OldSoul <---- LAZIEST. GARDENER. EVAR.
We've done container gardening forever, BECAUSE I AM LAZY.
Advantages:
Manageable
Little to no weeding
Up off the ground
Space efficient
Disadvantages:
Unless you can get super creative with soaker hoses or drip systems, you'll spend a surprising amount of time with the garden hose in your hand. Pro tip: just leave the ^*%%*%&&!!! hose out, alongside the containers. It's easier that way. Drain it in cold weather if you are cold weather planting. You may even have to unscrew it from the faucet if you think you're gonna have a hard enough freeze, so the faucet won't freeze. Be careful not to trip over the hose. But my gardening life got that much easier (AND MOAR LAZY!) when I gave myself permission to just leave the %&*%&&$!!! hose out.
We just put in our first garden of the season. I thought about this thread as we were doing it, so I came back to contribute.
Here's our set up:
We have several large planters, think the kind of half barrel and deep patio planters that you see at Costco. They have held up for us for YEARS. We drilled additional drain holes in the bottom of each. They are sitting on a portion of our yard that has a deep bed of gravel. When we had the driveway run we simply extended to this portion of the yard. So, our drainage is sort of backwards in that our gravel bed is under the planters, but with additional holes drilled in the bottom, it works.
We keep a tumbling composter for non-dairy, non-meat kitchen waste: egg shells, coffee grounds (you can leave the grounds in the paper filter if you use one) tea bags (ditto paper tea bag and string, I remove the tag with the staple because I don't want to stab myself with a rusty staple later) vegetable and fruit trimmings. It's probably too late for your own compost this season but you can certainly start it now. Throw a shovel full of moist dirt from your yard into the bin to get some worms/worm eggs in there. Or, you can buy some red wrigglers and put them in there, once you get some food (kitchen waste) in there for them. The worms are essential- they break down the components and their poop is the best fertilizer on earth.
We keep the same potting soil in our containers every year, but we do top off with mature compost from our composter and with more potting soil if needed. The mixture of compost and potting soil should look more like dirt than compost, if that makes sense.
For your first fill or topping off, find potting soil that contains slow release fertilizer to make your life easier. If you are using last year's soil, add compost and slow release fertilizer to the soil. Make sure it's slow release fertilizer only; you do not want products with insecticide or weed prevention in them. If you *must* use insecticide (sometimes it can't be helped, our fauna here is remarkable) you'll want the spray on or dust on kind that can be washed off, not the kind that's absorbed into the food you are going to eat.
SO- this year we didn't need more potting soil. We weeded out our containers, turned the soil with a shovel, just about emptied our composter to add compost to each container (a child's red wagon is just about perfect for this application!) then turned the soil again. Work the compost into the soil thoroughly to prevent "hot spots" from forming as it further decomposes.
Then, this is somewhat controversial, but it's a personal practice of mine for seed starting in containers, I sprinkled just a bit of granular Miracle Grow over the top of the soil. This is the stuff you mix with water or put in the garden feeder that you attach to your hose. I don't dump a ton into the planters but I sprinkle a light coat over the top of the dirt, kinda like you'd put sprinkles on a cupcake- about that much. Then I turned that under just the top layer of dirt.
Why do I do it that way? BECAUSE I'M LAZY. We start this season's vegetables from seed, so I'm going to be out there lightly watering the seeds every day anyway. The soil will stay moist- essential for starting seeds. Adding a little bit of granular Miracle Grow leaves it in the soil, and liquidates it gradually. It'll be there when the seeds germinate.
I will also add slow release fertilizer at the same time I add granular Miracle Grow, and work it into the top layer of dirt at the same time, if we are reusing dirt/not topping off with a substantial amount of new potting soil with fertilizer in it. (I forgot this step this year and didn't think about it until after I planted the seeds, so I just sprinkled the slow release fertilizer on top of the soil when we were done. That works too.)
Per above, turn the fertilizer in lightly, then plant seeds.
For leafy green vegetables, which we planted today, I sprinkle the seeds over the top of the soil, then rake them in lightly using a three prong hand cultivator. Lettuce seeds especially need light to germinate, so don't plant them too deeply. Spinach seeds don't need to go too deep either.
We planted five containers of spinach, two containers of spicy mesclun and two containers of gourmet lettuce blend.
BONUS ROUND:
When planting in containers (or even in the earth!) think in layers. We have five obelisks that we use in our planters for vegetables that want to grow on trellises like cucumbers, pole beans, etc.
We put the obelisks in the planters with the spinach and planted snow pea seeds around them. Poke the pea seeds into the soil a couple of inches with your finger around the base of the obelisk.
I used a half packet of spinach seeds for each container, a pack of lettuce seeds for each container, and about a half dozen pea seeds around each obelisk. I tend to pack my containers pretty full.
I planted more spinach than lettuce because we can freeze spinach, not so much with lettuce.
Potatoes of all types also grow well in containers, and can be paired with obelisk planting as well.
In the past I also used a cold frame in a garden bed in between my containers. It was a Juwel cold frame and it was really nice. We grew spinach and lettuce all winter long.
I no longer have the Juwel cold frame. It's so windy out here in the winter that the little Juwel cold frame wouldn't have made it. I'd love to construct a cold frame type of structure for some of the containers. Or, just break bad and get a greenhouse.
As the season turns, we'll sacrifice the containers one by one to summer veggies. We've grown tomatoes, peppers, peas, spinach, and squash in these containers.
The absolute best yield we ever had was a surprise! I played with bona fide full on vegetable hydroponics indoors for a while in our previous home. Because we used our cold frame for spinach and lettuce, the containers were empty over the winter and into the spring. We'd used our household compost in the containers, as usual. When I changed the water in the indoor hydroponics trays, I took the used water outside and poured it into the cold frame, and into the containers, just to put whatever nutrients were left into that soil. Two of our containers sprouted volunteer bell pepper plants- I'd not planted bell peppers in those containers at that time, so these plants were absolute volunteers. I didn't expect them to produce because my understanding is that commercially produced vegetables are from hybrid seeds. They will produce plants but not necessarily vegetables. But I kept watering the volunteer pepper plants with the used hydroponics water just to see what would happen.
Each of those containers produced a bushel of bell peppers! Beautiful bell peppers, as sweet as could be! We had frozen bell peppers FOREVAR. Best free peppers ever! The plants were packed in tight and I never thinned them, just let them do their thing.
I've not yet tried this but I'd like to do so one day. Look up 'keyhole gardens.' These gardens pack plants into raised containers, with a central compost bin for nutrients. These gardens sort of "self-fertilize" through the composter, and also retain moisture and require less water. Keyhole gardens and square foot gardens and my experience with the packed in volunteer pepper plants have encouraged me to pack more vegetables into our containers.
Hope this helps! Happy gardening!