Grow: How does your garden grow?

It’s a funny old business, gardening. We so often start out with the intention of letting nature know who’s boss, only to quickly find ourselves delighting in the horticulturally spontaneous, the unplanned and the unpredictable.

Take, for example, self-seeders, those plants with a generous habit of spreading themselves around, so that their offspring can be frequently seen popping up uninvited in stony crevices, paving joints or pebble paths, as well as in flower borders and vegetable beds.

Numerous examples in my own garden include the lime-green flowering lady’s mantle, beloved of flower arrangers (Alchemilla mollis), sky-blue forget-me-nots (Myosotis) and borage (Borago officinalis), perennial geraniums, granny’s bonnet in shades of plum, inky blue and dusty pink (Aquilegia), sweet william (Dianthus barbatus), lofty foxgloves (Digitalis), Mexican fleabane (Erigeron karvinskianus), fiery- golden pot marigolds (Calendula officinalis), edible nasturtiums (Tropaeolum majus), sweetly scented dame’s rocket (Hesperis matronalis), the wispy Mexican feather grass (Nassella tenuissima), decorative Briza maxima, with its daintily ornate seedheads, violet-flowered Verbena bonariensis and a lovely, orange-flowered strain of the Welsh poppy, Meconopsis cambrica.

How did all of these plants first arrive? Many are the self-seeded progeny of parent plants bought and grown many moons ago, or given to me as gifts.

Others came more stealthily, as tiny seed covertly hitching a lift inside compost or manur, or perhaps stuck to the soles of a muddy boot or even concealed within the droppings of a passing bird.

Then there are those that I like to think arrived in much the same way that Eryngium giganteum ‘Miss Wilmott’s Ghost’, the hardy, summer flowering perennial with silvery spikes of ruffled flowers, is fabled to have spread itself through countless Edwardian flower borders.

According to garden legend, this plant was sneakily distributed by the plantswoman and gardener Miss Wilmott herself – a sprinkle of seed here, a sprinkle there – is a way of ensuring its continued survival.

Such spontaneity, such unpredictability, as I’ve gradually learned, is good in any garden; it is the yeast that leavens the dough, the bubbles in a glass of champagne.

Which is why, uninvited as they might be, I’ve grown to treasure the habit of self-seeded plants to arrive unannounced.

Somehow they have a special way of making themselves at home, whether by softening the contours of a garden path or greening the hard verticals of a garden wall or livening up a planting scheme with a sudden, unexpected fizz of colour.

Left to my own devices, for example, I don’t think I’d have thought of under-planting a sea of Allium ‘Purple Sensation’ with generous drifts of orange Welsh poppies, a gaily colourful plant combination that appears in the garden every year in late May-early June.

Nor, when I started out gardening, could I ever have imagined that the self-seeded pot marigolds’ golden flowers could look so jewel- like sprinkled amongst lettuce and cabbages.

Nature’s also a far more accomplished gardener than most of us when it comes to encouraging self-seeding plants to grow in the (seemingly) most unlikely of places, artfully positioning them in the tightest of spots – tiny paving cracks, or dry, stony crevices – where they happily flourish, safe from the root systems of competing plants.

It’s not all good, of course. Some self-seeding plants can very quickly become too much of a good thing, a lesson I learned the hard way as a young gardener when I naively planted the beguilingly beautiful but horribly invasive Himalayan balsam (Impatiens glandulifera). Very soon, hundreds of plants began appearing, quickly shading out other, less vigorous species; it took years to rid it from the garden.

That, in a nutshell, is the key thing to bear in mind when it comes to self-seeders. These plants are the party-crashers of the garden; some are fun, a few are fabulous and others quickly become a bore, while there are a handful that you should never allow to gain entry.

Even those that you do welcome will need to be encouraged with a certain amount of caution. In other words, regularly and ruthlessly remove any self-sown seedlings that you judge to be in the wrong place with the aim of creating sustainable plant combinations that are a satisfying mixture of flowering seasons, colour, texture, form and height.

To deliberately introduce desirable new species into the garden, start by initially growing them in containers and then strategically placing these in suitable spots where the young self-sown seedlings have a good chance of gaining a foothold.

Yet another useful way of encouraging self-seeders is to remove a thin top layer of top soil (5-10cm) and replace it with fine grit or pebble, a growing medium conducive to many seedlings.

Most importantly, though, if you want your garden to be a place where these plants feel at home and where spontaneity is given a voice, then ditch the weedkiller and be sparing with the hoe. The results will surprise and delight you.

For more advice and inspiration on using self seeding plants in the garden, get your hands on a copy of Cultivating Chaos; How To Enrich Landscapes with Self-Seeding Plants by Jonas Reif, Christian Kress & Jurgen Becker (£25, Timber Press)

This week in your garden 

To ensure that colourful displays of summer bedding continue for as long as possible, keep deadheading any faded flowers to prevent plants from putting all of their energies into producing seed.

There’s a certain art to this ; rather like a good haircut, the end result should look completely natural. So use a sharp scissors or secateurs and always start by cutting the stem back either to just above a lateral flower bud or leaf, and then eventually (once there are no more flower buds left to flower on the stem) back to the base of the plant.

Net soft fruit plants from birds; an ideal mesh size is 19mm (¾ in), fine enough to deter smaller birds but still large enough to allow pollinating insects through. Drape the netting over temporary frames constructed out of bamboo/timber and flexible wavin piping and then make sure to peg/weigh it down.

Keep staking/ tying up tall border perennials such as delphiniums, verbascums, perennial sunflowers and dahlias to protect them collapsing under their own weight or being damaged by strong winds later in the summer.