Pot’s Growing On in May: self-seeding, hardy outdoor cactus and propagating tricky seeds

If I did nothing to our garden this year it would become an Echium, Allium, Ricinus, Verbena and Fennel jungle – these self-seeders have seriously self-sown everywhere! I’m puzzled how they managed to spread their seeds so evenly down the end of the garden I don’t grow them.

It’s times like these that I wish I had more space to pot up the whole planty army and take them to a charity sale. Sadly I don’t and they’ll all be weeded out. I am pleased however that they’re growing with such vigour, self-seeding is exactly what I wanted them to do – among a variety of other new plants I casted around last autumn. This is one of a few big changes in our small garden – I’ve added so many random self-seeders I can’t remember them all and now I can’t tell what should be there and what shouldn’t.

Over the last couple of years the designs I’ve been working on and my way of thinking have veered very much into this ‘natural way of things’ planting and so that’s influencing quite heavily the direction of our little patch. At first it seems chaotic and scary letting go of control but actually, by relaxing it’s easier.

Our Alliums are just starting to open – all at slightly different times, I’m guessing due to depth and temperature

Dahlias are grow

Over confident Dahlia grower over here thought it was fine to leave our dahlias out in pots, raised bed and ground on the allotment in winter. I’d found those left out performed significantly (and I mean significantly in the genuinely significant sense) better than those stored away. That confidence was mightily tested in March however when we had the coldest winter in eight years, a full week below 0C dropping to -7C on our patio, normally not going below freezing.

I’m ecstatic to report that I didn’t lose a single Dahlia despite those temperatures, which is surprising given just how cold it dropped – I didn’t really cover them with that much mulch either. As usual, over summer and winter the tubers have grown to epic proportions, some a foot large. Every plant is now sending up a large number of shoots, some plants growing incredibly rapidly. I thought this was early, but looking back at my blogs it’s the usual time.

One of a number of new additions this year, Fig ‘Ice Crystal’

Tricky seeds

I’m growing Persicaria orientalis and Eryngium giganteum from seed for our garden, Verbena hastata for a garden I’ve designed and two species of Echinacea for my allotment. These are tricky seeds to germinate indoors, all usually requiring a period of cold stratifying.

I thought leaving the packets of seed of Persicaria and Eryngium in the fridge over winter for 3 months would do the trick but no. After a month, nothing, so I threw them back in the fridge in seed trays for three weeks. They’ve been sitting outside in their covered trays for a week now – still nothing. Grr.

On the flip side, on my second attempt of E. giganteum in as many years, I planted and left the seeds outside to see if they’d germinate naturally. Still nothing! Last spring I had one chance tiny seedling I mollycoddled when I found it, it’s now happy in a pot as a second year plant. I’m very happy about this. I’m hoping the plant will self-sow naturally in time and propagate without my meddling.

And most mind-boggling of all, of the two Echinacea species I’m growing from seed, one germinated within two days! I planted them thinking they’d be in the tricksy bracket. Perhaps I just got lucky this time.

I found an old packet of spare Dolichos lablab seeds from last year. I soaked them overnight as recommended. They started germinating but now appear to have rotted away in the soil. Which is disappointing. I’ll try them again as I think the batch of seed was bad because last year only two germinated, one died and the second sulkily grew all summer but barely.

I have quite a collection of Sempervivums now – I do find these fancy cultivars and species occasionally quite fussy to grow

Cool as a cactus… wait what

I’d been wanting to grow a hardy Opuntia for a while and my friend Phillip heard my pleas, one day giving me Opuntia polyacantha. As an experiment I left it outside in its plastic pot and really quite sodden compost all winter – I know what you’re thinking “you dare devil”.

Guess what? It didn’t even bat a spine despite sitting in very wet, almost boggy compost all winter at -7C! Well, I am amazed. I was even wondering if Phillip had given me a plastic plant as a joke but no, yesterday I noticed it is erupting into growth with 12 new pads forming. Amazing.

What my family call Huffy, because the flowers close in a huff during cold weather. This plant originates from County Antrim in Northern Ireland where my gran grew up as a crofter.

Colour me happy

Over the last ten days buds have been forming across the garden. As we wave goodbye to my all white and green winter – early spring garden, it’s morphing into the hot pinks and dark purples that I love. It’s a relief to see colour again and I have that annual surprise of happiness seeing the plants I’ve had for a few years now back for more.

My Astrantia being one of my faves, accompanied by some very happy Allium ‘Purple Sensation’ this year, all returning with strong buds – last year they were quite weak, so I thought they’d gradually fade away.

As the Allium and Astrantia buds open, so is the Cirsium in its second year, and three times the size. Heuchera ‘Green Tea’ is flowering too, and the Lysimachia atropurpurea ‘Beaujolais’ I grew from seed last year are forming erect buds, which is extremely exciting.

Our Polystichum setiferum was the first fern to grow this year and it is now absolutely huge!

Prop til you drop

May is that point in the year where our front room and garden look extremely messy with me growing lots of things for the garden and allotment from seed. Given the lovely weather, I’m feeling the allotment seedlings can all go out to the plot this weekend freeing up a lot of space. And many of the flower seedlings for the garden are almost set too.

I really enjoy growing things from seed but it doesn’t make for great photos to share with you (and it drives me slightly nuts having so much visible mess!) By the time Chelsea Flower Show comes around, I’m hoping I can get our indoor and outdoor gardens ship-shape so I don’t feel dejected walking among the fabulousness of show gardens.

I’ll stop for now otherwise I’ll bore you – there’s a lot to talk about despite the diminutive size of our garden, I didn’t even cover off the excitement of our little conifer forest! Next time.

This part of the garden has some Japanese garden vibes about it.
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Jack Wallington

I'm an RHS qualified garden designer living in Clapham, London who loves growing plants and designing with them. Follow me on Twitter.

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