I think you'll find that walnut litter is more toxic to the dahlias than the allelopathy of juglone secretions from the root system. A good mulch layer of something other than walnut litter would probably be all you need to plant them within the root zone although for the sake of experimentation, try planting one that you can spare right at the dripline and then plant the others inside of the dripline as doss has said works. Juglans californica (nigra) is a heavy emitter of juglone, so most other walnuts would be less toxic than the California black walnut.
If doss says it's working for her I would plant my most precious things out of trust in her judgement. Worm castings or just plain old store bought mulch will work and do your best to keep the litter from the tree from getting too thick. Another solution might be to incorporate a little steer/cow manure into the bed as it will help to digest leaf litter more quickly, thus rendering the juglone issue moot.
Thank you so much. I've had no luck getting any info anywhere. I've scoured the internet, even called the local cooperative extension today. They had no clue.
These are standard juglans nigra. Virtually nothing from the tree falls into this flower bed but I've had a lot of plant losses there. I assumed after I learned about juglone they were caused by the trees. The trial and error method is killing a lot of plants.
Well, I have read whereby drainage can play a key roll as well ... if the drainage is exceptional, then there is less change of toxicity...I haven't had any trouble so far...gosh now I worry, I had NO idea about walnut toxicity...my patch has had no problems! Goodness
Hello Hart, Can you please give me an update on your dahlias? As the black walnut tree in my neighbor's yard grows, I am losing more and more plants, climbing roses, lilacs, viburnum. My rhubarb is the latest casualty. I am thinking of putting dahlias where the rhubarb was.
Does anyone have suggestions for plants or bushes that thrive near black walnuts?
Hello Hart, Thanks again. Tall phlox is an excellent idea, I would certainly love to see your garden. I have a city garden and not a lot of sunny space. I am trying to juggle dahlias, rhubarb and bonica roses, three long standing garden fixtures. I cannot bear to part with any of them. Now that I know that rhubarb and dalhias are not compatible with black walnut, I am wondering about the bonica roses. I have learned that rugosa roses work. Perhaps I will give it a shot, as you did with your now demised dalhias.
i have found that my daylilies have done fine with the black walnut...looking at a lot having been planted within the last year and are thriving with their growth so far this year...i've heard that clematis are fine and i'm testing that, most bulbs, wisteria (again, testing that this year), lung wort, hostas, decorative grasses, coral bells, lilies of the valley, trying ragwort, ferns, i have a mis-identified sedum that is happy, spiderwort, butterfly bushes, sweet william, elderberry, bee balm and bleeding heart...many are in very close proximity and all are within the drip line...i also have crab apple trees that are doing well...good luck :-)
May dahlia patch grows quite near a huge black walnut tree...no problems here. However I feel you might need faster draining soil to help leech out any of the juglone. Also there is a surplus of walnuts and walnut leaves around the patch, no problems.