When To Plant Spider Flower Seeds

The best time to plant spider flower seeds is in early spring, right after the last frost has passed.
 
When to plant spider flower seeds really comes down to giving them a long, warm growing season, because these tall, airy beauties thrive in heat and bloom from midsummer all the way into fall.
 
If you’re wondering when to plant spider flower seeds in your specific region, the golden rule is this: wait until soil temperatures have warmed to at least 65°F (18°C) before sowing them directly outdoors.
 
Planting spider flower seeds too early, when the soil is still cold and wet, is the number one reason they rot before they ever sprout.
 
In this post, we’ll dig into the exact timing for when to plant spider flower seeds, whether you’re starting them indoors or direct sowing, and how to get the most spectacular display from these unique annuals.
 
Let’s get started.
 

When to Plant Spider Flower Seeds: The Simple Answer

When to plant spider flower seeds depends on your growing zone, but the universal timing is after your last expected frost date in spring.
 
Spider flowers (Cleome hassleriana) are tender annuals, which means they absolutely cannot handle freezing temperatures.
 
A single frost will kill young seedlings instantly, so patience is your best friend here.
 
Generally, you should plan to plant spider flower seeds outdoors about two to three weeks after the final frost date in your area.
 
This waiting period gives the soil a chance to warm up, and warm soil is the trigger that tells those seeds it’s time to wake up and germinate.
 
For most gardeners in USDA zones 2 through 7, that translates to planting spider flower seeds anywhere from mid-April to late May.
 
Gardeners in warmer southern zones can often plant spider flower seeds as early as March, while those in cooler northern regions might wait until early June.
 
The key is not to rush, because cold, damp soil is the enemy of Cleome seeds.
 

How to Check Soil Temperature Before You Plant Spider Flower Seeds

If you want to be precise about when to plant spider flower seeds, grab a simple soil thermometer and check the ground temperature in the morning.
 
Stick the probe about two inches into the soil where you plan to sow them, and if it reads 65°F or higher, you’re good to go.
 
If the soil is still cooler, hold off for a few more days.
 
Alternatively, you can watch for nighttime temperatures to consistently stay above 50°F, which is another reliable signal that it’s finally safe to plant spider flower seeds.
 

Starting Spider Flower Seeds Indoors vs. Direct Sowing

When to plant spider flower seeds also depends on whether you want a head start indoors or prefer the simplicity of direct sowing.
 
Both methods work wonderfully, but the timing shifts for each approach.
 

When to Plant Spider Flower Seeds Indoors

Starting Cleome seeds indoors is a fantastic way to enjoy earlier blooms and is especially helpful in short-season climates.
 
When to plant spider flower seeds indoors is roughly six to eight weeks before your last predicted frost date.
 
So if your last frost is typically on May 15th, you would start your seeds indoors around late March or early April.
 
Sow the seeds in small pots or cell trays filled with a light, well-draining seed starting mix.
 
Press the seeds onto the surface and cover them very lightly with soil, because they need some light to germinate.
 
Keep the soil consistently moist but not soggy, and place the trays in a warm spot at around 70-75°F.
 
You’ll see seedlings emerge in about 10 to 14 days, and once they have their second set of true leaves, you can start hardening them off.
 
Harden them off by placing them outside for a few hours each day, gradually increasing their time outdoors over the course of a week before transplanting them into the garden.
 

When to Plant Spider Flower Seeds Directly in the Garden

If you prefer to skip the indoor setup, you can absolutely direct sow spider flower seeds right where you want them to grow.
 
When to plant spider flower seeds directly is after all danger of frost has passed and the soil has warmed as we discussed earlier.
 
Prepare your garden bed by loosening the soil and removing any weeds, then sprinkle the seeds on the surface and press them in gently.
 
Don’t bury them too deep, a light dusting of soil is all they need.
 
Water the area gently with a fine mist and keep the soil evenly moist until germination occurs, which typically takes a couple of weeks.
 
One great advantage of direct sowing is that the plants develop deep taproots that make them incredibly drought-tolerant and sturdy, even in windy spots.
 

How Late Can You Plant Spider Flower Seeds?

Many gardeners wonder how late they can plant spider flower seeds and still enjoy a good show of blooms.
 
When to plant spider flower seeds has a fairly flexible window, but you do need to account for their time to bloom.
 
Spider flowers take about 70 to 90 days from seed to first flower, so you need to make sure you have enough warm days left in your season.
 
As a rule of thumb, you want to plant spider flower seeds no later than 10 to 12 weeks before your first expected fall frost.
 
For most zones, this means you can safely plant spider flower seeds anywhere from late spring through early summer, even into June or early July in many areas.
 
If you plant later than that, you’ll still get lush, tall foliage, but the flower display may be cut short by cooler autumn temperatures.
 
That’s still fine, because the spiky, feathery foliage of Cleome looks great in the garden all on its own.
 

How Planting Time Affects Spider Flower Bloom Time

When to plant spider flower seeds directly influences when you’ll see those gorgeous, spider-like blossoms.
 
Early spring plantings, whether indoors or direct sown, will reward you with blooms starting in mid-to-late June.
 
Mid-spring plantings will push flowering into early July.
 
And summer plantings will bloom in late August or September.
 
Keep in mind that spider flowers are self-sowing annuals, so if you let a few seed pods dry on the plant at the end of the season, you’ll likely get volunteer seedlings next spring.
 
Those volunteers will naturally sprout at the perfect time when to plant spider flower seeds rolls around again, making them an easy and delightful surprise for the following year.
 

So, When to Plant Spider Flower Seeds for Best Results?

The ideal time to plant spider flower seeds is in early spring, after the last frost has passed and the soil has warmed to at least 65°F.
 
You can start them indoors six to eight weeks before that last frost for a head start, or direct sow them two to three weeks after the frost date for effortless growth.
 
Even if you miss the early spring window, you can still plant spider flower seeds throughout late spring and early summer and enjoy their unique, airy blooms well into fall.
 
No matter when you decide to sow them, just remember that warm soil, bright sunlight, and consistent moisture are the three secrets to a thriving patch of spider flowers.
 
Now that you know when to plant spider flower seeds, you can confidently add these tall, showy annuals to your garden for a season full of color and movement.
 
Happy planting.