I plan on having annuals (cosmos, globe thistle, mini sunflowers) and perennials (salvia, echinacea) that I can move around each year, so maybe saucers would be a good idea
With the annuals it shouldn't make any difference but with the perennials it would. Sooner or later you will have to do something with the perennials anyway as they will eventually outgrow a 20L pot.
What pot size would you suggest?
I would wait until the perennials were becoming rootbound and then get a larger pot. But the larger the pot the harder it is to move around. It will be quite some time before the salvia's become root bound so I wouldn't worry about now. I don't know about the other perennial and how its roots develope.
My sack barrow is a continuously useful tool. I am not up to heavy lifting anymore, but I can always manoeuvre something onto the platform.
I had my saucers so I only need to water once per week across our hot summer. I use those felt grow bags sometimes. I have about 20 of the 7 gallon but bought some 15 gallon this year. I really want to fallow some garden areas and then dump the soil there in the fall.
I plant on cement or metal racks off the floor. I would put a flat wide big concrete block underneath your pot. Now im not sure how big 20 liters is but, it would have to be bigger than your pot slightly. So, if or when you put plenty small holes though your pot. The water can just rush away from the pot. Rather than create more of a muddy environment. An you can see when the water is coming out on the flat concrete block or square. That's just an idea, if you don't have a spot with concrete. but also the saucer restricts air flow in my experience. I prefer airflow underneath the pot for air to roots helping dry the pot. But, I use multiple ways of growing
concrete that looks like this you its a big flat square put your pot under it. If you have any laying around or something you got around your home might work too.
I notice some plants like a nice even moisture and do well at the edge of stones or concrete steps. I surmise that should small brick size pavers be used the roots might grow down through the drains and cracks and under the stones.I plant on cement or metal racks off the floor. I would put a flat wide big concrete block underneath your pot. Now im not sure how big 20 liters is but, it would have to be bigger than your pot slightly. So, if or when you put plenty small holes though your pot. The water can just rush away from the pot. Rather than create more of a muddy environment. An you can see when the water is coming out on the flat concrete block or square. That's just an idea, if you don't have a spot with concrete. but also the saucer restricts air flow in my experience. I prefer airflow underneath the pot for air to roots helping dry the pot. But, I use multiple ways of growing
There's also hanging pots that are pretty cool. I hope to try one day. I've never had that issue with roots. But, I suppose it could be possible, but I would be more worried about the concrete getting hot an stressing or burning the plants roots. From the heat from the sun absorbed by the concrete.
I like to garden with little to no money. An take care not to lose all my gardening supplies from years back. Comes in handy when you really really need to make something like support for a plant or something. This is going to be one of my biggest grow seasons to date. So, super excited for this season.