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Wonderous Weeds: Tapping into an unloved resource


Prepared by SGA 2023

“A weed is a plant that has mastered every survival skill except for learning how to grow in rows” – Doug Larson
“A weed is but an unloved flower.” – Ella Wheeler Wilcox
“A wild plant growing where it is not wanted and in competition with cultivated plants.” – Oxford Dictionary

So what is a Weed?

A weed can be thought of as a plant that interferes with our desired use of a piece of land at a particular time. Whether a plant is classified as a weed depends on a number of elements. These being – Human values (how we see it or value it) and the context (when and where it is).

  • There are no weeds to nature – it’s all ecological evolution.
  • What you call a weed, someone else may not, they may actively grow / harvest it.
  • What you call a plant could be a weed to someone else / somewhere else.
  • You have environmental weeds / garden weeds / agricultural weeds

How People Create Weeds

Plants that are introduced into new regions can become weeds if:

  • They are better than indigenous plants at competing for resources (sun, nutrients, water, space)
  • Growing conditions are more favourable for the weeds
  • Predators, pests, diseases and competitors are absent in the new environment

Create empty ecological niches provide opportunities for weed growth. An empty ecological niche can be thought of as an empty space where a plant could be growing but where nothing is currently growing. These niches result from: Removal of indigenous vegetation. Leaving large areas of bare ground

Weeds often have adaptive mechanisms that allow them to fill difficult niches. By avoiding empty niches we can reduce the opportunities for weed growth.

Weedy Opportunities

What gardeners do can create the perfect opportunity for weeds

  • Removal of indigenous/existing vegetation
  • Preparing for crops and disturbing soil
  • Harvesting crops and leaving bare soil
  • Allowing weeds to go to seed
  • Inappropriate disposal of weeds

The First Responders

Nature tends to fill empty ecological niches. Weeds are often the plants best able to fill these niches because they have adaptive mechanisms that help them cope with stressful conditions. These include:

  • Rapid growth and seed formation
  • Prolific seeding
  • Ability to regrow from fragments
  • Tolerance of unfavourable conditions (drought, water logging, high/low nutrients, extreme temperatures)
  • Tolerance of disturbed soil environments

The first step in managing weeds effectively is understanding them

Food can be a weed – Blackberry

Berry plant that grows on thorny canes. Introduced to Australia in the 1840s as a horticultural plant for the production of fruit

Why it’s a problem: Outcompetes native plants. Intrudes upon grazing land

How it spreads: Seed Root fragments Suckers

What to do about it: A combination of strategies will be required – Hand-pull (only young plants) Foliar Spray, Cut stump Removing as much of the plant as possible, replanting and removing suckers as they appear may work

Plants can be a weed – Ivy

Climber/groundcover with small yellow/green flowers

Why it’s a problem: Smothers and kills other plants including indigenous plants. Can also cause damage to built structures

How it spreads: Seed Layering (new plants form when stems touch soil) Stem fragments

What to do about it: Do not allow to set seed – Control climbing stems first as these set seed. Ensure no birds nesting prior to removal. Hand-pull (young plants). Dig out. Cut and paint stump

Replace with: Common Appleberry (Billadiera scandens), Bower of Beauty (Pandorea jasminoides), Creeping Fig (Ficus pumila)

Native Plants can be a weed – Invasive Acacia

Shrub / tree, grows to H10m. Feathery leaves, smooth bark, distinctive ball-shaped golden yellow flower heads in late winter / spring

Why it’s a problem: competes with native shrubs, small trees and ground flora, impedes their health and growth.
cross breeds – threatening the integrity of native wattle populations

How it spreads: long-lived seeds, accumulate in the soil and germinate readily after disturbance / fire. Spread by birds / garden waste.

What to do about it: Don’t buy it Manual control – hand pull or dig out young. Herbicide application and sustained effort to remove soil-stored seedbank

Plants can be beautiful weeds Agapanthus

Strappy leaf plant with purple or white flowers

Why it’s a problem: Dense, clumping roots can displace and outcompete other plants. Large potential to change plant eco-systems and eliminate habitat

How it spreads: Seed, Root fragments

What to do about it: Do not allow to set seed. Dig out roots (all if possible) Monitor in the following months and remove new plants. Look for sterile varieties

Replace with: Tasman Flax Lily(Dianella tasmanica), Daylilies (Hemerocallis)

How to Remove Weeds

Integrated Weed Management – IWM An eco-system based approach to managing weeds where multiple techniques are used – physcial, cultural, biological and chemical (as a very last resort). Understanding the particular weeds that we are trying to get rid of is key to managing them.

Controlling Weeds Physically

  • Localised – Hand pulling, mowing, flame weeding, boiling water etc.
  • Mass removal in areas – solarising and sheet mulching
  • Early detection – Do a little weeding often rather than long but infrequent weeding sessions.
  • Usually best to remove all or as much as possible of the weed including its root system.

Physical control of Annuals

  • Annuals live for a year or less
  • They reproduce from seed and then die
  • Remove annuals before they flower or cut them down to ground level to avoid seed setting.

Physical control of Perennials

  • Perennials live for longer than a year
  • Foliage might die but underground parts can remain alive and reshoot the following season
  • Remove all fragments to prevent regrowth.

Responsible Weed Disposal

  • Appropriate weed disposal will prevent spreading and regrowth of weed plants
  • All garden waste should be composted at home or placed in green bins
  • Different types of weed may require different disposal methods or a combination!

Sheet mulching

  • No-dig method – does not disturb the soil.
  • Layers of cardboard or newspaper (6 or 7 sheets thick) are placed overlapping on top of weeds or lawn
  • Mulch (5-7cm) placed over the top
  • Can help break the cycle of annual weeds.
  • Might not work for really persistent running weeds such as kikuyu and couch grass


  • Weeds are cut and covered with thick clear or black plastic (clear plastic heats up quicker but the heat doesn’t last as long)
  • Leave for a few months over summer (temperatures need to be regularly in the 30s)
  • Most weeds and their seeds will be cooked and destroyed
  • Soil is also cooked but should recover fairly quickly

Composting Weeds

  • Whether weeds can go into your compost will depend on your composting method and the type of weed.
  • Some weeds will re-sprout in cold compost systems
  • Weeds contain lots of nutrients which you can add to your compost.
  • De-rooted annuals straight easy but perennials need to be careful.
  • Hot composting will kill most seeds and weed fragments, but cold composting may not
  • Weeds can be placed in a plastic garbage bag and left in the sun for a couple of months before composting
  • You can also drown them and make weed tea

Cultural Approach – Don’t Encourage Weeds

  • Don’t bring potential weeds into your garden
  • Purchase weed free seeds, mulches, soils and plants
  • Avoid bare ground – replant quickly and plant densely
  • Mulch (About 7cm deep)
  • Only irrigate plant root zones. e.g. drip irrigation
  • Avoid disturbing the soil

Weeds in Veggie Gardens

Some forms of vegetable gardening are based on seasonal soil disturbance. Reduce weeds in vegetable garden by:

  • Employing no-dig growing methods
  • Planting crops at high density (reduce distance between rows on seed packets)
  • Mulching well most of the year.
  • Using cover crops when resting beds
  • Intercropping annuals and perennials

No Dig Gardening Approach

  • Pioneered in Australia in the 1970s by Esther Dean
  • Based on not disturbing soil structure through digging
  • Can be built on existing garden beds, lawns, compacted soils, concrete surfaces or in large pots and planters
  • Layering of different organic materials in a raised garden bed – like a lasagne
  • Plants are planted in the top compost / soil layer
  • As organic layers break down they feed the soil food web
  • Additional layers added over time

Biological Approach / Controls

  • Livestock – Chooks. Pigs . Goats
  • Living Mulch – Cover bare ground with vegetation

Controlling Weeds Chemically

Only use as a last resort, sparingly and targeted. Concerns surrounding herbicides:

  • Herbicide drift – may affect cultivated/desired plants
  • Run-off – herbicides that end up in waterways can harm plant and animal life
  • Effects on beneficial insects, wildlife and soil microbes
  • Chemicals can be retained in the soil
  • Herbicide resistance
  • Concern about health effects and safety

Chemical Control – Contact Herbicides

  • Only affect parts of the plant that they come into contact with. Underground roots and stems may not die
  • Common household strength vinegar (5%) can be used on young soft weeds
  • Horticultural grade products (10-20%) should be used with care
  • Repeat applications necessary
  • Non-selective – affects all or most plants
  • Nonanoic acid (Slasher). Organic approved. Non-selective – affects all or most plants


Chemical Control – Systemic Herbicides

  • Absorbed by plants and carried to other parts of the plant not directly sprayed.
  • Glyphosate (e.g. Roundup) Non-selective – affects most plants. Sometimes mixed with other ingredients . Controversy surrounding health claims.
  • Prioritise use on invasive perennial weeds, not annuals. Should be applied direct (dap / localised spray) and avoid spraying over large areas.

Chemical control – Selective Herbicides

  • Only harm some specific types of plant
  • Bromoxynil – Kills broadleaf weeds without harming most lawn grasses
  • Iron – Alternative to bromoxynil based products. Same product used to correct iron deficiencies but at a much higher dose. Organically acceptable products believed to have minimal human health or environmental effects

Pre-emergent Herbicides

  • Prevent seeds from germinating
  • Pine oil (e.g. Amgrow Weed Blitz) – Approved organic input. Can also be effective on soft, young vegetation

Herbicide Application Methods

  • Dabber
    • Use same concentration of spray but dab direct onto plant either on leaf or cut stem as soon as cut (within 10 seconds)
  • Foliar Spray
    • Spray on a dry, sunny day that isn’t too windy
    • All leaves and stems should be visibly wet
    • Potential for spray to drift and affect other plants
  • Cut Stump
    • Used for woody weeds
    • Plants are cut to ground level and immediately (within 15 seconds) painted with herbicide
  • Drill and Fill
    • Used for woody weeds
    • Drill down on a 45 degree angle into trunk and use a syringe to insert herbicide

SGA Product Guide – Wise Gardening

SGA doesn’t recommend the use of herbicides in your garden. But understands that on some occasions they might need to be used. SGA has developed a product guide to help identify suitable products with minimal human and environmental impacts.

Weeds as Resources – Ecological Functions of Weeds

Weeds, as plants, do have positive purpose in nature. They protect the soil from heat, wind and heavy rain and begin ecological succession which can lead to re-establishment of desired plant species. Some weeds might provide habitat for beneficial and locally indigenous insects and wildlife. Some weeds provide food or other useful materials for animals (including humans) With deep tap roots weeds absorb and retain nutrients from the soil – resource!!

Weed Nutrients

Chickweed – phosphorus, potassium
Clover – Nitrogen, phosphorus
Dandelion – phosphorus, potassium, calcium, iron, copper
Plantain – Sulphur, Manganese, Iron
Purslane – Potassium, Sulphur, Calcium, Magnesium, Manganese
Nettle – Nitrogen, Potassium, Calcium, Magnesium, Iron, Copper
Yarrow – Nitrogen, Phosphorus, Potassium, Magnesium, Copper

Using Weeds

Boost Compost

  • Use weeds to boost your compost with all the nutrients your veggies will need.
  • Use annuals only. Do not use perennials – they may spread this way.
  • Ensure the weeds have no seeds or disease
  • Remove roots to be sure.
  • Weeds are classed as a green ingredient so need to be mixed with brown ingredients

Mulch Layer

Weeds are incredibly nutritious. Nutrients are in the bodies – mainly roots. Only use on annual weeds which reproduce from seeds. Perennial weeds tend to reproduce from fragments especially roots / leaves

To use as mulch –

  1. Chop / remove seeds.
  2. Chop up remaining weed into small pieces
  3. Drop pieces onto ground as a mulch.
    • OR bury in small trench or hole in your garden

Hot Compost

  • Hot composting will kill most seeds and weed fragments but cold composting may not
  • Hot compost is when temperature in a large 1m3 system reach over 70 degrees
  • Weeds can be placed in a plastic garbage bag and left in the sun for a couple of months before composting


Weed Tea

  • Collect weeds and weed fragments that cannot be composted
  • Place the weeds into a bucket of water, fully submerged.
  • Cover and leave for about 6 weeks.
  • Strain the liquid from the weed pieces and place solid pieces into the compost.
  • Dilute the liquid in water (1:10)
  • Apply liquid to your garden

Edible Weeds

  • Many weedy plants have edible parts which range in taste from delicious to barely palatable
  • Some wild food plants have a bitter or astringent taste
  • This is often related to their very high nutrient content

Foraging Weeds

  • Make sure that you are 100% sure of your identification.
  • Consider whether the area you are foraging in could have been sprayed – you can ask the local council whether they spray nature strips, parks etc. Air on side of caution.
  • Also consider whether the ground could be polluted – could there be dangerous levels of lead in the soil?
  • Best to eat your own weeds!

Oxalic Acid

Excessive amounts of oxalic acid can be harmful and extreme over-consumption can be fatal. Reasonable amounts of oxalic acid are perfectly safe for most people. Foods high in oxalic acid include spinach, chocolate, eggplant and tomatoes. A number of weeds, including dock and oxalis, have high levels of oxalic acid. Reduce oxalic acid by blanching leaves before eating. The oxalic acid will leach into the boiling water which can be tipped out. People who have been advised to avoid foods high in oxalic acid should take extra care when foraging (e.g. people with kidney stones or kidney disease).


Soursob oxalis (Oxalis pes-caprae)

What it is: Low growing perennial with clusters of 3 heart shaped leaflets and relatively large yellow flowers. This one is a lot more invasive than the creeping one. Picture – beautiful green carpet around the rock. Only there for a couple of months and then dies back.

Why it’s a problem: Quickly covers ground, smothering and preventing establishment of other plants. Difficult to remove as bulbils broken off when plants are pulled grow new plants.

How it spreads: Rarely produces seed in Australia. Spreads mostly via underground bulbils.

What to do about it: Do not pull – the little bulb breaks off and continue to grow. Dig plants out and remove all bulbs. Repeat treatment required. Or cut it down to deplete its resources, so it dies off, don’t let it flower.

Replace with: Native Violet (Viola hederacea)

Edible – You can eat Oxalis. Eat leaves in salads and sauces. Has a subtle lemon flavour. Add flowers to salads for colour. For best flavour choose plants growing in moist, shady positions. Caution – high in oxalic acid. Cooking removes this, so just don’t eat raw to be safe.

Dock (Rumex species)
What it is: Genus of perennial and annual plants with thick taproots and greenish-red flower stalks.

Why it’s a problem: Weed of bare/disturbed soils, agricultural land and gardens.

How it spreads: Seed.

What to do about it: Do not allow to set seed. Remove plant including taproot – difficult because they have fibrous roots like parsnip.

Eating Dock

Bitter taste. Can vary from delicious to inedible. Younger leaves are better. Eat leaves raw (sparingly – high in oxalic acid) or cooked.


Onion Weed (Asphodelus fistulosus)

What it is: Annual or biennial with round hollow leaves and white flowers with a red stripe down the petal. No onion smell.

How it spreads: Reproduces by seed.

What to do about it: Remove plants prior to flowering.

Eating it: make sure you have the right one, there is many that look like it. This one isn’t that flavoursome.

False Onion Weed (Nothoscordum borbonicum)

What it is: Perennial with white flowers and strap like leaves. Cylindrical flower stems. No detectable onion smell.

How it spreads: Bulbs and bulblets. Seed.

What to do about it: Carefully dig up all plant parts including bulbs and/or solarise/sheet mulch. Mow or remove prior to flowering.

Angled Onion (Allium triquetrum)

What it is: Strappy leaves. Drooping white flowers. Very Strong onion/garlic smell. Active from mid-winter to early summer leaving ground bare for 6 months of the year. Three angled / triangle flower stems.

How it spreads: Bulbs and bulblets. Seed.

What to do about it: Carefully dig up all plant parts including bulbs and/or solarise/sheet mulch. Mow or remove prior to flowering.

Eating Angled Onion (Allium triquetrum)
All parts are edible: leaves, bulbs and flowers. Subtle onion/garlic taste. Use as you would spring onions or chives. Best eaten raw – all parts lose flavour and become fibrous when cooked, can be turned into a pesto

Dandelion (Taraxacum officinale)
What it is: Very hardy and pop up everywhere. Tap rooted perennial with variable lobed leaves and yellow flowers. Flower head looks like a fluffy ball just before the seeds blow away.

Why it’s a problem: Weed of bare/disturbed ground. Found in agricultural land, lawns and backyards. Quickly grows and sets seed.

How it spreads: Seed is wind dispersed. What to do about it: Dandelions will regrow unless the whole taproot is removed. If root cannot be dug out, sever just below ground level and repeat as plant regrows until root is exhausted. Remove before seed is produced.

Eating Dandelion
Highly nutritious. All parts are edible. Use young leaves from the centre of the plant in salads, stir fries, omelettes and soups. Avoid plants that have flowered as the leaves become bitter. Flower petals are sweet and can be added to salads, sandwiches and veggie patties. Roots can be eaten as a vegetable but mostly used to make a coffee substitute. Have been used this way for years and years.

Chickweed (Stellaria media)
What it is: Very common. Delicate annual with tiny leaves and white flowers. Identified by the line of hairs along the stems. How it spreads: Seed. Remove before flowering.

Eating Chickweed
If confident that hasn’t been sprayed you can eat it raw or cooked in salads, stir fries, soups and omelettes. Chickens love to eat it too.

Sow Thistle (Sonchus oleraceus)
What it is: Yellow flowered annual. Looks a little like dandelion but with multiple flowers per stem. Exudes white latex when broken.

How it spreads: Seed. Remove before flowering.

Mallow (Malva parviflora)
What it is: Annual or biennial with lobed, slightly fuzzy leaves, like geranium. White or pink flowers followed by round ‘cheese-like’ fruits.

Why it’s a problem: Weed of farms, vegetable gardens and disturbed soils. Harbours a number of garden pests and diseases. Horse paddocks.

How it spreads: Seed. Remove plant by hand before flowering.

Eating Mallow
Pleasant, mild flavour. Mucilaginous like okra. Eat the young leaves before flowering. Seed heads (cheeses) can be harvested when pale green (not dry). Can steam and fry those as well

Stinging nettle (Urtica dioica)
What it is: A very nutritious weed. Upright annual covered in tiny stinging hairs.

Why it’s a problem: Weed of agricultural areas and gardens. Likes fertile soil.

How it spreads: Seed. Remove before flowering or remove heads.

Eating Stinging Nettle
Use young leaves and blanch leaves for a minute or so to remove the sting. Can be use in soups, stirs fries and can be made into a pesto. Eat in small amounts first. Can give you a tingle on the lips. Traditionally used to make a tea.


The Weed Foragers Handbook – Annie Raser-Rowland & Adam Grubb (Hyland House Publishing) – also dpes a poster.
The Weed Book – Mark Wolff (CSIRO)
The Wonderous World of Weeds – Pat Collins (New Holland Publishers)
Garden Alchemy – Stephanie Rose (Coll Springs Press)
Weeds Australia
Picture This Identification App