How do I get these weeds under control in a gravel patio without glyphosate?

For a large patch, I’d start by cutting or pulling out the existing growth, including as much root as practical, then rake out leaves and other debris. A torch can singe young weeds, but it usually won’t kill deep roots and needs repeating. Keep it well away from plastic edging, dry plants, trees, and buildings, and check local fire rules.

Afterward, regular leaf cleanup and quick removal of new seedlings can make the job much smaller. Gravel tends to collect dust and decaying plant matter over time, which gives seeds a place to grow.

You probably don’t need to wash every rock. If the gravel is still in decent shape, rake out the weeds and accumulated organic material, then top up thin spots. Washing a whole patio’s worth of gravel sounds like a lot of work for little benefit.

A barrier under the gravel can help with growth from below, but it won’t stop seeds or bits of soil settling on top. Replacing it would mean moving the gravel, and even then you’ll still need to keep the surface clear.

One caution on the vinegar-and-salt recipes: vinegar mostly burns the foliage it touches, so established weeds can return, while salt can build up and harm nearby plants or affect runoff. Strong vinegar can also injure skin and eyes. I wouldn’t treat either as a harmless fix, especially near fruit trees.

If you want a non-glyphosate product, check the label for the exact site and weeds before using it. A pre-emergent may limit some new seedlings, but it won’t remove what’s already growing, and its use around edible plants depends on the product label.