A lot of times they overstuff and fertilize. Those containers go downhill quickly because the plants are too stressed.

Some plants you can cut back a bit, to make them more full, and produce more flowers. They just wont get as high as otherwise. A better idea would be to plant (or sow) something that simply WANTS to produce so many flowers, that you can÷t see the leaves, like Sweet Alyssum, which is a favourite of mine. Especially the white ones are extremely easy to grow. If you think it gets too rangly, you can simply cut it back. Petunias are another option. I just don÷t grow them, as I don÷t like touching them (they feel a bit sticky), and hate the smell they produce when I÷m dead-heading them... and they need dead-heading to stay alive). Another solution would be to grow something with attractive leaves. To avoid seeing the soil, you could also plant something like sedums or sempervivum they both love the sun, so don÷t plant them with anything that will shade them out completely... they have very shallow roots and don÷t really compete with the other plants, though you have to take care, not to put the sempervivums in pots that contain water loving plants, as they might rot if overwatered (I÷m planning on putting them here and there this year, to see what they will actually accept, in regards of companions, as I have a LOT of them). Lobelia is another option, and Sweet Alyssum, as I mentioned, though they tend to get a bit of hight as well. Or you could just put a pretty mulch on top. Mulching also helps you keeping the watering down a bit.
And yes, as Julianna says, if you buy something that is already planted, it is most often overstuffed. They want it to look good in the shop, to make you buy it. Then when it dies from not having enough water in the soil to feed them all, you÷ll go back to buy another full planter.
Congratulations on your harvest last year! 6lbs of toms is not bad at all!

vgtar, thanks a lot. Thank you Julianna. Am sorry I didnt get back earlier , I was out of town and had bad net. I could only see your replies and was not able to post.

SO pinching sounds good. And I'll probably put a couple of companion plants together in a pot, when they have grown and stabilized a bit. I have never done that before.
And yeah the harvest last year makes me smile. They were so shiny plump and red. Oh so red and juicy. :D

About companion plants. I just plant them whenever they have enough root... Then they can establish in whatever way they feel like it. In my mind, anything you put together, will look good, as long as it's only three plants. I once put a pink peony with a white verbascum phoeniceum and a golden African daisy. Plants you would often think might clash, but it actually looked great! I think things with different textures often look more interesting, than let's say a pot of different coloured petunias. Textures and leaf colours, can also help it look lush, even if one of the plants is out of blooms (or have been pinched back a bit).

How many tomato plants did you have last year to get that many tomatoes? I've never had luck with tomatoes. -Mostly due to double shifts while we have had a heatwave. So far, I've harvested 3 tiny red tomatoes, and a few hard green ones, lol. This year, I'll be trying 2 kinds, and cross my fingers I can keep them watered.
I read an interesting article recently about tomato/basil companion planting. Some scientists had tried out if it was true, that basil would deter aphids in tomato plants, and it turned out it was a myth (the poor scientists actually COUNTED the aphids). HOWEVER, they found out, that for some unknown reason the tomatoes would give a better yield when grown with basil.

vgtar, Good luck with your tomatoes this year. I had 4 plants, one in 2.5 gallon pot and others in 1.5 gallon pots. And from a grocery store Roma tomato that I had used for cooking. It started out of curiosity and I am totally hooked. This year I bought some seeds.

This forum has been so helpful for a total black thumbed person like me. Everything about fighting against pests to saving grocery store potted mini roses!

p.s Having basil with tomatoes is super for one another reason. When u are in a mood for bruschetta / pasta .