Yes and yes. Columbine reseeds easily and will thrive in any container that has good drainage and is deep enough for the roots. My columbine blooms well in a 5 gallon pot with a mix of other perennial plants. As for tomatoes the smaller varieties such as the patio tomatoes such as Sweet 100 or Sweet one million, do best as the taller tomatoes can grow so high that they can be knocked over by the wind when staked and heavy with fruit. I have seen a great crop of tomatoes grown in recycled 5 gallon paint buckets but good drainage is key so be sure to drill at least 5 or 6 drainage holes in bottom of any recycled bucket. Black pots attract heat so if you live in a hot climate use white pots but in a cool summer climate black pots would be great. Just make sure you use potting soil not soil from the garden as it will be too dense and won't drain as fast as commercial potting soil. You will need to fertilize plants in containers and I use Osmocote Plus mixed into all my potting soil and have had great results for tomatoes and flowers. Full sun is a must for tomatoes so with a container, good soil, fertilizer and sun just add water and your tomato plants should be productive. Keep growing, Marianne Binetti