Keywords:Solanumsisymbriifolium ,Globoderapallida ,Globoderarostochiensis , germination, light use efficiency, crop growth, crop management, root length density, hatching, trap crop, tolerance,Phytophthorainfestans , resistance.Potato cyst nematodes (PCN),Globoderapallida (Stone) and G.rostochiensis (Woll.) continue to be a major pest in potato growing areas, in spite of existing control measures. Therefore,Solanumsisymbriifolium (Lam.) was introduced as a trap crop for PCN inWestern Europe. The current study was performed to collect quantitative information on the ecology, agronomy and potential nematode reduction of S.sisymbriifolium crops in The Netherlands.The emergence rate of S.sisymbriifolium was almost zero at temperatures below 8 °C. The relation between germination and temperature at sub-optimal temperatures is adequately described withexpolinearand quadratic equations. These are relatively simple, and applicable in modelling germination of other plant species grown in conditions near their base temperature. Plantings between May and the end of July led to a crop with full ground cover. Initial growth was slow, but indeterminate and accumulated amounts of above-ground biomass were high (more than 10 tons ha-1dry matter after 100 days). Root length density could be reasonably well assessed from above-ground crop characteristics, and was linked to theoretically possible nematode reductions. In a greenhouse study in containers, nematode population reduction was found to be related to root length density and length of the growth period of the crop. After 150 days of crop growth the PCN population density was reduced with 75% on average; in the soil layer with maximum root length density of 5.8 cm cm-3the PCN population reduction was 86%. A general formula was derived to calculate the time gained to reduce the PCN population density below threshold levels, comparing a scenario with cultivation of one crop of S.sisymbriifolium , followed by non-hosts or fallow, with a scenario with natural decay of the PCN ...