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How to Grow Blue Lobelia

Simple steps to successfully growing the Great Blue Lobelia

This list is the key requirements to growing the Great Blue Lobelia successfully;

  • Full sun to Partial Shade
  • Moist or wet soil
  • Will tolerate many types of soil, even clay.  Although probably not sand
  • Needs at least 1′ (30 cm) diameter of ground space
  • This plant is hardy in zones 4-8.  Find your garden zone here.

General Description and Facts

Great Blue Lobelia with Bumble Bee
Blue Lobelia with Cardinal Flower in the background

The Great Blue Lobelia, Lobelia siphilitica, is a perennial flower  native to most of North America.  It will grow 2-3′ tall in optimum conditions producing several stalks or spikes of dark blue/violet flowers.  So, it is erect in its footprint, and doesn’t branch out.  The blooms are quite showy, and are mainly pollinated by bees.  I’ve found this plant in partially shaded meadows along the Appalachian Trail near my home.  The soil/area didn’t seem that moist, but obviously this plant was happy there!

The flowers are short tubes that will have two petals stick up, above the tube.  And then 3 petals hanging down from the tube mouth, almost like 3 tongues hanging out.  Based on my familiarity of this bloom I’ve identified several other ‘weedy’ Lobelia species around my home such as Indian Tobacco (Lobelia inflata).  It always feels good to know that you can apply knowledge gained for one thing to something else!

Is the Blue Lobelia edible?

In a nutshell, no it isn’t.  This plant is toxic, but from what I have read you need to consume a lot of it for it to be fatal.  So don’t eat or consume it.  Apparently various Native American tribes used this plant as a remedy to treat coughing, nosebleeds, and general colds.  The Meskwaki even used the root as an ‘anti-divorce’ remedy.  They would grind up the roots and feed them to the couple that was having problems [1].

Great Blue Lobelia Growing Requirements and Care

The Great Blue Lobelia doesn’t require much space, as it will send stalks vertically.  Because of that, you can space them 1-2′ apart (30-60 cm).  I prefer to pack them in tight, as this will keep weeds down since there will be less sunlight available to the bare patches.  These plants will do best in partial shade with moist soil.  I’ve personally grown them in full sun, and clay soil – but needed to water them occasionally.

Blue Lobelia Flower
Detailed view of Blue Lobelia Bloom

As stated above, this species of plant will not tolerate drought as well as other native plants.  So make sure it doesn’t totally dry out.  Use your judgement, and if you see heat damage, or the edge of leaves start to turn brown/crispy, then it needs water.  Or just check the soil.

Overall, this plant is easy to grow and care for.  If you place it into conditions that it likes, you will not have any serious issues.  In optimal settings of partial shade and moist soil, there will basically be no maintenance (based on my experience).

I have not seen any damage from rabbits on my plants, nor any serious pest problems.  I’ve read that their leaves are slightly toxic, which probably is what helps keep foragers at bay.

Also, be sure to scroll to the bottom of this page to see the reference table that has all the main points for growing/caring for this plant in a structured manner.

How to Grow Blue Lobelia from seed

cardinal flower lobelia seeds and stalk with pods
Cardinal Flower or Blue Lobelia Seeds (Lobelia cardinalis / Lobelia siphilitica)

The most economical to get Blue Lobelia in your garden is to just grow it from seed.  It is pretty easy to do so, and you can get blooms the first year if you are early enough.  I’ve never actually seen this plant for sale in a garden center, so you might be forced to germinate them yourself.  But, as I will show you that isn’t an issue.  

So, to start the plant in pots, just fill them with potting soil (I just use regular Miracle Grow potting soil) and moisten so it is fully damp.  Then, sprinkle seed on top of the soil, and press in with your finger, but don’t bury it.  These seeds need light to germinate, so it is important that they stay on top of the soil.  Also, this seed is very tiny – like powder.  So be careful.  If you sneeze while doing this you could lose most of your seed!

Does Blue Lobelia Seed need stratification?

I personally don’t stratify these seeds, and I always get plenty of germination.  However, most references say it needs about two months of cold moist stratification.  And since this seed is so tiny, it pretty much means you have to winter sow them.  I believe that this seed would be too small to mix with vermiculite or sand, or even use a paper towel.  But as I said – I just sow the seed in early May, and this works just fine for me.  I always end up with a ridiculous number of seedlings, and have to thin/separate them with tweezers.

When can I transplant Blue Lobelia into the garden?

The earliest I will transplant my seedlings is when the basal rosette of leaves are about 1″ in diameter, for the whole plant.  At that point, the roots should be several inches deep, and the plant out to be large enough to survive just fine.  The video below discusses the entire sowing process I use in detail;

 

How long from seed to bloom for the Great Blue Lobelia?

How long does it take to get a flower when grown from seed?  Well that will depend on how early you start your seeds, and ultimately how early you transplant out into the garden.  I’m in zone 6, and I usually get blooms on Blue Lobelia if I transplant by July.  I also get blooms if I grow them in 4″x4″ pots.  I’ve transplanted blooming Blue Lobelia flowers from pot into the garden as late as October.  So, you should be able to get blooms the first year as long as you start early enough.  That is just another benefit of this perennial.

How and when to divide the Great Blue Lobelia?

Lobelias that are several years old, or well established can be divided in the spring.  Do not divide this plant in the fall, as the roots are quite shallow, and might get pushed out of the ground due to frost.  So, divide the offshoots from the main plant.  Then plant the offshoots into a new location, and water.  This root divisions don’t ‘store’ very well for Lobelia.

How to save Lobelia Seed

The process for saving Blue Lobelia seed is the same as its cousin, the Cardinal Flower.  Let the seed pods dry out on the stalk until they are brown/dry before collecting them.  If you collect the pods too early the seeds may not have developed fully, and therefore may not be viable to germinate.  Store seed in zip-bags if truly dry, or keep in paper bag or envelope.

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Depending on how much seed you want, and how much chaff you are willing to tolerate, saving seed from Blue Lobelia can be really easy or require a bit of effort.  If you just want some seeds, and aren’t worried about chaff then it is really easy.  Just crush some of the pods and save the seeds in a ziplock bag.  However, if you want to separate the chaff, then you better get out your kitchen strainer and sift the seed/chaff multiple times until you are satisfied.  The video I’ve linked to below gives a very thorough description of how to save seeds from this plant, and its cousin the Great Blue Lobelia.

 

Common Uses of Blue Lobelia

Blue Lobelia Plant Bloom
This sample of Blue Lobelia is grown in mostly shade, as there are much taller plants in front of it. Note how it is less than 1′ tall (30 cm). But it is still happy/healthy, just not as big.

The Great Blue Lobelia is pretty versatile.  This would be great for a rain garden, as it likes moist soil (but can’t be flooded for long!).  I use them as borders, alternating with Cardinal Flower in various flower beds.  Another neat idea for an arrangement in the garden would be do make a circle, about 3′ diameter with alternating Cardinal Flower and Blue Lobelia on the outer ring, and then keeping the spacing as you worked towards the center.  But, this is a hardy plant that gives stunning late season color.  I’m sure you would have no problem coming up with great ideas for this plant.

[UPDATE October 2018] – I just put a couple of these in our backyard micro prairie.  I’ll report back later in 2019 as to how they have fared.  I’m hoping I don’t need to water them much, but we will see.

Although this plant is primarily pollinated by bumblebees, hummingbirds will also visit it to get nectar.  Although, not as frequently as its cousin the Cardinal Flower.  But this can, and should be a great addition to any pollinator friendly garden!

Below you can see a short video that has the Blue Lobelia interspersed in a Native Plant garden at our old townhouse.  Since our yard was so small, this plant was one of our natural choices for maximizing color, pollinator food, and planting close together to keep weeds down.

Companion Plants for Blue Lobelia

The most obvious companion plant for Blue Lobelia would be its cousin, the Cardinal Flower.  But other species that would do nice and not encroach or crowd out Blue Lobelia would be Purple Coneflower, Blazing Star, and most varieties of Black-Eyed Susan (Rudbeckia).  Although you would probably have to keep an eye on the Rudbeckia to make sure it didn’t start new plants by going to seed next to Lobelia.

If you’ve enjoyed this article, please check out our other posts on Native Plants.  Don’t forget to subscribe to get our new content sent to you!

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Blue Lobelia Facts & Reference Table

Common Name Blue Lobelia, Great Blue Lobelia, Blue Cardinal Flower
Scientific name Lobelia siphilitica
USDA Zone 4-9
Bloom Time Late Summer – July / August / September
Bloom Duration Approximately 4-8 weeks
Color Blue, Dark Blue, Violet-Blue
Bloom Size Tubular flowers approximately 1/2″ diameter by 1″ long
Characteristics Single or multiple stalks containing many flowers, Blooming top to bottom
Height 2-3′ (0.5-1 m)
Spacing/Spread 1-2′ (30-60 cm)
Light Requirements Typically partial shade, but can tolerate full sun (will need water)
Soil Types Varied – medium loam to clay-loam.
Moisture Medium to Wet – mustn’t dry out completely
Maintenance Minimal, depending on conditions.
Typical Use Rain garden, border, wet meadow, or flower bed
Fauna Associations Bumblebees, and other bees.
Larval Host None
Sowing Depth Surface
Stratification Officially- 60 days cold moist stratification.  But I never bother with this, and they germinate for me.
Native Range Eastern North America
Notes This flower is beautiful.  I would describe it is strong, ornate, structured.

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[1] U.S. Department of Agriculture / Natural Resources Conservation Service. Great Blue Lobelia. By M. Kat Anderson and Michelle Stevens. Revised 21May2003.  USDA, NRCS, National Plant Data Center

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