Inspired by the world-famous laburnum arch at Bodnant Garden in north Wales, our mini version comes into full glory this month with cascading chains of golden yellow flowers. Aptly known by the common name of golden rain tree, laburnum can also be grown as a small, free-standing tree, given a sunny spot and moist, well-drained soil. When fashioned into an arch, it can create an elegant entry point or walkway, when several trees are grown together in a row, and the effect is spectacular when underplanted with purple alliums.

Laburnum x waterii ‘Vossii’ is our chosen variety and the trees are trained on a curved metal framework. A height of about 3m will ensure you can comfortably walk beneath and allow at least 2m width for a pathway. The trees are planted opposite each other on either side of the arch at about 2.5m spacings.

Laburnums are fast growers, putting on around 40cm of growth a year, and so annual pruning is essential. Pruning and training is done during winter while the trees are dormant – if pruned in spring or early summer, the tree is likely to bleed sap. The main vertical shoots are tied in and trained to meet in the middle over the arch while lateral shoots are attached horizontally along supporting wires. Shoots that are growing inward and outward are cut back to about three buds.

All parts of laburnum are poisonous and so, where young children or animals are a concern, an arch of flowering crab apple or wisteria makes a lovely alternative.

Managing pop-up plants

At this time of the year, our garden is full of seedlings of self-seeding plants such as foxgloves, poppies, Angelica archangelica, Mexica fleabane and aquilegias. These opportunistic guests pop up unexpectedly in the cracks and crevices of walls and paving while in borders they’ll intermingle with other plants, adding spontaneity to the planting and throwing up often pleasing combinations we would never have considered.

They can also provide free plants and offer a solution to steep banks and inaccessible areas of a garden where soil can’t be easily cultivated. Some will grow in the most inhospitable places with minimum work, giving weeds, the garden’s less-welcome opportunists, no place to settle.

But self-seeders can crowd out the plants you planted deliberately, competing with them for water and nutrients, and may require removal or thinning out to reduce their numbers, leaving just a few to grow.

One of my favourite self-seeders is the short-lived, biennial sea holly Eryngium giganteum.

I find this a good time to do some judicious culling as the seedlings or young plants of desirable ornamentals will now be big enough to distinguish them from unwanted weeds. Most surplus seedlings can be hoed off or easily pulled out while those that form a deep tap root may require digging out. Sometimes, new plants pop up exactly where needed. Other times, it’s necessary to weed out those growing in a less-than-ideal spot or transplant them to a more desirable location. You might even pot some up into small pots, grow them until they are larger, and then plant them back in the garden. Some plants, like Alchemilla mollis, self-seed so profusely that they become a nuisance and to avoid problems make sure to remove the withered flower heads before the seeds ripen.

Sharp edges

Straightening and shaping lawn edges is ideally done once a year after the first spring cut but better late than never.

Nothing sets off a garden like neatly defined edges to beds and borders. No matter if your borders are a little messy, or even if the lawn itself needs a bit of work, we find that keeping the edges smart makes everything look so much better. Straightening and shaping lawn edges is ideally done once a year after the first spring cut but better late than never. Use either a half-moon edging iron or a sharp spade to redefine the edge.

Aim for a clean, vertical edge between the grass and the soil. Powered lawn-edge trimmers make the task easier, but these perform best on firm soils.

To obtain a straight edge, cut against a straight plank of wood or use a tautly fixed garden line and for curves, trim along an old hosepipe laid on the ground. Once you’ve cut your edge, use a spade to lift out weeds and any loose, unwanted sod.

Where the edges crumble easily or are breaking down under heavy wear, insert plastic or metal edging strips. Make sure that the top edge of the strip lies below the level of the mower blades. To keep edges looking groomed, regularly cut away any long grass that is beginning to encroach into the borders using a long-handled lawn edging shears.

This Month’s To-Do List

  • Plant out summer bedding plants around the last week of May if there is no forecast of frost. If you have grown bedding plants from seed in the greenhouse then harden them off before planting by leaving them outside for gradually increasing periods of time.
  • Sow seeds of hardy annuals direct where you want them to bloom to fill gaps in borders.
  • Thin out congested pond plants.
  • Keep an eye out for greenfly congregating around new shoots or developing flower buds on roses. Treat them promptly using an organic spray or hose them off with a little pressure from your garden hose.
  • Timely Reminder

    Plant up summer hanging baskets as soon as possible and hang them in a greenhouse or conservatory to give them a boost and establish for a few weeks before putting them outside at the end of May or early June.

    Out and About

  • Sunday 22 May: Irish Specialist Nurseries Association - ISNA Plant Fair. Venue: Airfield Gardens, Dundrum, Co Dublin. An opportunity to source interesting and unusual plants directly from the growers.
  • 2-6 June: Bord Bia BLOOM. Venue: Phoenix Park, Dublin. Gardening and lifestyle festival with impressive show gardens, talks from garden experts, food features and family entertainment. For more information and to book tickets visit
  • Mary Keenan and Ross Doyle run Gash Gardens, Co Laois, which is open to the public.

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