I've always grown a few tagetes among the tomato plants, but must admit that last year the whitefly were so bad that they were all over the tagetes too. Thankfully they aren't nearly so bad this year and were only noticeable this month.

Another thing I've noticed is that if I have marigolds and borage among the brassicas they don't get so much caterpillar damage. Perhaps the butterflies don't have a green mass to home in on, or the marigolds attract insects that prey on the butterfly eggs and caterpillars.

Trying out different things in the garden is part of the fun. It doesn't need to be scientifically proven and if we find something that works for us that's fine.

Hi MikA

Could be because greenhouse whitefly and brassica whitefly are two separate things -

Glasshouse Trialeurodes vaporariorum

Brassica Aleyrodes proletella

Thanks Alan, it's good to keep learning new things.

I used tagetes in the greenhoude too and no whitefly, so maybe not just luck.

I usually have tagetes in the polytunnel and have never had whitefly. Certainly the case this year. But last year when I forgot to buy some plants the tunnel was totally free of whitefly. Maybe I'm scaring off a pest that isn't there. But I like the flowers and the smell.

I had no whitefly this year and I did not grow Tagetes either.

I had no whitefly or tagetes in fact I have no greenhouse either !!
Just putting up a tunnel on my plot and will be using companion planting as it clearly works and the extra benefits are worth the effort.

Hi TTM

All best wishes for the success of your polytunnel.

I hope you will keep us updated on your experiences and (hopefully) experiments with your various companion plantings.

Thanks Alan..just having an allotment I feel is a huge experiment, one thing I am convinced of though ..I always listen to the old boys in our tea room and around our plots...far better than all those so called gardening books for knowledge ..would love them to write a book on keeping an allotment and growing vegetables.