Interaction between Heracleum laciniatum and some other plants

The aim of this study was to find out whether the low plant production under a canopy of Heracleum laciniatum Horn was due to competition for water, nutrients or light or to chemical inhibitors produced by H. laciniatum .
The main conclusion is that the low plant production observed under the canopy is due to competition for light. There were also indications that the competition for nutrition was larger in the soil under H. laciniatum than in the meadow outside the stand, but it has not been shown that nutrient supply limits the plant growth under the canopy. There were no indications that competition for water was a limiting factor. Water percolated through pots with H. laciniatum plants slightly inhibited growth of Poa pratensis and Phleum pratense , but had no effect on H. laciniatum . In soil samples collected from mid of June to late October seeds of Phleum pratense germinated better in meadow-soil than in soil collected under H. laciniatum . Allelopathy is suggested to account for a minor part only of the suppressed plant production under a H. laciniatum canopy.