Great Blue Lobelia

Lobelia siphilitica

American Beauties®

Native Perennial Thrives in Wet Soil Where Most Plants Fail
Cold Hardy: Thrives in Zones 4-9
Grows 2-3 ft Tall, 1-2 ft Wide
Showy Blue, Purple Blooms From Late Summer to Early Fall
Native, Pollinator-Friendly - Attracts Butterflies and Hummingbirds

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Plant Size

Product variants

Planting & Care

Where to Plant

Sunlight: Aim for 4 to 6 hours of direct morning sun, or all-day dappled sunlight, which is ideal in warmer climates. While it will tolerate partial shade, too little light will cause it to stretch out and produce fewer, smaller flower spikes, reducing the intensity of its late-season color.
Soil: This plant prefers consistently moist, fertile soil that is rich in organic matter, mimicking its native streamside environment. If you have sandy soil, amend heavily with compost and peat moss to boost water retention. For heavy clay, mix in coarse sand and copious amounts of compost to ensure it is wet but not stagnant, which prevents root rot.

Watering Requirements

Great Blue Lobelia is a true moisture-lover and must have its roots consistently hydrated. During the establishment period (the first season), water deeply two to three times a week, never allowing the top inch of soil to fully dry out. Once mature, it has very limited drought tolerance; inconsistent watering will quickly stress the plant, causing browning leaf tips and significantly smaller bloom spikes. To ensure a gorgeous, dense plant, treat it as a perennial that requires consistent moisture, especially during the heat of summer.

Pruning Tips

This plant reliably blooms on new wood, producing its striking flower spikes from mid-summer into early fall. The best practice is to deadhead spent flower spikes by clipping them at the base to encourage a tidier appearance and sometimes a very limited rebloom. For a final cleanup, wait until late fall or early spring to cut the entire plant back to about 2 to 3 inches above the crown. This method helps protect the crown through the winter months and ensures the plant directs all its energy into robust new growth next spring.

Fertilizer Needs

Apply a balanced, slow-release granular fertilizer, such as a 10-10-10, around the plant in early spring as the new growth emerges. A light top-dressing is typically sufficient since this perennial thrives best when growing in naturally rich, organic soil. What to avoid: Never use a high-nitrogen liquid fertilizer, especially after mid-summer. Excessive late-season nitrogen encourages soft, lush growth that is highly susceptible to winter damage, which compromises the plant's hardiness.

Delivery and Shipping

Shipping Rates

Ships in 7-10 business days • Tracking provided • Weather protected

Under $50	$9.99
$50 - $99.99	$14.99
$100 - $149.99	$16.99
$150 - $198.99	$24.99
$199+	FREE

✓ Zone-specific timing • ✓ Professional packaging • ✓ Health guarantee

Understanding Our Container Sizes

At Nature Hills, our plants are sold in industry-standard nursery containers. You will notice we use the word "container" rather than "gallon." Container numbers follow a nursery trade size standard, not liquid volume. The number tells you the plant's size category and general maturity level. A larger container means a more established plant with a stronger root system.

Container Sizes

Quart

Plant age: 6 months to 1 year
Best for: Ground covers, perennials, ornamental grasses
What to expect: Our smallest and most affordable size. Well-suited for planting in multiples across a large area. Allow 1 to 2 seasons for full establishment.

#1 Container

Plant age: 1 to 2 years
Best for: Shrubs, perennials, smaller trees
What to expect: About the size of a large coffee can. A well-developed root system in a manageable size. Good value choice when you have time to let the plant grow into the space over a season or two.

#2 Container

Plant age: 2 to 3 years
Best for: Shrubs and trees where you want faster establishment
What to expect: A noticeable step up from a #1 in both plant size and root development. Good choice when you want visible presence without going to a larger size.

#3 Container

Plant age: 3 to 4 years
Best for: Most plants, most situations — flowering trees, shade trees, evergreen shrubs
What to expect: Our most popular size. Strong, developed root system. Plants in a #3 container make an immediate visual impact from day one. If you want a head start rather than waiting seasons for a plant to fill in, this is typically the right choice.

#5 Container and Larger

Plant age: 4 to 5+ years
Best for: Specimen plants, privacy screens, maximum instant impact
What to expect: Large, mature plants ready to make an immediate statement in your landscape. We also carry #7 and larger sizes for select varieties.

Why "Container" and Not "Gallon"?

Nursery container sizes follow an industry trade standard established for the nursery and horticulture industry. The number is a size designation, not a measurement of liquid volume. Actual soil volume varies by plant type, root mass, and growing medium. Using "container" is the accurate industry term. When you see #1, #2, or #3, think of it as the plant's size tier, not a gallon measurement.

Root Pouch Containers

Some Nature Hills plants arrive in a Root Pouch, a breathable fabric container made from 100% recycled materials. Root Pouches encourage denser root development through air pruning, which discourages root circling and promotes a stronger, more fibrous root ball at the time of planting.

Plants growing in Root Pouch fabric containers, showing the breathable woven fabric construction

There are two types. Knowing which one you have changes how you plant:

Degradable (brown or tan fabric): Plant the entire pouch directly in the ground. The fabric breaks down naturally in the soil over time.
Non-degradable (black or gray fabric): Remove the pouch before planting. Cut the bottom open with scissors, then peel the sides away. The fibrous root ball will hold its shape.

Not sure which type you have? Check the tag on your plant or contact us and we will confirm.

Full Root Pouch planting guide

Choosing the Right Size

Size	Plant Age	Best For
Quart	6 mo to 1 yr	Ground covers, perennials, grasses. Budget-friendly for mass plantings.
#1 Container	1 to 2 yrs	Shrubs, perennials, small trees. Value choice for patient gardeners.
#2 Container	2 to 3 yrs	Shrubs and trees where you want faster establishment.
#3 Container	3 to 4 yrs	Most plants. Immediate visual impact. Our most popular size.
#5 and larger	4+ yrs	Specimen plants, privacy screens, maximum instant impact.

Still not sure which size is right for your project? Our plant specialists are happy to help. Contact us and we will point you in the right direction.

Plant specifications
Plant Characteristics	Cold hardy, Native, Flowering, Wet Soils, Attracts Hummingbirds, Attracts pollinators, Deer-resistant, Container Friendly
Hardiness Zone	4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
Sunlight	Full sun
Height	2-3 ft
Width	1-2 ft
Watering Needs	High
Preferred Soil	Peaty
Growth Rate	Moderate
Growth Habit	Upright
Plant Life Cycle	Perennial
Blooms In	Fall, Summer
Flower Color	Blue, Purple
Foliage Color	Green
Native	Yes
Pet Safety	Toxic to pets
Suitable Space	Outdoors
Botanical Name	Lobelia siphilitica
Species	siphilitica
Class	Magnoliopsida
Does Not Ship To	AK, HI, ID, MT, PR

Need a gorgeous blue flowering perennial that handles wet to very moist soil? The Great Blue Lobelia (Lobelia siphilitica) is a hardy Cardinal Flower bearing tall, leafy spikes of clear blue flowers. Members of the Bellflower Family, this showy perennial can be branched or unbranched, which you can encourage with pruning if you want more flowers, versus one large towering spire!

Great Blue is a clump-forming perennial with upright leafy stems. It blooms from late summer to mid-autumn and bears dense spikes of light to bright blue, but can sometimes be lavender or purplish because of their wide native genetic variability. Forming many tubular, two-lipped flowers with a more prominent lower lip. These are wonderfully long-lasting because they flower from the bottom to the top!

Great Blue will attract a plethora of curious butterflies to their nectar resources and the tubular flowers might even have a Hummingbird visitor or two! Perennial throughout USDA planting zones 4 to 9, this wetland native plant features mounds of lance-shaped green leaves with tall wands of dramatic flowering spikes rising high above them.

Planting and Application:

These spikes make it the perfect back-of-the-border plant in your perennial flower beds, Cottage gardens, and Rain Gardens! This perky perennial was made for your backyard pollinator gardens! Create groupings in water gardens or pond edges to draw the eye and give beneficial insects, like dragonflies, a place to land as they search for more pesky prey, like mosquitoes. This will make your outdoor enjoyment even better without these pests!

Of course, this Blue Cardinal Flower can also be used near the back of your property to soften the moist woodland edges or used at the base of a water feature you've installed. No matter where you plant Great Blue, it'll look absolutely stunning!

The tall flower spikes can be clipped and bright indoors to complete a delightful bouquet. Place them in the kitchen or on the living room coffee table to freshen up your space. By snipping a few blooms, you'll encourage more to rebloom throughout the growing season!

Tall Spikes of Blue to Purple Florets
Long-Lasting Blooms Until Mid-Autumn
Lush Green Lance-Shaped Foliage
Wetland Native Perennial
Great For Pollinators, Hummingbirds & Cut Flowers
Tall Specimens, Groupings, Back-of-the-Border, Water Gardens & Rain Gardens

#ProPlantTips for Care:

This full-sun perennial grows 2-3 feet tall, so 6 hours of direct sunlight is needed to maintain strong upright flowering stems. The Blue Cardinal Flower prefers deep, moist soil and should be fertilized every two weeks in spring and early summer to improve flowering.

Pinching back young plants encourages branching, or pinch back offshoots to encourage a single large flower per plant. These herbaceous Perennials may be trimmed as they die back in hot summers. Deadhead to encourage new blooms, and clean the mounds up in the early spring before the growing season begins.

Full Sun Perennials
Almost Any Soil That Isn't Stagnant
Moist to Wetland Conditions
Pinch Back, Deadhead In Summer & Prune In Spring
Deer & Rabbits Seldom Bother These

The beautiful blue cousin to the red Cardinal Flower is a refreshing native perennial to enliven your landscape with its unique color and form! Order the Great Blue Lobelia today at Nature Hills, and go native!

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Frequently Asked Questions

What USDA hardiness zones can Great Blue Lobelia grow in?

Great Blue Lobelia is perennial throughout USDA hardiness zones 4 to 9. This hardy native thrives in cooler northern climates down to warmer southern regions. Plant it in your wettest garden spots where other perennials struggle.

Does Great Blue Lobelia prefer full sun, partial shade, or full shade?

Great Blue Lobelia thrives in partial shade to full sun, especially in consistently moist conditions. This wetland native adapts well to various light levels but performs best with morning sun and afternoon protection in zones 4-9. Plant it where soil stays wet to very moist for optimal blooms.

How often should I water Great Blue Lobelia and does it like wet or dry conditions?

Great Blue Lobelia thrives in wet to very moist soil conditions and actually prefers consistently damp ground. This wetland native performs best when planted in naturally moist areas like pond edges or rain gardens. Keep soil consistently moist but not waterlogged for optimal growth.

Is Great Blue Lobelia a fast-growing or slow-growing plant?

Great Blue Lobelia is a moderate grower that establishes well in zones 4-9. This clump-forming perennial develops sturdy root systems and tall flowering spikes over 2-3 seasons. Plant in consistently moist soil and consider pruning to encourage branching for fuller growth.

What color are the flowers on Great Blue Lobelia?

Great Blue Lobelia produces light to bright blue tubular flowers, though they can sometimes appear lavender or purplish due to natural genetic variation. The two-lipped blooms form dense spikes that flower from bottom to top from late summer through mid-autumn. Shop at Nature Hills for this stunning wetland native.

Is Great Blue Lobelia deer resistant?

Great Blue Lobelia is generally deer resistant due to its naturally occurring alkaloids that make it unpalatable to browsing animals. While no plant is 100% deer-proof, this native perennial is rarely damaged by deer in zones 4-9. Plant it in your back borders or rain gardens for reliable late summer blooms.

Can Great Blue Lobelia tolerate wet soil or does it need good drainage?

Great Blue Lobelia thrives in wet to very moist soil conditions, making it ideal for areas with poor drainage. This wetland native perennial actually prefers consistently moist environments over well-drained sites. Plant it in rain gardens, pond edges, or any soggy spots where other perennials struggle.

Great Blue Lobelia

Lobelia siphilitica