Garden Notebook for the Urban Organic Vegetable, Herb, and Flower Gardener  

Article and photos by Rob Danforth

Photo: Pigweed centre, crabgrass left, and lamb’s quarters right

“Weed” is a gardener and home owner’s term for any plant not wanted in a pot, plot, lawn, or between the patio/walkway/driveway bricks.  Some of my “weeds” are tomatoes and squash growing wherever I put our compost – like the flower beds and the lawn.  However, there are no “weeds” in nature!  Natural biodiversity provides the checks and balances needed to modify growth and behaviour which results in a multicultural community of plants suited to the advantages and stresses of a particular environment.  Nevertheless, only the fittest survive! 

“Invasive” is an interesting term.  In his book, Where do Camels Belong? K. Thompson (2014) points out that if conditions are right, organisms will move to and populate an area – there once were camels in North America and dinosaurs in Canada!   In practice, we can see that insects, animals, plants, shrubs, trees, fungi, diseases, and people will migrate toward better living conditions.  However, people move into a natural area and seriously change the environment from forest, meadow, stream & swamp, to cement, asphalt, storm sewers & lawns. Nevertheless, nature continually keeps trying to find a place in the cracks and crannies of our urban creations.   

Invasive plants are generally plants new to an area via wind, birds, moving surface water, or gardeners/home owners, and it may take time – sometimes a long time, sometimes never -– for the local environment to assimilate the plants into the local biodiversity and achieve a natural balance.  For a time, there may be no natural enemies or controls to keep growth in check and an “invasion” ensues.  Unfortunately, some plant newcomers change the local environment and local biodiversity may not rebalance itself until all evolves into a very different multicultural (multi cultivar?) environment.  However, during the period of invasion, invasive plants can lead to serious problems by reducing or eliminating natural food sources, changing the soil, and then changing the local flora & fauna.  Some local plants may become extinct in an area and this of course leads to a chain reaction involving many other plants, insects, and critters. 

If we remove the human factor, “Nature” on its own is resilient:  I have walked through abandoned WW2 military fortifications and bombed out towns in northern France and seen nature reclaim the territory (e.g., trees growing in what was left of front steps, stone foundations and bunkers, unexploded ordnance lying among the grasses and ferns that were swallowing them up, as well as exposed live shells in swamps that had dried up and nature was beginning to hide our sins in greenery). 

There are lessons such as cane toads, rabbits, and gazania flowers in Australia; kudzu vine, killer bees and carp moving north through the USA; as well as purple loosestrife, zebra mussels, and spruce budworm in North America that teach us the power of organisms moving from one environmental context and populating a new context in which the natural checks and balances are not available. 

We know that environmental conditions change or evolve continually, and thanks to us, “climate change” speeds up the process.  Nature is always a work in progress and continually seeking a balance – usually a slow, steady progression, with nothing happening overnight – the exceptions, of course, are catastrophes like volcanoes, tornadoes, earthquakes, floods, and wildfires!  After a forest fire, there is a progression of plant, insect, bird and animal life (I have seen many examples in western Ontario) as nature evolves and tries to re-balance itself.  As a bush camper and backcountry canoeist, I have seen this natural progression often (e.g., a waterway in Algonquin Park that I visited many times over the years was a wide, paddle-perfect, small river with foraging moose, otters, and aquatic birds. It changed every few years: shallower, narrower, fewer foragers, until now I can walk on a wet, spongy meadow dotted with grasses, shrubs and trees covering what once was a waterway; in the Gatineau Park near Luskville, I watched a small lake completely disappear under reeds and grasses).  You may know of foreign cities that once were on the coasts of waterways and are now either miles inland or on the verge of being swallowed by a sea.

Photo: Imported Beans under stress.

Unfortunately people can make changes by importing seeds, plants, insects, animals, and diseases, from other environments either by deliberate or accidental actions.  Many years ago, a fellow gardener offered me some bean seeds for the food bank garden that we managed. Only later did I discover that they were brought to Canada from overseas (Note: this is not legal!  Permits and declarations are required); the seeds were either diseased or the plants susceptible to local diseases and the crop failed.

(Photos: Dandelion & Dandelion Roots)

Dandelions are a good example of an invasive plant:  they germinate and mature quickly, spread large amounts of seed via the breezes, enjoy 2 or 3 flourishes in growth a season, have tap roots that penetrate deep into the soil (I pulled some roots at over a foot long) to get food many other plants cannot reach, enjoy both rich and poor soil conditions, spread their leaves out like an inverted umbrella to crowd out and shade out nearby plants, grow into clumps quite large (e.g., I found clumps 2 feet high in an abandoned farm field), and thrive in our urban grasses and pampered gardens (e.g., lawns, rose gardens, cabbage patches, tulip beds …) which provide excellent growing conditions. They also have few natural enemies which greatly improve the chances of their survival. In addition, if we dig part of a dandelion out of the soil but leave some of the root, the plant will be born again in a short time — and the root will be larger and stronger!  It is what they do!

Then there are the allelopathic plants – many more than you might think – which secrete enzymes into the soil to prevent seed germination in their immediate vicinity – like a walled community (e.g., black walnut, sunflowers, sumac, marigolds, …).  Note:  seeds will not germinate but seedlings can be planted.  Just another way organisms protect their home turf. 

My definition of “invasive” plants:  any plant for which environmental conditions are favourable and the plant is stronger or more virile than the neighbourhood plants via short germination & maturation times; reduced or absent natural enemies, vigorous repopulation (perennial growth, large seed production, overground runners – e.g., strawberries, underground runners – e.g.,  mint & Japanese anemone, or root/bulb/tuber naturalisations and divisions); drought resistance; and perhaps the spreading of allelopathic enzymes in the soil.  Of course, all of this is organic and very natural. Invasive plants are street fighters, survivors, or bullies that are stronger than the local plants.  What’s more, these invaders can be destructive (e.g., see Kudzu vine in the southern USA – AKA “the vine that ate the south”)! 

Our gardens are not natural.   

They are in defiance of nature and are usually plant paradises with plenty of food, water, shelter, and gardener care & protection.  Gardeners also provide naked soil as an open invitation to any passing weed seed!  So, in a way, we gardeners and home owners are responsible for setting up the conditions favoured by these invaders.  We might avoid or at least minimise invasive plants and weeds by being more careful with what we plant and how we garden.  Native plants and biodiversity are a good beginning.  Alternatively, you may decide to live with the invaders and plant what you will amongst the newcomers – some weeds can be very attractive in massed quantities (e.g., birds foot trefoil), in fall colour (e.g. wild Virginia creeper), and waving in the breezes (e.g., tall grasses).  I have seen some gardens in which both vegetables and weeds vie for success – unfortunately the weeds usually win.  However, a lawn full of dandelions or bugleweed, or yarrow, or clover, looks green and grassy after mowing – just don’t look too closely.   If there is enough sun, food, and water for all, then …. 

(Photo: Nature’s Choice on what was just grass 6 weeks ago) 

Some examples of strong invasive plants:  Ajuga (“BugleWeed”), Yarrow, Japanese Anemone, Sunchokes (“Jerusalem artichokes”), Lily of the Valley, Creeping Jenny, Lamium, Mint, Oregano, Comfrey, Violets, Dandelions, Manitoba Maple trees ….   

(Photo: Ajuga/BugleWeed – an invasive plant sold as an urban ground cover) 

Solutions:  

• Choose plants that are suited to the garden environment, and try biodiversity and high-density planting – as does nature – in garden spaces.  In large containers, plant tall fascinators with low fillers that cover the soil, and dangling fallers that climb out of the container.  Containers can help “contain” any invasive plants you may admire – but you must eliminate the seed heads.  Sometimes nature tells us that certain plants will cause a lot of problems and perhaps high blood pressure if we persist in growing them – insects, diseases, animals and climate may encourage us to rethink our gardening choices and practices.  There are Greek myths that teach us the futility of repeated actions that always end with the same results (e.g., the punishments of Sisyphus and of Tantalus ).  Significant change in what or how you retry is a must, or you are wasting your time!

• In early spring or on a wet day (or ground you wetted thoroughly) dig out all the roots you can find, add soil, and reseed.  This is easier with tap roots (e.g., dandelion, purslane, galinsoga) but not so easy with root runners (e.g., mint, Japanese Anemone) and the many fingered roots (e.g., plantain, creeping Charlie).  It is a muddy job, but roots can be pulled more easily from thoroughly wet ground. Get crabgrass and purslane before they go to seed – they are annuals, but very good at reseeding themselves. 

(Photo: lambs quarters, purslane, galinsoga).

(Photo: Crabgrass – many fingered root).

• Pull often or cut, cut, and cut again until the plant gives up! 
• Cover the area with plywood, cardboard, 5 sheets of newsprint hidden under leaves, or black plastic (I’m not a fan of plastic even here!), to deprive the unwanted plants of sun, water, & air.  Do not use old floor coverings; you do not want what leaches out of them to go in your gardens. 
• Apple cider Vinegar, dog urine, or a blow torch can reduce surface growth temporarily, but these solutions do not kill the roots and of course they leave a burn patch larger than the weed itself.
• If the problems are mild, then consider diverse, high-density planting.  This occupies available soil and shades out the competition or deprives the competition of nutrients – the same tactics used by “weeds.” For example, try the 3 sisters (corn, pole beans, & squash), or how about bush beans and squash together?   Cucumber and lettuce?  Vegetables and flowers?  Grass seed mix (usually a mix of at least 3 varieties) + Dutch white clover (20%), and perennial ryegrass?  Tip: we use this grass seed mix to strengthen lawn grass and discourage chinch bugs which dislike clover & ryegrass.  Clover conserves moisture, adds nitrogen to the soil, feeds pollinators (and rabbits), and shades out many weeds but not the grasses.  

(Photo:  grass thriving through the clover) 

• Always cover naked soil with an organic mulch such as leaves (shredded recommended), bark (no coloured dyes), woody bits, grass clippings, soft parts of spent plants cut & dropped, – all of which can significantly reduce weeds.  We have tried them all.  We now use mostly cut & drop in the fall, and shredded leaves (no underlay) all season, leaves saved over winter (in garbage bags or in a chicken wire leaf corral) for a 95% reduction in unwanted plants.  If you must use an underlay, non-woven landscape fabric is better for your soil than any plastic, but newsprint (5 sheets) or cardboard would be better for the environment than landscape fabric because they will eventually decompose and add needed carbon to the soil – or you can add the remnants to a composter.  Landscape fabric will eventually clog, and may disintegrate into annoying inorganic bits which you will have to remove.  Note:  Compost is a fertiliser, not a “mulch.”          

(Photo: shredded leaves as mulch on a tomato patch) 

Plants, like any living organism, reproduce themselves one way or another to ensure the survival of the species, and increase their population.  Since any plant can act like an “invader” if conditions are right, perhaps our take-home lesson is that we should be mindful of what we are creating in our gardens and lawns.  There is certainly truth to the claim, “if you build it, they will come” – and some newcomers will prosper far better than others, particularly because of the extended care we offer our urban gardens and lawns. 

Notes:  biodiversity and high density are better than any monoculture; naked soil is an invitation to invaders (nature will cover it in greenery within 2 weeks); some weeds and plants, both domestic & non-native, can out-compete the plants we want to nurture; and all plants have the genetic code and territorial imperative to go forth and multiply.   

By the way, some suburban people let their lawns go wild (true in parts of my neighbourhood) and end up with yards similar to the ungroomed areas around a cabin in the woods. These cabin dwellers let nature be all that it can be.  They set aside lawn and garden tools (and all that labour!), stick a chair in the greenery, and enjoy a sunset, a beverage, and all nature, which hums happily alongside. 

Unfortunately, a lawn of nature’s choice can influence an entire neighbourhood, as seeds and spores do like to travel about.  The neighbours may not be as thrilled with their good fortune as you are.  Please consider a measure of control, preferably before seed production. 

Happy Gardening, whether you choose growing environments that are nature’s choice, or shabby chic (a measure of control), or tuxedo style (constantly fighting to impose your will).