This post contains affiliate links. As an Amazon Associate I earn from qualifying purchases. If you click a link and make a purchase, I may receive a small commission at no extra cost to you.
The best time to plant nasturtiums outside is after the last frost has passed and the soil has warmed to at least 55°F.
This timing is crucial because nasturtiums are tender annuals that simply cannot handle freezing temperatures.
If you plant nasturtiums outside too early, a late frost will likely kill them off before they even get a chance to grow.
On the flip side, waiting too long to plant nasturtiums outside might mean you miss out on their beautiful blooms during the peak of summer.
In this post, we’ll cover exactly when to plant nasturtiums outside, how to check your local frost dates, and some handy tips for getting the timing just right.
Let’s dig in and make sure you give these vibrant flowers the best possible start.
When To Plant Nasturtiums Outside: The Perfect Timing
So, when to plant nasturtiums outside? The answer really depends on your specific growing zone and the weather patterns in your area.
As a general rule, you should plan to plant nasturtiums outside in the spring, roughly two to four weeks after your region’s last average frost date.
This window gives the soil enough time to warm up, which is essential for seed germination and healthy root development.
If you’re eager to get a head start, you can also plant nasturtiums outside as seeds directly in the garden, which they actually prefer due to their sensitive root systems.
1. Understanding Your Last Frost Date
The single most important factor in knowing when to plant nasturtiums outside is your last frost date.
You can find this date by checking with your local agricultural extension office or using online frost date calculators.
Once you know this date, simply count forward a couple of weeks to get your ideal planting window.
For example, if your last frost date is April 15th, you would plant nasturtiums outside around the end of April or very beginning of May.
This buffer period ensures that any unexpected cold snaps won’t harm your young seedlings.
2. Checking Soil Temperature Before You Plant Nasturtiums Outside
Even if the air feels warm, the soil might still be too cold for planting nasturtiums outside.
Nasturtium seeds germinate best when the soil temperature is consistently between 55°F and 65°F.
You can use a simple soil thermometer to check the temperature at a depth of about two inches.
If the soil is still too cold, hold off on planting nasturtiums outside for another week or so.
Planting seeds into cold, wet soil can cause them to rot rather than sprout, so patience pays off here.
3. Considering Your USDA Hardiness Zone
Your USDA hardiness zone is another great indicator of when to plant nasturtiums outside.
In warmer zones like 8 through 11, you can often plant nasturtiums outside as early as late winter or early spring.
In cooler zones like 3 through 5, you’ll likely need to wait until late spring or even early summer.
Gardeners in zones 6 and 7 usually find that planting nasturtiums outside in mid-spring works perfectly.
No matter your zone, the key is to watch your local weather forecast and avoid planting before the danger of frost has truly passed.
How To Plant Nasturtiums Outside For Success
Once you’ve nailed down the timing, the next step is knowing how to actually plant nasturtiums outside so they thrive.
These cheerful flowers are remarkably easy to grow, but they do have a few preferences.
Let’s look at the best practices for ensuring your nasturtiums flourish from day one.
1. Choose a Sunny or Partially Shaded Spot
Nasturtiums love sunshine, so pick a spot in your garden that receives at least six hours of direct sunlight each day.
However, if you live in a region with scorching hot summers, they’ll actually appreciate some afternoon shade.
Too much intense heat can sometimes cause the leaves to yellow and reduce the number of blooms.
Finding that sweet spot of sun and shade will help your nasturtiums look their absolute best.
2. Prepare Well-Draining Soil
When you plant nasturtiums outside, keep in mind that they prefer poor to average soil that drains well.
Rich, overly fertile soil will actually encourage lush foliage growth at the expense of flowers.
Avoid adding too much compost or fertilizer, as this makes for a leafy plant with very few blooms.
Instead, just loosen the soil and remove any large stones or debris before sowing your seeds.
Good drainage is vital because waterlogged roots can quickly lead to rot and other fungal issues.
3. Sow Seeds Directly and Keep Them Moist
Nasturtiums have delicate root systems that don’t like being disturbed, so direct sowing is highly recommended.
When you plant nasturtiums outside, press each seed about half an inch deep into the soil.
Space the seeds about 10 to 12 inches apart, as the plants can spread out quite a bit.
Water the area gently but thoroughly after planting, and keep the soil consistently moist until germination.
You should see seedlings emerge within 7 to 14 days, depending on soil temperature and moisture levels.
Can You Plant Nasturtiums Outside In Containers?
Absolutely, you can plant nasturtiums outside in containers, and this is a fantastic option for small spaces.
Make sure your container has good drainage holes and is filled with a light, well-draining potting mix.
When you plant nasturtiums outside in pots, you can follow the same frost-date guidelines as for ground planting.
Container gardening also allows you to move the pots inside or to a sheltered spot if a late frost threatens.
This flexibility makes containers a great choice for less predictable climates.
1. Pot Size and Depth
Choose a pot that is at least 10 to 12 inches in diameter for bush varieties.
Trailing or climbing types will need even more room, so look for a larger planter or hanging basket.
The bigger the container, the more moisture and nutrients the soil can hold for your plants.
A good rule of thumb is to give each nasturtium plant at least one square foot of space in the pot.
2. Watering Needs in Containers
Container nasturtiums dry out faster than those in the ground, so you’ll need to water them more frequently.
Check the top inch of the soil daily, and water whenever it feels dry to the touch.
During hot, dry spells, you might even need to water your potted nasturtiums twice a day.
Just be careful not to overwater, as sitting in soggy soil can cause root rot.
Frequently Asked Questions About Planting Nasturtiums Outside
Many gardeners have similar questions when it comes to the timing and technique for planting nasturtiums outside.
Let’s address some of the most common queries to help you avoid any guesswork.
1. Can I Start Nasturtium Seeds Indoors?
Yes, you can start seeds indoors, but it’s not always the best method.
Because nasturtiums dislike root disturbance, you’ll need to use biodegradable pots that can be planted directly into the ground.
If you do start indoors, begin about four to six weeks before your planned date to plant nasturtiums outside.
Harden off the seedlings gradually before transplanting to minimize shock though.
Direct sowing is usually more reliable and definitely easier.
2. What Happens If I Plant Nasturtiums Outside Too Late?
If you plant nasturtiums outside too late in the season, they might not have enough time to bloom before fall arrives.
Nasturtiums generally take about 35 to 52 days to flower after germination.
In cooler regions, a late planting could mean you only get a short burst of blooms before the first frost kills them.
For a prolonged flowering season, you can even stagger your planting every few weeks until midsummer.
This way, you’ll enjoy a continuous display of colorful blossoms.
3. Should I Soak Nasturtium Seeds Before Planting?
Soaking seeds overnight in lukewarm water can help speed up germination.
The seeds have a hard outer shell, so soaking softens that coating and allows moisture in faster.
Just be careful not to soak them for too long, as that can cause them to rot.
Twelve to twenty-four hours is the ideal soak time before you plant nasturtiums outside.
After soaking, sow them right away into their final growing spot.
So, When To Plant Nasturtiums Outside?
You should plant nasturtiums outside in the spring, after the last frost has passed and the soil has warmed up properly.
The exact timing varies based on your location, but waiting two weeks past your last frost date is a safe bet.
Checking soil temperature and your USDA hardiness zone will give you even more precise guidance.
Whether you’re sowing directly in the garden or into containers, the principles of good timing remain the same.
Hope this guide has cleared up when to plant nasturtiums outside and given you the confidence to get growing.
So grab your seeds, check that forecast, and get ready for a summer full of vibrant, edible flowers.