Getting it to bloom

Why won't my Lobelia cardinalis bloom? (and how to make it flower)

Also called Cardinal Flower, Red Lobelia (Lobelia cardinalis).

More about lobelia cardinalis

About Lobelia cardinalis

Lobelia cardinalis · also called Cardinal Flower, Red Lobelia · flowering

Lobelia cardinalis is a striking moisture-loving perennial bearing tall spikes of vivid scarlet, tubular flowers above upright leafy stems in mid to late summer. Native to streamsides and wet meadows, it is a celebrated hummingbird and pollinator plant for pond margins, rain gardens and consistently damp borders.

Plant type: flowering

Watch for — Poor flowering: Too much shade or soil that dries reduces the spikes. Site in sun-to-part-shade with constant moisture for the best scarlet display.

The reasons lobelia cardinalis isn't blooming

Almost every non-blooming lobelia cardinalis traces back to one of these, roughly in order of how common they are:

Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
Too much nitrogen feed, driving lush foliage at the expense of flowers (very common with general or lawn feeds).
The plant has not been deadheaded, so it stops flowering once it sets seed.
Irregular watering — drought or waterlogging at the budding stage makes buds abort.
It is still too young or was checked by a transplant and is rebuilding before flowering.

Feeding lobelia cardinalis a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.

The fix — how to get lobelia cardinalis to flower

Maximise sun. Give lobelia cardinalis the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers.
Switch the feed. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
Deadhead regularly. Remove spent flowers often to keep it producing more rather than stopping to set seed.
Water consistently. Keep moisture even through budding and flowering — drought-then-flood swings make buds drop.

Light and feeding do most of the heavy lifting here. Dial in the spot with the light guide for lobelia cardinalis and get the feeding right with the lobelia cardinalis fertilising schedule — the wrong feed (too much nitrogen) is one of the most common silent reasons a healthy plant makes leaves instead of flowers.

Bloom season and what to expect

Lobelia cardinalis flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.

Post-bloom care so it flowers again

Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.

For everything else this plant needs day to day, see the full lobelia cardinalis care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Lobelia cardinalis blooming — frequently asked questions

Why won't my lobelia cardinalis flower?

Lobelia cardinalis blooms on the season's growth given enough sun, warmth and the right feed — there is no cold or photoperiod trick, just good growing conditions and a bloom-leaning feed. The most common reason it is not happening: Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.

How do I make lobelia cardinalis bloom?

Give lobelia cardinalis the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.

When does lobelia cardinalis normally bloom?