Winter Plant Protection On Blueberries in Northern Minnesota
Raising blueberries in Northern Minnesota can be a profitable operation if adequate snow cover comes in a timely manner, and the grower has the ability to cover the plants and provide winter protection of the fruit buds. In years past, adequate snow cover has not been a problem, but for the past 5 out of 6 years, there has been little snow, or it has arrived too late in the winter to provide any protection for the plants. Our project will investigate the feasibility of using different types of winter plant protection, including the ability to make snow to cover the blueberry plants.
Our farm is located 40 miles north of Duluth, MN where winter temperatures typically bottom out at -40 F. we raise sheep; have laying hens, a large garden and a pick your own blueberry operation of 1000 plants. Our blueberries consist of Northblue, Northcountry and St. Cloud varieties, and we can typically market 900-1500 lbs of berries. We use drip irrigation, with water provided from a nearby creek. Fertilizing consists of one application of Ammonium Sulfate in the spring, and the plants are mulched with aged wood shavings.
The idea for our grant project came during the winter of 2006-07 when we had a snow cover of only 3” for most of the winter, with most of the snow coming in March 2007. Our low in February was -34 F. that berry season we picked a total of 5 pounds of berries from 1000 plants. We realized we needed to provide some sort of plant protection for those winters when snow does not cover the plants. But what sort of cover to provide? We picked representative plots of Northcountry and Northblue varieties and used the following covers:
– Loose straw
– Loose straw covered with 1.5 ox polypropylene row cover
– 1.5 oz polypropylene row cover alone
– 1.0 oz polyester draw string plant bags
– 55 gallon plastic barrels
The plants were covered on November 14, 2008.
The questions we wanted to answer were:
– Would the loose straw blow off of the plants?
– Would the plants with straw attract rodents?
– Would the row cover cause the branches to break if we received a large dump of snow early?
– Would it be hard to remove the straw in the spring and what would we do with it?
– Can we reuse the row cover, and if so, for how many seasons?
– And most important of all, would any or all of the treatments provide the winter protection that we are looking for?
Because our grant has just started, we won’t know the answers until next summer, when berry season starts and we can measure the effects of each treatment, and the feasibility of each.
The second part of our project involved making snow. We knew that natural snow provided excellent protection. When it fell, it filtered thru the branches, and protected the fruit buds form the cold and drying winds. Was it feasible to make snow to cover the plants? Snow is made on ski hills, but could it be made on a small farm scale? We researched snow making on the internet, and found a company in Connecticut that made small scale snow equipment, basically for families in the south to make the ground white on Christmas Eve for their kids. The setup is basically a set of nozzles, a pressure washer and an air compressor. What we found out is that snow making is an energy, water and time intensive project. We tried using water from our well, but we had to run a hose 150’ to the snowmaker, and we didn’t get adequate water flow. The next option was to use our irrigating pump and pump from the creek. This gave us a good flow of water, and worked fairly well until a fitting on one of the high pressure hoses broke. After repairs were made, the operation worked well with the following things to consider:
– The snowmaking process uses at least 500 gallons of water per hour and it takes quite a while to cover many plants.
– The temperature needs to be below 27F with low humidity for the best snow.
– Any wind will blow the snow away from where you want it placed.
– Energy is used by the water pump; the pressure washer and the air compressor be it electricity or gas.
– When any part of the operation stops, water will start to freeze in the hoses, pumps etc. so the process needs to be monitored frequently. We’ll have to see if the whole snow making process is worthwhile.
Robert Olen – visited farm to provide guidance on the proposed project, including plot locations, types of coverings, and how the analysis would be done.
Dave Olafson, local berry grower – helped cover plants with the various types of row cover
Kathleen Anderson, local gardener – helped cover plants.
Our farm is located 12 miles north of Two Harbors on Hwy 2, then 12 miles west on Cty Rd 14 to Hugo’s Bar, left for ½ mile, then right on Jackpine Rd for 1 mile to Pine Creek Farm sign.
Next year is when we see if any of our winter treatment worked. We have marked off the plots for each treatment and will be measuring:
1. Plant vigor
2. Pounds of berries/plant versus control plots
3. Rodent damage
4. Branches breaking
5. Ease of removing straw
6. Ability to reuse or recycle coverings
7. Any other problems or benefits we don’t know about yet.
1. May 16, 2008 interviewd on KAXE radio grant rapids, MN about project
2. November 26, 2008 newspaper article in Duluth News Tribune about project
3. Talk at Gardening Club December 2, 2008 – 12 people
4. Tour planned for May 12, 2009
5. Tour during berry season July- August