Carolyn Singer
Special to The Union

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March 22, 2013
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Raspberries and rhubarb; Two crops with very different cultural requirements

Brightened with daffodils, permeated with the heady spring fragrances of flowering shrubs and trees, this season of renewal once again excites the senses.

Planning for the edible garden continues in earnest. March is the perfect month to prepare for an abundant harvest of two of my favorite perennial edible crops.

Each year I share sections of root from my very red rhubarb, carefully digging a piece from the main plant to include a shoot already showing red, a thick section of the primary root and secondary roots that absorb nutrients and moisture.

This week is my last week to divide rhubarb. Already white roots are showing, tiny and delicate, although the soil is still cold.

The root section I dug most recently is going to one of the hosts of the “Garden Guru” Saturday show at KAHI in Auburn.

Recently we chatted about rhubarb on the show to answer his questions about this amazing plant. Last year I harvested about 30 pounds from two 20-year-old plants.

Growing in heavy clay soil liberally amended with composted manure and rock powders (rock phosphate and oyster shell), the original planting holes need to be 2 feet deep and as wide.

Mulches of decomposed straw and manure close to the crown may be renewed each year, but the crown itself should be free of mulch to avoid damage.

Good drainage is essential. Once mature, rhubarb requires very little irrigation.

In our hot summer, the plant is usually dormant.

Warming weather in late spring provides an extended harvest if there are no hot spells.

In cool summer microclimates, rhubarb harvest is enjoyed for several weeks.

Each stalk is pulled at the base, not cut, to remove it from the crown without leaving any portion of the stalk.

The raspberry harvest comes later in the summer, its timing and duration determined by several factors: age of the plant, pruning technique, elevation, exposure (sun and shade) and cultural practices (soil fertility, irrigation and mulch).

Even timing of the first fall frost, which is completely unpredictable, affects the late harvest.

In my garden at the 2,650-foot elevation, I grow primarily ‘Heritage’ raspberries, although I continue to experiment with other cultivars for comparison. The raspberries growing in full sun are the most productive.

However, in nearby Peardale, I have seen very healthy plants and harvest where some afternoon shade gave a break from the summer heat.

The soil is prepared with compost and rock powders to a depth of 8 inches. Raspberries have shallow roots, and while the soil preparation does not need to be deep, the mulch is critical.

Each year, I mulch with 2 to 3 inches of decomposed straw (oat or wheat, not rice) topped with an inch of composted chicken manure.

This is a winter activity before growth shows at the crown of the primary plant. One of my raspberry patches is now 20 years old and still very productive.

Water the raspberries a minimum of once a week during the warm and dry summer months. They thrive with consistent moisture.

Maintaining moisture in the mulch cools the roots. The plants may almost believe they are growing in the Pacific Northwest.

A portion of the patch is pruned to an early crop (June in my garden), removing only the tip of canes that grew last year but did not produce fruit. Most of the plants are pruned to the crown in winter, leaving no portion of the cane from last year. New canes will provide this year’s fruit, beginning in July in my garden.

In early summer, some of the taller canes are tip-pruned, removing the top 1 to 2 inches, before buds form for bloom, to force laterals to develop for heavier fruiting.

This practice delays the harvest and is not advised for gardeners in cold fall climates or for raspberries growing where they are shaded when the sun is lower in the sky in September and October.

In the Sierra foothills, with the warm days we usually enjoy into November, my small patch of raspberries tip-pruned usually gives me two quarts of raspberries a day.

Only one year, when fall cold slowed ripening, the raspberries pruned for late production did not yield the anticipated November harvest.

However, each year I will continue to tip-prune a portion of the plants. It’s worth the gamble!

Carolyn Singer has gardened organically in Nevada County since 1977. She is the author of “The Seasoned Gardener, 5 decades of sustainable and practical garden wisdom”, now available locally. For more information, visit www.carolynsingergardens.com.


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The Union Updated Mar 28, 2013 03:32PM Published Mar 27, 2013 05:49PM Copyright 2013 The Union. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.