Round Robin: Herbal Insecticide and Herb Sale Advice

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NEWBERG, Oregon–April is the month of plant sales here in the ­Pacific Northwest. They are listed in the paper every weekend, and with the participation of local botanical ­gardens and garden societies, the selection of plant material is great, and plant buyers are in earnest. Even among genteel gardeners, the law of the jungle reigns: the first in line get the choicest plants. After a long, cold winter, I relish visiting as many sales as ­possible and returning home with an armload of plant booty. This year, I’m particularly interested in acquiring some of the newer lungwort introductions, among them Pulmonaria ‘Little Star’, P. ‘Benediction’, and the superb P. ‘Roy Davidson’. Lungworts are excellent choices for moisture-retentive soil in partial shade. These cultivars all form low, clumping mats of robust, dark green foliage with beautiful silver spotting, followed by deep blue flowers (sky blue and pink for ‘Roy Davidson’) in spring. They go particularly well with our native dogtooth violets (Erythronium spp.) and with the foliage of wild ginger (Asarum canadense), whose curious brown flower is hard to spot.

I use variegated comfrey (Symphytum grandiflorum ‘Variegatum’) in my shade garden for foliage contrast to make the garden less gloomy. This noninvasive cultivar has rich, golden-creamy leaf margins and creeps modestly above the ground. The much rarer upright variegated comfrey (S. ¥ uplandicum ‘Variegatum’) has white margins.

In Seattle last year, I acquired an unusual cultivar of buckler sorrel known as Rumex scutatus ‘Silver Shield’. The leaves have the tart taste of French sorrel (R. acetosa) but shimmer like small silver shields (bucklers). The plant survived last winter easily in partial shade.

The aphid populations have successfully overwintered and, with the warmer temperatures, are now massing for an all-out attack on the garden. In the greenhouse, I use yellow sticky cards to monitor pest populations, but outside, I periodically inspect the undersides of the leaves of indicator plants such as bronze fennel and sweet violets to tell me when things are getting out of hand. A tea made from the flower heads of feverfew (Tanacetum parthenium) combined with a teaspoon of dishwashing liquid per quart of solution has proven to be a most effective contact insecticide against aphids.

I also keep an eye out for the strawberry root weevil. Notorious for damaging strawberry and rhododendrons alike, it will also chew the leaf margins of my beautiful yellow-flowered English cowslips (Primula veris). This weevil is persistent and destructive and has inspired me to use some fairly lethal soil drenches.

With the birth of our new baby, Kathleen, in January, I am only now getting around to preparing the soil for a new herb garden. The straw that I put on last fall is nicely composted; I plan to double-dig the entire area (turn the soil to two spades’ depth) to place the organic matter down where the roots can appreciate it. This method will break up any compaction of our acidic, heavy clay soil. The organic matter I’ve added will improve aeration, increase the availability of nutrients, and create better drainage, and I’ve topdressed with a water-soluble pelleted lime called Calpril to lower the soil’s acidity. Now, all I need is the time to go out and start digging!

Andy Van Hevelingen operates Van Hevelingen Herb Nursery in Newberg, Oregon.

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