Raising horticultural crops in high tunnel (HT) systems in temperate climates contributes in multiple ways. In raspberries, return on investment (ROI) can be realized within 2 seasons, sometimes sooner.

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Unheated coldframes are compatible with perennial crops that require vernalization, such as raspberry. While most fruiting plants bear just once per season, certain varieties of raspberries may produce thrice inside coldframes, depending on winter survival of canes.

We planted several ‘everbearing’ raspberry varieties inside HT, in order to prevent crop damage from frosts during fall (September – October). We assumed that berries will mature if protected, possibly producing early berries as well (season extension), since overwintering canes are capable of producing second crop. Little did we anticipate the extent that protected environment can play on yield & quality of berries: 4-5 fold higher yield, larger, more firm berries & higher brix, compared to field grown ones. Native pollinators & honey bees accompany the crop until the very end.

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Marketing high tunnel grown raspberries through local stores & PYO has been rewarding. Though priced higher than non-local, customers are willing to pay premium for high quality, organic local berries.

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Basic setup of HT include: side vents (roll-up curtains), irrigation & 6-10’ high parallel trellis, depending on variety. It’s best to grow assortment of 3 or more varieties, including red, yellow & black; packaged multi-color berries sell well.

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Minimum spacing between rows is 6’, for ease of pruning & harvest. Preplant incorporation of manure (green ok) will benefit in higher production early on. Landscape fabric helps to manage weeds, as well as spotted wing Drosophila (SWD) population. Harvest season ends in late October, 4-5 weeks on average past field grown raspberries.

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Impervious netted vents to SWD (60-80 holes per square inch, 1.35 mm size) prevent infestation, though materials are quite pricy at this time. Japanese beetles were not encountered in HT, whereas significant damage has been sustained on those grown outside. Bird damage can be significant, therefore preventing their entrance is important.

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Return on Investment

Return on investment can be realized quickly when you raise raspberries in a high tunnel, for the following reasons:

• Season extension

• High quality & yield

• Predictability & reliability

• Protection from adverse weather & pests

• Changing hardiness zone enables more varieties to be grown locally

• Ease of harvest & improved working environment during off season.

About the Author

Sam Kedem owns and operates Sam Kedem Nursey & Garden in Hastings, MN. Established in 1996, the farm became certified organic in 2006. The farm offers an extended season of pick your own and picked strawberries, raspberries, blueberries, gooseberries, currants, apples, plums, cherries, pears and vegetables, and also features a diverse farm store.

Please contact us if you would like to get in touch with Sam.