I planted a single borage plant in 2014 but it succumbed very early to an infestation of squash bugs. So I don't have much experience
with it, although I found the leaves and flowers very tasty. I hope to plant a lot more in 2015.
I just stumbled by accident over this detail in a post by John Polk
in a honeybee plantings discussion:
As a companion plant for tomatoes, it [borage] will eliminate, or reduce hornworm problems.
John also posted a very nice borage photo:
Searching on permies turned up another reference
to a line on an external website
Borage acts as a deterrent to tomato hornworms and cabbage worms and is known to attract bees and wasps.
Some independent Googling turns up hundreds of references to the notion that borage deters hornworms and is therefore a good companion planting for tomatoes
. But most of those references are like the ones here -- brief sentences without much detail. And often (out on the web) prefaced by weasel words like "it is said" and "I have heard". The way this lore appears in so many places with so little detail, it "feels" like one of those things that everybody thinks they know but nobody really has tested or tried to prove. Often if you really did into these bits of lore they turn out to be something printed in a farmer's almanac 200 years ago by some almanac-selling dude prone to making stuff up.
In the course
of this searching, I found one lovely page with gorgeous photos of borage, tomatoes, and green hornworms. That gardener's experience is that hornworms don't care if you plant borage or not: http://www.shenandoahvalleyflowers.com/gardening/the-borage-the-hornworm-and-the-bumble-bee
So I thought I'd make this post to create a central spot for collecting borage versus hornworm lore, knowledge, and experience. Permies, what say you?