I heard somewhere that wild blackberry used to be used as a natural border/barrier. I've been thinking about bordering my property in NW Ohio with something less dramatic than barb wire or concertina, but still effective enough to deter casual wanderings I grew up with woods and fields that had some pretty thick patches, and I remember never having any desire to try and force my way through one, but I was really hoping not to have to wait 20 - 30 years.
I have no problem with attracting four legged critters visiting to feast on the berries. I don't even mind the two legged critters, as long as they don't try to push through into the property interior.
I was hoping somebody might have some knowledge on quickly propagating the blackberries along my property line and getting them tall and thick enough to be effective. I'm hoping to get them about 15 - 20 foot wide in just a few years.
Once you get a line of Blackberries established it will only take them around 7 years to become thick enough to keep deer from going through the thicket.
Blackberries are easy to propagate with a rooting hormone either powder or liquid, just coat the base of the cane and plant where you want it to grow.
Black berries are considered an invasive growing plant since they reproduce from the roots, with new plants popping up about every foot of root growth.
If you want to force this type of rhizome activity all you have to do is cut the canes down, the plant will respond by putting up new crowns all over the near root system.
Here are some videos from my favorite permaculture Youtuber (Edible Acres).
Stool Layering Black Currants:
Tip Layering Blackberries (or similar):
Seems like if you get them started every 10 feet (or closer if you can), then the next year you can tip layer a bunch of them to fill in the gaps. You don't even have to cut and transplant them if you are happy with them growing where the tip touches. Think of it like the growth habit of strawberries just on a bigger scale.