When planting large patio pots it is customary to put something in the bottom of the pot to keep the drainage holes from clogging. The addition may be a layer of gravel or pieces of broken pot sufficient to cover the holes. After this is accomplished you start adding soil, and adding soil and adding soil. These large pots take a lot of soil and consequently are quite heavy.
Do you really need all that soil? The annuals that go into these summer pots tend to have shallow root systems. Rarely do they go more than 6 inches into the soil. What if you didn’t have to put all that soil into the pot? The pot would be lighter should you need to move it and you wouldn’t need to deal with such large quantities of expensive soil. There is indeed an alternative to the usual assembly of these large pots.
Find a large sturdy pot that comes to within about a foot of the rim of the pot. This pot must be of a stiff plastic or clay. The more flexible plastic pots will collapse and not fulfill their designated purpose. . Place the pot upside down over the central drainage hole. If there are other drainage holes they can be covered with pieces of pots or smaller sturdy pot in an inverted position.
After the pots are in place start filling with soil. You will need a much smaller quantity to fill the large planters as the inverted pots are taking up the space that you would be filling with soil. You have essentially created an air space in the center of the planter.
I’ve been doing this for a number of years with larger pots and haven’t found a down side to the method yet. Theoretically, the pots might not hold as much water since there is less soil but it doesn’t seem to harm the plants. The roots are better aerated and less likely to rot from excess watering. Give it a try. It works!