blackberry trellis

How to Build a Blackberry Trellis

Building a blackberry trellis may seem like a difficult task, but constructing one for your backyard garden can easily be achieved in an afternoon. Beginning with the right materials is key to the success of your trellis. While a number of different materials can be used to build a blackberry trellis, experts lean toward building them with sturdy, wooden posts and galvanized steel wire. 

The best way to build a blackberry trellis:

  1. Set heavy posts, at least 4”x4” and 8’ in length, buried 2-3’ deep at the ends of each row.
  2. Set lighter posts about 15 feet apart in each row.
  3. Tie 2-3 heavy-duty galvanized wires, spaced 2-3 feet apart, to each post, wrapping tightly enough to remain in place. 

Some varieties of blackberries can grow without a support system. However, even erect cultivars can benefit from a support structure since a trellis can make harvesting easier, and it can also help keep fruit from rotting near the ground. There are many ways in which expert gardeners build their trellises, and there are benefits to each structure. 

Related: How to Grow Blackberries

Blackberry Trellis

How Tall Should a Blackberry Trellis Be?

Experts recommend building a bramble trellis that stands 5-6 feet tall. This height creates enough space for blackberries to grow but also allows gardeners to pick the fruit when it’s ready to harvest. 

Short brambles can grow beautifully on a 4-foot trellis. However, since they will have less space to spread, there may be less sunlight and air circulation, creating problems with rot, low yield, and difficult harvests. You will likely want to grow blackberries that bloom and fruit beautifully with a high yield, so experts recommend building higher.

To achieve this height, it is best to begin with end poles that are 8 feet in length. The poles must be buried 2-3 feet underground, poking into gravel or sand to keep water around the poles well-drained. In order to keep your trellis steady in poor weather, some expert gardeners recommend securing the end poles with concrete. 

When Should I Build a Blackberry Trellis?

Your blackberry trellis should be completed at or before the time of planting. As most trellis systems take the better part of a day to build, consider erecting the trellis one day then planting your brambles the next day. If you are planting more than just a small backyard bramble, you may need more time to erect a larger trellis. 

The best time to plant blackberries is when their canes are dormant, preferably in early spring. Planting may be done in late fall in some areas where the climate is warmer. Your trellis system will be secure for many years if it is erected with care, so it may be used for many seasons. 

Blackberry Trellis

What you Need to Build a Blackberry Trellis

Building a blackberry trellis begins with the proper tools and materials. If you do not already have the essential equipment to build a trellis, you may want to visit your local hardware store.

  • Pen and paper: to draw up your design
  • A saw: to cut your lumber to the right dimensions
  • Chalk or marker: to mark measurements properly
  • Electric drill: to create holes for screws, and to secure screws to your trellis
  • Posthole digger: for creating a 2 foot depth to bury your poles
  • Shovel: to backfill soil, gravel, or sand into your post holes
  • Lumber or metal poles: to construct the trellis
  • Gravel or sand: for backfill
  • Concrete: though this is optional, some builders recommend filling your post holes with concrete
  • Wood treatment: several options are available including chemical treatments and wax
Blackberry Trellis

How to Wrap Galvanized Wire for your Trellis

You’ll need 2 wire supports or tensioners to begin wrapping your wire. Make sure to secure your wire horizontal to the ground and at about 18″ above the ground.

If you are creating a trellis with 2 rows of wire, make sure the second row is near the top of your supports. If you are wrapping three wires, be sure they are at least 18” apart, spaced out evenly from top to bottom leaving an 18” gap at the bottom. 

Begin by wrapping the end or corner stake, and wrap the wire around the stake a few times. If you are using a tensioner, place it here at the end or corner stake, and place another at the other end or farthest corner.

Then, stretch the wire to the next stake, repeating the process until you have outlined your bed and returned to the original stake.

Repeat this process with another wire near the top of the stakes, and again with a third wire if you’re building a trellis with three wires.

Related: How to Grow Blackberries

bushes

What is the Best Trellis for Growing Blackberries?

Every trellis system has its pros and cons. It’s up to you which system you prefer to try. Some methods are more costly and time-consuming than others, but they may also last longer. If you have a small garden, a simpler design may suit you best.

I-trellis

The I-trellis is the simplest and most cost-effective trellis you can construct. The design consists of two poles planted into the ground 25-30 feet apart. You may add more poles depending on how much fruit you’d like to grow. Then, you need to secure the galvanized wire to the posts. You may choose to wrap one wire between each of the two poles or two wires between each of the poles.

As with other trellis designs, the poles need to stand at least 4 feet tall, although 6 feet is better. The poles also need to be buried at least 2 feet into the earth. With the I-trellis design, the posts used can be made of treated wood or metal.

If you choose to construct an I-trellis, you’ll need to secure the blackberry canes loosely to the wires. If you secure two wires to each pole, you can tuck the canes in between the two wires.

Pros:

  • Fast construction
  • Inexpensive to build
  • Easy to maintain

Cons:

  • Less sunlight than other trellis designs
  • Fruit yields may be lower
  • Crowded canopy may lead to disease

V-trellis

The most common type of blackberry trellis is the V-trellis To create the “V” in a V-trellis, steel posts are placed and secured in the ground. Typically, the V is 20 to 30 degrees from vertical, creating a 3 foot to 3 ½ foot gap between the tops of the posts.

Like the I-trellis, experts recommend allowing 2 feet of each post to be secured into the ground and also recommend that the posts stand around 6 feet in height.

Pros:

  • More sunlight
  • Better air circulation
  • Higher yields than I-trellis

Cons:

  • More costly than I-trellis
  • Difficult to move wires
  • Metal may rust

California V-trellis

The California V-trellis is an American version of a trellis system originally developed in Norway, called the Gjerde system. This design is a bit more intricate than a typical V-trellis. For one thing, the V-shape is created using 1-inch by 1-inch lumber instead of metal. These are connected to a center post made of thicker, more sturdy wood.

In the winter, the thin, moving posts should be tied vertical to keep from collapsing under the weight of the snow. They can be released in springtime when new fruit begins to grow outward. The growth of the berries pushes the thin lumber outwards. With this design, blackberries are encouraged to bloom on the outer parts of the canopy allowing you to harvest your berries more easily.

Pros:

  • Good sunlight and air circulation
  • Easy to water thoroughly
  • Harvest on one side

Cons:

  • Expensive to build
  • Can break in winter weather
  • Requires seasonal maintenance

T-trellis

The T-trellis built in a T-shape, where each heavy end post is topped with another heavy, but shorter post. This design creates a divided canopy design where the blackberry canes are secured to wires on either side of the trellis. This system divides primocanes from floricanes, making pruning and harvesting easier every season.

A T-trellis can be built out of metal—typically rebar, or wood.

Metal T-trellis

When building a T-trellis from metal, the main post should be made of 1⁄2-inch rebar while the cross arms should be made of 3⁄8-inch rebar. 

Pros:

  • Economical
  • Recyclable
  • Good light and air penetration

Cons:

  • Smaller yeild
  • Berry canes do not grow as tall
  • Can’t handle a lot of weight

Wood T-trellis

You may also build a T-trellis out of wood. If you are building your T-trellis with lumber, set 8-foot posts 2 feet into the ground. Also, be sure to use 2×4 inch pressure-treated lumber for the cross arms. The posts will need to be set 20-30 feet apart in a row.

Pros:

  • Good sunlight exposure
  • Easy harvest
  • Separates floricanes

Cons:

  • Most costly
  • Smaller yeild than a V-trellis
  • Time-cosuming to construct

There is no one right answer for building a blackberry trellis. If you are looking for a smaller system in your backyard, a simpler design that is affordable and long-lasting may be your best bet. But if you want to put the work into a higher-yielding blackberry harvest, a more expensive and time-consuming structure may be what you need.

Blackberry Trellis

How Long Will My Blackberry Trellis Last?

Blackberry trellises are generally more structurally sound than those built to support fruit trees. In fact, a well-built trellis can last 20 or more years. Taking the proper steps can guarantee a long life for your trellis.

Metal Components

The galvanized steel wire can survive the elements for 35-50 years before rusting, but it will eventually rust. A metal trellis system will also last several decades, but the structure may be less sound under extreme weather than a trellis made of lumber, and it may need to be replaced if damaged. 

Wooden Poles

Choose a type of wood for the trellis stakes that is shown to resist rot or rot slowly, such as redwood, cypress, or pressure-treated lumber.

Be sure to treat your poles in order to preserve them for as long as possible. Follow these steps for treating the lumber:

  • Treat the trellis stakes with a product containing sodium borate or disodium octaborate tetrahydrate, products used to protect wood against decay and insects that rot the wood.
  • Only treat your lumber in the area that will be above ground. Chemical treatments can cause issues with your soil.
  • Brush your product directly on the wood trellis with a paintbrush to keep the wood from rotting.
  • You may also choose to paint the wood structure with a waterproofing wood sealer that saturates the wood and repels water.
  • Grade the area for the trellis so water flows away from the trellis and doesn’t pool around the trellis stakes.
  • Create a small hill at the center of the trellis location so the water runs down away from the trellis. 
  • Dig a hole about 1 foot deep where each stake rests on or enters the ground. Fill the hole with gravel or sand to grade to increase drainage away from the trellis stakes. You can push the stakes in through the sand, but if using gravel, it’s best to add a few inches of gravel, set the trellis in place, then add gravel to grade around the trellis stakes.
  • At this time, many experts then seal the stakes into the ground with concrete. If you are in an area with a lot of moisture or loose, sandy loam soil, this step is highly recommended. If you are in an area with heavy, clay soil, this step may be skipped. 
  • If you choose to have a completely chemical-free trellis, you may choose to wax your poles with a natural product, like beeswax. However, you will need to wax your poles every 2-5 years if using a solid wax and every 1-2 years if using liquid wax. 
  • When treating lumber with natural wax, be sure to do so as soon as the wood is exposed to the elements, then repeat the process as stated above.

Once you decide which trellis to build for your crop, you may begin sourcing the right materials for your trellis. Just make sure that you are building it before planting your crop. Make sure you have the right height, and that your wires are properly spaced. Be sure the wood you use for your poles is treated or the metal is stainless or another kind that will not rust quickly. And finally, make sure to wrap your wire tightly so it does not come loose. Loose wire cannot support a growing blackberry bramble.

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