Variability of production environments challenges wheat (Triticum aestivum L.) breeders to develop genotypes with the potential to perform well under different levels of resource availability. An important trait that may provide plasticity to wheat is productive tiller number (PTN). This paper reports two studies. The first study tested the impact of a quantitative trait locus (QTL) for PTN on yield and other traits in a set of near‐isogenic lines (NILs) grown over nine environments in the Pacific Northwest. Results showed that an allele for high tiller number at QTn.mst‐6B enhanced early tiller (ETN) formation regardless of environments. Under favorable conditions, the large number of early tillers translated into a capacity for high PTN. Seed weight and seed diameter were negatively affected by the QTn.mst‐6B high tiller allele. The second study assessed the impact of QTn.mst‐6B under different competition and soil resource levels in three trials in Bozeman, MT. Three treatments were imposed on NIL pairs in replicated experiments: (i) bordered rows that limited soil resources to each NIL, (ii) nonbordered rows with less competition that provided more soil resources to each NIL, and (iii) space‐planted plants with limited competition for soil resources. Results complemented those found in the multienvironment trials, as the high tiller allele caused high PTN at low competition levels when soil resources were more abundant. Increased yield as a result of the high tiller allele at QTn.mst‐6B was only detectable in the highest resource treatment and environment.