Root elongation in drying soil is limited by mechanical impedance and water stress. The study reviews the interactions between root elongation rate, water stress (matric potential), and mechanical impedance (penetration resistance). Root elongation is halved in repacked soils with penetrometer resistances >0.8–2 MPa, and by matric potentials below -0.5 MPa. Mechanical impedance is a major limitation to root elongation in many soils, even under moderately wet conditions. Root tip traits that improve root penetration are considered, including overcoming external (soil) and internal (cell wall) pressures. Root hairs may mechanically anchor root tips, especially in biopores or loose seed beds into compacted soil. Soil strength increases with drying due to increased effective stress between soil particles. Penetrometer resistance increases with decreasing matric potential and is related to effective stress. In 19 Scottish soils, 10% of penetrometer resistances were >2 MPa at -10 kPa, rising to 47% at -200 kPa. This suggests mechanical impedance is a major limitation to root elongation in these soils. Root elongation is limited by both water stress and mechanical impedance, with their interactions being complex. Root elongation is influenced by cavity expansion pressure, frictional resistance, and cell wall tension. Root traits that reduce these pressures are beneficial for root penetration. Thicker roots penetrate hard soils more effectively. Root hairs may provide anchorage, especially in compacted soils. Root hairs may also help in locating cracks and channels in the soil. The study highlights the importance of considering root responses to soil strength when breeding drought-resistant crops. Novel screening methods are needed to develop varieties that can better utilize pre-existing channels. Root elongation is crucial for plant growth, especially in soils with limited water and nutrients. Roots grow more slowly in drying soil due to water stress and mechanical impedance. Root tip traits that reduce cavity expansion pressure, frictional resistance, or axial cell wall tension are beneficial for root penetration. In soils with macropores and channels, the ability to exploit these channels is also beneficial. Root hairs may provide sufficient anchorage to aid root tip advancement in hard soil. It is essential to consider root responses to soil strength when developing strategies to breed drought-resistant crops.Root elongation in drying soil is limited by mechanical impedance and water stress. The study reviews the interactions between root elongation rate, water stress (matric potential), and mechanical impedance (penetration resistance). Root elongation is halved in repacked soils with penetrometer resistances >0.8–2 MPa, and by matric potentials below -0.5 MPa. Mechanical impedance is a major limitation to root elongation in many soils, even under moderately wet conditions. Root tip traits that improve root penetration are considered, including overcoming external (soil) and internal (cell wall) pressures. Root hairs may mechanically anchor root tips, especially in biopores or loose seed beds into compacted soil. Soil strength increases with drying due to increased effective stress between soil particles. Penetrometer resistance increases with decreasing matric potential and is related to effective stress. In 19 Scottish soils, 10% of penetrometer resistances were >2 MPa at -10 kPa, rising to 47% at -200 kPa. This suggests mechanical impedance is a major limitation to root elongation in these soils. Root elongation is limited by both water stress and mechanical impedance, with their interactions being complex. Root elongation is influenced by cavity expansion pressure, frictional resistance, and cell wall tension. Root traits that reduce these pressures are beneficial for root penetration. Thicker roots penetrate hard soils more effectively. Root hairs may provide anchorage, especially in compacted soils. Root hairs may also help in locating cracks and channels in the soil. The study highlights the importance of considering root responses to soil strength when breeding drought-resistant crops. Novel screening methods are needed to develop varieties that can better utilize pre-existing channels. Root elongation is crucial for plant growth, especially in soils with limited water and nutrients. Roots grow more slowly in drying soil due to water stress and mechanical impedance. Root tip traits that reduce cavity expansion pressure, frictional resistance, or axial cell wall tension are beneficial for root penetration. In soils with macropores and channels, the ability to exploit these channels is also beneficial. Root hairs may provide sufficient anchorage to aid root tip advancement in hard soil. It is essential to consider root responses to soil strength when developing strategies to breed drought-resistant crops.