Building a Two-Wire Raspberry Trellis with 12-Gauge Galvanized Wire: 24-Inch Crossarms at 48 Inches, Posts 20 Feet Apart, and 92 Feet of Wire for a 40-Foot Row

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Set three 7-foot posts 30 inches deep at 20-foot spacing, bolt a 24-inch 2x4 crossarm to each at 48 inches, and run two strands of 12-gauge galvanized wire through holes near the arm ends. The canes grow between the wires, which sit 22 inches apart.

What wire and spacing does a home raspberry trellis need?

Number 12 or 14 galvanized wire on wood posts 15 to 20 feet apart, with two wires about 18 to 24 inches apart carried on crossarms 3 to 4 feet above the ground. The canes grow up between the wires, so the row stays upright and you can pick from both sides.

Iowa State University Extension's raspberry trellis answer lists No. 12 or 14 galvanized wire, posts 3 to 5 inches in diameter and 6 to 8 feet long set 2 to 3 feet deep, and 15 to 20 feet apart. It puts a 24- to 30-inch crosspiece near the top, with wires about 18 to 24 inches apart and 3 to 4 feet up.

Penn State Extension's raspberry production guide describes the supported hedgerow trellis as wires running the length of each side of the row. It also says mowing along the sides keeps the base of the row about 12 inches wide.

Trellis Math for a 40-Foot Row

Part Qty Size How it is figured
Wood posts 3 7 ft., 4 in. diameter 40 ft. / 20 ft. = 2 spans
Post above ground - 54 in. 84 in. minus 30 in. set depth
Crossarms, 2x4 3 24 in. One per post
Wire spacing - 22 in. Holes 1 in. in from each arm end
Wire, 12 gauge 2 runs 46 ft. each 40 ft. row + 3 ft. per end for wraps
Total wire - 92 ft. 2 x 46 ft.

Materials and Tools

  • Hillman 12-gauge utility wire, enough for 92 feet; check the length on the spool label
  • Three treated round posts, 7 feet by 4 inches
  • Three 24-inch 2x4 crossarms and six 3/8 x 6-inch carriage bolts with washers
  • A drill with a 3/16-inch bit, a post hole digger, and a tamping bar
  • Fencing pliers for cutting and twisting, plus gloves and safety glasses

Build Steps

  1. Mark the row. Snap a line down the center of the 40-foot row and mark posts at 0, 20, and 40 feet.
  2. Set the posts. Dig each hole 30 inches deep, set the post plumb, and tamp the backfill in 4-inch lifts.
  3. Drill the arms. Drill a 3/16-inch hole 1 inch in from each end of every crossarm.
  4. Mount the arms. Bolt each arm square to the row at 48 inches above the soil, centered on the post.
  5. Anchor the first wire. Pass the wire through one end-post hole and wrap the tail back on itself 6 times.
  6. Run it down the row. Thread it through the matching hole on the middle and far arms.
  7. Pull it snug. Draw out the sag by hand or with pliers, then wrap the far tail 6 times.
  8. Repeat on the other side. Run the second wire through the opposite holes.
  9. Tuck the canes. Train new canes up between the two wires as they grow.

Tighten the wires each spring before the canes leaf out, since soft wire stretches a little under fruit load.

Trellis Errors

  • Crossarms below 36 inches let tall canes flop over the top wire
  • Posts set under 2 feet deep lean in toward the row
  • A single center wire bunches the canes and shades the fruit
  • Wires left slack over winter let snow load drop the canes

The same post and wire approach carries vines over a path in building a T-post and cattle-panel arch trellis over a raised-bed path. Hand-dug holes for these posts follow hand-digging 8-inch holes for wood line posts.

Voles in a berry bed call for a buried barrier from the hardware cloth mesh size and gauge guide.

A wire that snaps later can be joined with a Western Union splice on a broken line wire.

FAQ

Do fall-bearing raspberries need two wires?

A two-wire trellis still keeps them tidy, though they need less support than summer-bearing types.

Can I use T-posts instead of wood?

Yes, with crossarms clamped on, but wood takes bolts and holds the arms square more easily.

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