For this experiment, your observations should include a visual observation, notes and a measurement.
The visual observation should be a drawing that represents what your 6 cell currently looks like.
The notes should be any information you think it is important to share about your experiment.
One example would be “water seems to be pooling in the rocks”
The measurement should be consistent for all plants. Measure the plants at the same time and use the same measurement tool (an inch or centimetre ruler should be sufficient for this experiment). It will be a few days at least until there are any plants to measure but keep checking.