Q. I am looking for a spring companion list for Las Vegas. I have an easy to read chart for fall in order to know where to put different plants and which ones don't like to be next to each other but can’t find the same resource for spring.
A. The topic of companion planting is very large and has a lot of good information but unfortunately it also has a lot of folklore that is either regional in nature or lacks validation.
Companion planting can focus on the inter-planting of crops, the use of understory crops, the planting of trap crops, suppression of pests by other plants, planting to increase the levels of predators, and more.
For the general public, the term has evolved into the planting of crops for mutual benefit. These companion plants are sometimes referred to as “friends” to other crops without getting into much detail.
There is good evidence for the planting of trap crops for aphids, whiteflies, nematodes and a few other pests. I have heard anecdotal evidence for the use of plants like garlic for repelling certain types of insects or even rabbits. Some people will swear by it and other people who have tried it may say it doesn't work.
This opens another set of problems because in some cases it may work and in other cases it may not which causes confusion. I have tried to maintain neutrality on these issues and recommend situations where I am comfortable there is solid scientific research to support it or not support it. People are free to post their suggestions on my blog and I will publish them provided they are commercial neutral.
Where I am comfortable recommending companion plants are in the areas of trap cropping, inter-cropping and the planting of understory plants. There are some very good evidence that interplanting of crops can have some big benefits including a reduction of pest problems compared to large-scale monoculture where only one crop is grown.
Without getting into detail, there are areas I am very uncomfortable making recommendations because there is contradictory information or the research flatly does not support it.
For people like yourself who want to experiment in these areas, I strongly support it and test it for yourself. No one can dispute it if it works for you. There are publications that do support this kind of gardening activity such as
Other sources you may be familiar with include MotherEarth News, Old Farmer's Almanac, and many others.They are fun to read!
A balanced assessment of companion planting was done by Cornell and can be found at http://www.gardening.cornell.edu/factsheets/ecogardening/complant.html