Garden index

Perennial Lobelia

August is prime time for these rewarding plants. They are very different from the half-hardy bedding types that are great for edging paths or cascading from baskets and tubs.

The easiest and hardiest perennial ones are varieties of cardinalis and speciosa – both from North America and considered as bog plants. Indeed, they grow wonderfully in moist or wet soils in summer and can even succeed at pond edge plants.

However, winter hardiness can be a big problem in wet soils in the UK – we are just not cold enough compared to North America and warm wet is not what they seem to want. So, the usual wisdom is to pot them up in winter. I did hear from one gardener on the very mild Wirral that they left their lobelias in the pond all year so perhaps it is worth experimenting.

The other problem with wet winter soils is slugs that can nestle down in the centre of a rosette and eat to their heart’s content. Try removing the old flower stems as soon as possible and fill the resulting holes in the centre of the plant with dry soil. This removes a favourite slug home.

In the growing season plants can be attacked by usually a single snail. Damage to a flower stem should result in a detailed search for the culprit.

We’ve found that they perform wonderfully in full sun in our very well drained soil. The only side effect seems to be that they don’t get so tall, which we love as it means we don’t have to stake them. In wetter soils they can get 3-4ft 90-120cm tall, whereas in dry soils it’s 2-3ft 60-90cm. Slugs in winter don’t seem to be a problem in dry soils. Winter hardiness with most varieties doesn’t seem to be problem either. Prolonged hunger will see the plants diminish and disappear so keep them fed on poor, dry soils.

I say most varieties are hardy because some seem less hardy than others. We never had much success with Queen Victoria; some years she was fine others she definitely wasn’t amused and passed peacefully away.

Bees are attracted to the flowers. Some flowers have longer tubes than the bees' tongues so they make a hole in the rear of the flower to get at the nectar.

Propagation can be by division in spring. Clumps can be sliced up into chunks and replanted. Sometimes it’s possible to divide down to individual rosettes, but these take longer to make good plants.

The seed is tiny and can be expensive. In spring, sow on the surface of moistened seed compost; cover with a clear top or bag or better still use a heated propagator. Pricking out the tiny seedlings can be tricky.

Once we’d cracked the North American varieties, we had a go at the less hardy South American ones. The most impressive and easy was Lobelia tupa, known as Devil’s Tobacco. This grows to 8ft / 240cm flower stems studded with red or orange-red flowers from July to October. It needs very well drained soil in winter. Alas our 10-year old clump succumbed to a recent very cold and wet winter. We have some seed again now, so we’ll be trying again. We’re told that two strains exist – one from the beaches and one from the mountains of Peru and the mountain one is hardier, but commercial seed is just seed so you can’t choose. We will protect plants in winter with a covering of pine prunings or dry leaves for their first few winters.

We also tried the species bridgesii and laxiflora but these seem to only survive the mildest winters outdoors here.

We grow five hardy varieties and we’ll let know how we get on with Devil’s Tobacco.

All lobelias are toxic if eaten.

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