Seedlings of Quercus robur L. were grown in tubes containing peat and perlite and observations of the periodicity of root and shoot growth were made. Root and shoot growth were not closely coupled. The rate of elongation of the tap root was approximately constant and did not decline during periods of stem growth and leaf expansion. The complexity of the root system increased throughout growth; tap roots emerged without lateral roots but by the start of the third flush of shoot growth plants had about 10 metres of lateral root and 6500 root tips. There were about 6 first order laterals per cm of tap root but the relationships between length of the lateral root system, number of root tips and tap root length changed during growth. There was no evidence that rhythmic growth in oak is related to an unfavourable root:shoot ratio caused by rapid growth of the shoot and leaves during a flush.