Palm trees (Arecaceae or Palmaceae family) are found in the tropics around the world. While most are not poisonous to humans or their pets, there are other plant species that include "palm tree" in their common name. Seeds' toxic elements vary according to the plant family and species. Hardy in U.S. Department of Agriculture plant hardiness zones 5 through 13 depending on the species and/or cultivar, the true palms are more than just ornamental; they provide fruit, sap, oil and building materials in their native habitats.
About the Palm Family
With approximately 2,600 palm tree species worldwide, ranging from the 200-foot-tall wax palm (Ceroxylon quindiuense), hardy in USDA zones 8b through 11, to Madagascar's Dypsis minuta, which rarely grows more than 12 inches tall in USDA zones 10b through 11, there is a palm for nearly every garden. There are numerous slow-growing palm trees that thrive as houseplants as long as you provide sufficient water, humidity and light.
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Dwarf palm trees, such as the Sabal minor 'McCurtain' dwarf palmetto, can be used as a backdrop in a tropical garden even in some USDA zone 6 gardens. These relatively fast-growing, hardy palms grow up to 6 feet tall in USDA zones 6b through 10b. Other cold-hardy palms include the needle palm (Rhapidophyllum hystrix) and pindo palm (Butia capitata), hardy in USDA zones 5b and 9 through 11, respectively.
Edible Palm Tree Seeds
Palm trees are known for their tasty fruits. Dates, harvested from date palms (Phoenix spp.), have been a Middle Eastern, Asian and African staple for centuries. The date palms thrive in USDA zones 9 through 11 depending on the species. Less cold hardy but with a more manageable size for a home garden is the pygmy date palm (Phoenix roebelenii). At only 12 feet tall, the pygmy date palm produces edible but mostly seed-filled fruits in USDA zones 10 through 11. Protect it from freezing temperatures if you are growing it outdoors or take it inside for the winter in cooler hardiness zones.
Another well-known fruit of the palm tree family is the coconut. Borne on coconut trees (Cocos nucifera) in USDA zones 10 through 12, the hard-shelled fruits provide tasty flesh, juice and oil, while the tree's fronds are used for weaving, the sap for sugar and the wood for construction.
The pindo palm, also known as the South American jelly palm, provides 1-inch-wide yellow to yellow-orange fruits. The sweet and juicy apricot-flavored fruits are used to make jelly or are fermented for wine.
Dangers of the True Palms
There are a few palms that produce toxic fruits, including the Australian arenga palm (Arenga australisica), also known as the native sugar palm, and fishtail palm (Caryota mitis), hardy in USDA zones 10b through 11 and 9b through 10, respectively. The fleshy coating surrounding these palm tree seeds contains oxalic acid. Avoid contact with the fruits and sap. In the Arenaga and Caryota genera, the entire plant can cause severe itching, burning and a rash due to the needlelike crystals of calcium oxalate in its tissues.
While most of the true palms may not be toxic, they have their own dangers. Put on thorn-resistant gloves, long sleeves, long pants, closed-toe shoes and safety goggles when working around palm trees. Needle palms have sharp spines on their leaves, making them hazardous for gardeners, children and pets. The Mexican fan palm (Washingtonia robusta), native to USDA zones 9 through 11 of the South and Southwest, sports sharp, hooked "teeth" on its petioles (leaf stalks) that hold the leaves and are ready to grab an unwary gardener or passerby.
Other "Palm Tree" Seeds Toxicity
While not actually palm trees, the members of the family Cycadaceae often carry the common name of "palm." This includes the sago palm (Cycas revoluta), hardy in USDA zones 9 through 12. All parts of the plant are poisonous to humans and pets, particularly the seeds. Cats, dogs and horses that consume the seeds suffer from drooling, vomiting and diarrhea as well as liver and neurological damage.
Also commonly called a palm, the cabbage or grass palm (Cordyline australis) thrives in USDA zones 9 through 11. While the plant may produce small white fruits, they are not edible. The saponins in the plant cause vomiting and other symptoms in humans, cats and dogs.