Palm trees (Arecaceae family) tend to grow in tropical areas with no shortage of water. Therefore, their roots tend to be very shallow, spreading outward rather than straight down. This makes the roots more accessible for removal when it's time to get rid of a palm tree on your property. If you don't want to dig them up, there are other ways you can kill palm tree roots to prevent future growth.
Dig Out the Roots
The most effective and environmentally friendly way to prevent palm regrowth is to physically dig up the roots. Of course, this is also the most labor-intensive strategy, but it's a little more bearable thanks to easy-to-dig sandy soils and the palm tree's shallow root system. Tackle this project when the soil is dry, because sand becomes very heavy when waterlogged.
With the palm tree already safely cut to a stump, dig a trench around the stump. Use a shovel, saw or hatchet to sever roots emanating from the stump. Then work your way outward, plunging the shovel straight down into the soil and pushing the handle down to lift manageable sections of the roots. Shake loose soil out of the roots and discard the roots in a yard-waste bag.
Rent a Stump Grinder
Digging the main stump out by hand is also an option, but often unmanageable due to the stump's weight. It can be cut into smaller sections using a chainsaw while following applicable safety precautions (e.g., wearing eye protection, ear protection and chaps). Or you can rent a stump grinder to turn it into instant mulch. Tree removal companies can also perform this task for you, if preferred.
Cover Roots With Landscape Fabric
Another way to kill palm roots involves starving them of sunlight. Cover the entire root system with thick landscape fabric and leave it in place for at least one year. The fabric will also prevent any new shoots from breaking through. Cover the fabric with a thin layer of sand or stone for a more attractive landscape in the meantime.
The dead roots can remain in the ground without issue, but it's still a good idea to dig them out at a later time if you'd like to plant something else in the area.
Natural Palm Tree Root Killers
A high concentration of Epsom salts will also kill tree roots by causing the tissues to quickly dry out. Use a half-inch drill bit to create deep holes in the stump. Then pour a solution of 2 parts water and 1 part Epsom salts into the holes. Cover the stump with a tarp to accelerate the decomposition process.
After about a week, chisel away at the top of the stump with a shovel until you reach firm tissue. Drill new holes and repeat the process.
You can also pour undiluted white vinegar into the drill holes instead of Epsom salts.
Chemical Palm Tree Root Killers
Because chemical root killers (herbicides) can affect the environment and contaminate waterways, they should be used only as a last resort. Palm trees can be killed by herbicides that contain triclopyr. Paint the herbicide directly onto the stump within 30 minutes of cutting it. Follow all safety precautions and application instructions to minimize environmental impact.