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The best time to plant nasturtium seeds in Australia is during the cooler months of early spring, from August to October, or in autumn.
This timing is perfect because nasturtiums thrive in mild weather and will reward you with masses of vibrant, edible flowers before the harsh summer heat arrives.
If you are planting nasturtium seeds in Australia, understanding your local climate zone is the key to getting it right.
Whether you’re in the temperate south or the subtropical north, these hardy annuals are incredibly forgiving, but they do have a sweet spot for sowing.
In this post, we’ll break down exactly when to plant nasturtium seeds in Australia, how to adjust for your region, and the best methods to get them sprouting quickly.
Let’s dive in and get those seeds in the ground.
When To Plant Nasturtium Seeds In Australia By Region
Nasturtiums are not frost-tolerant, so the right time to plant nasturtium seeds in Australia is all about dodging the cold snaps.
Here is a simple regional breakdown so you can plan your sowing with confidence.
Temperate Regions (Sydney, Adelaide, Perth)
In temperate zones, you can plant nasturtium seeds in Australia from early spring, which is around August through October.
You can also sow again in late summer, from February to March, for a beautiful autumn display.
The soil is starting to warm up in spring, which encourages quick germination, usually within 7 to 12 days.
Just keep an eye on the forecast, as a late frost can damage young seedlings, so you may want to wait until after the last frost date.
Planting nasturtium seeds in Australia during these windows ensures they have plenty of time to establish before the heat peaks.
Subtropical Regions (Brisbane, NNSW, Coastal QLD)
For gardeners in the subtropics, the best time to plant nasturtium seeds in Australia is during the cooler months, from March to August.
Your summers are too hot and humid, which can cause nasturtiums to become leggy and produce mostly leaves with very few flowers.
By sowing in autumn or early winter, you give them the mild, dry conditions they absolutely love.
They will bloom right through the winter and into spring, putting on a spectacular show when the rest of the garden is quiet.
If you missed that window, a second sowing in late April can still work well before the winter chill sets in.
Cool & Mountainous Regions (Melbourne, Canberra, Hobart)
If you live in a cooler climate, you need to plant nasturtium seeds in Australia a bit later in spring, usually from October to November.
The soil needs to reach at least 15°C for reliable germination, so resist the urge to sow too early.
You can also do a summer sowing in December for a late-season flush, but be prepared to water more frequently.
In these areas, frost is your biggest enemy, so starting seeds indoors or under a cloche is a smart way to get a head start.
Once the risk of frost has passed, transplant them out or sow directly, and they’ll catch up quickly.
Key Factors For Planting Nasturtium Seeds In Australia
Beyond just the calendar, there are a few environmental keys to nailing the perfect sowing time for nasturtiums.
Getting these right will make the difference between a lush plant and a struggling one.
Soil Temperature Matters More Than Air Temperature
When you plant nasturtium seeds in Australia, it is the soil temperature that triggers germination, not the ambient air.
Nasturtium seeds need soil that is consistently between 15°C and 20°C to sprout readily.
If you sow when the soil is too cold, the seeds may sit dormant in the ground and rot from excess moisture.
A simple soil thermometer can take the guesswork out of it and tell you exactly when the conditions are right to plant nasturtium seeds in Australia.
Alternatively, a good rule of thumb is to wait until the morning soil feels cool but not freezing, and daytime temps hover around 20°C.
Frost is the Ultimate Deal Breaker
Nasturtiums are tender annuals, and a single frost event can kill them overnight.
So when deciding when to plant nasturtium seeds in Australia, always count back from your local average last frost date.
If you are in a frost-prone area, it’s safer to plant nasturtium seeds in Australia after this date to avoid any surprises.
You can push the limits by using frost cloth or planting in pots that you can move undercover during cold snaps.
However, for most home gardeners, it’s far easier to simply wait a few extra weeks until the weather stabilises.
Late spring is almost always a safe bet for planting nasturtium seeds in Australia if you’re unsure.
Rainfall and Moisture Levels
Nasturtiums hate having wet feet, so your planting schedule should also consider your rainy season.
In Australia, the northern regions get heavy summer rains, which is why autumn sowing in Australia is recommended there.
In the south, winter rains can be relentless, so holding off until spring is the better choice to plant nasturtium seeds in Australia.
If you are in a dry winter area, like parts of Perth, you can actually sow throughout winter if you keep them lightly watered.
The goal is to have well-draining soil and to avoid sowing right before a massive downpour, as the seeds will wash away.
How To Plant Nasturtium Seeds In Australia For Best Results
Now that you know the best season, let’s look at the actual sowing process to guarantee a high germination rate.
Nasturtium seeds have a hard outer shell, so they benefit from a little prep and the right technique.
Direct Sowing vs. Starting Indoors
Nasturtiums are notoriously sensitive to root disturbance, so direct sowing is almost always the best method.
You can plant nasturtium seeds in Australia straight into the garden bed where you want them to flower and climb.
If you do prefer to start them indoors, use biodegradable peat pots and plant the entire pot in the ground when ready.
This way, you can plant nasturtium seeds in Australia slightly earlier in the season without risking root shock.
However, direct sowing into warm soil will always give you the sturdier, more drought-tolerant plants.
Scarify Your Seeds For Faster Germination
To speed things up when you plant nasturtium seeds in Australia, you can nick the seed coat with a nail file.
Alternatively, soak the seeds in warm water for 12 to 24 hours before planting.
This softens the outer shell, allowing water to penetrate and kickstart the germination process.
You’ll see sprouts emerge almost twice as fast with this simple step.
Plant the seeds about 1cm deep and space them 20cm apart to allow for bushy growth.
Position and Soil Conditions
When choosing a spot to plant nasturtium seeds in Australia, pick a location that gets full sun to partial shade.
They actually prefer poor, slightly dry soil, so don’t add rich compost or too much fertilizer, as this creates lush leaves but few flowers.
If the soil is too fertile, you get lots of foliage and very few blooms, so keep it lean.
Just make sure the spot has good drainage and isn’t a spot that puddles after rain.
A sunny, somewhat neglected corner of the garden is actually the perfect home for them.
So, When To Plant Nasturtium Seeds In Australia?
The best time to plant nasturtium seeds in Australia is generally early spring for most regions and late summer to autumn for the tropics.
Winter sowing in Australia should be avoided in cold areas, but it’s perfectly fine in warmer coastal zones.
If you’re still wondering when to plant nasturtium seeds in Australia, just remember: aim for mild, frost-free conditions.
Getting the timing right will lead to a cascade of cheerful, edible flowers that attract pollinators and brighten up any space.
Happy gardening, and enjoy the splash of colour these wonderful plants will bring to your Aussie garden.