Peony problems and pillaging pests

It’s peony season in our cottage borders and few plants can match them when it comes to flamboyant flowers.

Growing them can be a bit of a lottery though as each year’s blossom is very weather dependant — if it rains at the wrong moment, their opulent blooms may become so waterlogged that they look like soggy tissues. But if the sun shines, they are captivatingly beautiful.

I am often asked by our garden visitors why their peonies do not flower? Peonies are fussy about planting depth and they fail to flower, most often, when planted too deeply. Plant them so that the ‘eyes’ or buds are no more than about 3cm below the soil surface. Sometimes plants that started out at the right depth end up too deep where the soil level is raised over time by layers of mulch and they stop flowering. The solution is to lift the plant in autumn and replant it.

Plant fair

It’s good to make time to visit other people’s gardens too as this can be a great source of ideas and introductions to previously unfamiliar plants. A few weeks back, I went along to a plant fair, organised by the Irish Specialist Nursery Association, at Airfield Gardens in Dundrum, Dublin. The gardens were picture-perfect on the day with some breathtakingly beautiful plant associations.

I was particularly awestruck by the walled garden which presented a romantic confection of drum-stick alliums rising above a sea of catmints and other low perennials, all perfectly complementing the wisteria-clad pergola and one of the best-flowering specimens of the Judas tree, Cercis siliquastrum, that I have ever seen.

It was a very inspiring day out and of course, I also came away from the plant fair with some new gems including a gorgeous perennial geranium, Geranium nodosum ‘Blueberry Ice’ from Gortkelly Nursery. Highly desirable, its rich, velvety purple flowers are edged with lilac and overlaid with a shimmering lustre.

Red lily beetle alert

While planting my new acquisitions, it was with horror that I discovered chewed leaves on a group of lily plants, a sure sign that the dreaded red lily beetle has found our garden. The spread of this relatively new garden pest is on the increase across Ireland and closer inspection revealed just two of the bright red beetles which are easy to spot. They attack not only lilies, but also fritillaries, cardiocrinums and Solomon’s seal. Day lilies are not affected. Both the adults and their larvae have a voracious appetite and can devour a lily plant in a few days.

Adult beetles overwinter in the soil and reappear in spring, flying to find newly emerging host plants and laying eggs resembling tiny grains of orange rice on the underside of leaves from April until September. When they emerge, possibly to deter predators, the larvae cover themselves in their own disgusting-looking, brown-black excrement.

So far, I have found only those initial two invaders and some eggs, but I’m now on full alert.

The best way to keep these beetles under control is to be vigilant and to diligently pick them off and dispose of them as soon as you see them. Examine your lilies carefully, several times a week, beginning as soon as the plants emerge from the ground in spring. If they sense disturbance, the adults immediately drop to the ground and quickly vanish into the soil.

Be prepared to capture them quickly by holding a jar of hot, soapy water under them so that they drop into the water and you can then destroy them. Make sure to scrape off the larvae and remove any eggs as well.

Sunflower oil and neem oil, a botanical insecticide from the neem tree, are both used as effective organic controls. These should be applied at the first sign of attack. Treatment is more effective on larvae than on adults.

This Month’s To-Do List

Timely reminder

Box plants that are trained into geometric shapes or grown as a hedge should be trimmed once a year around the end of June. This gives the plant enough growing season to develop mature wood before autumn which reduces risk of frost damage and strengthens resistance to box blight. Avoid the urge to trim more frequently to maintain shape as over-clipping weakens the plant. Application of a liquid seaweed feed post-clipping also helps boost the plants ability to resist box blight. Only prune in dry conditions and make sure to disinfect any pruning tools used both before and after trimming and between each plant to minimise potential spread of blight disease. Choose a dull day for trimming as hot sun may cause scorching of leaves.

Out and About

Mary Keenan and Ross Doyle run Gash Gardens, Co Laois, open to the public. www.gashgardens.ie

Read more

Mary’s Garden: train a laburnum arch

Mary's Garden: Embracing shade and tantalising tulips