This is the palm that epitomises the Hollywood Films. Almost as famous as the Canary Island Date Palm
The name, robusta, is Latin for "robust" or "stout." Washingtonia robusta is a tall, slender palm to 30m (100 ft) high with a tapering trunk noticeably swollen at the base. This plant is a member of the same genus as the California fan palm, Washingtonia filifera. Compared with W. filifera, W. robusta is usually taller but with a less massive trunk. These two species may also hybridize. Leaves are fan shaped and glossy. The dead, dry leaves hang down the trunk in shaggy layers. For this reason it is also known as the petticoat palm .
Long inflorescences of small fleshy flowers are produced in the late spring, followed by black-brown berry-like, small fruits that have a thin, sweet pulp that tastes somewhat like dates or butterscotch. Each fruit contains a single seed. The small fruits are harvested when ripe and eaten fresh or dried, or made into jellies and drinks. The seeds are also edible and were widely used by Native Americans who ground them into meal for making bread or porridge.
Thrives in hot, dry climates, but normally near to springs or river beds. Prefers a well drained soil but is very adaptable. The Washingtonia robusta, at Chalk, is planted in modeling clay.
Reputed to survive temperatures down to -8C (18F), but I have found that temps lower than -5C (23F) damage the leaves.
Let me introduce you to my W.Robusta, which started out life on the mother tree in Playa de las Americas, Tenerife in Oct 1992. The mother stands at the bottom of a flight of steps near the beach between the Bouganville Player and Gran Tenerfe hotels. She was about 35 feet tall, so still quite a young adult.
I collected about 30 seed from the ground around the base. These were sown in spring 1993 and germinated in about 4 weeks. The seedlings grew quite quickly compared to most other palms, having 4 strap leaves when 6 months old.
I gave many away over the next couple of years ending up with 2 nice palms. One of them was potted up into a large pot while the other remained in a 3 litre pot. I thought it was doing rather well in such a small pot, and after about 4 years in the covered area it had reached the roof. I named this palm Ruby
In summer of 2000 I decided she needed to be planted out in the ground, but… yes you’ve guessed it…. She wasn’t rooted in the pot at all, she was rooted through the bottom into the ground. I suppose I was a bit naive thinking a 6 foot palm was happy in a 3 litre pot. (arrowed white). The trunk was as wide as the pot.
So, in order to move Washie to her new home, next to the West facing wall outside of the covered area, I had to dig her out. I could not believe how heavy the clay was in the outer conservatory. I could have thrown pots with it. This was a problem trying to dig it out, the weight of the soil pulled it off the roots, so it was a very bad transplanting, with virtually no soil on the root ball.
Following the move Washie went into a deep, deep, sulk that a teenager would have been proud of, for 3 years, and actually grew smaller. She was growing leaves but they became smaller and her overall height dropped.
At first I was worried about the hardiness of robusta as they are more tender than filifera (California fan palm). This was born out when temps dropped to -6C (21F) and all the leaves burned. This didn’t help in her first year after transplanting, and it took the whole of 2001 to grow out the damaged leaves.
The winter of 2001/2 I used fleece held in place by bricks on the top of the wall, draped over Washie. She sailed through that winter completely unscathed, although still in a deep sulk. It was 2003 before she showed signs of her previous young growth energy.
From 2003 she has has been back on her old form and rocketed skyward, doubling in height in 3 years. In the winter of 2005/6 I could no longer put fleece over her, so she had to take her chances. Some of the lower leaves fully exposed to the frost were burned, but the younger, more upright leaves were undamaged. The speed at which she now grows meant all the damaged leaves were cut off in May. 2006 was a great year for Washie, growing 15 leaves from March to October.2007 saw 20 leaves and 2008 18 so far, so growing Washingtonia robusta from seed is not a lifetimes work as with some palms. Ruby has grown from seed to 9 feet in 15 years, and that includes a 3 year sulk.
Washingtonia robusta is one of the easiest palms to grow from seed, providing you don't eat them. The seeds can germinate in as little as two weeks, but this relies on a high germination temperature, maybe as high as 40C. Reasonable germination is entirely achievable at 25C to 35C. If you pick your own seed, clean off the fruit flesh, and sow after a 24hour soak in warm water. If the seed is already cleaned and dry, soak for 48 to 72 hours in warm water before sowing. There are many methods of sowing palm seed, so I will leave it up to you how you sow. Personally, I use coarse moss peat wetted and the excess water squeezed out. Then placed in a plastic bag with the seed. Happy Sowing and growing.
The changing face of Washingtonia robusta. These are summer and Autumn pics showing how the petioles (leaf stalks) lengthening and shorten