Alaska Pioneer Fruit Growers Association

Raspberry Production in South-Central Alaska

December 23, 2007

Dwight Bradley

 

We’ve been growing raspberries organically for at least 10 years and now have about 600 feet of raspberry row.  Here are some lessons learned.

 

Raspberry basics

Raspberry roots live for many years, but the canes themselves are on a two-year life cycle.  During year one, a new cane will sprout from the crown of the mother plant and grow in one year to as tall as 8 feet.  This is called the primocane.  During year two, last year’s primocane becomes this year’s floricane.  It produces side branches on which the berries form.  Then, in the fall or early winter of year two, the floricane dies.

 

Raspberries spread (and propagate) by rhizomes, from which new canes will sprout, usually a few feet from the mother plant but occasionally farther out.

 

Fatter canes tend to have bigger berries.  Also, the higher up the plant, the smaller the berry.  These facts are behind the recommendations on thinning and topping, below.

 

In Peters Creek, the first berries are usually ripe in late July to early August.  The height of the season comes quickly, about two weeks after the first berries.  Fruit production then tapers off, but continues until a succession of killing frosts in late September or October.

 

Row spacing

We have no shortage of land. So, when we put in the berry patch (behind 8-foot fencing, to keep out moose and llamas) we decided to space the rows a comfortable distance apart—10 feet on centers, or eight feet between trellis wires.  This was meant to be wide enough to drive our tractor between the rows so that (1) we could spread an annual dose of composted manure, and (2) cultivate with a disc harrow.  In hindsight, the disc harrow was not the right tool for this job because over time, it gradually moved soil from the walkways into the rows, until after a few years, the discs would no longer even touch the ground in the middles of the walkways.  If we were to do it over again, we’d space the rows 7 feet on center.  Anything less will be too crowded during picking season, when wet, thickly vegetated canes lean into the walkways.

 

Plant spacing

Both in Alaska and the lower 48, the standard practice is to grow raspberries as one would a hedge—thickly spaced.  To us, it makes more sense to treat them like grape vines in a vineyard: individual, well-spaced plants, which all happen to share the same wire trellis for support.

 

When we planted our berry patch, we followed instructions from somewhere in the Lower 48, planting our rows 2 feet wide.  After a couple of years, the original plants had spread nicely and we were thinning them down to two or three floricanes per foot of row.  This turned out to be way too dense.  We now think that the optimum spacing is one robust floricane per two feet of row, so that each floricane has plenty of elbow room.  (For Fallgold, which has a three-foot diameter, use a three-foot spacing.)  More about this under “Rain and mold”, below.  As for the width of the row, two feet is too much.  If we were to start over, we’d go with 12 to 16 inches. Two feet is so wide that it gets to be a jungle, and many berries are lost in the middle, falling ripe to the ground or molding before ever being noticed.  Also, two feet of row means two feet of weeds.

 

Pruning and Training

A well-kept Alaskan raspberry patch needs to be pruned several times a year.

 

Mid to late May.  As the snow leaves, there will be two types of canes: last year’s dead canes and the current year’s floricanes; new primocanes will soon be poking up but are not yet visible.  Remove any dead canes that fruited last year.  These are pretty easy to spot because there have side branches, often with shriveled berries. Don’t remove any of the new year’s floricanes except those that are obviously broken beyond healing.  Some canes may need to be picked up and tied to the trellis wires.  Sometimes it takes longer for some canes to leaf out than others, so the best bet is to wait awhile before deciding what’s dead and what’s alive.  Also, the higher buds on a cane will leaf out later, so don’t prune off any “dead” tips prematurely.

 

Late June to early July.  Now is the time to thin the floricanes to 2-foot spacing in the row, and to take out any that turned out to be dead.   Also, by now there will be many new entirely green primocanes that might be anywhere from a few inches to a few feet tall.  Select a few nice fat ones about a foot apart, and cut the rest out.  By now the weeds (especially nettles, lamb’s quarters, and various grasses) will be a couple of feet tall and we usually do battle with them at this point. We use long-bladed hand shears for pruning and weeding because they are strong enough for even the toughest canes, and will efficiently handle big handfuls of grass and weeds.

 

Early August.  A third pruning is called for about when the first berries are getting ripe. Some floricanes will tend to lean out into the walkways or parallel to the trellis wires, and these need to be set upright and tied (with a bag-tie or flagging tape) to the trellis wires.  Use the long-bladed hand shears on any tall weeds and any new primocanes that are more closely spaced than one foot.  This is important, as a lush wall of primocanes will completely block air circulation and this is key to mold control (see below).  Also, top all primocanes 4 to 5 feet off the ground.  This will make them put more energy into thickening and less into growing taller.  Tall canes are more likely to be badly bent or broken by the snow.

 

Late September to early October.  After the killing frost, cut out all spent floricanes.  If any were missed in August, top primocanes at 4-5 feet.  Burn, chip, or compost all prunings.

 

Mid October or later.  In early winter, there is a real danger of early snow or ice storms that will destroy what are due to be floricanes next year.  The best defense is to make sure that all the green leaves are off, so that the canes won’t be so badly weighed down. Leaves come off best when they’re frozen, below 20°F or so.

 

Throughout the growing season, another thing that is always an issue is encroachment into the walkways. New primocanes will constantly be sprouting in the walkways.  Usually there will be really nice thick ones that come up just outside the trellis wire.  Be ruthless and keep the walkways mowed and clear of all primocanes, even the big ones that just miss being in the rows.  The one exception is that if you foresee a need for some new plants, you can leave some in the walkways that will be dug up next spring.
Trellising

We use a trellising system resembling a line of short telephone poles, with two cross boards on each pole, and two wires on each side.  Six-foot treated fence posts (5-6” diameter) are buried 2 feet.  The end posts need to be braced to prevent tipping, which will happen over the years from the tug of the wires.   The posts are spaced about every 20’ in the row.  Two feet and four feet off the ground, 2” by 4” cross boards are spiked into each fence post.  Steel cable (about 1/8”) is tightly strung along the ends of these cross boards.  The length of each cross board will dictate the width of the raspberry row.  As mentioned above, our rows are 24 inches wide and this is too much: 12 to 16 inches would be better.

 

Cultivation

We gave up cultivating years ago after the problem with disking.  Now the walkways are in grass which is kept down to the extent possible with mulch of straw, wood chips, and chipped raspberry canes.  The ground is level and smooth enough to mow but the grass does get pretty tall sometimes, being low on our priority list.  We weed by hand among the canes in July, but never very thoroughly.  Also, we have a mower-style weed whacker.

 

Fertilization

One shovelful of composted horse manure per foot of row, every spring.  If we had more time to do the work, we’d double the dose.  Raspberries love nitrogen.  In fact, the reason they send out rhizomes is because they quickly deplete the soil near the mother plant.  To keep the plants happy in their rows, they need annual feeding.

 

Picking

We pick into green plastic one-pint mesh containers that we bought in a batch of 1000 from a supplier in the Lower 48.  At the height of the season, rows need picking every two days.  During the peak, a person can pick a pint of Canbys in a couple of minutes.  This year we picked 60 pints in a single weekend.

 

Rain and mold

Every year, around the start of picking season, the rains begin and the temperature drops into the 60s and then 50s.  Perfect weather for the mold Botrytis.  The mold attacks ripe berries, unripe berries, flower buds, leaves and twigs.  Some berries (for example Canby and Fallgold) will taste horrible when first infected, before they show any outward sign beyond a certain damp softness that one quickly learns to recognize by feel.

 

There are two common-sense remedies.  The first is to pick off any moldy berries.  In this it pays to be assiduous, because one moldy berry high up will shed millions of spores that can and will land on anything nearby or below.

 

The second remedy involves very through pruning to ensure that lots of air can flow all around each plant. This is the main reason behind the drastic pruning recommendations given above.  Rain and mold can be a real problem at picking time. The rain makes it unpleasant to pick, so ripe berries sit there and then get moldy. The moldy berries make it even more unpleasant to pick, so they sit there and shed millions of spores that infect more berries.

 

Cultivars

Red raspberries: 

Canby. This is by far the best.  Big, thornless, sweet, tasty, good keeper, productive, vigorous, hardy.  In 2006 it was still yielding a few sweet, reasonably large berries as late as Oct. 10, a couple of weeks after a killing frost.

 

Killarney and Boyne. Good commercial types for the Lower 48 but not as good here as Canby.  In Peters Creek, they tend to be more tart than Canby, and not quite as prolific.  Both are hardy.  Killarney bears well into the fall, while Boyne plays out a bit sooner.  Killarney once won us a Grand Champion ribbon at the Alaska State Fair.

 

Purple raspberries:

Royalty.  A cross between red raspberry and black raspberry, though not as good as either.  I appear to be the only Bradley who cares much for the taste. Prolific and much loved by yellow jackets, who will mar each berry.  Supposedly not too hardy but ours have been thriving for six years or so.

 

Yellow raspberries:

Fallgold.  Vigorous, heavy bearing.  The fruiting season doesn’t end until winter sets in.   Some people (myself included) like them quite a lot, though most prefer red varieties.  The fruit forms on long side branches, so the fruiting bush has a 3-foot “footprint”.  (The red varieties have diameters closer to 2 feet.

 

Propagation

As noted above, raspberries spread by sending up new canes from rhizomes that spread underground from the mother plant.  Raspberry plants are easily propagated in the spring when the soil has thawed, but before much new growth has started.  It is far better to dig up a floricane that started the previous summer than a new, tender green primocane.

 

Raspberries also propagate by seed but they cannot be relied on to come true to seed, so this technique is only used in breeding new varieties.