Poplar Trees and vegetables...do they mix?

If it's a Lombardy type poplar it's not going to cast much shade because they don't have much spread. What it will do though, is draw a lot of moisture from the soil. I have some large cypresses in the garden and even after a torrential downpour the soil is bone dry just below the surface.

I seem to remember Carol Klien (sp?) doing her veg thing a while ago, and some of her veg were underneath trees. They didn't do as well as other veg because the soil was dry and depleted of nutrients. Having said this, part of my veg patch at home is under next doors old christmas tree which is huge. I have grown shade tolerant chard, etc., and even my runners did quite well one year under it. Just had to make sure bed was well looked after - fed and watered.
You can't grow under walnuts because (i've read somewhere) they exude a poison into the ground a bit like rhododendrons, to stop other things growing. Never heard anything like this about poplars though.

Poplars are horrendous trees for sucking moisture out of the soil. A fully grown poplar will take out a phenomenal amount of water - equivalent to a massive oak. That's why they have such a bad reputation with surveyors, insurers (and some luckless homeowners) for causing subsidence in nearby houses in dry weather. Some insurance policies insist no poplars planted within 50m of a house; like willows, their roots are notorious for travelling a long way along drains etc.
That said, you might find that if you put down something like builder's damp proof membrane, maybe with a few piercings to let excessive water drain, then put a raised bed on top, you would still be able to keep enough moisture to grow salad crops. The problem is likely to be that any water draining down to the roots on a regular basis will encourage them to grow up to the source of the moisture.
If I was you, I would think of continuing your acacia policy, get rid of it and plant a couple of nice wee apple trees. (Or even full size, given the size of your plot from the look of things.) Still green and carbon negative, but not such a water-thief.

I think I'm with Snohare on this one J, I'd get rid of it. Either that or put a seat around it instead of veg

thankyou people...next winter its going ....there are loads more on the river bank.......
and the fruit trees will be going in at the other end as soon as we can clear it again....and a few sweet chestnuts ...i like them......