Dave Burton wrote:Welcome to permies Bruce!
Since asparagus grows to be bigger than onions and garlic vertically, I think a good planting pattern would be to have the asparagus in the back or wherever they will not shade out the garlic and onions; the garlic and onions look like they are similar enough to each other that they will behave nicely with each other. None of the three plants appear to antagonize each other. When deciding on how to setup a companion planting area, I think it would be useful to consider how the plants are structured and grow above and below ground. For independent research on plants, I think the Plants For a Future Database is useful.
Here is a neat companion planting guide I think would be useful:
Then, there is a more detailed guide:
**right clicking the images and selecting "open in new tab" will allow you to see a larger picture**