Companion Planting: Relationships in Plant Communities


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Companion Planting: Relationships in Plant Communities

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Companion Planting: Relationships in Plant Communities

  1. 1. Companion planting:relationships in plantcommunitiesBy Tina FraserTHERE’S A PARTY GOING ON IN THE GARDEN. To be sure there’s more going on than meetsthe eye. Over there is the life of the party. Everyone is attracted to that one. The three inthe corner are making a business deal. One wears outrageous clothes; another wearstoo little. There’s a joker, a loud talker and a couple of love birds. Several arecongregated around the buffet table discussing a food that they all love. Plants, like humans, have very complex relationships—friends, lovers, family,business liaisons and companions. You could name a few of these plant relationshipsand imagine a lot more. We know that companion planting has been a field and gardenpractice for centuries. As organic growers, we know that companion planting is morethan folk art or romantic myth. In the broad sense of applying companion planting techniques to our growing plans,some traits become more useful than others. Here are some types of companion plants,and a few examples of each.AttractorsThere is seduction at work amongst the pollen and perfume. Some plants attractpollinators and/or predators of pests. Farmers and gardeners can grow a wide variety offlowers producing volatile oils, nectar and pollen to encourage pollinators. I use aformula of fennel, dill, alyssum, thyme, borage and anise along with blue bachelors’buttons and other flowers with tubular blooms. Large beds of the same plants and longrows of sunflowers, zinnias or laceflowers are dynamic attractors in a market garden.• Parsley, Phacelia tanacetifolia and the poached egg plant attracts the hoverfly (apredator that devours aphids).• Buddleia, lavender and zinnias attract butterflies that pollinate.• Hedgerows with berries and fruit attract birds which eat weed seeds and pests.DeterrentsThese are the strong and silent types—the dissuaders. Deterrents provide weed control.Leaf and root exudates from these plants discourage other plants from thriving in thesame vicinity.• Sunflowers in generous congregations deter plants around them by inhibitingnitrogen-fixing bacteria in the soil. Weeds requiring nitrogen suffer. As for sunflowersthemselves, they are not nitrogen-hungry.• Pungent root and leaf exudates of French and African marigolds deter harmfulcyst-forming nematodes. These marigolds are always present in my tomato greenhouseand along rows of cabbages and potatoes.Confusers
  2. 2. As handsome masked bewilderers and befuddlers, these plants can confuse pests andmask crops by their strong odour. They are also tricksters, using camouflage in the formof similar flowers and leaf patterns.• Chrysanthemum partenium and feverfew have strong scents that hide the scent ofother plants from pests.• Flax hides potatoes from the Colorado potato beetle.• Leeks, carrots and onions intermingled confuse carrot rust flies and onion flies.• Parsley masks carrots and onions from root flies.RepellentsAs offensive and disagreeable types, this group includes the smelly and the scratchy—both traits that irritate pests.• Onions repel rabbits and mice.• Nasturtiums are odoriferous enough to deter white flies around tomato plants.• Slugs and wireworms are repelled by the pungent smell of marigolds.• Catnip repels aphids and flea beetles.• Thorns such as hawthorn and blackberries deter cats and dogs.• Basil repels whitefly, aphids and fruit flies.EnchantersAs good neighbours and good bedfellows, enchanters enhance the growth, flavour andsize of other plants. They grow together for mutual benefit, at different storeys and withcomplementary rooting patterns.• Clover fixes nitrogen, providing it to companions and following crops. An understoreyof Dutch white dwarf clover enhances the growth of brassicas, keeping the soil cool andadding nitrogen. The clover also deters cabbage root fly.• Phacelia is an annual flower that also makes an excellent green manure. Itsgentian-blue flowers attract bees, and the ferny foliage is a graceful addition to thegarden.• Basil enhances the taste and size of tomatoes. This is most likely due to hormonesaffecting the growth and nutrient uptake of the tomatoes.• Taproots are good bedfellows with shallow-rooted crops. Shallow- and deep-rootedcrops can coexist with little competition, such as carrots with lettuce.• German chamomile improves flavour of cabbages, onions and mint. The Latin namemeans “capable of anything.”TrappersThese are the sacrificial lambs of the plant world. They lure pests, surrender and thenare destroyed by the pests or by the gardener. Once these crops become infested withpests, the plants should be destroyed. Otherwise, they can provide a haven for pests.• Turnips lure harlequin beetles from raspberries.• Mustards are favourites of pests, more so than their cousins, the cauliflower andcabbage.• Zinnias (pale colours only) lure Japanese beetles, and dill attracts the tomatohornworm.• Nasturtiums attract aphids. I grow them in abundance to keep an eye on aphidpopulations both in the greenhouse and outdoors.Accumulators
  3. 3. Like pack rats, saving gems for another time, these plants often have long, far-reachingtaproots which take up minerals and nutrients from deep in the soil. The nutrientsaccumulate in their tissue and are released when plant tissue decomposes.• Comfrey accumulates nitrogen, potassium, calcium, phosphorous and manganese.Comfrey leaves can be added to mulch or compost.• Horsetail provides magnesium and is high in silica which makes plants tougher andmore resistant to disease.• Garlic accumulates sulphur which is important for disease resistance in humans.• Buckwheat makes phosphorous and calcium more available to other plants after itdecomposes.ProtectorsSome plants are the guardians of the garden. Earth’s elements can create havoc anddevastation via too much wind, sun and rain.• Peas, beans and other trellised crops provide shade to heat sensitive plants likelettuce.• Sunflowers create effective windbreaks.• Clover and poached eggs create a ground cover to shade and cool the soil.Common groundersAlso known as the communal and the collective, some specific groups of plants aresuited to the same conditions, sharing similar soil and nutrient requirements. Or, thesedifferent crops have something in common that makes it worthwhile to spend timetogether and are easier for the gardener to manage.• Heavy feeders such as brassicas and corn can grow together in rich soil.• Light feeders including carrots and Swiss chard have similar nutrient needs.• Moisture loving plants such as spinach and cucumbers grow in wet or irrigated soil.CirculatorsThey make the work go ‘round. Learn your plant families and their habits. Create croprotations to decrease pest and disease problems and to ensure better nutrients for thefollowing crop.• For example: beans followed by lettuce—beneficial nitrogen-fixing legumes beforeleafy greens.• Alliums and squash serve as beneficial preceding crops for many other crops. Thealliums have few predators; the squash shades out weeds.• Apple trees followed by cherry trees: some plants such as apple trees should not bereplanted in the same space.Pollinating plantsThe desire for more of our own kind is universal.• Most apple trees need a good companion at blossom stage to cross-pollinate. GoldenDelicious is a great pollinator, blooming over a long period of time. Transparent appletrees produce lots of pollen. If you have room for only one precious variety, graft abranch or two of a good pollinator onto it.• Corn requires lots of its own kind in a block instead of long slender rows. Each kernelmust be fertilized by pollen, carried from the tassel by the silk to the kernel.Conclusions
  4. 4. Weashumanscannotpossiblyknoworunderstandallthedeep,dark,velvetysecretsofplants.Idoknowthatplantsareadelighttomysenses.Theirmedicinalandculinaryproperties,colourandfragranceenhanceandrestoremyphysicalhealthandmymentalwell-being.Theyaremycompanionstoo.Sources of informationA-Z of Companion Planting. Pamela Allardice. HarperCollins. Australia. 1993. Nicely illustrated.Roses Love Garlic. L. Riotte. Mackenzie Press, Vancouver, B.C. 1987.Companion Plants. Dr. H. Philbrick and R. Gregg. Kangaroo Press. Australia. 1991. 8Tina Fraser is a certified organic grower in the Victoria area of British Columbia. She has a greatappreciation for her plant companions