Friday, March 11, 2016

Ready or Not, Spring is Here

I haven't been able to post for a couple of months, and now stuff is happening all over the garden. Let's start with this Monarch butterfly on a Giant Coreopsis (Leptosyne gigantea).

This Leptosyne (formerly Coreiopsis) is native to the Channel Islands and just a handful of locations along the coast, such as the Pt. Mugu to Malibu region and maybe Torrey Pines. It has been planted in many locations by Caltrans so now you will see it along I-5.

Here's another butterfly, a small one. This one is a Mournful Duskywing. It is distinguished by the white band along the bottom edge of the hind wings.  I was lucky that it stayed there so long to feed so I could get a good shot of it. Although they use oaks as host plants, this one is feeding on a Dichelostemma capitatum. I hope it found a mate and deposited some eggs in my oak tree. Speaking of the oak tree, it is putting out tons of new growth, but I don't have a good photo of that.

The Dichelostemma is pretty popular with the butterflies. Here's some kind of Skipper. You are supposed to be able to identify them to species by the pattern on the under hind wing, but I can't do it.

While I'm talking about Dichelostemma, it reminds me that in a previous post I talked about how I have this fairly large patch of them that don't flower much but produce lush foliage. Here's what they look like now. I don't give them any supplemental water. When it rains, they just put out huge quantities of foliage and a handful of flowers. I should probably dig up some of these and move them to a sunnier area, but I can't bring myself to do it.

Here's a bumble bee feeding on the flowers of my Mission Manzanita (Xylococcus bicolor). I am really happy to be seeing bumble bees this year because last year there were almost none due to the drought. The one below was crawling all over the Manzanita flowers in order to get to every flower. I am not able to identify the species of bumble bee. I'm just glad to see it.

Here are a few more plants that are blooming right now. First is Wind Poppy (Papaver heterophyllum). It is native to the coastal strip from the Bay Area down to Baja and the southern Sierra foothills. It is often found in oak woodlands, so I have it planted under my oak tree.

Next are some Dudleya candida that are endemic to the Coronados Islands, just off the coast of Tijuana. They seem to like it in my garden with other Baja species. With so much flowering, I am hopeful that I'll get some seedlings coming up nearby. The taller cactus in the background is Cochemeia halei from the Magdalena region of Baja.

The Dudleya pulverulaenta (Green form) are also putting up lots of flower stalks. They have already produced numerous seedling which I have written about previously. Pretty soon I'm going to have more of these than I know what to do with.

Continuing with the Baja theme, below is a Baja Bush Snapdragon (Gambelia juncea) followed by a Baja Chuparosa (Justicia purpusii). The flowers have a strong resemblance to each other even though they are in different families (Plantaginaceae vs. Acanthaceae). It doesn't make any difference to the hummingbirds who love them both equally.

In the shade area on the north side of my house, the Ribes viburnifolium is trying hard to attract some pollinators. It is native to Catalina Island and probably should be with my other Channel Islands plants, except it really likes shade so this is the best spot for it. I'm not seeing any seedlings from it, but it is spreading itself by tip-rooting. It has a great fragrance even when not in flower.

The Blue-eyed Grass that I have in a container on the west side of the house is doing fabulously well.

Lastly, the Mojave Yucca (Yucca schidigera) that blooms consistently is doing so again. Here is a shot of it after the rain. It seems pretty happy. It has never produced any fruit, so the Yucca Moths must not be able to find it yet. However, I have seen fruits on other Yuccas in Encinitas, so I know they are around.

Wednesday, March 9, 2016

One More Tree

This is a continuation of my garden in the desert, Borrego Springs. Having covered all of my trees (except one) in previous posts, I now devote this one to the remaining tree in my desert garden, California Fan Palm (Wahsingtonia filifera).

Many people (out of pure ignorance) associate palm trees with southern California, based on the huge number of exotic palms that have been planted in places like San Diego and L.A. There is really only one palm that is native to California, and it is this one. And it is not found near the coast. It only occurs in canyons with perennial water on the east slope of the mountains leading into the desert and in a few isolated desert oases where a spring delivers water close to the surface.

To understand this palm we must start with its botanical classification. It is a monocot, like the grasses (including wheat and rice), agaves, yuccas, onions, rushes, reeds, sedges, brodiaeas, lilies, iris, orchids, tulips, corn, bananas, bamboo, and much more. There are several distinguishing characteristics of monocots compared with eudicots. First, they have a one-piece cotyledon (seed leaf), unlike the two-part cotyledons of eudicots. Secondly, they have parallel veins rather than branching network veins. Compare a palm frond to a maple leaf. The veins in the maple branch and re-branch all over the place, while the veins in a palm frond run straight and parallel to each other from the base to the tip. Thirdly, the monocots lack a cambium layer; their vascular bundles are scattered throughout the main stem or trunk of the plant. Eudicots have their vascular bundles in a thin layer right under the bark, which makes the visible rings in tree wood. About a quarter of all flowering plants in the world are monocots.

To illustrate the vascular bundles, here's a photo of a cross sections of a palm trunk. Note the total absence of rings or layers.

Because of this distributed pattern of vessels, palms are somewhat less vulnerable to fire compared with eudicot trees. The latter are killed if fire destroys the cambium layer just under the bark. But palms can get seriously burned and still survive by virtue of the bundles of tubes that are in the middle of the trunk. An example of this is the palm in the forground below that has been burned but is still quite healthy. However, palms are killed if the apical meristem is burned. That's the place at the top where all the fronds emerge from. If that gets cut off or burned, the palm is dead.

Palms are vulnerable to fire in large part due to the dried fronds which either hang onto the crown to form a skirt or fall to the ground, as below. This accumulation of dry, flammable material can easily transmit from the ground up to the crown. There is evidence that the native Cahuilla people intentionally burned the palm groves for various reasons.

 Palms also have very shallow roots, as shown in the photo below. This palm and many others were uprooted from the palm oasis in Borrego Palm Canyon (Anza-Borrego Desert State Park) by a major flood event about ten years ago.

Some of these trees had been weakened by the palm borer beetle which is a natural resident of all palm groves. These palms can tolerate a lot of damage from the beetles, but eventually they will succumb.

On the other hand, there are plenty of seedlings just outside the main grove.

 These palms are not at all drought tolerant. They are only found in the canyons that have water year round, such as Borrego Palm Canyon.

The palms tend to grow in dense groves. I have read no explanation for this. Certainly they are going to grow in the stream, so they will form a linear patch. Maybe the fruits and seeds just tend to stay close to home.

The largest of the three palms in my garden does not produce dates every year, but when it does produce it is impressive. The dates were eaten by the native people, and they are enjoyed today by coyotes, birds, rodents, and other wildlife. I've eaten them, and while they aren't the tastiest dates I've ever had, they were okay. The palm groves are used by many wildlife species including nesting birds, bats, snakes, lizards, frogs, ringtails and more.

There is a really good book about Washintonia filifera. It is titled Desert Palm Oasis, and the author is James W. Cornett who was Director of Natural Sciences at the Palm Springs Desert Museum. I have based a lot of the following on his book.

For a long time it was widely believed that California Fan Palms are a relict species that had survived from an earlier epoch. It was believed to have been much more common in the past, their numbers declining as the climate changed to become warmer and drier. This is certainly the case with Torrey Pines and a few other species, so it was not unlikely that California Fan Palms would be similar. However, Cornett found two problems with this hypothesis. One is that there is no indication of these palms in the fossil record, which doesn't make sense if it was more common in the past. Secondly, the range and population of W. filifera in California appears to be expanding.

Cornett's hypothesis is that W. filifera was not present in our area until the climate changed. It moved northward from Mexico into the desert canyons of California as conditions became warmer and drier. Cornett's studies of palm groves throughout southern California shows that the number of trees in the groves is increasing. Furthermore, groves are appearing in more northerly places where they did not exist previously, such as Death Valley and southern Nevada. Cornett's conclusion: "...the desert fan palm is a recently evolved, invasive species that is rapidly expanding both in range as well as in numbers."

When Cornett says "invasive" he is not suggesting that W. filifera is an unwanted weed. Rather, he is simply describing the plant's behavior as it spreads and occupies new territory. W. filifera is now a permanent resident of the southern California deserts, and it plays several important roles in the ecology of the deserts.

Several years ago I met a man who said he lived in our house back in the 50's and 60's, and he said he planted this palm. That would make it about fifty to sixty years old now, and still going strong. I wish I had more.