By Sunbeam
West Midlands,
United Kingdom 
using some compost from last year's gro bags. I'm growing potatoes in bags in my greenhouse and have used up loads of new (bought) compost,and it's getting expensive! . The potatoes are now nearly getting to the top of the bags. Would it be a problem to use the compost from old gro bags to fill the last few inches? they had tomatoes growing in them in the greenhouse last year
25 Apr, 2012
Answers
I wouldn't use old tomato compost either, for the reasons that Sbg has given. You could top up with garden soil plus some added fertiliser if cash is an issue.
25 Apr, 2012
Thank you, I guess it would be spoiling the ship etc having got the potatoes so far!!
25 Apr, 2012
yep thats true. and with the damp due to the 'drought' we are having, it would be tempting fate.
26 Apr, 2012
as tomatoes and potatoes are in the same family I wouldnt. they both suffer from blight and if there are any spores from last year's toms they will destroy your spuds.
Use the old stuff else where and use fresh would be my advice.
25 Apr, 2012