An odd question has been nagging me for years but ive never got around to asking advice:
Is there a standard way of calculating how many companion plants (per square metre) are required for effective protection against pests? For example, for every eggplant, how many marigolds / calendula would i need to plant to increase their yield? To keep whitefly away from my cabbages, how many marigolds / calendula should I plant?
I know it sounds odd, but there must be an answer..i can safely say that 3 calendula for a 100 metre square garden doesnt work!
Cheers and thank you for any suggestions,
Hi Steph, Two helpful books, "Carrots Love Tomatoes, Secrets of Companion Planting for Successful Gardening" & "Roses Love Garlic, Secrets of Companion Planting with Flowers", both books by Louise Riotte published through "A Garden Way Publishing".
From what I understand Marigolds/Calendula, discourage bad nematodes in the soil and they need to be planted and grown for several seasons/years. Marigolds control the nematodes by producing a chemical in the roots which is slowly released into the soil and it's benefits become apparent in the following years as the nematode population is reduced. I compost all my marigolds at the end of their life but I'm sure side dressing them right into the garden soil would also be helpful.
White fly thrive on certain shortages of minerals in the soil, with growing tomatoes it's phosphorus or magnesium deficient. Botanical controls include nasturtium, burning Oak leaves in your greenhouse and nicotine sprays, I myself would not go with anything nicotine. White fly can also be controlled biologically by a small parasite called encorsia formosa and Ladybugs. I've found that making a "pounce bag" from cheese cloth and filling it with Diatomaceous Earth (DE) and gently pouncing the leaves of my fruit trees helps with aphids. I also use (DE) to control many other pest in the garden including snails and slugs. It must be re-applied after rain and is very safe to use.
Hope this helps a bit and I look forward to reading other peoples thoughts on this subject also.
Thank you for the info. Thats very good advice. I will check my local library and see if those books are available. Cheers and thanks again, Steph