Amazing annuals: lobelia

Beloved as essential for formal Victorian bedding, they remain essential for summer baskets.

I have grown lobelia almost as long as I have grown anything. Unfortunately, my view of the plant is slightly coloured by my childhood. Dad used to grow and sell bedding plants at the front gate but it was down to Mum and me to do the pricking out each spring. It was not as bad doing dozens of wooden trays of marigolds but pricking out (transplanting) lobelia was awful. The seedlings are SO tiny and it was a labour of love, or rather duty, to transplant 48 plants per tray – 6×8.

In reality, it was not quite as bad as it could have been. We would mix the tiny seeds with silver sand and would sow in rows. In fact we even made a wooden ‘firmer’ with triangular beading on the base so that, when firming the compost, it made shallow ‘drills’ along which we sowed the sand and seeds. It made it easier to prick out the seedlings. And we did not prick them out as individuals but tiny clusters. This also tended to prevent damping off, a fungal disease that is very common in antirrhinums and lobelia seedlings.

But, back to the basics. Lobelias are in the campanulaceae but, instead of having actinomorphic flowers like campanulas the blooms are zygomorphic with a pronounced lower lip composed of the three lower petals with the other two petals erect. The five stamens are fused and around the long stigma and arch over the lower lip. There are more than 400 species and few genera are as varied. There is constant moving of species around related genera and Pratias may really be lobelias (they look like it to me). But as it is, this genus, found almost everywhere around the world, varies from small perennials to robust perennials and even monstrous gigantic herbs such as the monocarpic Lobelia deckenii from the mountain tops of Tanzania. There are plenty of familiar and exciting garden plants, such as flaming L. cardinalis and blue L. siphilitica and the Chilean L. tupa. But here we are talking about the South African L. erinus.

This lobelia is a small, frost-tender perennial that we usually treat as a half-hardy annual, grown from seed every spring in gentle heat, the plants set out in late spring after the last frost. The many cultivars are usually either small, clumpy plants no more than 15cm high or are looser-growing, ‘trailing’ lobelia that will cascade over the edge of baskets or pots about 20cm. If the plants have a fault it is that the flowers are tiny and cannot be deadheaded unless you have the patience of a saint and so the plants have a limited useful lifespan, especially in warm weather. But shearing over the plants to remove most of the growth and watering and feeding will result in new growth and flowers. Because of this failing, plant breeders have produced new strains that are propagated vegetatively and set no seeds (below). These are bought as plants in spring and are a great improvement if you only need a few plants – they are too expensive for general bedding or to use in the traditional way to surround beds of salvias and pelargoniums.

The idea of raising these lobelia from cuttings is actually not that new. Many years ago I used to grow the double blue ‘Kathleen Mallard’. It has small, cobalt blue flowers that are heavily doubled and look like little roses. They are about 1cm across and utterly charming. The plants are neat and only 10cm or so across. It is easily propagated by cuttings or pulling apart the plants – the lower parts of the stems usually have root initials. I hope it is still available and I would dearly love to have it again. It is usually said to be Victorian and I have found a reference to it in a book from 1911. Robinson (1883) mentions a double blue lobelia but not by name and suggests that it is unreliable while I always found ‘Kathleen Mallard’ a simple plant to grow, though prone to mould in winter if not cut back in autumn to reduce the foliage and improve air circulation.

We think of lobelia as blue but they can be so much more. As well as every shade of blue, often in combination with white splashes on the lip, there is cherry red, pinks and mauves and white. I think it is a fact that white is never 100% for some genetic reason and you always get a number of blues in a batch of white. Of course it could just be sloppy seed companies.

Although grown as a half-hardy annual and I would never suggest treating it as a hardy annual it is a fact that it often resows in the garden, especially in well-drained sites such as the gravel and paving under and around pots and baskets where it has been grown the previous year.

Lobelia is a bit old fashioned and easy to overlook when choosing bedding plants but it has a special combination of grace and charm that makes it well worth adding to your summer garden.

18 Comments on “Amazing annuals: lobelia”

  1. tonytomeo
    January 4, 2021 at 7:38 am #

    This is another annual that works longer than it should in the mild climate here. Incidentally, it is popularly planted as edging, alternated with alyssum, which does the same. I suppose it is best as a warm season annual like it is everywhere else. However, if planted in autumn, it performs reasonably well as a cool season annual through our mild winters.Just like alyssum, those that live through summer do not continue through winter; and those that perform through winter do not continue through summer. What is different from alyssum and also nasturtium, is that they do not self sow reliably, so must be replanted.

    • tonytomeo
      January 4, 2021 at 7:44 am #

      Actually, I should mention that they do not ‘need’ to be replaced here. They can perform well through summer, get overplanted with cool season annuals, and then allowed to regenerate in spring for the next summer, or the other way around (performing through winter and overplanted for summer). They just need an ‘off’ season. Now I am wondering if they could be planted both in spring and autumn, so that one batch could take over for the other as it rests. Oh, too much effort.

    • thebikinggardener
      January 4, 2021 at 3:47 pm #

      Traditionally dwarf lobelia was interplanted with lobularia (alyssum) surrounding scarlet Salvia splendens.

      • tonytomeo
        January 8, 2021 at 1:59 am #

        That is a good combination for Independence Day. Salvia splendens is one that I have not seen in quite a while.

        • thebikinggardener
          January 8, 2021 at 7:57 am #

          It gets used for patriotic displays here too!

          • tonytomeo
            January 8, 2021 at 8:08 am #

            ?! Aren’t they the wrong colors?

            • thebikinggardener
              January 8, 2021 at 8:10 am #

              Red white and blue! just like the USA, France and Russia!

              • tonytomeo
                January 8, 2021 at 8:40 am #

                Do you mean the English colors? I was thinking of the Irish colors, green, white and orange.

              • thebikinggardener
                January 8, 2021 at 4:28 pm #

                Ah yes – you are right. I forgot where I as living for a moment!

              • tonytomeo
                January 9, 2021 at 7:38 am #

                Where are you?

              • thebikinggardener
                January 10, 2021 at 9:49 am #

                LOL – in south east Ireland

              • tonytomeo
                January 11, 2021 at 4:57 am #

                So, not even British?

              • thebikinggardener
                January 11, 2021 at 9:11 am #

                Yes, British but been in Ireland for seven years

              • tonytomeo
                January 12, 2021 at 12:58 am #

                But that part of Ireland is not British like Northern Ireland?

              • thebikinggardener
                January 12, 2021 at 9:12 am #

                Absolutely. I live in the Republic which is most definitely not British and it is still part of the EU. I am British by birth but European by choice.

  2. derrickjknight
    January 4, 2021 at 9:50 am #

    Our hanging baskets are well stocked with them. I noticed one in bloom yesterday

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