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Monthly Archives: December 2016

Garden Blue Flag Iris

Many gardeners think blue flag iris, I. versicolor, are only useful for water gardens but as long as the soil remains evenly moist, they make admirable plants for the standard garden. With over 20 selections to choose from, this iris demands a second look.

For gardeners interested in water features, one of the premier native plants is the blue flag iris, Iris versicolor. However, this plant is not restricted for use only in water gardens. If the soil remains evenly moist, blue flags will grow quite happily in a regular garden setting, thus they can be utilized in the border or in wildflower gardens. They prefer organic-rich, acidic soil and full sun. They are very hardy plants, surviving into zone 3, even 2 if there is adequate winter mulch. In height, they can vary from 30 cm to over 100cm.

In the wild, blue flags grow from Minnesota east to New England, south to Virginia and north into eastern Canada, from Manitoba east to Newfoundland. Flowers are mostly in various shades of violet-blue, from mid tones to dark velvety shades. However, with such a large distributional range, other more interesting colour forms often spontaneously arise. Gardeners, nurseries and plant breeders are quick to notice these aberrant forms and introduce them into their gardens. The result is that today there are well over 20 named selections, ranging in colour from white through reddish-pink to nearly black.

Among the more classic blue cultivars are ‘Cat Mousam’, ‘China West Lake’ and ‘Whodunit’. I have been fortunate in the wilds of Newfoundland to find a couple of light blue selections with darker veining. These appear somewhat similar to the popular ‘Between the Lines’. Others in the light violet-blue category are ‘Light Verse’ and ‘Epic Poem’. Both of these are essentially white but have such dense light violet-blue veins that, from a distance, the flowers appear pale blue.

‘Murrayana’ is a true alba form, being completely snow-white with yellow at the base of the falls. There is some dispute if this plant is a true I. versicolor (refer to my earlier article ‘The Story of Iris versicolor ‘Murrayana’) as the flower shape is somewhat unusual but according to the current literature, it is indeed considered an alba form of I. versicolor. ‘Little Rhyme’ is a white form with a classical blue flag shape but on a dwarf 30 cm plant. ‘Versicle’ is also white but has scattered pale lavender-blue veins which imparts an attractive ice-blue colour.

The rest of the more popular selections are varying shades of reddish-violet. These include ‘Party Line’, ‘Shape Up’, ‘Raspberry Slurp’, ‘Versijack’ and ‘Kermesina’. ‘Mint Fresh’ and ‘Candystriper’ are notable in being white with heavy reddish-violet veins, which from a distance, impart a light pink colour to the blooms. ‘Pink Peaks’ is a medium reddish-violet selection that is quite dwarf, under 30 cm.

Among the darkest selections are ‘Wild Wine’ which is deep velvety reddish-violet. Perhaps the most striking is ‘Mysterious Monique’. This selection is rich, dark purple and from a distance appears nearly black. The signal of most blue flags is yellow but the signal of ‘Mysterious Monique’ is white, which only adds to the striking appearance of this selection. No doubt, more selections of I. versicolor will arise. As an active breeder of this group of iris, I hope to one day release selections of my own…stay tuned!

Among the dark selections are ‘Wild Wine’ and ‘Mysterious Monique’


At 45 letters, “Pneumonoultramicroscopicsilicovolcanoconiosis” is considered to be the longest word in the dictionary. It’s the name for a disease of the lungs, caused by the inhalation of silica dust. “Phytoremediation” comes nowhere close to this length, but is still a mouthful. It comes from the Greek word “phyto” meaning “plant” and the Latin word “remedium” which means “restoring balance.”

(Editor’s Note: This article was originally published on July 28,2010. Your comments are welcome, but please be aware that authors of previously published articles may not be able to respond to your questions.)

What, precisely, is phytoremediation?

Enough etymology. Simply put, phytoremediation is the use of plants to clean up environmental pollution in soil and water. Contaminants include metals, pesticides, fertilizers, and–our biggest worry at the moment-crude oil. These plants also help to prevent weather and groundwater from transporting pollution away from a polluted site to other areas.

How does it work?

Certain plants have the amazing ability to break down pollutants or contain and stabilize them by acting as filters or traps. In most cases, this involves the root system of the plant. Roots in these plants provide a very large surface area to absorb and accumulate not only nutrients essential to growth, but also most contaminants. These are either stored or broken down into benign compounds.

The use of trees in this process is gaining popularity, primarily because of their extensive and deep-seated root systems. Their roots can more effectively trap and absorb pollutants, even those that leach down into ground water many feet beneath the soil surface.

Case in pointThe use of poplar trees (Populus spp.)– or any other tree for that matter–in phytoremediation was pioneered by Lou Licht, a graduate student in Civil and Environmental Engineering at the University of Iowa. In 1991 he planted a test plot of 11,000 poplar trees along a creek that serves as drainage for the surrounding farm fields about eight miles from my home in South Amana. The creek drains directly into a local lake called simply “The Lily Lake,” because of its lotus lilies and their spectacular bloom in July and August. See photos of plaques at right for further information.

Licht’s experiment was a great success, and proved instrumental in boosting the recognition and fortunes of his company, Ecolotree, founded in 1990. It has the distinction of being the oldest phytoremediation firm in the world.

Why use poplars?

o Greater than 25 species worldwide (Species most commonly used in phytoremediation include P. deltoids, P. trichocarpa, P. simonii, and P. nigra.)
o Fast growing (3 to 5 meters/year)
o High transpiration rates (100 liters/day optimally for a 5 year old tree) for drawing moisture and contaminants from the soil
o Not part of the food chain
o Can be used for paper production or as biomass for energy
o Relatively long-lived (up to 30 years)
o Easily grown from cuttings
o Can be harvested and then regrown from the stump
o Can extend roots down to the water table and pump from the zone of saturation, making them natural solar-driven pump and treat systems.

A lone Canadian Goose paddles among the lily pads, and Trumpeter swans enjoy the peacefulness of a cove at the Lily Lake. Wildlife now flourishes in the lake and its surroundings as never before. New species since the onset of the phytoremediation project include a multitude of Canadian Geese, wild Trumpeter Swans, Bald Eagles, otters, and mink. Other denizens include muskrats, turtles, and many different species of birds and fish. Fishing is not a common activity at the lake, since the waterlilies cover almost the entire surface of the water for most of the season.

What is that Dracaenas ??

Dracaenas are Agave relatives and are a large group of plants that include some of the more popular house plants as well as some of the most striking xeric and massive trees used in outdoor landscaping. This article is an introduction to this interesting group of plants.

Dracaena is a large genus of primarily African monocot plants of which there are well over 100 accepted species, most which will not be covered in this article and are virtually unknown in cultivation. However, some are commonly grown landscape trees in some areas of the world, and others are easily among the most popular of all the house plants. Currently most plant sites list Dracaenas in the family Asparagaceae, along with a lot of other similar plants, such as Cordylines, Beaucarneas and Dasylirions (etc.). But they have been bumped about a bit, from the family Liliaceae and Agavaceae to Ruscaceae (which is where they are in the Davesgarden Plantfiles at the time this article was written, but should probably be moved). It sometimes gets old when your plants are continually being reclassified and lumped in different ways. Still, the plants themselves could not care less. It will be difficult to discuss Dracaenas without also discussing Cordylines, their southern cousins from Australia and nearby exotic places (exotic to me, at least). So I will sort of touch upon them, too, but leave the bulk of Cordyline talk for a subsequent article.

Some generalities about Dracaenas are that they are generally solitary plants with single stems (or trunks, or sometimes called ‘canes’) and are either branched or not- most species seem to branch eventually once they get older, but start out as palm-like plants with a top rosette of leaves and a naked stem. Dracaenas are often mistaken for palms, and are often seen in the plant identification section of Davesgarden with a query as to what species of palm they are. Some are immensely tall and massive, such as the very old Dracaena dracos from the Canary Islands (and commonly grown here in California). And some are pretty tiny such as the ‘Lucky Bamboo’ (actually a Dracaena species) often sold at curiosity shops with their canes braided in various ornamental patterns. Some are very drought tolerant and can survive months without any water, performing quite well as xeric landscape plants. While others are very tropical and can grow with their stems in water all the time (again, the ‘Lucky Bamboo’ tolerate this quite well). Most Dracaenas are listed frequently on toxic plant lists, but none are very toxic. However, unlike their close cousins, the Cordylines, these are not cultivated as a food source.

Dracaena draco in a cactus garden, looking somewhat like a palm, Dracaena braunii, aka Lucky Bamboo.

They grow like a typical monocot with leaves erupting from a central meristem and forming a circular rosette of leaves that hang on along the stem until, with age, they slough off. These leaves anchor themselves around the stem, unlike dicot leaves which tend to grow straight out of stems from a single point. This makes their removal or ‘pruning’ quite easy, as one can simply pull the lowest leaf off the stem one at a time by unsheathing it with a downward pull. This is usually preferred in smaller cultivated plants, rather than leaving the dead leaves to fall off constantly, and creates a neat, tidy appearance.

Dracaena draco showing leaves erupting all from same point (meristem) shows leaf bases and scars where leaves have been removed from

One of the common names of the Dracaenas, as a group, is the Dragon Tree. However only a few Dracaenas develop into ‘tree’s- the rest being are smaller, shrubby plants. Though these do not look anything like dragons, at least some of the tree species (Dracaena draco and Dracaena cinnabari) have reddish sap when cut. That red dye has mythological ties to dragon blood, which was shed by Hercules killing a dragon who’s blood then somehow stimulated the subsequent growth of the dragon trees. Dracaena means female dragon in ancient Greek). The problem with the name Dragon Tree is it also applies to a very dissimilar tree called the Paulowania tree (a very fast growing lumber tree from Australia- a true dicot tree). And some Dragon Fruit does not common from the Dragon Tree, but from a cactus.

Another common name applied to one of the most common indoor house plants is the Corn Plant, thanks to is vague similarity to a real corn plant (another upright slender monocot). This name specifically refers to Dracaena fragrans, but sometimes is used to describe other species as well.

Dracaena draco– the Dragon Tree: This is a large, very long-lived species from the Canary Islands, some nearby islands and the very western edge of Morocco (African mainland). One of the most massive trees on the planet is an estimated 650 year old Dracaena draco specimen on the Canary Islands. I have seen large, old specimens here in California, but they are dwarfed by this monster (see below). Older specimens have been known and reportedly grow over seventy feet in height.

This species of Dracaena has very thick, leathery, rough-surfaced and somewhat fleshy, succulent leaves unlike most of the other commonly grown Dracaenas in cultivation. The tips of the leaves are blunted. Removing a living leaf from the trunk will result in a minor ‘bleed’ as some of the red dye this tree is named for will show up as a moist red ring at the leaf scar. This dye is used in cultivation as source of lacquer color (supposedly Stradivarius violins were dyed with this substance). As the leaves age, they dry up and fall from the trunk, leaving a ringed but very smooth, almost shiny trunk that is very ornamental in younger plants. The fresh leaf scars leave an almost woven-like pattern that unfortunately fades with age. This pattern, from a distance, gives the trunks a basket-weave appearance. Older trunks become more woody and ordinary in appearance. At the point of branching, each new stem has a narrow base giving the overall plant a somewhat cartoon appearance as though it had muscular arms relatively to their skinnier joints.The overall effect is unique and ornamental.

Dragon trees are commonly grown xeriscape plants in Mediterranean and desert climates as they are extremely drought, heat and wind tolerant. Though starting out as branchless, palm-like plants, they eventually start to branch at their flowering points, and then branch again, and again at each point the tree makes a flower. Eventually massive heads of thick green agave-like leaves topping smooth, succulent stems cover a wide area and threaten to come crashing down, even bringing down the entire plant if too top heavy. Many older, top-heavy specimens in botanical gardens can be seen held up with supporting poles.

Even these plants can fall over in heavy winds as they are so top heavy. This tree has some root rot from being planted in very clayey soil (left); right shows a yound plant flowering- likely it will branch at that point now.

These trees are very slow growing and it can take several lifetimes to get these to a tree-like landscaping size. But if given plenty of water in the summers and grown in well draining soils, their growth rates can be maximized. Plants grown from seed can reach several feet in under 10 years if grown well.

Some similar species to Dracaena draco include Dracaena cinnabari, a native to Socotra where it dominates much of the landscape (a landscape known for its striking and bizarre flora). This species differs primarily in having many more leaves per crown and the leaves are longer, stiffer and end in a definite point. If anything, these magnificent trees are even more spectacular than Dracaena dracos, forming nearly perfect symmetrical umbrella-like crowns on thick stalks. Photos of this plant are often stunning and ornamental. It is a threatened species collected locally for its red dye.

Dracaena serrulata is another similar species even rarer in cultivation. This species is native to Oman and Yemen. Though not quite as ornamental as it cousins, it still is an impressive tree-like plant growing up over thirty feet. Leaves a more scimitar-like, stiff and blue-grey.

The remainder of the Dracaenas commonly encountered in cultivation are shrubby plants who’s stems are referred to as canes rather than trunks. Some of these (notably Dracaena fragrans, marginata and reflexa) are very popular and relatively easy house plants. They are not only popular for their ornamental appeal, but they reported are natural low level air filters and have been known to reduce formaldehyde levels in room air (is formaldehyde a common problem in room air?).

Dracaena fragrans, aka the Cornstalk Dracaena, is probably the best known of all the Dracaena species. Numerous cultivar variations of this plant can be found in virtually all malls throughout the US and show up in many nurseries for sale as common house plants. This plant is native to much of tropical Africa where it can grow up over forty feet in height, though looking more like a clump of skinny palm trees rather than an impressive tree with a single large trunk. Most Dracaeana fragrans have thin, arching, sometimes undulating and usually glossy lancelote leaves that radiate out from the central canes in rosettes typical of the monocotyledonous plan. There is some variation in leaf thickness, length and waviness. But the primary variations in cultivation are the color and striping patterns which there seem to be a nearly endless variety. Though most Dracaena fragrans have narrow canes or stems from one half to one inch in diameter, at least one variety (Dracanea fragrans ‘Massageana’), the corn plant, has a trunk-like stem up to four inches in diameter. Flowers are quite showy and exceptionally sweet smelling (hence the name fragrans).Indoor plants may even flower now and then filling the entire home with their scent.

Though these plants are from tropical Africa and they look like palms, one should not treat them like palms when growing them indoors. They are extremely hardy, tolerant of low light and humidity, but do not tolerate being constantly wet. Rotting of the root ball is probably the most common cultivational problem of these indoor plants. Most recommendations on caring for these as indoor plants suggest letting the soil dry out before watering again. On the other hand, letting this plant dry out too long will result in brown tipping and death of the lower leaves prematurely. Reportedly many of the indoor Dracaena species are sensitive to fluoride in tap water. For treating plants that seem to brown tipping too much, one might try treated (reverse osmosis) water or rain water. A good soaking of the soil every now and then (yearly for example) to flush out accumulated salts that collect on the root hairs is a good idea. Fertilization should be kept to a minimum as well (but that pretty much goes for most indoor plants).

One of the best things about these plants is they can be pruned easily and will often result in two plants instead of just a shorter one. These are very easy to reroot and propagate in such a fashion.If one happens to rot their plant by overwatering, all one usually needs to do is remove all the rotted tissue (with some margin for safety) and reroot the entire plant. And if they grow too tall or leggy, again, chop the tops off and re-root them. The original plant will usually regrow from the cut area, often branching into multiple canes as well.

These need plenty of light indoors and though they do tolerate very low light situations, they will not stay healthy that way long, and their colors will be abnormal. Direct sun, however, is not recommended for indoor plants. Outdoors, most of these tolerate some direct sun except in very hot, arid climates.

Note that this species has many synonyms. Dracaena massangeana and Dracaena compacta are two common ones, but also Dracaena deremensis and Dracaena warneckii are two more

Dracaena marginata, also referred to as the Dragon Tree (though apparently less accurately as these do not bleed red) or Red Margined Dracaena, is nearly equally popular as a house plant though far less varieties are available in cultivation. This Madagascan native has even thinner stems and far thinner leaves than do Dracaena fragrans. The multicolor or rainbow variety is the most popular by far, but all green or maroon- leaf varieties are still very commonly encountered in cultivation. Dracaena marginata flowers are fairly small and do not that great an odor.

Dracaena marginatas ‘type’ species in mall left; Dracaena marginata growing outdoors in Hawaii showing it can become a relatively large tree in the right situatiion (never gets this large indoors) center; right shows close up of leaves on plant in my yard

Some sources have Dracaena marginata as a supspecies of Dracaena reflexa, but somehow both names are accepted in the World Check List of Plants, so I unclear which is the correct scientific name for this species (or subspecies). Either way, Draceana reflexa is a very similar species and some forms are so similar I cannot tell them apart. Additionally, some forms are very similar to some of the Dracaena fragrans varieties in terms of variegation and leaf size/shape. In general, Dracaena reflexa leaves seem to be shorter and the canes tend to snake about more not always growing upright. Some of the common names for Dracaena reflexa include ‘Song of India’, ‘Song of Jamaica’, ‘Song of Java’ etc (depending on the cultivar leaf color). Dracaena reflexa are native to several islands of the Indian Ocean (and Madagascar, if one includes Dracaena marginata into Dracaena reflexa).

More Dracaena reflexa ‘Song of India’ shots- left at a nursery; right showing flowers on plant in Hawaii. These flowers are not nearly as nice smelling as those of Dracaena fragrans and are typical of this species as well as Dracaena marginata.

Dracaena marginata and Dracaena reflexa are treated pretty much the same in cultivation as Dracaena fragrans. However, in my experience, Dracaena reflexa is more cold sensitive and one rarely sees these grown as outdoor plants in southern California, while Dracaena marginatas are commonly encountered

Other species of Dracaena one may come across in cultivation include some of these plants below.

Dracaena braunii (aka Dracaena sanderiana) aka Lucky Bamboo: this is a very common plant in cultivation and amazing, intricate weavings of its canes are often seen in shops around the world. This is a very tropical species from Africa and parts of Asia where it grows in the dense undergrowth, rarely seeing full sun. Unlike some of the above species, this is a small caned plant that grows very well if its roots are kept in just an inch or two of water. It will grow very slowly in this manner, with regular changes of water (weekly), and occasional fertiliization (very dilute liquid fertilizer). The better the water quality, the better the plant will look (water high in salts and flouride will be hard on this plant, as it is on most plants). Dracaena braunii can also be grown in soil, but there one should let the top of the soil dry out a little between waterings or even this species can rot.

More Dracaena plants below. Note that some of these species are much more highly branched and look a lot less typical of the monocot rosette-on-a-pole growth plan.

Dracaena cantleyi is a rare plant in cultivation, but my palm growing friend has it in his backyard and it is doing quite well here in California. This is the more typical monocot style.

Dracaena ‘Juanita’ at a nursery , Dracaena goldiana at same nursery. These two Dracaenas do not show the typical monocot shape or growth pattern and I am unsure how they fit into the genus in terms of relationship.

The Genus Cordyline, as mentioned above, is a very closely related genus in the family Asparagaceae but a different subfamily (Lomandroidea instead of Nolinoideae). Both Dracaenas and Cordylines look very much like their Yucca cousins. Some sources lump the two genera together. Cordylines are primarily used in as outdoor plants in cultivation with the exception of the most popular species, Cordyline fruiticosa (the Ti Plants). Below are a few photos of Cordylines, but more about these plants will be discussed in a future article.

What is that Selaginella ??

Every once in a while the gardener discovers, quite by accident, one plant or another that becomes an all-time favorite. Such is my experience with arborvitae fern (Selaginella braunii). My introduction to this plant happened a few years back when I visited the garden of a neighbor. I was smitten from the beginning.

On the day of my visit, my neighbor showed me a beautiful mass of plants growing in a container. She called it Selaginella.That was easy for me to remember because my neighbor’s name is Sally, and my sister-in-law’s name is Gennella. Put the two together, and you have sallygennella, which is close enough to help me remember the generic name.

Selaginella braunii (Arborvitae Fern)

Even though this plant has arborvitae fern as its common name, it is not a fern at all, but is a prehistoric fern relative called club moss or spike moss. Since it is a vascular plant that produces spores, it is often mistaken for a fern. Scaly foliage resembles that of arborvitae or cedar. Fronds of finely dissected foliage look delicate, but quite the opposite is true. Arborvitae fern is a tough, hard-working plant that fulfils its groundcover role quite admirably.

Several years ago I planted three one-gallon containers of arborvitae fern in my garden. Gradually it has grown to cover the ground with a solid mass that inhibits weed growth and remains attractive year round. In fall it turns a rusty color, and often, by spring it turns tan after hard frosts kill the above-ground portion of the plant.

Experimentation has taught me to leave the winter-burned foliage to its own devices. This past year, I mowed about half of the arborvitae fern and left the other half as it was. Spring brought about a new flush of growth that soon covered both areas. I was hard-pressed to tell which side had been mowed. From now on I won’t bother with the extra work involved in mowing the area.

Planting and Caring for Arborvitae Fern

Site arborvitae fern in a moist but well drained spot in shade to part shade. Amend sand or heavy clay soil by incorporating a two- or three-inch layer of compost or humus. Plant quart or gallon-sized containers a foot or so apart. Water as needed to maintain damp soil. Fertilize in early spring just as new growth begins with all-purpose, slow-release fertilizer.

The club mosses can be divided easily at any time of year. Simply separate mature clumps and replant the divisions. Cuttings root easily if inserted in soil and kept damp. It is also possible to grow from spores.

Other Species of Selaginella

The GRIN website lists 33 species of Selaginella, although other references list 56 or more. Some accounting for the differences in opinion has to do with the taxonomic splitters who separate plants into different species based on very minute differences. and the lumpers who tend to group plants with similar traits into one species. All agree that the family is Selaginellaceae, and Selaginella is the only genus in the family.

Peacock fern (Selaginella uncinata), also sometimes known as blue spike-moss or rainbow fern, is a diminutive (6 inches tall, spreading to 2 feet) club moss noted for its bluish green iridescent leaves. It is hardy from zones 6 to 10.

Gemmiferous spikemoss (Selaginella moellendorffii) (zones 7 to 10) is an easy-to-grow species from China that bears tiny plantlets that drop off and form new colonies. Dave’s Garden PlantScout lists four sources for this plant.

Golden club moss (Selaginella kraussiana) is a popular species. Native to South Africa, this small, creeping species forms dense mats of green foliage. Some cultivars, with such apt names as ‘Aurea’ and ‘Gold Tip’ have golden yellow leaves and stems, or stems tipped with bright, lime green.

Several species are native to the United States and Canada, and like those from other parts of the world, they vary from wetland species to those that grow in dry deserts, such as Selaginella lepidophylla (flower of stone). Sometimes sold as a novelty plant in its dry state, this “resurrection plant” turns green when water is added.

Red spike-moss or rock spike moss (Selaginella rupestris) is native to all of the eastern United States and the Southern Canadian provinces. Threatened in Indiana and presumed extirpated in Ohio, the range of this spike moss is sporadic and limited to mostly rocky places.

The ornamental Selaginellas look great in hanging baskets or in containers skirting taller plants. Small selections are useful in terrariums. It is excellent in front of taller shade plants such as caladium, aspidistra, and impatiens.

Following the visit to my neighbor’s garden, I began to notice Selaginella in garden centers. Keep your eyes open as you visit your favorite nurseries, and investigate on-line sources. You may find several species that would make great additions to your garden.