Daffodils and Allelopathy
Many years ago, I planted some daffodils and crocuses in our wooded back yard. The daffodils and crocuses would emerge and flower then lots of may apple would emerge. Today, the crocuses have spread greatly, blanketing an expanding area each year, and in that area, there are no may apples. The daffocils have also naturalized and spread, in clumps, and there I see fewer and fewer may apples. Can you explain. Are the daffodils and crocuses allelopathic? Are they toxic to may apples? Should I remove them so that the native may apples can come back?
Howard County Maryland
Daffodils are known to produce alkaloid chemicals, some of which have been observed to be allelopathic. Saffron Crocus (Crocus sativus) has also been researched for allelopathy, though we do not know if other Crocus share this trait. We do not know if Mayapples (Podophyllum) are vulnerable to these compounds or not, but it's possible the bulbs are merely crowding-out the Mayapples. We suggest that, if you wish to keep the colony of Mayapples prospering, that you remove the bulbs from that location and re-plant elsewhere in the garden.
Thanks a lot. This is helpful advice.