When To Plant Nasturtium Seedlings

When to plant nasturtium seedlings is one of the most common questions I get from gardeners who want those vibrant, edible flowers in their yard.
 
You can plant nasturtium seedlings outdoors only after the last frost has passed and the soil has warmed up.
 
But that’s just the short answer, and there’s a lot more nuance to timing if you want strong, healthy plants.
 
Nasturtiums are tender annuals, which means they absolutely hate cold weather and will sulk or even die if they get hit by frost.
 
In this post, we’ll dig into the best timing for planting nasturtium seedlings, how to harden them off, and what to do if you started them too early.
 
Let’s get those pretty blooms growing.
 

When to Plant Nasturtium Seedlings for Best Results

The exact time to plant nasturtium seedlings depends on your local climate and the last frost date in your area.
 
Generally, you should plant nasturtium seedlings outdoors when nighttime temperatures stay consistently above 50°F (10°C).
 
Here’s how to nail the timing no matter where you live.
 

1. Wait Until After Your Last Spring Frost

Nasturtium seedlings are not frost hardy at all, even a light frost will turn their leaves to mush.
 
So, your very first step is to find your average last frost date for spring.
 
Once that date has passed, you can start thinking about planting nasturtium seedlings outside.
 
But don’t just rush out the day after, because a late cold snap can still surprise you.
 
A good rule of thumb is to wait one full week after your last frost date before planting nasturtium seedlings in the ground.
 

2. Check the Soil Temperature

Even if the air feels warm, the soil might still be cold and damp.
 
You want to plant nasturtium seedlings when the soil temperature is at least 60°F (15°C) for optimal growth.
 
Cold soil can cause your seedlings to sit there and sulk, and it also increases the risk of root rot.
 
You can use a simple soil thermometer to check, or just stick your hand in the dirt and see if it feels warm, not just cool to the touch.
 
Planting nasturtium seedlings in warm soil encourages faster establishment and earlier blooming.
 

3. Morning Planting for Less Shock

When you decide the timing is right, try to plant your nasturtium seedlings in the early morning or late afternoon.
 
Planting nasturtium seedlings during the heat of the day can stress them out because they lose water quickly through their leaves.
 
Morning planting gives them the whole day to start settling in before the hot sun hits.
 
Also, make sure to water them well right after planting to help the roots make good contact with the soil.
 

How to Harden Off Nasturtium Seedlings Before Planting

You can’t just take seedlings from a warm indoor windowsill and plant nasturtium seedlings straight into the garden.
 
They need a gradual transition to the outdoors, a process called hardening off.
 
Skipping this step is one of the biggest reasons why transplanted seedlings fail.
 

1. Start Slowly with Shade

About 7 to 10 days before you plan to plant nasturtium seedlings, start bringing them outside for a couple of hours a day.
 
Place them in a sheltered, shady spot so they can get used to gentle breezes and natural light.
 
Each day, add an hour or two of outdoor time and gradually introduce them to more direct sunlight.
 
This slow exposure helps the leaves thicken up and reduces the shock of a big environmental change.
 

2. Bring Them Back Inside at Night

During the hardening off period, always bring your nasturtium seedlings back inside at night.
 
Nighttime temperatures can still dip even if the days are warm.
 
You want to plant nasturtium seedlings only after they’ve been outside both day and night for at least two consecutive days.
 
If a frost warning happens during this week, just keep them inside until it passes.
 

3. Watch for Wind Stress

Indoor seedlings aren’t used to wind, which can dry them out quickly and snap their delicate stems.
 
Choose a protected spot for your hardening off sessions, or use a cold frame if you have one.
 
If you notice the leaves looking pale or scorched, that’s a sign you moved them into the sun too fast.
 
Just pull them back into shade for a day and restart the acclimation process.
 

What If You Missed the Perfect Planting Window?

Life happens, and sometimes you forget about those seedlings on the windowsill.
 
Don’t worry, because planting nasturtium seedlings a little late isn’t the end of the world.
 

1. You Can Still Plant in Early Summer

Nasturtiums are fast growers, so even if you plant nasturtium seedlings in early June, you’ll still get plenty of blooms.
 
They may just start flowering a bit later than you hoped.
 
As long as you water them regularly and give them full sun, they’ll catch up quickly.
 
The key is to avoid planting during a heatwave, because extreme heat can also stress young plants.
 

2. Skip the Seedlings and Sow Seeds Directly

If your seedlings have become leggy or root-bound from waiting too long, it might be easier to just sow nasturtium seeds directly into the garden.
 
Nasturtium seeds germinate quickly in warm soil, often within 7 to 10 days.
 
Direct sowing is actually many gardeners’ preferred method because nasturtiums hate having their roots disturbed.
 
So, if the timing for planting nasturtium seedlings feels off, just opt for seeds.
 

3. Use Containers for More Flexibility

Planting nasturtium seedlings in pots gives you way more flexibility with timing.
 
You can move containers around to follow the sun or protect them from unexpected cold nights.
 
If you’re unsure about the ground temperature, containers warm up faster in the spring.
 
That means you can plant nasturtium seedlings into pots a bit earlier than you would in the garden bed.
 

So, When to Plant Nasturtium Seedlings?

You should plant nasturtium seedlings outdoors after the last frost and once soil temperatures are above 60°F.
 
That timing usually falls in late spring or early summer, depending on where you live.
 
Make sure to harden them off for a week, and never rush them into cold, wet soil.
 
If you’re ever unsure, just wait a few extra days because nasturtiums thrive in warm weather.
 
So, when to plant nasturtium seedlings is all about patience, warmth, and careful observation of your local conditions.
 
With the right timing, you’ll be rewarded with cascades of cheerful, edible flowers all summer long.
 
Happy planting, and enjoy those beautiful nasturtiums.