Container Gardening with Harriet Rycroft, week 2

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What’s the difference between growing in containers, as opposed to growing in the ground? I’ve already written about how there’s less margin for error with a plant in a pot, the rootball having access only to the nutrients available in the container, and that much more vulnerable to sudden changes in temperature. In this week’s lesson, we were again considering the materials used to construct containers, but this time rather than from a purely aesthetic point of view, we’ve been looking at how, for example, a plastic or metal pot will typically have less thermal insulation than one made of good quality terracotta or stone, and how this should affect how you think about siting different containers.

Just as you need to develop an awareness of different microclimates in your garden when planting in the beds and borders, so too this needs to be factored in when planning displays of containers. Not just things like aspect, the location of frost pockets and wind tunnels, but also the potential for strong gusts to be bounced off walls and corners against which pots are placed, potentially causing harm to plant material through air turbulence. And, while you may think that your treasured plants are entirely independent of the ground, being safely ensconced within their pot and with roots nestled into your choice of an ideal growing medium, it turns out that the hard surfaces on which the containers are standing can still have a bearing on how well (or not) the plant thrives. As an example, and rather like an inverted version of the storage heater in my old Muswell Hill bedsit, a dark-coloured ground surface will absorb heat during the day, and slowly radiate the warmth back out at night. I remember this arrangement was pretty hopeless for me, as it meant the bedsit was toasty during the day when I was out at work, and freezing during the evening and night, but careful attention to the needs of your plants should mean that you can take better advantage of the principle.

Practical matters covered this week also included arranging containers in groups, watering and drainage, including the thorny issue of crocks, and the desirable properties of a good compost. Already having packed quite a lot to pack into one week, Harriet ended the tutorial with a consideration of what to look for when selecting plants for your containers, with criteria including foliage, flower and form, as well as texture and habit, and seasons of interest. Much to remember, and to help it sink in, this week’s assignment asked us to choose four perennials or shrubs which we thought would earn their keep in a container display.

Here are my choices.

Sarcococca confusa
Perhaps the least fancy Sarcococca, the Christmas box is nonetheless a plant I wouldn’t be without, growing it both in the ground and in containers. An evergreen shrub with a potential to grow over a metre in height after many years, I treasure it for its deep glossy, spear-shaped leaves, and the clusters of black berries. But mostly for the rich, heady, vanilla fragrance of its tiny white flowers in the depths of winter, filling the air with a delicious, warming scent at the most miserable time of year. During the spring and summer months, it lurks within the groups of containers, overshadowed by more flamboyant flowers and foliage, but once the tender things have been put to bed, it begins to come to the fore.

Close-up of Sarcococca confusa. Sadly not scratch-and-sniff.

Good drainage is essential – in fact, I’m learning you can go as sharp as you like with this plant, which will happily seed itself into sand and gravel (we discovered it when a friend noticed seedlings below the window from which she’d periodically lob spent, cut stems that had been brought into the house for the scent). It will also need a certain amount of clipping, as it doesn’t naturally assume a particularly neat habit, and with age it begins to throw out shoots in unexpected directions. A happy Sarcococca will begin to sucker from the root stock, so you’ll need to keep an eye out for an appropriate time to repot, or else pull the suckers off and pot up into a free-draining compost for free plants.

Euphorbia characias subsp. wulfenii
This evergreen subshrub might not be the rarest of specimens, but it certainly earns its place in many different settings. Growing to 1.5m in height, and often rather larger around, the most striking feature for me is the colour – grey-blue foliage, topped with huge acid green flower heads in spring which persist for months. It’s not known for its fragrance, but having worked around it in several locations, I can confidently announce that it gives off a pronounced smell which might be described as bitterly earthy, or woody, but which reminds me of nothing so much as coffee grounds. 

Euphorbia characias subsp. wulfenii in flower. Less yellow, more blue in real life.

The leaves are long and narrow and, in common with many spurges, arranged in whorls around the long, serpentine stems, which leak a toxic latex sap when cut or broken (the sap can cause contact dermatitis, so best avoided or quickly washed off). It will survive in a large container, and is relatively tolerant of most soil conditions except waterlogging – err towards the dry to be on the safe side.


Melianthus major
The most tender of my selections, practically herbaceous in my part of the UK, but growing as an evergreen subshrub in climates more akin to its native antipodes, where it has become something of a weed. Here, we love it for its large, pleated glaucous foliage with deeply serrated edges. I was once told by the head gardener of one of our major gardens that it wouldn’t flower in the south east of England, but mine decided to contradict this pronouncement, producing a massive maroon flower spike that November. Just before the frost and the wind reduced the entire thing to black mush.

The leaves of Melianthus major. Remember, not all peanut-scented things are edible.

I have quite a knack for killing this plant, so timely winter protection is a must, and growing it in a pot rather than the ground is, I am convinced, the way to go, at least for me. It will also let me get it up a little higher off the ground than might ordinarily be the case, away from the reach of Bill, with his leaf munching mania, as the peanut-scented leaves (another woody fragrance) are toxic to dogs.

Fatsia japonica
I have heard this glamorous relative of ivy sneeringly classified as a ‘carpark plant’. But, as every plant so labelled is an utterly reliable, unfussy, robust and attractive affair presenting year-round interest, I don’t see it as anything to be sniffy about, and I can’t get enough of its large, glossy palmate leaves. Even better, in summer, older plants flower with the most eerie-looking white umbels. A statuesque presence, in the ground it will happily grow to eight feet in both height and circumference, although in a container it will assume more modest proportions. Happy in shade, dry or damp, it will provide a luxuriant, tropical backdrop to any planting all year round.

Glossy palmate leaves of Fatsia japonica.

Do have a look at the My Garden School website, which is still running its  Back to School campaign for 15% off all £145.00 4 week online courses in October. (Course start dates: Wednesday 7 October 2015). Click here and remember to use the code MGSBTS at the checkout for the discount.

Notes from the greenhouse

Mission Control has been looking a little sorry for itself of late. A wet winter and a less than watertight structure have taken their toll on the end of the greenhouse where I station myself to sow seeds, pot on, check the temperature, listen to the radio and drink tea (although the last two activities invariably occur wherever I find myself in the garden). This isn’t to say I’ve not been using it – far from it – but ‘making do’ has very much been the order of the day, as I’ve watched with a growing consciousness of my own inadequacy the seemingly endless stream of tweets testifying to the ruthless efficiency of my gardening friends, all of whom have appear to have cleaned, repaired and rearranged their greenhouses in good time over winter in preparation for the new season. Social media is wonderful for providing support and encouragement, particularly I’ve found in the gardening world. Just sometimes, it reminds me that I’m still very much a journeyman at this game.

My greenhouse, of course, couldn’t agree more. The leaky roof has decided that the main cascade is shown to its greatest advantage when falling directly over the potting bench, the plywood surface of which became badly waterstained, the grain not so much raised as mountainous. The max/min/in/out thermometer has been staring at me blankly for weeks, due in part to the absence of a sensible battery compartment, necessitating the irksome removal of six fiddly screws and a rubber gasket just to discover what manner of exhausted power source lurks within. It doesn't sound like much of an obstacle to overcome, but by the time I’ve made the short journey along the wavy grass path back to the house, I've passed several other more pressing things-which-need-doing along the way, and all thoughts of batteries and screwdrivers have been forgotten.

Clearly some TLC was in order, and so making the most of the extra hours of light we’re now enjoying, the potting bench has now had a rub down and several fresh coats of Briwax, which ought to see it through for a while longer. The thermometer is restored to an operational state (triple A cells in there, who’d have thought? I was expecting those annoying watch batteries), and I’ve built a new shelf above the bench for essentials so I can keep the working surface clear. Suddenly, it feels like a much more efficient operation.

I’ve also got a plan to add in a lower level of staging to create a third tier – there won’t be the height for anything taller than moderately sized seedlings, but then there won’t be the light levels for anything that’s exhausted its onboard store of energy, and by the time the first pairs of true leaves are unfurled and seeking out the sun I’ll be needing to pot them on anyway. It will just give me an extra (slight) defence from the mollusc army, though it is tempting to clad the vertical surfaces in copper. Now there’s a thought... but perhaps I’m getting carried away.

If the weekend stays sufficiently dry, I shall attack the roof seam with some silicone, a slightly fiddly process as I need to do this from the outside rather than from below to prevent the water from gathering between the roof timbers and causing them to rot. I’d rather be sowing seeds.

What’s growing in the greenhouse this month

Sweet peas in root trainers. Sown these into Carbon Gold GroChar seed compost, which I think might have been a bad idea due to the length of time they’ll be in there –they’re beginning to show signs of nutrient deficiency. Silly me; I’ve given them a shot or two of Maxicrop seaweed-based plant tonic and will get them into the ground in a few days.

Tomatoes in modules – these need potting on now. A snail got up onto the staging and munched all the 'Gardeners Delight'. Only one of the measley eight-in-a-packet 'Red Robin' have germinated (a new variety for containers), so I’d better look after this. All the 'Moneymaker' look good.

Cleomes – germination rate rather good, and potted on now into 9cm square pots. These were also looking a bit yellow (also sown in GroChar seed compost. I think it might only be good if you’re sowing into seed trays and pricking out fairly swiftly after germination, I tend to sow into modules and so need more food for the seedling as it’ll be in there for a while. I will stick with the GroChar but use sieved multi-purpose I think).

Butternut squash and courgettes – the first signs of life just showing, sown straight into multi-purpose in 9cm pots.

Hanging basket of petunias waiting to go out the front of the house, for some retro gardening cool!

A knackered looking melianthus in a 2 litre pot, a favourite plant I was intending to plant out till I discovered its toxicity to dogs.

Not to mention the posh pelargoniums, astilbes and misc cuttings/splittings, which all need some attention.

The cosmos will get sown today. Or maybe tomorrow.

What’s in yours? Do leave a comment, or send me a tweet!

If he’s not going to hurry up in there, he could at least let me in to munch on the astilbes

Honey bush

This gorgeous foliage belongs to the honey bush, Melianthus major. Year after year, I grow it in my garden and, sure enough, year after year it expires.

Admittedly we have had two exceptionally harsh winters, the last of which arrived several weeks early – rather unsporting, I thought. I adore this plant, and have done since we first encountered it in Cornwall, where it grows alongside enormous spires of echiums and other fantastical looking things. I love everything from the dusky, glaucous blue green of its sharply toothed leaves, to the smell of peanuts it gives off when touched; the amazing sight of new foliage unfurling, and the outrageous, dark red flower spike that appear from some admittedly rude-looking buds. In its native South Africa it grows like a weed. (Typically, like so many of my favourite plants, it’s horribly poisonous and will kill you as soon as look at you. Fortunately, the odd smell tends to prevent any animals from even considering munching upon its leaves, and it’s the roots which are the most toxic.) Technically an evergreen perennial, hardiness in our climate is not something with which this plant has been blessed, and protection is really required in order for it to survive anything other than the mildest of winters. Up until the point at which the cold November winds whip it to kingdom come, just before the frost renders each stem a necrotic black, it does exceptionally well in my garden. If I have to grow it as an annual then I will, just to enjoy its presence.

Recently, I’ve been scouting about for a replacement plant, my usual sources not being able to help this year. My search took me to the RHS plantfinder, and from there to the very wonderful Plantbase near Wadhurst where Graham Blunt, the effervescent owner, had not only several specimens of what I sought in stock, but also two other related species (M. comosus and M. villosus), both a little hardier and better suited to our climate.

Graham is evidently a person who knows his subject, belying modest assertions that he’s entirely self taught, eschewing book learning for a more hands-on approach. His nursery is an Aladdin’s Cave for the plant enthusiast, with some truly amazing specimens — as we arrived, he was waxing lyrical about some very evil, spiny-looking solanums, one with bright orange thorns which was very special. We were completely won over by the many echeverias he has — one of which, E. cante (a present from Kew), is truly beautiful and seems to radiate light, but is alas not for sale this year until he has had a chance to propagate from it. I particularly loved the colour and form of the ghost echeverias, Echeveria lilacina – powdery lilac-grey rosettes which seem somehow both architectural and entirely other-worldly. The plants are laid out loosely in terms of habitat – jungle, woodland, alpine, waterside, prairie - and visitors are encouraged to roam, and to ask questions, the answers to which Graham is only too happy to provide. I would thoroughly recommend a visit — we left with our wallets slightly thinner, but with massive smiles on our faces a whole list of plants we will be coming back for.

Did I take the sensible route and opt for the hardier relatives of my precious honey bush? I confess, not. It may well end in tears once more, but at least I’ve found someone who can feed my honey bush habit.