Bush Rue

Cneoridium dumosum, commonly called bush rue, is an occasional component of the chaparral community in southern California. It is not as common or as well known as some other chaparral species such as manzanita, and it is not often found in gardens. It should be used more. I love it because I see it in native habitats around Encinitas. I am trying to recreate that look at home. Here's a large, old plant that I saw earlier this year in one of the few remaining patches of native vegetation in Encinitas.

I have one bush rue in my garden. It is only about three years old and still rather small, but this year it decided to bloom. It is blooming right now with just a few flowers but still worth celebrating.

A surprising fact about bush rue is that it is a member of the Rutaceae or citrus family. The flower is very similar to those found on orange trees, and the fragrance is similar too. In the wild it is found on the coastal side of the mountains from Orange County to northern Baja. The leaves are simple, linear to obovate and dotted with glands which give it that distinctive citrus smell. Because of these glands and the chemicals that create the odor, some people have a dermatitis reaction to it. According to The Baja California Plant Field Guide (Rebman and Roberts, 3rd ed. 2012) the dermatitis is caused by light-sensitizing plant chemicals reacting to long-wave ultraviolet light.

Cneoridium is a genus with only one species in it, which I always find interesting. Why did this part of the citrus family not give rise to any other species, either here or elsewhere in the world? 

Calscape says the shrub grows to around 3 ft. by 3 ft., but I have seen taller ones in the wild, up to 6 ft. The big ones develop a large woody trunk. The leaves turn gold in dry periods but generally remain on the plant. Below is a photo of one from near Lake Hodges in October.

I highly recommend Cneoridium dumosum for native plant gardens in San Diego and Orange Counties. Calscape says that 9 nurseries carry it. For additional information on growing it, see Calscape.

Shaw's Agave in Flower

 My last post about the Agave was on November 9. Day by day the tip of the inflorescence continued to swell and began to open up a bit. On November 12 we went to Borrego Springs for a few days. When we returned on November 15 the inflorescence had really opened up and I could see the yellow flower buds peeking out a bit. I have to admit I was pretty excited.

After that the inflorescence continued to open up further. Yesterday, November 23, I saw flowers that were actually open for the first time. The inflorescence had assumed its full candelabra shape, and I could see the large anthers protruding out. I observed hummingbirds feeding from the flowers but I couldn't get photos of them. In fact, I had to get on a ladder to get the photos below.

It's not unusual to see an Agave blooming somewhere in the county, but they are typically non-native species such as attenuata or americana. I think my Agave is special because shawii is so seldom seen in gardens and much less often seen blooming. As the bloom continues I'll post again.

Shaw's Agave About to Flower

 People sometimes refer to Agaves as century plants, suggesting that they only bloom once every hundred years. That isn't quite accurate, but they do take a long time to bloom. I have one in my front garden that I planted around 30 years ago and it is finally ready to flower. It's a Shaw's agave which is native to northwestern Baja and just barely makes it into San Diego County. It was probably more common here in the past, but decades of agriculture and urban development have left only remnant populations at Torrey Pines and Point Loma. From Tijuana southward it becomes quite common.

The one in my garden started looking a little different in early August. The center of the rosette began looking very congested. Instead of the usual one or two new leaves coming up there was a dense cluster of smaller leaves, giving me the impression that it was going to flower. The two photos below were taken on Aug. 5, 2021, when I first noticed it.

Only three days later, an inflorescence was definitely coming up and growing rapidly.

By Aug. 13 ( five days after the previous photo) it was significantly taller. At this time it was growing about an inch in height every day.

By August 21 it had reached up into the branches of the neighboring elderberry tree. It had been growing for 16 days.

At that point I began pruning the elderberry to give the agave more room to flower. The elderberry is deciduous, so I cut it back every year. Note that the agave has many of its lower leaves trimmed back. This is because it sticks out into our guest parking space, and cars tend to hit those lower leaves. They get ratty looking so I trimmed them off.

By September 17 it looked like this. Note that the tip is starting to swell a bit.

All through the rest of September and early October the inflorescence grew little more. It seemed to have stalled at about 6 ft. in height (that's a guess because I didn't actually measure it). Around the middle of October the tip started to flare out more dramatically as seen in the next photo from October 27.

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By this time I was a little surprised that it had not flowered yet. Its growth started off so fast that I thought it would have bloomed and maybe finished by now. But in fact it still seems to have some time to go before the actual flowers come out.

When it actually begins to produce flower buds I will post new photos.

Summer Bloomers, Part 2

This is part 2 of what's blooming in my garden right now.

White/Cream Flowers

I'll start with Baja California Spurge (Euphorbia xanti). Like the Baja Fairyduster, it is not native to our region but it is adaptable, very easy to grow, highly drought tolerant, and flowers abundantly in spring and summer. The plant consists of a dense cluster of densely branching stems that start out slender but become thicker and semi-woody with age. Mine has an unusual shape due to the way I keep it pruned. The flowers can be either white or pink on the same plant.

Next is a small tree, Blue Elderberry (Sambucus nigra caerulea). It is common and widespread in California, and it is an important wildlife plant. The flowers which appear in spring or summer are much valued by pollinators. In late summer clusters of small blue fruit are prized by various birds. If given plenty of water it will be evergreen, or deciduous if allowed to dry out in summer. Mine is never irrigated without effect on the flowers or fruit. Mine is also a somewhat unusual shape due to the way I keep it pruned.

Next up we have a foundational plant of our chaparral and coastal sage scrub - California Buckwheat (Eriogonum fasciculatum). This plant is abundant from the Bay Area down into Baja and is one of the most important pollinator plants. There are several horticultural varieties as well as other species that can be used. Mine is just the plain old species. It is literally crawling with pollinators right now.

Another option for Buckwheat is St. Cathrine's Lace (Eriogonum giganteum), a Channel Islands native. The flowers are similar to California Buckwheat, as you can see, but the leaves are considerably larger. Although it's a coastal plant in the wild, it is tolerant of a variety of conditions. 

Concluding the white flowers, we have Matilija Poppy (Romney coulteri). It's a perennial herb that spreads from rhizomes. It goes semi-dormant in winter, not losing all its leaves but not growing until it warms up in spring. The rhizome means it will pop up where you least expect it or don't want it. Fortunately it is easy to control. The payoff is big, impressive flowers in summer. It is generally recommended to cut back all the stems in fall.

Pink/Purple Flowers

To finish up this review of summer bloomers, I have just a couple of plants with flowers in the pink/purple category. The first is another buckwheat, Red-Flowered Buckwheat (Eriogonum grande rubescens). It is native to the Channel Islands, and although the name is red-flowered, that's not accurate. It's really pink-flowered in my opinion.

The last plant is Blair's Cliffaster (Munzothamnus blairii). Yet another Channel Islands native, this species is more rare and seldom seen in gardens. I got mine from Tree of Life Nursery, and it is a solid performer. The leaves are pretty large compared with most of my other plants, producing a different visual texture. The flowers are great (obviously).

Summer Bloomers, Part 1

 Most of my plants are winter/spring bloomers, which  is typical for California. However, I want to support pollinators year-round, so I have several plants that flower in summer. They attract a lot of honey bees, but I'm more concerned about native pollinators such as bumblebees, digger bees, wasps, and hover flies. They need sources of nectar and pollen all through the summer, which these plants can provide. All of the following are very drought tolerant and all are blooming right now in my garden. Here's a rundown of them, arranged by flower color.

Yellow Flowers

Yellow seems to be the most common flower color in our region. Below is a Gumweed (Grindelia camporum). It is called Gumweed or Gum Plant because the flower bud produces an very sticky white sap that is almost like Elmer's Glue. This plant is in the Asteraceae family and has the standard structure of central disk flowers surrounded by ray flowers (ligules). It is a perennial that is widespread in California and easy to grow. Both the buds and flowers are attractive to pollinators of various kinds. It can bloom between April and October, depending on your exact location. After it blooms the stem will dry up and you can cut it back to the ground. If it's happy it will produce seedlings elsewhere in your garden.

Our next yellow-flowered species is Common Madia (Madia elegans), a lovely and fragrant plant that I got from Annie's Annuals. It's another Asteraceae and a sticky one, but no bowl of glue. It too is widespread in California, though somewhat less common in the southern part of the state. It flowers from June through September. Mine have red/burgundy markings at the base of the ligules, but flower coloration can vary quite a bit. It's strictly an annual so it needs to go to seed in order to have plants next year.

Next up is yet another Asteraceae, this one from several of the California Channel Islands including Catalina, Nevin's Woolly Sunflower (Constancea nevinii and also called Eriophyllum nevinii). Both the foliage and flowers are pretty, which is good because the foliage is retained all year. The leaves are almost pure white, they look lush and healthy all year, and when the flowers are open the color contrast is quite nice. It is considered a rare plant in the wild because feral goats ate it almost to extinction. It is now recovering on the islands and is popular in coastal gardens. I have mine under an Island Ironwood tree (Lyonothamnus floribundus).

One more Asteraceae - the next plant is San Diego County Viguiera (Bahiopsis laciniata). A perennial shrub, it is found only in southern California and northern Baja, from the coast to the foothills. It blooms 7 months of the year, maybe even longer if it likes where you plant it. The leaves are small, deep green and retained all year. It develops more woody stems than the others mentioned here, but it takes pruning and shaping quite well. It is extremely drought tolerant and low maintenance. It should be planted more often in our parks and large landscaped areas in place of the non-natives that we usually see.

Finally a different plant family. This one is Island Bush Poppy (Dendromecon harfordii), also known as Island Tree Poppy. As the name suggests, it is native to the Channel Islands. A close cousin from mainland California is Bush Poppy (Dendromecon rigida), but I think the island species is better looking and better suited to garden conditions, especially near the coast. In the places where I hike, the mainland species is pretty much done flowering now and is dropping a lot of leaves, while the Island Bush Poppy in my garden is looking fabulous without any supplemental water. This plant gets pretty large, not quite tree size but mine is about 10 ft. x 10 ft. So it needs plenty of room. It's also not super happy about being pruned, so again give it enough space so it doesn't need pruning. The leaves are blue-gray-green and retained all year. The flowers are not profuse but they are fairly large and showy. In coastal locations it can have some flowers 9 months of the year, a real boon for pollinators.

Red Flowers

Red flowering plants are very attractive to hummingbirds and butterflies. First up is Baja Fairyduster (Calliandra californica). It is native to central Baja and not our region, but I love Baja plants and this one is a proven performer. The long filaments of the anthers give it the fairyduster look. It blooms prolifically, virtually all year long, and needs very little water. It does well on the coast, in the foothills, and even in the desert.

Right next to my fairyduster is the perennial shrub Chuparosa (Justicia sp.) in the Acanthus family. The species is somewhat in question. It was sold to me as Justicia purpurea, another Baja species, but it looks exactly like Justicia californica which is native to our local deserts. Either way, it is a prolific bloomer, extremely drought tolerant, and bulletproof. In addition it is an excellent nectar producer, and hummingbirds love it. It does well on the coast as well as in hotter inland areas.

To finish up the red flowers, one of my favorites is Scarlet Delphinium (Delphinium cardinale) in the Ranunculaceae (Buttercup) family. The funnel-shaped flowers grow at the tops of very tall, spindly stems. They can get to be 8 ft. tall and sometimes grow underneath shrubs that help hold them up. In the wild they are found along the coast and into the mountains, from Monterey County south into Baja. It is a perennial herb, meaning that individual plants live more than a year but go dormant each year after flowering. During their fall dormancy they must be kept dry. In response to winter rain the plant will resprout from its tuberous roots. They also produce numerous seeds and can spread around your garden if they find it suitable.

Next time - Summer Bloomers, Part 2

Update on Hesperocallis undulata Study

 I have been studying desert lilies (Hesperocallis undulata) for a few years. I started in 2017 when we had enough rain to produce a bumper crop of lilies. At the end of that season I collected several fruit which contained a few hundred seeds. I planted some of these seeds in the ground in Borrego Springs and a few others in a container that I took home to Encinitas. In the winter of 2017-18 a number of the seeds germinated and produced their first hair-like leaves.

The ones in the container in Encinitas did better than the ones in the ground in Borrego, most likely due to receiving a little more rain and some supplemental water from me, as well as cooler summertime temperatures. The container now has three individual plants in it. My goal was not just to grow them but to observe the bulbs after a few years of growth. This year felt like the right year to do so. I waited until the leaves had dried, indicating that the plant was finished for this season. The following photo shows the container with three leaves emerging from the sandy soil.

Today I dumped the soil out of the container and broke it up to find the bulbs, such as they might be. The following photo shows the baby bulbs after three full seasons of growth.

I cut the leaves off at ground level and finished removing the bulbs from the soils so they could be measured and weighed as shown in the next series of photos.

All three bulbs were approximately three inches below the soil surface. The bulb immediately above has the most intact root system, reaching more than 3 inches below the base of the bulb. Next I weighed them. The weight of each is shown in grams below. Clearly these are small bulbs, still immature but having the characteristic bulb structure.

One of the things I have been curious about is how geophytes reach their optimal depth in the soil after germinating on the surface of the soil. These particular bulbs germinated on the surface of the soil 2018. Between then and now, they have descended 3 inches as the bulbs have grown in size. By what mechanism does this occur?

One possibility that I have considered is some kind of contractile root. I examined the roots of these bulbs to see if anything like a contractile root can be found. Two of the bulbs have very fine roots that could not possibly be contractile. However, the bulb weighing 0.34 grams has a thicker root than the others. This bulb also has a more typical root adjacent to the thickened one. Below is a closeup photo of those roots.

Although it isn't a clear-cut case, this thickened root appears to have some ridges or rings similar to a true contractile root. It is interesting that this bulb is also the largest by weight, but what this means is unclear. Why this thickened root is not present on the other bulbs is also not clear to me. It could be that the other bulbs had such a structure but it was detached when I removed it from the soil. I didn't see anything like this, but it is still a possibility. Another possibility is that the other two bulbs lost their thickened root earlier, while the larger bulb retained it longer. A third possibility is that the other two bulbs never had such a root, but that raises the question how they came to the same depth in the soil as the larger bulb. These are questions that will have to wait for an answer.

In addition to these bulbs that were produced from seed, I have one bulb that I collected when it was already more-or-less full size. I put it in a container and brought it to Encinitas to see how well it would do in a mild, coastal environment. It did quite well, even flowering one year. This year it didn't receive enough rain to leaf-out, and I didn't give it enough supplemental water. I decided to remove this bulb from the soil to see what its condition might be. 

There isn't much to be learned from this bulb because it has no visible roots, I don't have a previous weight for it, and I was unable to get an accurate measurement of its depth. However, this weight is one data point that I can use as a baseline for measurements in future years.