Lesson 2 culture of native plants

 

Weed control before planting 

All weed growth should be removed before planting to reduce competition while new plants are 

establishing. In particular all parts of creeping plants such as couch, kikuyu, bent and buffalo grasses and 

bulbous plants such as oxalis should be carefully removed by hand or killed with a trans-located 

weedicide (moves through all parts of the weed including roots) such as Zero. Chemical control should 

be done prior to disturbing the soil so that broken off sections of weeds are not buried in the disturbed soil 

where they might strike as new plants.  

 

Weed control after planting 

Weed control after planting is best achieved by non-chemical means, unless the problem is really 

extensive, as you run the risk of damaging your natives. Heavy mulches, or weed mat laid down at the 

time of planting and regularly maintained will greatly reduce the likelihood of weeds becoming 

established. Maintaining plants in a healthy condition through good fertilising, watering, pruning, etc. 

practices will allow them to out compete any weed growth. As weeds develop hand weeding, slashing, 

mowing, etc. can be used. 

  

 

PROPAGATION OF AUSTRALIAN PLANTS 

Life of seeds 

Some seed remains viable for years other seeds keep for very little time at all. 

•

  Banksia seed will keep longer if left in the cone (provided cones are treated to kill insects which might 

cause damage). In the cone, Banksia seed lasts up to 6 years, out of the cone it lasts only 3 years. 

•

  Eucalypt seed keeps much longer if stored with the chaff. When cleaned, the lifespan decreases 

•

  Seed stored in glass or metal is better than that stored in plastic.  

•

  Plastic containers give off ethylene gas which is an inhibitor to germination. 

   

Sexual versus - Asexual propagation methods 

There are various reasons for choosing sexual propagation instead of asexual methods and vice versa.  

 

Sexual propagation is often used for the following reasons: 

•

  When plants cannot readily be grown by asexual methods. 

•

  Production by seed is a lot cheaper, and often quicker than by asexual methods. 

•

  Seed of a particular plant may be plentiful, while cutting material is not. 

•

  Seed propagation is important in maintaining genetic diversity. 

•

  Seed propagation is used to breed new varieties. 

 

Asexual propagation methods are often used for the following reasons: 

•

  To produce plants with the identical genetic characteristics as the parent plant (eg. flower colour, 

variegation). Some plants do not produce viable seed, or their seed may be difficult to germinate, or 

the seed may be unavailable at the time you are in the area collecting propagation material, or that 

you need to produce that plant (you have orders from a customer) when seed is not available, or is 

perhaps too costly. 

•

  Plants produced by asexual methods from a plant that has already flowered will usually flower 

quicker than plants grown from seed. 

•

  Budding/grafting methods can be used to establish selected plants onto selected rootstocks (eg. 

resistant to particular soil conditions or pests and diseases, or to create standard or weeping 

plants). 

 

Seed sources 

It is absolutely vital that any source of seed for propagation is: 

•

  Totally reliable - you must know where it comes from, that the collector knows what they are doing. 

•

  From plants which are not likely to have hybridised. 

 

Consider: Variation within a species 

•

  A form of Myoporum insulare native to the coast may tolerate a pH of 9 

•

 Another 

form 

of 

M. insulare from the inland may only tolerate a pH of 7.5 

•

  There are red flowering forms of Eucalyptus ficifolia (also known as Corymbia ficifolia) growing in 

south west Western Australia which produce flowers virtually every month of the year. The time of 

flowering on the plants grown will vary according to where the seed came from. 

•

  Eucalyptus calophylla occurs in the wild on the W.A. coast from 1600km to 450 km south of the 

Tropic of Capricorn. The plants which occur in the north would produce seed more adapted to 

warmer climates, while seed collected in the south would grow plants more suited to cooler climates. 

 

If you buy seed, do you know where it came from, and what sort of plants it is likely to produce? 

 

Where can you get your seed from? This is very important in terms of: 

a. Quality  

•

  Some seed suppliers do not supply pure seed (rubbish or weed seeds can be mixed with the seed). 

•

  Some seeds have not been harvested at the right time, hence % viability is lower. 

•

  Some seeds have not come from strong and healthy plants hence the vigour of the seed may be 

less. 

•

  The seed may have been stored poorly (eg. allowed to dry out), and hence the percentage of 

viability is reduced. 

•

  The seed may be infested with diseases or pests (eg. insects eating seed). 

 

b/ Gene pool 

The place which a particular plant originated from gives it a range of characteristics which are very 

specific to that plant (eg. Eucalyptus camaldulensis seed from one stand of trees might be very tolerant 

of salt, while seed from another stand of Eucalyptus camaldulensis might not tolerate salt at all). Seed 

sourced from local plants will enable you to produce plants that are adapted to local conditions (eg. 

soil, climate). 

 

There are four main sources of seed: 

 

1. Seed collected from the wild 

Seed collected from plants growing in their natural habitat is less likely to be cross-pollinated, and you 

can be more certain of where it came from and how it will grow than if you had purchased it. This can 

be a cheap method of getting your seeds if you don't have to far to travel, and have the time to spare. 

Many people get great satisfaction out of collecting their own seed. This may also be the only way to 

get some particular species. Permission should be sought from landowners of privately owned 

properties, or from the relevant state authority for public land. In Victoria this is the Dept. of Natural 

Resources and Environment (Contact them) 

 

2.  Seed exchanges/Seed banks 

Many Botanic gardens operate seed exchange programs, where they produce annual seed lists, and 

swap seed with others who involve themselves with the program.  

Such programs are particularly valuable as a source of more scarce varieties of plants. Some 

associations and societies (eg. Society for Growing Australian Plants, Greening Australia, Landcare, 

Community Environmental Groups and Nurseries) also participate in exchange programs, or maintain 

seed banks for members and groups involved in re-vegetation programs. For example, the Victorian 

Branch of Greening Australia hold the "Melbourne Indigenous Seed Bank". 

 

3.  Commercial seed suppliers 

There are many hundreds of seed companies operating throughout the world. Some breed new 

varieties of plants and grow seed crops to harvest. Others buy seed from collectors (who collect from 

the wild or from gardens). Major problems of using this source include: 

•

  Collectors identifying seed source plants incorrectly. 

•

  Unreliable supply (if they can't supply, it's too late for you to collect for yourself). 

•

  Uncertainty about the quality. 

•

  Developing a dependence on the supplier. 

 

Major advantages of using this source include: 

•

 Convenience 

•

  Obtaining a seed source for plants which do not set seed well locally. 

•

  Savings on labour costs. 

 

4.  Collecting seed yourself locally 

You or your representative might collect seed from plants on your property, or on other nearby 

properties as it matures throughout the year. 

They might also be collected from public parks and gardens or private gardens (with permission). The 

major advantages of this source are: 

•

  You have a great deal of control over collection, storage and treatment. 

•

  You can be sure you have got exactly what you want. 

•

  You learn a lot more about the plants you are growing, because you see them in their mature state. 

•

  You can save on the cost of purchasing seed, though collecting can be time consuming, particularly 

if you have to travel to collection sites. 

 

Why do plants produce so much seed? 

Much of the seed produced by plants gets eaten before it has a chance to germinate. 

A lot of the seed produced will not end up in conditions suitable for germination. 

Some of the seed will not germinate readily, even if it is in good conditions for germination due to 

dormancy factors within the seed.  

Some seed will form a "Seed Bank" that may survive for many years in the soil until conditions are 

suitable for germination. A good example is the reappearance of species not seen in decades in areas 

where the Rabbit Calicivirus Disease (RCD) has had a big impact on rabbit populations. 

By providing suitable conditions we can generally get much higher rates of germination than would 

naturally occur in the wild.  

 

Collecting and harvesting seed – Guidelines 

Always seek permission before collecting seed from private or public land.  

•

  Find a site: this may be as simple as keeping your eyes open or by seeking advice from local 

forestry or conservation bodies or departments. 

•

  Take necessary equipment:  plastic bags; writing equipment, labels, or small cards to write 

collection details on. For larger scale collecting you might need handsaws, long handled loppers, 

tarpaulins, a step ladder and more. 

•

  For tall plants you are best to obtain seed from commercial collectors. They generally use 

equipment such as cherry pickers, climbing equipment, or even high-powered rifles to shoot down 

branches from high in trees.  

•

  Use gloves when harvesting. Many native plants have prickly or thorny foliage, some (eg.  

Grevilleas) can cause skin allergies many will have resident populations of spiders, ants, etc. Use 

common sense when choosing which clothes you are going to wear. Long trousers, long sleeved 

shirts, and tough durable footwear are recommended. Safety helmets might be necessary if there is 

a risk of heavy limbs falling. 

•

  While many seed pods can be readily picked off the parent plant without damaging the plant some 

are a lot tougher to remove. Avoid pulling or ripping these off. Use sharp secateurs or similar hand 

tools. This will reduce the likelihood of damage to the parent plants. 

•

  Always use sharp, and sterilised (pest and disease free) hand tools. A small container of a 

disinfectant (eg. bleach, methylated spirits) can be carried to dip or wash tools in regularly. 

•

  Avoid harvesting seed pods when they are wet. This will reduce the likelihood of losses due to 

fungal problems. 

•

  Avoid damaging other plants. In your desire to get to a particular plant you could easily trample on, 

or break branches off other plants. Be observant, take your time, and carefully pick where you 

place your feet, and you will minimise the likelihood of causing damage to other plants. 

•

  Always label each batch of seed you collect, when you collect it. Information should include such 

things as the species collected, the date collected, who collected it, where it was collected. This will 

enable others who use the seed at a later date to be sure of what seed you have, how old it is, 

where to go if you want more, and who to ask if you want more information. 

 

Selecting plants to collect from 

•

  Collect your seeds from healthy, vigorous trees of desirable form, or having desirable 

characteristics (eg. flower size and colour). 

•

  Where possible avoid collecting from isolated specimens, as self-pollination generally yields seed 

of low vigour, and a limited gene pool. 

•

  To promote biodiversity take roughly equal amounts of seed from a variety of well spaced, 

desirable plants. Ideally only harvest a little from each plant, particularly when there are lots of that 

particular species available. As a rough guide no more than 10percent of available seed should be 

taken from each plant. This will ensure that plenty of seed is left on the plant to maximise the 

survival of the species locally, and helps ensure you have as wide a gene pool as possible in the 

seed you have collected. 

•

  If you are quite sure that all of the plants you have collected from in a particular location are from 

the same species then you can mix all of that seed together. If you are not sure then keep each 

batch of seed separate (and separately labelled). 

 

Timing 

Knowing when to harvest seed is one of the most difficult tasks you will face when collecting seeds. 

The time taken for seed to reach a harvestable stage from flowering will vary considerably from species 

to species, and can range from a month or two up to several years.  

 

Experience plays a very important role. Regular observation of plants you are interested in harvesting 

from can often be critical, particularly for those plants whose seed ripens over a short period of time 

and are not retained for long on the plant. Obtaining advice from others familiar with the plants you 

wish to collect can be very worthwhile, as can research from relevant publications. 

 

For many species the fruits are mature when they reach their full size and turn darker in colour and 

become woody. Once mature many (eg. capsules, pods) will split open allowing their seed to be 

dispersed. Some species will shed all of their seed within a few weeks of maturity (eg. Acacia). Some 

species will retain their seed for a long time (eg. many Banksia, Hakea, some Eucalyptus.).  

 

The seed of some plants will ripen over an extended period, while others will mature all around the 

same time. 

 

Fleshy fruits, common amongst rainforest species, will usually soften, and often change colour when 

mature. These fruits are commonly eaten by birds and other animals, and the seed excreted from the 

animals, and so dispersed away from the parent plant. 

 

Methods of collecting 

•

  Natural seed fall 

Large seeds or fruit can be collected from the ground. This method is most commonly used for 

rainforest plants. 

 

•

  From low growing plants or branches 

Readily detachable fruit or seeds can easily be handpicked. A tarpaulin or plastic sheet can be placed 

under the plant and the plant is shaken, or branches are knocked with a stick to dislodge seed and/or 

seeds. Some fruit might not be readily handpicked, but can be carefully pulled away from the parent 

plant with a little effort, making sure to minimise any damage to the parent plant. Other fruit might need 

to be cleanly cut away from the plant with a sharp knife or pair of secateurs.   

 

•

  From higher branches 

Long handled saws, loppers or pruners can be used to remove selected branches. A rope saw can be 

thrown over a branch, and the saw drawn backwards and forwards to cut the branch. Ladders can be 

used (carefully), but they are cumbersome to carry around in the bush. A rope with a weighted end can 

be swung around and thrown up into a tall plant to either wrap around a branch so that it can be 

carefully pulled down within reach, or to dislodge fruit or seed so they fall to the ground.  A rifle with a 

telescopic sight is sometimes used to shoot through branches causing them to fall. This should only be 

done by qualified (and licensed) people. Expert climbers with suitable equipment can climb tall trees 

and cut down selected branches.  

 

Ideally safety helmets should be worn when harvesting using any of these overhead methods to reduce 

the likelihood of injury from falling objects such as branches or large, hard fruits. 

 

•

  Felled trees 

If a tree has been cut down for harvesting then it may be possible to collect seeds from it. Trees should 

not be cut down just to harvest seeds. 

 

Removing seeds 

The mature fruits of many natives normally need to be dried before seed will be released. They can be 

spread loosely on sheets of plastic or a tarpaulin. They should ideally be exposed to the sun, in a site 

protected from wind, or placed in a well ventilated site under cover. Check regularly for pests (eg. 

spiders, insects, birds, mice), and turn the fruits regularly. The outer pulp of fleshy fruit should be 

removed prior to drying.  

 

Drying may only take a few days in warm, dry weather, but may take weeks or even longer in cooler 

weather. 

 

Fruit of some rainforest species should not be dried. 

 

Extracting the seed 

Some seed is readily separated from the fruit (eg. Acacias, Hoveas, Hardenbergias), some is actually 

dispelled as the fruit matures. 

 

Seed held in hard woody fruits (eg. Hakeas, Eucalypts, Callistemons, Melaleucas, Leptospermums, 

Kunzeas) generally open naturally over time, once removed from the parent plant. The fruits may need 

to be banged to dislodge some of the seed. 

 

Some seed however, might need a little help in being released. Many Banksias, for example, will retain 

seed in their fruit (technically called multiple woody follicles - more commonly called "cobs") for many 

years. The fruit generally require exposure to heat before they will open. This can be done in a variety 

of ways including: 

Throwing the Banksia cobs onto a BBQ for a short time (eg. a couple of minutes); this will burn off any 

residual dried floral parts, and will often result in the follicles opening as the cob cools. 

Putting the cobs in an oven at around 180 degrees C for about 15-20 minutes; remove them and allow 

them to cool naturally, or dip them in cool water. 

 

Once the follicles have opened, the seed can often be easily removed by banging the cob onto 

something hard which will hopefully dislodge many of the seeds. There will often be two (winged) 

seeds per follicle. Some seeds may need to be removed carefully using a pair of flat pronged tweezers. 

 

Seeds with fleshy coverings should have the outer fleshy layer removed carefully using your fingers, or 

a knife, and water. Alternatively the fruits can be pulped and seeds carefully strained off then dried. 

 

Cleaning seed 

Any chaff (infertile ovules in with the actual seed), leaf litter, old seed pod material, insects, spiders, 

etc. should be carefully removed, making sure you don't damage the seed. For heavier seed such 

debris can often be blown away carefully by blowing on them, or even with a hair drier held at a 

suitable distance away. Some seeds can be separated from other material through a wire mesh sieve. 

 

Storing seed 

Seeds are alive and like any living thing they can be harmed by adverse conditions. Seeds of some 

species do not store for very long at all...propagation should be done with fresh seed only. Most seeds 

however will store for at least 6 months without loss of viability, provided the environmental conditions 

of their storage are right. 

 

Dusting seeds with an insecticide in powder form (eg. Carbaryl) can be effective in minimising damage 

due to insect pests. Make sure when handling such pesticides, and seed treated with them, that you 

use suitable rubber protective gloves. Also avoid breathing in any of the powder. Always wash exposed 

skin after handling seeds treated in this manner. 

 

The seed of many natives, particularly those from drier regions, and including many of the Eucalypts, 

Acacias, Cassias, Melaleucas, Casaurinas, Callistemons, Kunzeas, Leptospermums, Hoveas, and 

Hardenbergias are ideally kept under low humidity and temperature conditions with little fluctuation in 

these factors. The seeds are commonly stored in airtight, re-sealable glass, plastic or metal containers. 

Alternatively snap-lock plastic bags can be used.  Keep the containers in a cool, dark spot where they 

are safe from vermin. 

 

Seed from many of the fleshy fruited species has a short life span, and should be sown as soon as 

possible. 

 

At all times seed batches should be properly identified (ie. labelled). 

 

 

DIFFICULT SEEDS 

Some types of seeds are much more difficult to germinate than others. In their natural state most 

species have adopted mechanisms which allow germination to occur with relative ease. For many 

"difficult to germinate seeds", it is possible to carry out some type of pre-germination treatment which 

will increase the chances of success: 

 

Germination treatments 

Seed of many native species will germinate readily if suitable conditions are supplied however the seed 

of some species have built in dormancies that prevent them germinating immediately. This is an 

adaptation that promotes survival. Such seeds will often germinate only after fire has passed through 

the area, or after an extended period of time. To get such seeds to germinate they need to be treated 

in some manner.  

 

Typical treatments include: 

•

  Scarification is any process of breaking, scratching, mechanically altering or softening hard seed 

coverings to make them more permeable to water. These treatments are commonly used on 

species from the following genera: Acacia, Hovea, Hardenbergia, Pultenaea, Kennedya. Three 

types of treatments are commonly used to scarify seeds. These are mechanical, chemical and hot 

water: 

•

  Mechanical Scarification involves such methods as rubbing them with sandpaper to thin the seed 

covering, filing through the seed coat, nicking the seed covering with a sharp knife, cracking the 

seed coat with a hammer or a vice. With each technique it is important to avoid damage to the 

internal parts of the seed (and to yourself!).  These techniques are used for larger seeds (easier to 

handle), and where the amount of seed to be treated is small.  

•

  Acid Scarification is where dry seeds are placed in containers and covered with concentrated 

sulphuric acid in the ratio of about one part seeds to two parts acid. Suitable acid resistant 

containers should be used and great care taken in handling the acid (eg. chemical safety gloves 

and face masks used). Time of treatment will vary from as little as ten minutes up to six hours 

depending on the species.  

 

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