Six on Saturday – Cool flower spikes for a hot summer


Last week I looked around the garden for plants with flower spikes at the hot end of the colour spectrum, so it is only fair to look to the cool end this week. Once again there were many candidates, but here are six of my current favourites (plants with spikes at the icy end of the spectrum).

1) Delphinium requienii

This one (and only) example is a self-seed from last year. I saved and re-sowed seeds in spring, but since the plants are biennial I will have to wait until next year for those to flower.


Delphinium requienii

2 Berkheya purpurea

Much stronger (and upright) for being three years old now, this prickly south African, pale lilac perennial is enjoying our current run of hot dry weather. It always surprises me that the flowers open from top to bottom, when nearly all the other flowering spikes in the garden open upwards.


Berkheya purpurea

3) White nettle-leaved mullein

These were grown from seed shared by a colleague a couple of years ago. The other day I noticed that at their feet there is now a dense carpet of seedlings, so it looks like I will soon be sharing back!


Verbascum chaixii album

4 Agastache ‘Blue Boa’

I’ve planted Agastache ‘Blue Boa’ in the new island bed dug out around a tree stump left behind by the storms a couple of years back. Its deep purple is working nicely along side the new Amazing Grey poppies and Monarda ‘Cambridge Scarlet’.


Agastache ‘Blue Boa’

5 White foxglove

I love all foxgloves, but in terms of drama it is hard to beat tall plain white spires!


White (with a sprinkling of freckles) foxglove

6 Penstemon ‘Sour Grapes’

In spite of its name, this penstemon is really lovely and is probably my favourite variety. Its colouring is a soft blue tinged with pink. At dusk the plant seems luminous and unearthly. In the meantime, it seems to be a popular nectar stop for common carder bumblebees.


Penstemon ‘Sour Grapes’

That’s my six! Have you got different favourite flowers with spikes I should try?

Check out our propagating leader’s blog for his Six on Saturday meme and check the comment section for links to many enthusiastic SOS postings.

Have a good weekend and take care if you are gardening in the midday sun!


About Frogend_dweller

Living in the damp middle of nowhere
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19 Responses to Six on Saturday – Cool flower spikes for a hot summer

  1. Eliza Waters says:

    A lovely six, Allison. That delphinium is esp. nice!

    • Thanks Eliza. I am a fan of its smokey, slate-blue shade. Plus it is slug resistant, which is always a positive when you live in Frog End 🀣!

      • Eliza Waters says:

        Good to know, the slugs this year have been rather destructive. It’s getting to the point where all plants I grow must be resistant to slugs, rodents and deer. Thank goodness for pungent, hairy herbs!

  2. shoreacres says:

    I laughed to see your mullein serving as a very dignified garden flower. We have a native — Verbascum thapsus that carries the common name ‘cowboy toilet paper’ because of the soft and relatively non-irritating large leaves it produces. You can have a look at it here!

  3. Pauline says:

    A lovely six, tall spires are so essential in the making of a garden! Love the colours of the penstemon.

  4. Rosie Amber says:

    You have made me think about other plants that might open from the top down with your Berkheya purpurea. Some of my sunflowers do that, open the top one, then produce lots of small heads lower down.

  5. Cathy says:

    Using flower form is an interesting theme for SoS and has introduced us to some plants we haven’t come across. I had no joy with berkheya when I tried a few years back – no germination! Your soil clearly has some advantages as I have not been able to overwinter agastache at all, even with mulching, and to keep them I think I will need to lift them each year – any advice?

    • I was surprised by the agastache too, since our soil is heavy and waterlogged most of the winter (although, to be fair, the last winter was dry here). I’m always in two minds about mulching around the necks of such plants, as it ends up with frozen wet compost at the delicate regenerating part, unless it is pretty deep. Maybe you are just colder? What a pain to have to lift them though. It’s bad enough with all the salvias πŸ€·β€β™€οΈ. I’ll look into splitting Berkheya and see if I can send you some.

      • Cathy says:

        Hmm yes, that’s a thought about the mulching… Don’t think we will be colder though… One I did bring inside this last winter has done really well, although it was growing in a pot and is now planted out – will probably lift it again. It was grown (easily) from seed, but they do take a couple of tears to begin to establish. Thanks for the offer of some berkheya, but please don’t split yours unless you are sure it won’t adversely affect it

      • I’ll check to find out when it’s best to divide berkheya, but one bit of the clump looks pretty detached already. I’ll let you know.

      • Cathy says:

        Thanks Allison πŸ‘

  6. fredgardener says:

    Stunning Berkheya seen not long ago on Twitter/Insta. It made me want to grow some but according to Cathy, it might be hard to germinate the seeds…

  7. Cathy says:

    The Penstemon is so lovely. I have never tried growing them. Maybe I should! And the Verbascum also caught my eye. πŸ˜ƒ The Agastache is a lovely rich colour. I have a paler one just starting to flower. They go on and on flowering for weeks. πŸ˜ƒ

    • I think that penstemon would really suit your landscape. Verbascum chaixii is often used in meadow mixes. Yes, agastache rock! Shame I’ve lost my Kudos series ones though. I don’t think that they are so hardy.

  8. The white mullein is a new one to me. Next on my to-do list now. Lovely!

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