Question
QUESTION: I am attempting to grow ground cover under a cluster of live oak trees without much success. I was wondering if the tree roots are giving off a chemical (such as walnut trees do) to eliminate competition. Or do you think that the ground cover just cannot compete with the tree roots for the nourishment that they require?
ANSWER: Hi Victor,
Thanx for your question.  I have all kinds of shade plants underneath my oak that do just fine.  Here's my list.  Wood poppy, crested iris, wild ginger, lysimachia, lungwort, columbines, liveforever, comfrey.  Vinca minor also does well underneath my oak tree.  What kind of ground cover are you trying to grow?  You need something that will tolerate a lot of shade I'm sure.  What about ferns?  Most local nurseries have an entire section of nothing but shade plants.  Certain low growing sedums do well in partial shade.  I hope this helps.
Tom

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QUESTION: The ground cover is Asian Jasmine.  Thanks for your response.

Answer
Hi Victor,
I was doing some reading on the Asian jasmine.  Hardy down to zone 7, moderate water needs.  And oak does not put out a chemical that will impede the growth of ground cover.  Walnuts and hickories do.  I believe the enzyme is called juglone.  I hope this helps.
thx,
Tom