Posted on

Insider Tour – Palms

The Palms of Peckerwood Garden
Introduction – Palms are a diverse (approximately 2500 species) family (Arecaceae) of flowering plants (angiosperms) which start as a single-root producing seed (monocot) that eventually produces a trunk (stem) from which are produced leaves or flowers and fruit (drupe). Unless otherwise noted, palms mostly propagate by seed. Typical of monocots, palms have heavily branched root systems (adventitious), scattered trunk vascular bundles (atactostele as opposed to dicot cambium) and leaf parallel veining. Not typical of monocots though, palms have secondary trunk growth of parenchyma and lignin or fiber depositing cells that allows them to achieve massive size. The wood is so tough that in parts of the world where palms are common, salt water piers are made of palm logs. Further to the point, during the Revolutionary War, Sabal palmetto logs were used to build a fort on Sullivan Island to defend Charleston. Rather than shattering under heavy British cannon fire, the palm logs deflected the cannonballs and gave the Americans time to accurately set their cannon sights to inflict maximum damage. The British left without taking Charleston that time. Hence, South Carolina has a large Sabal palmetto in the center of its flag.

Unfortunately, living palms are usually not quite so tough. Most species grow only in the tropics, wilting below 50 F. Most species also need tropical humidity. Luckily, there are cold tolerant xeric and mesic palms, a few of which can be found at Peckerwood Garden. The Achilles heel of the palm is its meristem. Located near the tip of the stem, the meristem is a group of cells in which plant growth occurs. Should this meristem be damaged by fungus, lightning or cold (or very likely a combination), that palm stem will die, especially during drought-related stress. In the case of solitary palms, that means death of the entire plant. Palms also suffer from several fungal diseases, such as ganoderma which rots the trunk from the inside out.

Palms come in many different shapes and sizes. Some small (e.g. Chamaedorea radicalis), while some are extremely large (Sabal causiarum). Palm trunks may take several forms: solitary (butia), clustering (Serenoa repens), aerial branching, subterranean (acaulescent) or climbing – or a combination (Nannorrhops ritchieana). The trunk surface may be smooth or rough and may be totally or partially covered by leaf bases. Leaf bases may fall off the trunk (absciss) of their own accord or may be held for very prolonged periods. Leaf bases may be split (sabals) and/or crossed (Sabal palmetto and S. mexicana) or may be straight (brahea). A fibrous tomentum left from old leaf sheaths (bases) may hang about the trunk (Trachycarpus fortunei), or a tomentum may grow out of the trunk like cotton candy (N. ritchieana). The petioles may be long or short and may (butia) or may not (sabals) have teeth. Inflorescence lengths vary along with the color of the flowers (usually off-white or yellow) and the fruit (usually green, turning yellow, possibly then brown or black). Flowers may be dioecious (phoenix), monoecious (sabal) or hermaphrodite (Trithrinax campestris) – or a combination (T. fortunei). Palm leaves are extremely variable, though most are either fan-shaped (palmate) (Sabal tamaulipana) or feather-like (pinnate) (P. canariensis).

Despite that palms are apparently like cycads, such as (Cycas revoluta, or sago), the two groups are completely unrelated. Cycads are gymnosperms which of course means they reproduce using cones, not flowers as with palms. Cycad trunks (stems) contain meristem throughout such that only a piece is needed for propagation. Cycads have fleshy tap-like and secondary roots that extend in all directions. They have coralloidal roots near the surface that fix nitrogen and other nutrients. Another difference is that all parts of the cycad are deadly toxic, while the palm fruit or seed is usually nontoxic. Despite toxicity, cycads are a source of food mainly as flour from processed seeds (e.g. arrowroot from Zamia floridana, coontie). Yet the economic benefit is limited. On the other hand, the economic benefit from palms is substantial. Fruits (Butia capitata), dates (Phoenix dactylifera), and seeds (Cocos nucifera) are a huge source of food around the globe. Palm leaves are used extensively for thatching and clothing; coconut husk is a common soil amendment.

The Garden – The palm collection at Peckerwood Garden is quite diverse both regionally and taxonomically. They are both very cold hardy and either xeric or dry-side mesic. They are planted in every section of the garden and throughout the undeveloped property where they depend solely on rainfall. The conservation status of palms at Peckerwood Garden either has not been assessed or is of least concern unless otherwise noted.

Phoenix canariensis: Dioecious. Endemic Canary I. To 120 ft. Sun. Zone 9. Black thin edible date.
Sabal mexicana: Critically endangered in the US. Monoecious. TX-MX-C.A. 50 ft. Zone 8. Edible black fruit. Xeric. The last native groves of Texas palmetto are in the Audubon Sabal Palm Grove Sanctuary in Cameron County.
Sabal minor: Monoecious. NC-TX. Partial sun/light shade. Moist. 5 ft. Acaulescent with below ground 5 ft. trunk. Zone 8. Short midrib. Small black fruit.
Butia odorata: Monoecious. Dry savannah S.A. Dry 15 ft. Sun/PS. Zone 8. Yellow edible fruit. Xeric.
Butia capitata: Monoecious. Dry savannah S.A. 20 ft. Sun/PS. Zone 8. Yellow edible fruit. Xeric.
Sabal uresana: Vuln. Monoecious. Endemic S. M. Occ. MX. in thorn forests and dry oak watercourses. 30 ft. Zone 8.
Brahea dulcis: Monoecious. Tex-Mex. 15 ft. Solitary, occasionally suckering. Slow growth. Xeric only. Zone 8.
Brahea decumbens x ?: Monoecious. Sierra Madre, MX. 3×10 ft. Sun. Cluster. Zone 8b. Very slow. Green to blue Xeric only.
x Butyagrus nabonnandii: Intergeneric Butia capitata x Syagrus romanzoffiana. Sterile: mule palm. 30 ft. Zone 8b.
Trithrinax campestris: Hermaphrodite. Savannah and upper elevations AR-UR. 12 ft. Slow. Xeric. Zone 8.
Nannorrhops ritchieana: Dioecious. YM-AF, elev. to 5000 ft. Sun. Zone 8. 20 ft. Aerial branch. Xeric. Usually, hapaxanthic. Arguably monotypic.
Sabal causiarum: Monoecious. Puerto Rico & Carib. 50 ft. Sun. Zone 8. Slow. Black fruit. To 4 ft. smooth gray trunk.
Sabal minor ‘Louisiana’: Caulescent form of S. minor possibly due to growth required to stay above deposited then subsided river soil. 12 ft. Slow. Zone 8 or better.
Sabal ‘Birmingham’: Origin unknown. 15-30 ft. Sun/PS. Slow. Zone 7.
Sabal bermudana: Endangered. Endemic Bermuda. 80 ft. Salt tolerant. Zone 8b. Fast.
Sabal tamaulipana: Monoecious. N.E. MX, elev. 1500 ft. 8 ft. Leaves 6ft. Yucca Do 1988. Zone 7b.
Brahea moorei: Monoecious. Endemic MX, S.M. Orient. Mid-high elev. Zone 8. 4 ft. Extremely slow. Solitary. Acaulescent. Purple fruit. Xeric. Silver abaxial.
Serenoa repens: Monoecious. TX-SC, every county in FL. 10 ft. Clustering, running, branching. Zone 8. Full sun to PS. Slow. Blue or blue-gray. Propagate by seed/rhizome/division. Xeric. Salt tolerance. Tough! Wildlife food. Sereno Watson. Monotypic.
Trachycarpus fortunei: Dioecious-Hermaphrodite. China-Japan. 20-50 ft. Zone 7. Fast. Part sun.
Chamaedorea radicalis: Dioecious. Tropical MX. Solitary. 4 ft. Very slow. Pinnate. Orange to red showy toxic fruit on young plants. Shade-PS. Dry mesic once est. Zone 8-11.
Livistona chinensis: Possibly invasive. Hermaphrodite. JA-TA-SCS. Solitary. 30 ft. Medium. Prodigious black fruit. Sun/part shade. Dry mesic, deep tap root. Zone 8b.
Rhapidophyllum hystrix: Dioecious, occas. herm. MS-SC. 6×8 ft. Sucker. Acaulescent. Spines at the base. Light shade. Zone 6. Propagate by seed/division. Mesic. Monotypic.
Guihaia argyrata: Dioecious. S. China/Viet. Cluster. 4 ft. Zone 8b. Shade/PS. Silver abaxial. Edible black fruit. Slow.
Chamaedorea microspadix: Dioecious. E. MX. Clustering. 8 ft. Pinnate. Zone 8. Shade. Orange/red toxic fruit.
Sabal x brazoriensis: Rare. S. minor x palmetto. Monoecious. Brazoria Co., TX. 20 ft. Zone 7b. Visit them in the Palm Unit of San Bernard National Wildlife Refuge.
Brahea armata (across the creek): Monoecious. Baja, CA – NW. MX. Zone 8. Blue leaves. Sun/PS. Very long golden spadix. Moisture during dry periods.
Trithrinax acanthacoma: Hermaphrodite. SA savannah. Solitary wrapped in fibrous needled leaf bases. 20 ft. Forked spiked leaves. White/pale green fruit. Sun. Zone 8.
Brahea sp.:
Chamaerops humilis var. argentea: Usually dioecious. Morocco. Zone 7b. 12×15 ft. Silver leaf. Sun. Mid-elev. Xeric. Monotypic.