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.

Tuesday, December 29, 2015

More Desert Gardening

I have come to know the Anza-Borrego Desert fairly well over the last 15 years. There is a lot more complexity and variety than I originally expected. The following photos illustrate some of the landforms and ecotypes that make up this desert.

Rocky hills and mountains

Desert Washes - this one is Fish Creek

Alluvial fans and bajadas

Steep walled slot canyons

Canyons with year-round water

Desert Transition Chaparral at higher elevations

Borrego Valley
As I mentioned in my last post, my philosophy of gardening is to use plants that would normally be found where the garden is located. I need to add a phrase to that: "...or reasonably nearby." In my Encinitas garden I use plants from other parts of California and Baja, as long as I can create suitable conditions for them without extraordinary measures. 

The same principle applies in my Borrego Springs garden. My garden is located in the Borrego Valley. I could restrict myself to plants that are native to the valley where the dominant plant community is Creosote Bush Scrub, but that would eliminate a number of plants that I want to grow, including some Baja species. So my task is to try to replicate the conditions in which these other plants would normally occur. Desert wash species such as Smoketree (Psorothamnus spinosus) can do just fine in the valley if I put it in deep, loose sand and give it an occasional flood. Plants found higher up in the rocky hills can do okay if I surround them with lots of rocks. This method doesn't work perfectly because my knowledge of what plants want isn't perfect. But it has been reasonably successful.

In this post I want to continue the discussion of trees, this time focusing on the Palo Verde group (genus Parkinsonia, formerly classified as Cercidium). The most common Parkinsonia in this area is Blue Palo Verde (P. florida). It is a handsome, fast growing, relatively trouble-free tree. One of the special adaptations of all Parkinsonias is the smooth green bark on the trunk, branches and twigs, which is the origin of the name Palo Verde. The bark contains chlorophyll so the tree can conduct at least some photosynthesis even when all the leaves are gone. As the tree ages its lower trunk loses the green color and becomes a more typical rough, brown bark. The blue-green leaves are small, like those of Ironwood and many other desert plants, which helps conserve water but cuts down on photosynthetic productivity. Green bark helps make up for this shortcoming. Here's one of the Blue Palo Verdes in my garden.

This tree is approaching 10 years old. Blue Palo Verdes are not terribly long-lived, but their longevity is improved by not giving them too much water. Although they will accept any amount of water you want to give them, the result in often excessively fast growth, brittle limbs, and short life span. I recommend weaning them off supplemental water after the first year. Blue Palo Verdes accept pruning well, but they do have some spines so use gloves when handling. One of the best features of Blue Palo Verde is the flowers which come out in late spring or summer.

Here are the seed pods, which are edible but reportedly not as tasty as Mesquite.

There is a hybrid variety called 'Desert Museum' which many people like because it has no spines. I'm not big on hybrids but this one does seem to be a good choice.

The next species of Parkinsonia is Little Leaf Palo Verde or Foothill Palo Verde (P. microphylla) which grows in Imperial, Riverside and San Bernardino Counties and Baja. It differs from Blue Palo Verde in having even smaller leaves and slightly smaller stature, but otherwise they are quite similar. 

The flowers look very similar to Blue Palo Verde, but the seed pods look a little different.

Both of the above species have produced seedlings around my yard after a winter of good rainfall.

The last Parkinsonia that I have in my garden is called Palo Brea (Parkinsonia praecox). It is a Baja species that does not occur in the wild north of the border. Jon Rebman says it occurs from the Sierra San Francisco south to the Cape Region and a few spots in South America. I like it because it has a slightly different appearance from the other two and works well in Borrego Springs. In my experience it has not been a prolific seed producer, so it would appear that its chances of become invasive are low.

One member of this genus that I do not recommend is Mexican Palo Verde (P. aculeata). It is more weedy than other Parkinsonias and could become invasive in California deserts, although it is said to be better behaved near the coast. Pacific Horticulture Magazine says, "Since both its growth and seed production are markedly stronger where temperatures are high, in some parts of the world where it has been introduced, it has become a weed species that can overwhelm weaker indigenous plants." It has already become a noxious weed in Australia. Unfortunately, it is popular with some landscapers and homeowners because it is even faster growing than Blue Palo Verde. Its fast growth makes it brittle, poorly shaped and short-lived, but apparently some people don't know or don't care about that. It could also hybridize with native Palo Verdes and introduce undesirable genetics into local populations. The 'Desert Museum' hybrid Palo Verde that I mentioned earlier is reportedly a three-way cross between P. aculeata, P. Florida and P. microphylla. This kind of controlled and intentional hybridization may be a good thing, but random hybridization in wild populations is definitely not. If you want the look and performance of a Palo Verde, choose one of the others.

Parkinsonia aculeata (Mexican Palo Verde)     Photo by Carolyn Martus
 That's all for the Palo Verdes in my garden.

Sunday, December 6, 2015

A Desert Garden

Many people think that southern California is all desert, but that isn't really true. The confusion comes from the seasonally arid nature of the Mediterranean climate which, to people who come from other areas, feels a lot like desert weather. However, we do have true desert in San Diego County, about 90 miles east of the coast. The differences between the coast and the desert are dramatic, in terms of climate and ecology.

Borrego Springs
 In April 2001 my wife and I bought a very rundown old house in Borrego Springs. We have fixed it up and use it as a weekend getaway. One of my primary reasons for buying this house was to have a native desert garden. I have been working on this garden for amost 15 years and I'm now ready to start blogging about it. Thus, I am departing from the "Encinitas" nature of this blog and expanding into the more general discussion of gardening with California native plants throughout the state. First, here's a couple of early shots of our house in Borrego Springs...

 It sits on an acre lot with about 10 acres of vacant lots around it. Plenty of room to do some gardening. There wasn't a lot of landscaping when we bought it and the house was in very rough condition. What it did have was lots of rocks (always good), and some really large, mature barrel cactus (Ferocactus cylindraceus). There was also a big, old Ocotillo (Fouquieria splendens) in the front yard and three palms (I think two are native Washingtonia filifera and one is W. robusta).

 The biggest problem area was the west side of the house which had very compacted, bare soil. I think the previous residents must have parked heavy vehicles on it. To be able to garden there, I had to bring in some loads of loose sand to create artificial dunes. Then I was able to plant. My gardening philosophy there as well as in Encinitas is to use plants that would normally be found growing wild in that area. I think this just makes sense because those plants are going to be the easiest to grow with the least amount of human intervention. They are also going to fit best into the local ecology, and they will "look right" in that area.

I started with a number of trees. The first is a Desert Ironwood (Olneya tesota). This tree is found in a number of locations in the Anza-Borrego area as well as parts of Arizona and Baja. It is a very attractive tree in the Fabaceae (Legume) family, slow growing but worth the wait. The one I planted was a 15 gal. about 2 ft. tall. It is doing very nicely, still not huge but quite healthy and happy. I planted it right on top of one of the new dunes so that it would have plenty of room for root growth and very fast drainage.

Ironwood is an interesting plant because its wood is so dense that it will not float. In Baja the wood is used to carve curios for tourists to buy. It also makes very long-lasting firewood, but that seems like such a waste. It has very small, grey-green leaves for water conservation, and it will drop its leaves in very dry periods (usually summer). It will leaf out in response to winter rain. It has spines so caution should be used in working around it. It is usually found on alluvial fans and bajadas that are dry in summer but have subsurface water in winter. It blooms in summer with very pretty flowers that few people see due to the summer heat. Below is a photo (sorry, it's not in very good focus) of my Ironwood in bloom. Now that this tree is well established, it requires almost no supplemental water and minimal care.

Here's a shot of a mature tree in the wild in Borrego Palm Canyon.

Another tree I planted was a Desert Willow (Chilopsis linearis). This tree is almost the complete opposite of Ironwood. It is in the Bignoniaceae (Begonia) family. It's origin was probably tropical, and it looks like it. It has long, bright-green leaves. The leaves resemble those of willow species (genus Salix) which led to the common name. It drops its leaves and goes dormant in winter. It is typically found in desert creeks or wet areas where there is year-round water. It blooms from late spring into summer with large, extravagant flowers of pink, purple and white. It has some resemblance to Oleander and can be used as an effective substitute. It's biggest drawback is the fact that it is deciduous in winter; that's when most people are in the desert and they want their plants to look good.

The other important thing to note about Desert Willow is that it must be kept watered, unlike most other desert plants. To accomplish this, I planted mine in a shallow basin in the sand, not on one of the dunes. I put a bunch of rocks in this depression to mimic a stream. When I think it needs water, I put the hose into the rocks and flood the basin. The rocks help keep the soil moist for a long time, so I don't need to water it all that often, maybe once a month. This is a great tree for using greywater. If you could run an outlet hose from your washing machine out to a Desert Willow, it would be the happiest tree in the world.

One more tree that I planted early was Smoketree (Psorothamnus spinosus). This is a truly iconic tree of the desert with a totally unique appearance. Its grey-green, almost leafless stems really do look a bit like smoke from a campfire when seen in the distance. Smoketrees grow in desert washes where the sand is very deep and there is a dependable supply of subsurface water. below are some Smoketrees in the Split Mountain wash.

I took a big risk with the Smoketree that I bought because it is a notoriously tricky tree to get established. It has a deep taproot that helps it find water in desert washes, and this taproot can get damaged easily when in a container or in moving it from container to ground. The ideal way to grow Smoketree would be from seed, but that's not easy either. The seed must be scarified and/or soaked before sowing. This usually occurs in a big storm that tumbles the seeds in the sand of a wash. Surprisingly, a lot of smoketrees pop up on road shoulders in Borrego Springs when there is a mature tree nearby. The seeds get scattered out on the road and get run over by cars which scarifies them. Then winter rain triggers germination. Below is a photo of one such tree.

My big risk was that I bought a 24" box tree, and it was expensive. Fortunately, it has done well. As with the Desert Willow, I did not plant it on a dune. I just felt it would do better on flat ground. Below is a photo of it in my garden.

Smoketrees have terminal spines. That is, the stem ends in a very hard, sharp point. 

On the plus side, the flowers are beautiful. Like Ironwood, it blooms in late spring or summer and many people never see it. Also like Ironwood, it is in the Fabaceae (Legume) family. In fact, very many of the native trees and shrubs of the desert are in this family, including Palo Verde, Mesquite and Indigo Bush. They all have typical "pea" flowers and seed pods. I'll highlight more of these in future posts.

That's all for now.