There is a lot of hocus - pocus gardening frill on the Internet . Because of that , one of the lead precept of The Dallas Garden is to only present advice and teaching that is supported by scientific discipline .
For example , when it comes to the concept of companion planting , there are lots of barbaric claims out there but few scientific study to back those claim up . So , I rarely advocate the practice unless I have verbatim grounds to suffer it .
For that reason , when asked about the welfare of planting marigolds with love apple , I ’ve always said , “ Do n’t get your hopes up . ” But has the clock time get for me to interchange my tune ? And could the benefit of marigold for love apple mean larger benefits for our ecosystem ?
The theory of companion planting and why we should take care with that term
The theory behind companion planting is that certain plant make good relationships with other flora when grown in close proximity .
The report benefit of fellow traveler planting admit pest deterrence , disease opposition , and heighten maturation and productivity .
However , many scientist harmonise that the term “ companion planting ” is used too loosely – particularly on the net – blurring the parentage between genuine science , pseudoscience , and the supernatural .
Linda Chalker - Scott , extension horticulturist and associate professor at Washington State University , makes it very exonerated that “ associate planting ” lore should not be confused with the research - base concept of intercropping and flora connexion .
She asserts , “ There is no scientific fundament [ … ] for any of the several tilt that exist distinguish ‘ traditional fellow plant ’ . Like horoscopes , these lists may be fun to use , but they should not be perceived or promoted as scientifically valid any more than star divination . what is more , those of us who value the science behind our horticultural pattern should debar using this musical phrase for precisely the same cause . ”
Newcastle study tests French marigolds against whiteflies
One works connexion long conceive to be merely companion planting traditional knowledge is that of marigold and tomatoes . For generation , gardeners reported fewer pest problems when marigolds were around , but the scientific support for the hypothesis was n’t useable .
In 2019 , scientist from Newcastle University ’s School of Natural and Environmental Sciences set out to alter that .
Knowing that gardener were convince of the marigold ’s ability to ward off sealed pests – specifically whiteflies – the Newcastle scientists sought to found a scientific footing for uprise French marigolds alongside Lycopersicon esculentum plants from the starting of the uprise season to protect tomatoes from whitefly plague . They also wanted to know if the pest control force of marigold could be enhanced by the presence of other flora .
The studyrevealed that when French marigolds were grown next to tomato throughout the growing geological period , the development of a whitefly population was significantly slowed . However , when marigolds were added as an emergency discussion around Lycopersicon esculentum after a whitefly universe was allowed to get quite high , it did little to slim down the existing whitefly population . The only emergency intervention found to be effective was the initiation of limonene dispenser .
order more manifestly : marigolds are most effective against whiteflies on tomatoes when both industrial plant are grown together . They do n’t help oneself much when introduced after an plague occur .
What is limonene?
Limonene is a major chemical component of French marigolds and whiteflies have a negative reaction to the chemical compound .
According to theBiomimicry Institute , limonene belong to a grouping of chemical substances called volatile plant compounds ( VPCs ) . VPCs are emitted by industrial plant to institutionalise signals to other flora or to attract or drive back insects . An insect ’s antenna or other centripetal organs detect the VPCs , just as a human nose detects many chemical compounds . VPCs can be isolate from a plant life .
It’s not just marigolds that are effective
When the Newcastle scientist introduced whitefly - attract works around the love apple plants to test whether the marigold control could be enhance , the “ draw plant ” did little to slow up whitefly . Interestingly though , when the marigold universe was reduced and supersede by other non - innkeeper of whiteflies ( St. Basil , genus Nasturtium , and Chinese cabbage ) the whitefly universe still fall .
Because of this result , the scientists argue that their body of work supports the possibility of develop of a mixture of plants to intercrop with tomatoes that would make an ‘ associational opposition ’ against many major Lycopersicon esculentum blighter .
They go on to paint a picture that such a mix , if it includes edible or decorative species , could be economically viable for agriculturist and provide numerous societal benefits such asreducing pesticide use , diversifying horticultural production , increasing the variety of invertebrate fauna within agro - ecosystems , and increase the diversity of produce on food market shelvesin a worldly concern increasingly dominated by few food type .
How to grow marigolds in North Texas
marigold are gentle yearly to uprise in our mood . They are widely usable as transplants at local garden centers , and they are very easy tostart by seed indoors .
Plant them after all chance of Robert Frost has go ( mid - to - late March ) in an expanse with full sun and well - drained soil . ( If you struggle with compacted clay grease , contain expanded shale to a depth of 6 - 8 inches before found . )
Marigolds are not water Sus scrofa , but like most plants they will involve at least one in of water per week for maximum performance .
When plant life bulge to lag in July , trim down back by 1/3 to encourage a strong fall bloom and to conserve the works ’s overall embodiment . Deadheading spend flower throughout the season will also promote longer flower times .
French marigolds vs. African marigolds
There are two common types of marigolds : French and African ( sometimes scream American ) . African marigolds are the large , double - blossom , yellow and orange marigolds that are often grow as bedding plant .
Gallic marigolds are smaller , bushier plants with individual or double flowers in colors ramble from yellow to orange to rust cherry . They have a longer blooming season than African marigolds .
Both African and French marigolds check limonene .
Sample tomato intercropping layout
Here is a sample layout of tomato intercropping in a bring up bottom using marigolds , basil , and nasturtium . All three of these plants – shown to repel whiteflies when set together – will fit nicely around tomato plants without push them .
Summary
Thanks to thescientists at Newcastle , gardeners can now stick out unwavering in their conviction that planting marigolds with tomatoes is an effective means of repelling sure pestilence . The fact that love apple plant are equally protected by impart basil , nasturtiums or Chinese dinero into the mix is icing on the cake . How gracious that we can have vegetable gardens that are both sustainable and beautiful !
It is significant , however , that we begin to move away from using the phrase “ fellow planting ” . Instead , when we hash out the practice session of growing industrial plant together in parliamentary law to trim back pesticide use and increase biodiversity lease ’s use the scientifically - recognise and scientifically - supported terms “ intercropping ” or “ plant life tie ” .
Further reading
Conboy NJA , McDaniel T , Ormerod A , George D , Gatehouse AMR , Wharton E , et al . ( 2019)Companion planting with Gallic marigolds protect love apple flora from glasshouse whiteflies through the emission of airborne limonene . PLoS ONE 14(3 ): e0213071 . https://doi.org/10.1371/journal.pone.0213071
Linda Chalker - Scott , Ph.D. , Extension Horticulturist and Associate Professor , Puyallup Research and Extension Center , Washington State University,“The Myth of Companion Plantings ”
“ Limonene from marigold repels whiteflies ” , Biomimicry Institute
Resources
Marigold seeds
Tomato seeds
Basil seeds
Nasturtium seeds
