I want to plant Raspberries and Blackberries in a six-foot wide side yard. How might I control the underground runners? I'm considering planting the vines in the ground or building a raised bed with a root barrier. Which option do you favor?
You’re correct in being concerned about the underground stems or rhizomes.
Raspberries and Blackberries, also known as cane berries, are very intrusive and do not respect a property line. Planting them on any type of shared fence is a major mistake. You’ll have a difficult time controlling the vegetative growth that grows through and under the fence into your neighbor's yard. Cane berries are a guaranteed expensive, neighbor dispute waiting to happen.
So, I’d be looking to plant them off the fence line in a two-foot high, four-foot wide raised bed. A 'root barrier' is always a good idea whether the vines are in a raised bed or in the ground as another layer of protection. In the center of the bed construct a 'T' bar trellis, 4x8 post every six feet with a 2x4 cross beam, with wires running between the supports and attach the vines to the wire. Also, with the vines off the fence line, you are able to harvest the berries from both sides as each side should get an equal amount of light.
Cane berries fruit only on the second year wood, so once you have finished harvesting the crop, you cut the fruiting canes off at the ground; otherwise, you’ll create a thick, thorny, unmanageable, vegetative mess. The new growth at the base of the plants is then attached to the trellis for next year's crop. Runners will eventually escape and appear in the space between the bed and the fence. The shoots are controlled by hand pulling them or spraying them with a nonselective herbicide.
There is now two dwarf varieties, Raspberry Shortcakes, and Baby Cakes Blackberry, that gives you a third option and it’s the option I prefer.
They have a compact, upright growth habit, growing three to four feet, so they don’t require staking or trellising. I’d plant them in a raised bed and grow them as a fruiting hedge. The fruit is borne on the second year growth so you still have to prune off the stems after harvesting. Raspberry Shortcakes and Baby Cakes Blackberry are ideal for individual containers. Joining strawberries and blueberries, they expand the homegrown fruit available to be grown on a deck, patio, or balcony. Fresh raspberries and blackberries are a now reality for all types of gardeners.
Does rock salt or table salt kill weeds? If so, do I have to spray water on it to dissolve?
Yes, salt can be used as a herbicide.
It’s not recommended around plants but it can be used for weed control in brick walkways, driveways, and between pavers. You need to be careful as salt will sterilize the ground and kill desirable plants for an extended period of time. It can be applied dry or dissolved in water.