Plants - Roses

Scents and Sensibility

Judith Adam
Photography by
Photography by Tracy Cox

By choosing wisely and planting well, most Canadian gardeners can grow armloads of fragrant roses

The Austin English roses are among the most highly perfumed shrubs and set standards in colour and form. Most are reliably hardy to Zone 6, (Zone 5 with winter protection), though the Canadian Rose Society Web site recommends 'Graham Thomas', 'Mary Rose', 'Sweet Juliet' and 'Charles Austin' for gardens in Zones 2 to 4. Austin roses are especially attractive when planted in groups of three or five with a complementary underplanting of perennial alpine strawberries. The plants are hybridized cultivars of Fragaria vesca, the woodland wild strawberry. Alpine strawberries, which have no runners, are reliably hardy (Zone 4) and form thick, leafy clumps that shade the soil and help to keep rose roots cool in hot weather. The plants produce charming white flowers from May through October and tiny, delicious berries.

Understanding some of the principles of rose scent helps in selecting plants with strong fragrance. The essence of fragrance is stored in tiny chloroplast cells on the undersides of petals. Thicker petals with a velvety sheen have more scent potential than thin, paper-like petals. Colour is also an indicator of types of fragrance. Red and pink petals tend to exude pure Old Rose perfume, with hints of raspberry and anise, while yellow and white petals are more complex, combining scents of orrisroot, nasturtium, violet and lemon. Banana, citrus, honey and clover frequently perfume orange shades.

Human olfactory abilities are calculated to be 10,000 times more sensitive than our sense of taste, allowing us to appreciate subtle differences in scent between rose cultivars and to remember the fragrance of a favourite rose. When sunlight heats the petal chloroplasts, production of scent-making chemicals is increased and released as vapour to waft through the garden (scented roses give off more fragrance midday, after the air has warmed). Drought and inconsistent watering are the greatest hindrances to the intensity of the scent of fragrant roses. And so, a word to the garden-wise: water in the morning, and swoon all afternoon.

Trade secrets
Professional growers accelerate plant maturity by giving roses three growth stimulants.

When planting roses, use a transplant solution containing vitamin B1 (thiamine). Thiamine increases plant metabolism, helps to avoid transplant shock and will increase the plant's ability to absorb carbohydrate nutrients-and grow faster!

Magnesium sulfate, sold as Epsom salts (9.8 per cent magnesium and six per cent sulfur), encourages new and strong canes to sprout from just above the graft union. These are the main structural canes and will eventually carry many flowers. Apply 125 millilitres (1/2 cup) of Epsom salts to each plant in early May and again in early July, either dissolved in water or lightly scratched into the soil. Or make a foliar spray of 15 millilitres (one tablespoon) of Epsom salts to 4.5 litres (one gallon) of water.

A foliage drench of liquid kelp extract every four weeks, applied early in the day, increases rose scent, cold hardiness and disease resistance. Follow product instructions.

Fighting blotches and beasties
Rose flowers and foliage can be burned and disfigured by the overuse of synthetic pesticides. Most homemade pesticides are safe and effective.

To prevent blackspot diseases on leaves, spray rose foliage every seven to 10 days with a solution of 15 milli-litres (one tablespoon) each of baking soda and liquid soap dissolved in 4.5 litres (one gallon) of water.

Kill green aphids and whiteflies with a spray of equal parts water and three per cent hydrogen peroxide (which can be purchased at a drugstore) applied weekly during dry weather and twice weekly during wet weather. The peroxide also promotes bud sprouting and deepens green leaf colour.

Spray slugs with a mixture of one part household ammonia and 10 parts water. Slugs are most active between 10 p.m. and 2 a.m., so bring a flashlight.

A decent meal & a good drink
It takes a lot of energy to produce armfuls of scented roses. Plan on providing a meal of rose fertilizer in early May and then again immediately after the June blossoms are finished. A third application can be applied no later than the first week of August to trigger a flush of autumn flowers in re-blooming types. Be sure to provide only the amount recommended on the fertilizer package: rose roots are easily burned by excessive fertilizer. In October, give each rosebush a generous meal of one bucket of rotted manure, gently trowelled into the soil over their roots.

Rose petals are almost entirely composed of water; consequently, the size and scent of roses are dependent on adequate and regular water availability. On a hot day at the peak of summer, roses growing in full sun will take nine litres of water from the soil. Organic mulch around the roses will help to prevent moisture loss, and a regular irrigation schedule (at least twice a week in warm weather) is absolutely necessary for maximum flower production. Avoid wetting rose foliage by watering at ground level, laying a slowly running hose at the base of each plant or using a soaker hose system. Water long enough to moisten the soil to a depth of 30 centimetres.

The best hole possible
The day a rose shrub is planted into the garden is the most important of its life. If the hole is inadequate-too small and with poorly prepared soil-the shrub's root development will be truncated and unable to support a strong plant. To create the best hole pos-sible, dig out a 60-centimetre-square area for each rose and remove the soil entirely. Prepare a backfill soil of one part coarse sand, one part peat moss mixed with shredded bark and one part good-quality loam enriched with well-rotted manure. Set the plant's bud union (the bulging green knob just above the roots) five centimetres below soil level and backfill with the prepared soil mix. Mulch the soil surface over the rose's roots with 7.5 centimetres of shredded bark or leaves and slowly pour 4.5 litres (one gallon) of water through the mulch and into the hole.

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