Co-Habituating Plants in Small Raised Beds
I don't have a lot of space in my garden, just 5 raised beds of about 30 square feet each (10 long x 3 wide), so I often plant things under the recommended spacing and also put plants together very close. Here is some observations of what I've seen.
Onions and Cherry Tomatoes
Onions require some "me" time to get big enough to compete with companions. Their leaves are small and tall. Plant them a month or more before you plant what you want with them. Cherry tomatos are good if you have a trestle and are brutal about clipping any tomato branches which might over shadow the onions.
Here the tomatoes are on one of my wall beds and on a trestle. The onions never bulked up though. This could be because they didn't get enough sun. or this year was too wet. I'll keep watch on these for a later report.
Onions and Squash
Not the best combo, even planting onions a month before the squash. Squash tends to spread, very much. Probably better to give them their own bed. Putting them together, you must be ready to be brutal and trim back any leaves that grow over the onions. Though if you do that, it makes harvesting the squash easier. Squash seems to send a stalk towards the light. Keeping the leaves trimmed exposes the fruit and makes it easier to watch its development.
Keep an eye, animals like rabbits can eat early squash.
Carrots and Onions
Carrots and Onions do well if the onions are planted a month or more before the carrots. Carrots are bushy and can over shadow young onions. The one time I planted them together, the carrots quickly spread so much the onions died.
Carrots and Determinate Tomatoes
Tomatoes come in two types, determinate (which means they grow to a predeterminate height then stop), or indeterminate (which means they keep growing taller all season).
Pairing these two seems to work well, though I would plant the carrots a month early and be watchful of any leaves that might over shadow the carrots.
I will keep reporting on my mixes.