by Sara Williams
Saskatchewan Perennial Society
“There was a man in our town
And he was wondrous wise;
He jumped into a bramble bush
And scratched out both his eyes.” Mother Goose
Yes, they can be thorny, but there was a time when there was a raspberry row in every prairie garden. And why not? They’re hardy, easy to care for, generally insect and disease-free, making them well worth the effort. Nothing beats a handful of sun-kissed raspberries, fresh off the canes in July and August.
The genus name, Rubus, is from the Latin word for red, while the species name, idaeus, was named by Linnaeus to honor Mount Ida in Greece where raspberries were believed to have originated and where the Greek gods were said to have gone berry picking.
The red raspberry is native to temperate regions of North America, Europe and Asia. Wild raspberries were gathered in the wild for thousands of years before they were grown in gardens. The Greeks and the Romans used them medicinally before they were commonly eaten as a fruit. By the 16th century, they were a common plant in English gardens, and European settlers brought raspberry selections with them when they arrived in North America.
Raspberries should remain productive for ten to twenty years, so careful site selection and soil preparation is important. A good loam-based soil in full sun is recommended. Ensure that the soil is weed-free (especially of perennial weeds like quack grass) and well amended with organic matter (e.g. compost, peat moss, well-rotted manure). Provide shelter from wind and avoid low-lying, frost-prone or poorly drained areas.
Plant in the spring as plants break dormancy fairly early. This also allows a healthy root system to develop during their first year. Canes should be set at the same depth or up to 5 cm (2 in.) deeper than they were previously planted. Space the raspberry canes about 23 cm (9 in.) apart within the rows, with rows 90 cm (3 ft.) apart. Water immediately after planting. Within three years, a continuous “hedgerow” should develop.
Do not allow the canes to dry out during their establishment year. In subsequent years, water your raspberries from bud development through to fruiting. They’ll require about 2.5 cm (1 in.) of water per week from first bloom to last harvest. After August, water only enough to prevent stress on the newly formed canes. Once canes have entered dormancy in late fall, give them one final watering prior to freeze-up.
There is a direct relationship between fruit yield and the vigor and diameter of the canes – the thicker the canes, the larger the fruit. Therefore, it is important to promote vigorous cane growth early in the growing season with consistent watering and a spring application of a high phosphorous fertilizer such as 16-20-0.
Control weeds through shallow (5-8 cm / 2-3 in.) cultivation. Raspberries have a fibrous, long-lived perennial root system. Remember, 70% of the root system is within the top 25 cm (10 in.) of the soil surface and deep or careless cultivation may damage the roots. Avoid cultivation once fruit begins to form in mid- to late June.
A better option than cultivation for controlling weeds is mulching (placing a permanent 10 cm / 4 in. layer of organic material on the soil surface between the rows). Weed-free straw, post peelings, leaves and grass-clippings will all do the job. Besides weed control, other advantages of using mulch include moisture conservation, decreased daily soil temperature fluctuation and cleaner picking. Apply the mulch in the fall following the first season of establishment.
Depending on the cultivar, raspberries may be grown in unsupported hedgerows or with the support of a trellis made of poles and wires. Trellises are used when canes are very tall, weak, or simply to make picking easier.
Most raspberries have a biennial growth habit. First year (“primocane”) growth is rapid and vegetative (leafy), taking place in spring and early summer. These canes are mostly unbranched. During their second year, these canes (now called “floricanes”) flower and fruit. Buds in the middle portion of the cane are the most fruitful. Canes do not increase in height during their second year, and after fruiting, they die. At the same time, new canes are produced to replace them for the coming season.
There are a number of reasons to prune raspberries. If left uncontrolled, plantings become jungle-like with fruit in the centre often going unpicked. Keep the row width to 30-45 cm (12-18 in.). Suckers are usually initiated in the fall, when they grow only to the soil surface. Additional above-ground growth of the suckers occurs the following spring. Each spring, remove the small, thin, less productive canes, produced randomly from the roots (further from the established row). Also remove last year’s fruiting canes – these canes will be have side branches (alternatively, this can be done in fall following harvest). Keep the vigorous, more productive canes that are produced from the crown at the base of the plant. Aim for 15 canes of 1.3 cm (0.5 in.) or greater diameter per meter (40 in.). Thinning increases yield, berry size and berry quality on the remaining canes.
Sara Williams, with Bob Bors, is the author of Growing Fruit in Northern Gardens.
This column is provided courtesy of the Saskatchewan Perennial Society (SPS; firstname.lastname@example.org ). Check our website saskperennial.ca) or Facebook page (facebook.com/saskperennial). All Saskatchewan Perennial Society events are on hold until further notice.