by Cathy Heidenreich and Marvin Pritts

There’s nothing like fresh raspberries – summer isn’t the same without them. Wouldn’t it be great to have that farm-fresh taste from May to December? Whether growing for on-farm use or commercial sales, an extended season of fresh raspberries is within your reach using “protected production”.

Raspberries can be coaxed (or hoaxed) into fruiting over long periods of time. Protected production techniques such as using row covers or tunnels, together with cultural practices such as pinching or tipping, can lengthen raspberry season, even in cold climates. This article briefly describes techniques to use in order to keep those mouthwatering berries coming!

Heritage is one of several fall-fruiting red raspberry varieties recommended for protected production under floating row covers.

 

Raspberry Types

The first step in producing season long berries is to know which types of raspberries respond best to which protected production practices. Let’s start with a quick review of raspberry types.

Raspberries provide two seasons of berries if you plant both summer fruiting (floricane-fruiting) and fall fruiting (primocane-fruiting) varieties. The difference between the two? Summer-fruiting raspberries flower and fruit only on second year canes. Fall-fruiting raspberries flower and fruit on the tips of first year canes.   You can buy early, mid, or late-season varieties of both types to further extend your growing season.

 

FLOATING ROW COVERS

Floating row covers (FRC) applied in early spring can help get a jump on the fall raspberry season by accelerating flower production and fruiting.  Fruit production may begin 14-21 days earlier with March applied row covers. April applied row covers produce fruit 10-14 days earlier. FRC plants begin to fruit earlier, reach peak harvest sooner, and have higher yields that non-covered plants.

For raspberries, 0.6 oz per square yard is the recommended row cover weight. Apply row covers in early spring after snow melts but before new canes emerge from the ground. Keep some slack in the covers to allow for cane growth underneath. Anchor it well (bricks, wood strips, irrigation pipes, sand bags, pins) as spring can be very windy!

Remove FRC once canes reach 18” in height or in mid-May, whichever comes first. Remember raspberries are heat-sensitive; delays in removing covers at this point could negate any early fruiting gains.

Temperatures inside this multi-bay high tunnel are regulated by rolling plastic sides up and down and opening and closing end walls.

Kick your FRC production up a notch by applying cover only to portions of the planting at various times during the season.  Divide the planting into 3 sections, covering one in March, another in April, and leaving the final section uncovered to get the longest harvest period.

Want to extend fall raspberry harvest on the other end?  Apply FRC on cooler fall nights while primocane raspberries are fruiting to protect them from occasional frosts. Remove covers the next morning to continue gaining the benefit of late fall sunshine.

Suggested fall-fruiting red raspberry varieties for protected production under floating row covers include ‘Heritage’, ‘Caroline’, ‘Autumn Britten’, ‘Autumn Bliss’, and ‘Polana’. ‘Anne’ is a good choice for a yellow-fruiting fall-raspberry.

What’s the cost of FRC? Approximately $500 to $600 dollars per acre, and it can be used for 2 seasons. Yields for the 2-3 week harvest extension period should more than offset the cost of covers.

 

HIGH TUNNELS

High tunnels are large plastic hoop houses. Generally less expensive to build and maintain than their greenhouse cousins, hoop houses provide shelter from the elements, a protected environment for more tender varieties, and season extension for both summer and fall-fruiting raspberries.

Tunnels don’t usually have heaters, lights, or power sources. Temperatures inside are regulated by rolling plastic sides up and down and opening and closing end walls. Plants are primarily grown in the ground under tunnel covers, which are applied or removed at various points during the growing season, depending on the desired fruiting period and raspberry type. Drip irrigation is a must as no rain falls within the confines of the tunnel.

Floating row covers can be used to extend the raspberry harvest both early and late.

Choose a tunnel that will give you enough room to plant, monitor, and harvest your berry crop from inside the structure. Better results are obtained with larger tunnels that are 30 ft wide and 15 ft tall (better ventilation and heat regulation). Multiple bays can be linked together to cover even larger areas

Tunnel frames usually consist of steel pipe or tubing driven into the ground (2 ft) at approximately 4 ft intervals for the length of the tunnel. The tunnel covering consists of a single layer of 6 ml polyethylene plastic; various types of plastics are available. Vertical side walls are constructed to roll up and down to protect plants from rain and wind, and to ventilate the tunnel.

End walls should open and close as well. Peak style tunnels will shed snow better during the winter than the more rounded Quonset style tunnels. Tunnels may be single bay or multi-bay.

Summer-fruiting raspberries may begin fruiting as early as May when overwintered under a tunnel. At the other extreme, fall-fruiting varieties may continue to fruit into November. To delay harvest of fall fruiting types, pinch the tips of primocanes when canes reach approximately 3 feet in height, then wait to cover the tunnel until late summer just as bloom begins. Floating row covers may be added over plants under tunnels for occasional nights when predicted temperatures are expected to dip below 220F to protect maturing fruit from damage. FRC also can be applied in early spring under the tunnel to accelerate emergence of primocanes.

Benefits of tunnel raspberry production include protection from rain, wind, and hail, reduced disease and pest pressure, larger fruit size, increased yields due to a longer harvest period, and better shelf life in refrigerated storage.

Suggested varieties for tunnel production include ‘Autumn Britten’, ‘Caroline’, ‘Heritage’, and ‘Josephine’ (my personal favorite!).

Tunnels vary in price depending on style, materials and size. A 30 x 96 ft tunnel with 4 rows of fall-bearing raspberries constructed in Ithaca, NY cost approximately $11,000 to purchase and install, including tunnel, land prep, and plants. Planting life is estimated to be 10 years. Initial investment for this tunnel is calculated to be recouped in year 3, along with a $4,300 profit. Gross revenue in subsequent years is estimated to be $8,100 excluding $2,500 in production and harvesting costs; projected yields are expected to be 2,700 half pints per season each year.

Cathy Heidenreich is Berry Extension Support Specialist for Western NY. She can be reached at 315-787-2367 or mcm4@cornell.edu. Marvin Pritts is professor and chair of the department of Horticulture at Cornell University College of Agriculture and Life Sciences. He may be reached at 607-255-1778 or mpp3@cornell.edu .

Resource Spotlight: Raspberry Resources

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