There are several ways to kill goat heads, which are a type of weed with sharp, spiky seeds that can puncture tires and hurt pets. Here are some methods:

1. Chemical herbicides: Herbicides that contain glyphosate, oryzalin, 2,4-D, or dicamba can be effective in killing established goat head plants, but they are most effective on young plants. However, glyphosate has been linked to cancer, so it may not be the best option.

2. Natural herbicides: Products with citric acid, acetic acid, or garlic have been noted as effective against broadleaf plants like goat heads. Household vinegar with about 5-10% concentration can also be used as a weed killer. However, stronger vinegars such as horticultural vinegar may require registration to use as a pesticide, so its important to check with your agricultural department.

3. Fire: Burning the plants with a blowtorch can be an effective way to kill them. This method is best done in the spring when plants are new or in the summer when all parts of the plant are present. However, its important to consult local laws before trying this method.

4. Physical removal: Pulling the plants by hand or using a hoe to sever their taproots can be effective in killing mature goat head weeds. Turning the soil over with a hoe also helps remove small weeds.

5. Goat head weevils: If you can find them, you can order Puncturevine Weevils, and put them out - they bore into the seed head and hatch, then eat the roots.

Its important to note that some of these methods may harm other plants in your garden, so its important to use them with care.