On Oct 14, 1:20*pm, stuart noble wrote:
Having just removed my sweet peas after a summer of non-stop blooming, I
was surprised to see that the roots are no longer than about 6". I was
under the impression they had a deep root system, so was I wasting my
time digging down a spade and a half last autumn? Perhaps regular
watering meant they didn't need to go deeper? Confused, so thanks for
any opinions.

The roots that matter are too small to be easily seen.
The other reason for deep digging is to improve the drainage, few
plants like a water logged soil.