Direct seeding for native revegetation

What is direct seeding?

Direct seeding is the process of sowing seeds directly into the soil. This can be achieved mechanically or by hand.  It is ideal for the larger seeded species and site preparation is not as intensive as for seedlings.

The results of direct seeding are generally inconsistent. It produces ‘patchy’ rows with clumps of seedlings in some areas and little to no cover in others, this is ideal for environmental plantings. The patchiness creates habitat complexity through a mixture of open and dense areas.

Direct seeding suits planting for wildlife corridors.

Direct seeding is not recommended when you need planting patterns. For example patterns for windbreaks or spray barriers.

Benefits of direct seeding

The are several benefits of growing native vegetation from seed rather than planting out seedlings.

• Trees and shrubs grow healthier root systems.
• More efficient for large areas of revegetation.
• Can be done at low cost.
• Relatively easy to establish a diversity of species.
• Promotes survival of plants with the strongest genetics and regional suitability.

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Video transcript

The fundamentals of direct seeding for native revegetation projects

Hi, my name's Dominic Nowlan.
I'm a Senior Land Service Officer with the Central West LLS here at Grenfell.
Today I'm just going to have a bit of a quick chat to you
about the pros and cons of direct seeding
and using it to establish corridors or enhance existing remnant vegetation.
When considering to enhance an existing piece of remnant vegetation
or alternatively planting a new corridor,
direct seeding is a very viable option.
When choosing direct seeding as an option to either enhance
an existing piece of remnant vegetation or plant a new corridor,
the first thing and most important thing to consider is preparation.
Preparation for direct seeding
is best achieved by baring a one metre piece of ground
the full length of your anticipated planting,
and keeping that bare for at least three months before planting.
This will give the direct seeding the best chance to survive
and flourish once germinated.
When choosing the species or seeds to direct seed,
my experience has been that the understory species work best.
This includes things like your acacias or wattles,
and dodonaeas and another understory species.
The success of eucalypts is never
as good as it is with those understory species.
Probably the two biggest advantages when choosing to do your revegetation
with their direct seeding is its cost effectiveness and its efficiency.
It's not unreasonable to plant up to ten, 20,
30km a day when direct seeding with one person.
You cannot do that when you're using tube stock.
When choosing to direct seed, you must consider
that some of your seed may or may not need seed treatment prior to planting.
For many of the understory species, like the acacias and dodonaeas
is this as simple as placing the seed into off boiled hot water
for maybe an hour or two, allowing it to dry before planting.
Another one of the benefits of direct
seeding, is the way in which the plantings establish.
Sometimes unintentionally the plantings germinate
sporadically in clumps and gaps
and somewhat imitate more of a natural setting.
For anyone thinking about undertaking direct seeding,
or even just wishing to learn more about it, please contact
your local LLS office and ask to speak to someone from the NRM team.

Direct seeding methods

Site preparation and seed species selection is vital for success when direct seeding.

Depending on the scale and aim of your seeding project, it may be possible to direct seed by hand. 

Hand broadcasting is suitable for steep sites, riverbanks and for seeding in areas where you may want to cause minimal disturbance, for example among existing trees or on sites that already have good native groundcover. If you have the time, you can use this technique on larger areas.

Mechanical seeding is recommended for property-scale and larger direct-seeding projects where vehicle access is possible.

Hand broadcasting methods

For small native seeding projects, you could just scatter the seed and hope for the best, but any preparation will improve success.

Creating a seed bed

This hand broadcasting method generally involves spot spraying followed by sowing into a roughened seed bed. This could be done by using a rake hoe to scrape away the topsoil to prepare a suitable seed bed and remove herbicide–treated soil if a residual herbicide has been used. Seed should then be lightly raked in, or pressed into the soil with the rake–hoe or your boot. 

Niche seeding

This involves preparing the seed to the point where it is on the cusp of sending out a small root and then planting it in a small, prepared hole with some growing medium. This gives the seed an advantage over any weeds that may be present and compete for nutrients, water and light with the small seedling.

Brush matting

This low-input technique involves laying seed bearing branches or leaf litter on bare areas. Fallen branches often hold immature seed. When sap stops flowing, the fruit will open and release the seed. The branch will protect any emerging seedlings. 

While this method may have a lower germination rate, retaining fallen branches will protect an existing eroded area, allowing for grasses to heal the site without stock impacting on its recovery. Brush matting is suited to sensitive sites where it is difficult to prepare the soil or within existing stands of remnant vegetation where you want to encourage regeneration.

Mechanical seeding  

Small direct seeding machines can be towed behind a 4WD. These work by placing a native seed mix into a hopper. A disc attached at the back of the machine cuts into the ground and simultaneously inserts seeds into the soil.  Some machines will offer separate hoppers from small and large seed. 

Seed is metered out at approximately 300 to 400 grams per linear kilometre. Only dry seed should be used.

A 25 m wide site that is 1 kilometre long with four rows would require around 1,200 grams of seed for the 2.5 hectares.

Site preparation for direct sowing

Direct seeding can occur with little preparation. For example, a spray fallow with no soil cultivation, or the full works (soil scalped and then deep cultivated). 

The choice is best guided by using a soil probe to test soil conditions along the rows. Sites with compacted soils should be aerated with a deep soil fracture to assist root penetration.

Many native plant seeds have evolved to stay dormant until certain conditions provoke their germination, such as bushfires. To aid germination, some seed may need to be treated prior to sowing. 

For greatest success, preparation of your site should begin 12 months before the seeds are to be planted. 

Good site preparation will: 

• reduce competition from grasses and weeds
• help build soil moisture
• provide the best opportunity for rainfall to infiltrate the soil
• allow for rapid and healthy root development.

Site preparation for mechanical direct sowing

Slashing and obstacle removal

If direct seeding will be completed using a 4WD, slashing provides a clear path to follow when seeding takes place. Remove any debris (stumps, logs, sticks, rocks) that will impede the 4WD and seeding machine’s progress.

Control weeds and grasses

Ideally 3 applications of a broad-spectrum herbicide should be applied over a strip 1m wide in each row. 

• Spray 1 – for new weed growth after slashing
• Spray 2 – follow up 3 to 6 months later
• Spray 3 – can be completed at the time of seeding or in the weeks before.

If using a residual chemical at the final spray, allow a withholding period of 25 days or 25mm of rain before planting.

Ripping (optional)

Ripping prior to direct seeding should be done to a depth of at least 300mm with rip lines at least 4 metres apart. Ripping will allow rainfall to be stored in the soil profile. 

When ripping sloping terrain, the rip line should run along the contour (not down the slope).

You should avoid ripping:

• under the canopy of existing trees
• in sandy soils unless clay subsoil is present
• in clay soils when wet.

We recommend you do a 'Dial Before You Dig' search before any ripping occurs to obtain information on underground cable or pipe networks in the area.

Timing a direct seeding project

Many people wait for a good rainfall season to commit to planting or direct seeding. However, this often leaves little time for adequate site preparation, which impacts on the germination success of direct seeding and the survival rate and vigour of planted seedlings.

To ensure your direct seeding has the best possible start, follow the recommended site preparation activities in the seasonal guide below.

Calendar guide for direct seeding

Late spring into summer the year before you plan to seed

• Order seeds as soon as possible, ideally before Christmas. Select species local to your area and landscape/soil conditions.
• Control exotic perennial plants if they are actively growing. Phalaris, cocksfoot and lucerne can be challenging to kill and will out-compete native vegetation seedlings.

Mid-autumn to early winter:

• Control pest herbivores such as rabbits, hares and deer.

Ensure chosen pest control methods do not irreparably damage existing native plants, native animal habitat or culturally important sites.  Local Land Services can provide advice on the control methods suitable for your situation and site.

• Control weeds when they are actively growing (around one month after the autumn break) in a 1.5 m band over the planned direct seeding lines with a knockdown herbicide. Blanket spraying of sites is not recommended.
• If there is a lot of vegetation cover crash grazing of the site or slashing of the rip/seeding line is recommended before weed control.

Mid-winter to early spring:

• If needed, control pest herbivores such as rabbits, hares and deer.
• If needed, control weeds and perennial plants again with a knockdown herbicide.
• Ensure the site is fenced out and stock-proof before seeding
• Direct seed into weed-free rip/spray lines.

After direct seeding:

• The greatest risks to germination are grazing, trampling by feral animals, rabbits and insect damage.
• Monitor for pest animals and insects such as grasshoppers and red-legged earth mites. If you notice red-legged earth mite activity after seeding, you will need to spray an appropriate insecticide over the seeded lines.
• Most planted sites will require watering over the first summer. Depending on the season and the site one water may be all that is needed. Other seasons/sites may require up to 5 waterings to get them through hot summers.
• Stock must be excluded from the site for about 3 – 5 years to enable seedling establishment.

Germination

After direct sowing native trees, it is important to know how to identify newly germinated native seedlings from weeds.

Read the guide to identifying germinated seedlings.

Depending on soil moisture, temperature conditions, and light availability, native seeds can germinate within a few weeks to 3 months or even longer.

Murray Seed Services have reported several instances of direct-seeded sites where seeds have remained dormant for up to nine years until seasonal and soil conditions improved, prompting a germination event.

Scarifying seed to improve germination

Many natives, such as wattles, are hard seeded. These seeds will need to be scarified to assist them to germinate quickly to compete with weeds. 

This is simply done by scratching the seed or soaking overnight starting with hot water and allowing it to cool. 

A bit of agitation in the morning to remove the outer coating and they are right to sow. 

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