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I have been trying to attract hummingbirds for a few years by planting flowers that they like. Two of these are Lobelia cardinalis and Lobelia siphilitica. They are both said to:

  • be perennial
  • need constant access to water but not to be sitting in water

I've grown the species them from seed, bought the cultivars at nurseries and in all cases their performance is the same. They grow quickly, flower profusely and fail to return the following spring.

The growing conditions are in a tussock of soil just above water level with morning sun and some afternoon shade.

How can I get these plants to overwinter?

USDA zone 4 with lows to minus 30 deg celsius

kevinskio
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2 Answers2

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Lobelia cardinalis is a characteristic species of hardwood swamps and Lobelia siphilitica is a characteristic species of fens in Minnesota and Wisconsin [1]. So both plants are native in USDA hardiness zone 4 and portions of zone 3. Yet, when I grew both plants in St. Paul Minnesota, I found they wintered inconsistently. I think there are a few issues involved.

First and most importantly, both plants have a huge range: L. siphilitica's range goes to Texas and L. cardinalis's range goes into Mexico. Plants from seeds collected in the southern portion of the range are likely not hardy at the northern edge of the range. My success with L. cardinalis was better when grown from a local seed source. Even so, the plants only lasted three years. The plants are probably naturally short lived. After a strong flowering and good seed set, the plant may die.

Finally, I think the plants can be overwatered. Neither plant is commonly found in areas that flood, but rather areas with high water tables. Moreover, the soil were the plants are found is typically moist but organic and well aerated (with pH 6.5 or higher) [1]. If the plant gets flooded with too little oxygen available to the roots late in the season, it may not winter well. This last bit is speculation, but it correlates well with my successes and failures.

[1] Vegetation of Wisconsin, John T. Curtis (1959)

Eric Nitardy
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  • Great information! I, too, have struggled to get Lobelia Cardinalis to grow, and I live in its native range. I do not, however, live on a fen and have clearly not succeeded in replicating one, as I have yet to have a plant come back in the spring. – michelle Sep 16 '13 at 14:37
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There are some species of cardinalis that are recommended for zone 6 and higher. I would mulch it real well or try to propagate/cut off a stem just below leaf node to root it and once rooted, over winter it inside.

Amy Dionne
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  • HI Amy, I am in USDA zone 4 so other species are not a solution. Have you overwintered a cutting of lobelia? – kevinskio Jan 28 '24 at 23:16