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Raspberries – planting and maintenance

There was a time when every prairie garden had a row of raspberries. And, why not? They’re hardy, not difficult to care for, generally insect and disease-free and well worth the effort.

There was a time when every prairie garden had a row of raspberries. And, why not? They’re hardy, not difficult to care for, generally insect and disease-free and well worth the effort. Nothing can beat a handful of sun-kissed raspberries, fresh off the canes in July and August.

Raspberries should remain productive for 10 to 20 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 such as compost, peat moss or well-rotted manure. Avoid frost pockets or areas of poor drainage and provide shelter from wind.

Spring planting is preferred as plants break dormancy fairly early. This also allows for the development of a healthy root system during the first year. Canes should be set at the same depth or up to five centimetres deeper than they were previously planted. Water immediately. Space raspberry canes 25 centimetres apart within the rows, with rows one metre apart. Within three years, a continuous “hedgerow” will develop.

Do not allow the canes to dry out during their year of establishment. Thereafter, ensure they are watered from bud development through fruiting. They’ll require about 2.5 centimtres of water per week from first bloom to last harvest. After August, irrigate only enough to prevent stress on the new canes (primocanes) that will fruit the following year. Once canes have entered dormancy in late fall, give them one final watering prior to freeze-up.

Because there is a direct relationship between the vigor and diameter of canes and fruit yield, it is important to promote vigorous cane growth early in the growing season. A spring application of a high phosphorous fertilizer such as 16-20-0 is recommended.

Control weeds through shallow (five to eight centimetres) cultivation. Remember, 70 per cent of the root system is within the top 25 centimetres 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.

Mulching (i.e. placing a permanent 10 centimetre layer of organic material on the soil surface between the rows) may be a better alternative to cultivation. Weed-free straw, post peelings, leaves and grass clippings will all do the job. The advantages of using mulch include moisture conservation, decreased daily soil temperature fluctuation, weed control 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 provide easier picking.

There are a number of reasons for pruning raspberries. If left uncontrolled, plantings can become jungle-like with fruit in the centre going unpicked. Restrict the row width to 30 to 45 centimetres. Each spring, limit cane density by removing the less productive smaller, weaker and later-developing canes. Also remove last year’s fruiting canes (alternatively, can be down in fall following harvest). Aim for 15 canes of 1.3 centimetres or greater diameter per metre. Thinning increases yield, berry size and berry quality on the remaining canes. Fruit size is directly related to cane diameter. Larger canes produce larger fruit.

Sara Williams is the author of the newly expanded and revised Creating the Prairie Xeriscape; Gardening, Naturally: A chemical-free handbook for the Prairies; and the Saskatoon Forestry Farm Park & Zoo: A Photographic History. Sara will be leading a garden tour to Great Britain in May, 2016 and co-leading, with Melanie Elliot, a tour of Fauna and Flora of Iceland in July, 2016. Call Ruth (1-888-778-2378) for more information.

GardenLine is open for the season to solve your garden problems: 306-966-5865; gardenline@usask.ca

— This column is provided courtesy of the Saskatchewan Perennial Society (www.saskperennial.ca; hortscene@yahoo.com). Check out our Bulletin Board or Calendar for upcoming garden information sessions, workshops and tours: Labour & Learn (Aug. 29); Forestry Farm House: Open House and Walking Tour (Aug. 30).