Christmas cactus belongs to the large cacti family and is also commonly referred to as crab's claw cactus. The plant has flat, pendulous, spineless branches that are distinctly notched at the borders. The flowers bloom in shades of red, pink, lavender, orange and yellow around Christmas time, hence the name of the plant. The delicate stems break easily and may be cut and planted to propagate new plants. The best way to kill an unwanted Christmas cactus or any plant in the garden is to use a recommended herbicide, advises the Ohio State University Extension.
Select products containing picloram for effectively killing Christmas cactus, as recommended by the Texas A&M University Extension. You can use the herbicide at any time of the year.
Fix a small garden sprayer with a 3-gallon tank and fitted with a coarse spray nozzle to will administer large drops of herbicide.
Fill the tank with water and add 4 oz. of herbicide to water. Mix in 1 oz. of liquid dishwashing detergent. This will act as a surfactant that will help the chemical stick to the cactus.
Mix in 1 to 2 oz. of blue dye to the herbicide mixture. Though this is not necessary, it will help you to identify the plant areas that you have already treated and make it easier to determine if you have used herbicide equally on all areas.
Spray plants and make sure you cover all the cactus branches or pads on the front and back. Avoid treating wet or moist plants. Do not use during extremely cold weather. Do not drench plants to the point of runoff.
Avoid the use of herbicide on windy days, as this will cause the chemical to drift to non-target landscape areas. Also, do not use picloram within 100 feet of land fractures or sinkholes, as this can lead to serious groundwater contamination.
Dig out and remove dead plants entirely, including roots.