Electrical treeing is a pre-breakdown phenomenon which occurs in polymers and can lead to power failure in cables. Common electrode configurations used to initiate tree growth in laboratories use an HV needle and grounded plane, which may be impractical for some experimental situations. This paper investigates the influence of earthing the needle and energizing the planar electrode on electrical treeing characteristics, such as initiation and propagation. Testing was conducted under 50 Hz AC stress, in samples cut from XLPE cables. Experimental parameters such as tree initiation time, growth rate, fractal dimension, and phase-resolved partial discharge (PRPD) patterns were measured. Analysis shows that there is negligible difference in treeing behavior as a result of changing the earthing arrangement, verifying that the experimental arrangements are equivalent.