These are soil type and natural fertility, water drainage, air drainage, wind protection, sunlight, water availability, isolation from wild brambles, and previous crops in the field.
Brambles prefer sandy loams or loams to coarse sands or clays.
Sandy loams retain enough moisture in the summer while allowing water to get away from the roots in the spring and fall. Trailing type blackberries tolerate heavier clay soils better than other brambles. Water drainage is a critical issue in site selection, because the root systems of bramble fruits extend to a depth of three feet. Avoid subsoils that are tight and impervious. The water table should not come within three feet of the soil surface, because bramble roots are sensitive to low oxygen supplies.