with the drought I'm having to use the sprinkler in my newly planted herbaceous border and with the continueous dry spell, what is the general rule of thumb for how long to leave the sprinkler on each section.
thank you in advance
It all depends upon your soil. Nice sandy free draining will need a lot more than heavier clay soils.
We have no need of such things in Devon. It's raining right now.
I tend to leave it for 20-40 minutes in one place once every couple of weeks when it's all really dry.A long sprinkle every 7-10 days is much better than a quick sprinkle every day as the water gets down into the soil. A quick sprinkle just makes the surface wet and attracts the roots upward in search of water, which is not the way you want roots growing