I hope you get an answer to this, because I'm still waiting to learn more about a feedback I got on my vegetable garden, which was not to combine annuals (tomatoes, melons and squash) with perennials (strawberries). I did quickly realize that the vines overwhelmed the strawberries, despite all of my efforts to train them on trellises and fences, and so will just plant them outside the garden next year, probably right on top of the compost pile where they can sprawl. I am still waiting to learn the reason behind the principle of keeping perennials separate..

Wow, that was a quick answer. Thanks! I guess my question is solved right there, but I hope others chime in on the perennial/annual issue.

My guess would be to avoid disease. In the worst cases viral problems.

For example Tomato ringspot virus has a wide variety of hosts. Many of which happen to be perennials, such as hydrangea and chrysanthemums, corms and bulbs too, I believe glads among others.

TRV is pretty serious as it stunts and disfigures all new growth.

Like it's name suggests, it is often found on tomatoes, so planting one infected by your mums would be a bad idea.

Sometimes perennials too are already infected with milder viruses that we don't even notice, and whatever annuals we plant might turn out to be hosts too.

Like I said, just my guess on what the reason could be, though.

Watermelon vines will quickly overwhelm strawberries. The melons grow many times faster than strawberry. The melon vines will shade out the berries. That's the main reason I'd keep them in separate areas.

^^ Exactly!! One will overwhelm the other. Otherwise, there is no issue with planting annuals and perennials together, as long as they share similar growing conditions and each has enough space to mature and set flowers and fruit. Since strawberries are a spreading crop, I'd keep them separate just for ease of handling.