced growth for the 6-8 weeks most seedling will need before heading out to the garden.

To make enough mix for about 500 blocs, mix the following ingredients in a wheelbarrow:

10 quarts of dry peat moss
1/4 cup limestone
1 cup azomite or granite dust (optional)
Then add and mix well:
10 quarts coarse sand
10 quarts of peat humus
1/2 cup colloidal or rock phosphate
1/2 cup greensand
1/2 cup organic blood meal

Finally add and mix well :

8 quarts of compost
8 quarts of garden soil.
To make enough mix for about 500 blocs, mix the following ingredients in a wheelbarrow:

The mix is somewhat dry, and needs to be moistened and used in small batches. For a start, mix 4 quarts of mix with 1-2 quarts of water, stirring it with your hand (wearing a rubber glove). It should be gooey, but firm, not watery. Experiment with it until you find just the right consistency.

To make the blocs, make a pile of the gooey stuff 4-5 inches deep in a recycling bin or other flat bottomed container. Then compress it by squishing it with the bloc maker. Fill up the cavities of the blocker, then get rid of any excess by pushing the blocker down and rotating it against the bottom of the bin. You can eject the blocs with the squeeze of the spring-equipped handle. Line up the rows of blocs so that they do not touch.

Each soil block has a divot on top where you should drop a single seed. Most seeds do fine without any soil covering, though vermiculite can be sprinkled on top if you prefer. A sharpened wood dowel that is moistened will pick up tiny seeds easily, and drop them onto the bloc when you touch it.

You can easily make a self-watering system for the soil blocs. Use those plastic trays that are sold to hold for seed flats as water reservoirs. Make platforms that will sit above the water by cutting 1/2-inch plywood into pieces 9" by 19 ", and attach 1 1/2 inch cubes of scrap wood for feet with screws. Place these platforms in the trays and cover them with a sheet of polyester backing material to wick up water. The material should fit over the platforms and dangle into the water. The material keeps the blocs evenly and consistently moist, but not soggy.

The advantages of this system are numerous: Germination rates tend to be very high because they hold lots of moisture. The cubes also contain more soil than most six packs, too, allowing for better root development. Plants don't get root bound as they do in plastic containers because the roots stop, poised for action, when they hit free air at the edge of the bloc. And they transplant into the garden beautifully, with no root disturbance. Once you have the tool for making the blocs, it is a less expensive system than buying those disposable plastic six packs every year.
Good planting, Sandy