Backgrounds and aims <p>Allelopathic species can be key components of successful integrated weed management. We evaluated the suppressive potential of buckwheat (<i>Fagopyrum esculentum</i>), simulating the effect allelochemicals exert through crop residues or root exudates on weeds, with minimal harm to crops.</p> Methods <p>We investigated the effect of two buckwheat (BW) water extracts (weight ratio 1:5 and 1:10) on seed germination and root growth of weeds (<i>Echinochloa crus-galli</i>, <i>Cynodon dactylon</i>, <i>Amaranthus retroflexus</i>, <i>Setaria italica</i>) and crops (barley, chickpea, cress, lentil, quinoa, soybean and tobacco) in Petri dishes. Then, a pot experiment was conducted to test BW’s root exudates on the growth of weeds (<i>Abutilon theophrasti</i> and <i>Amaranthus retroflexus</i>) and crops (chickpea and lentil), either intercropped with BW, or supplied with leached water from BW pots. The content of quercetin and rutin was assessed in all BW samples.</p> Results <p>Both experiments demonstrated a suppressive effect of BW, with intensity varying by species susceptibility. Quercetin and rutin were found in ground buckwheat and in water extracts, but only quercetin in leached water. In the germination experiment, osmotic potential of the water extracts may also be a factor reducing germination rate, but the effect was not unequivocal.</p> Conclusion <p>This study confirms the potential of BW for weed suppression in low-input systems: 1) the inhibition of weed germination from BW water extracts can support its use as mulch from crop residues; 2) since some crops were also affected in both experiments, BW use in intercropping or cover cropping should be adapted to the crops. Further research is needed to understand the mechanisms of buckwheat allelopathy and to test these results in field conditions.</p>