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Welcome to Crawford's Corner!

If you have further questions, please write to Bruce at Crawford@njaes.rutgers.edu

March 2021 Plant of the Month – Snowdrops – The Start of the Garden Symphony

March 4, 2021 By Bruce Crawford

Every autumn, gardeners visit their favorite garden center and are confronted by rack upon rack of rather unsexy appearing ‘bulbs’. Occasionally, a gardener will take a leap of faith and buy a few of the dry, papery brown objects in the hopes of flowers, similar to those prominently presented on the display will magically appear the following spring. And magically, appear they do! With the first promise of warmer weather, bulbs begin to awaken and start their spring ‘symphony’ of color. Of the bevy of bulbs available to brighten your garden, there is none as iconic nor as willing to lead the symphony as the white flowering Snowdrop.

Snowdrops are botanically known as Galanthus with roughly 20 species stretching from the Pyrenees of northern Spain and southern France east through southern Poland and Italy to Syria and Northern Iran. Although a member of the Amaryllis family or Amaryllidaceae, their physical appearance certainly does not bear any resemblance to the Amaryllis flowers that adorn many a January windowsill. I realize it will never happen, but plants growing from dormant underground structures should technically be called geophytes, not bulbs. A true bulb consists of layers of modified leaves, such as seen when slicing open an onion. Aside from true bulbs, geophytes include corms and rhizomes, which are actually modified stems and are solid when cut open. Snowdrops are a true bulb, composed of modified leaves with each bulb roughly the size of a thumbnail. The common name of Snowdrop first appeared in 1663 in the book ‘Great Herbal’ written by the English botanist John Gerard (1545-1610). The origin of the word is uncertain, although it certainly does look like a drop of snow emerging from the ground. Galanthus was initially penned in 1735 by the Swedish botanist Carl Linnaeus (1717-1778) in his first major document named Systema Naturae. Honoring the milky white flower, the name is derived from the Greek Gála or milk and Ánthos for flower.

SnowdropsThe most common species planted in Gardens, and very deservedly so I might add, is Galanthus nivalis. This species is also the type species for the genus, against which all species are evaluated and compared. This species was also named by Linnaeus in 1753, with the species epithet coming from the Latin meaning ‘of the snow’ or ‘snow-covered’. Typical to the genus, each bulb produces two linear leaves that ultimately grow to 6-8” long. The flower scape emerges from in-between the leaves when they are merely 1-2” tall as seen at left. The flower scape ultimately stretches to 6-8” tall as well and terminates in what appears like a shepherd’s crook, with the flower dangling from the center of the crook (see image below of Galanthus elwesii). When the flower initially emerges from between the leaves, the bud is held upright and is enclosed by a protective leafy bract or spathe. The spathe consists of two modified leaves called spathe valves and two transparent membranes. The spathe valves are located on either side of the flower bud and appear as slender green lines, as seen in the image above.

SnowdropsThe two transparent membranes are connected to the spathe valves and wrap around the bud. As the bud expands, the membranes split open and fall away, while the 2 spathe valves elongate and curl downward, forming the ‘shepherd’s crook’, as the image of Galanthus elwesii depicts at right. As the spathe valves elongate, the flower bud transitions from an upright bud to a dangling flower, located near the center of the spathe valves. An incredible ‘dance’ and fun to watch evolve if time permits!

As is typical to all members of the genus, the flowers are composed of 6 white tepals. A tepal is an organ whose function is to attract pollinators, but there is no true distinction between the inner petals and the outer leaf-like sepals. The 3 outer tepals are usually pure white in color with a longer and more linear shape, although some seedlings have a more rounded form. They are convex in cross section and are roughly ¾” long for this species. Initially hanging downward, they flair outwards on warmer days, giving the flower greater presence and expose the three inner tepals to pollinators. The inner 3 tepals are bilobed at their tip, roughly 1/3 the length of the outer whirl and grow tightly together to form a central cone. Each inner tepal bears green markings, which vary by species. G. nivalis has a single green mark spanning the two lobes at the tip of the tepal. These markings not only act as nectar guides for pollinators, but are photosynthetic and aid in producing sugars for the production of seed. Snowdrops go dormant by late May. SnowdropsThe compressed growing period pressures the genus to produce as many carbohydrates as possible for generating seed and developing new bulbs for the following year. Albeit small, these green markings aid in the production of the needed sugars! Interestingly, the foliage and tepals also contain small air-filled spaces that allow the flowers to tolerate subfreezing temperatures as they begin to bloom. The globe shaped ovary is located above the tepals, with the small black seeds maturing in mid to late May. The seeds have an attached lipid rich structure called an elaiosome, which not only feeds and attracts ants, but serves as a means of seed dispersal.

‘Flora Plena’ is one of several cultivars that has numerous additional tepals, producing a ‘double’ flower (pictured left). When viewed from above, the additional whirls of tepals gives the flower a fuller appearance, much like how a Hoop Petticoat impacts a dress. Unfortunately, the extra tepals also add weight to the flower, causing it to droop and the details of the bloom are not evident unless it is physically turned towards the viewer. It is also one of the last forms to bloom, typically still attractive and in color in April!

SnowdropsAnother readily available species is the formerly mentioned Galanthus elwesii. The plant resembles its cousin in all aspects except it is larger with the outer tepals reaching an inch or longer in length. They are often the first species to emerge and feature green markings on both the upper and lower ends of the inner tepals. They can even be connected, as seen at right. The larger outer tepals results in a flower upwards of 2” in diameter when fully open! The species honors the British botanist and entomologist Henry John Elwes (1846-1922), who came across a mass of large flowered Snowdrops in 1874 while botanizing in the mountainous regions near Smyrna, Greece. In 1875, the English botanist Dalton Hooker (1817-1911) honored Elwes with the species epithet. Interestingly, the plant that Elwes found was actually a previously described species named Galanthus gracilis and Hooker’s species name was used to describe another, as of yet unnamed large flowered species!

SnowdropsAnother delicate and very attractive species is Galanthus ikariae. Named by John Gilbert Baker (1834-1920) in 1893, it is native to several Greek islands in the Aegean Sea, including the island of Ikaria for which it is named. If the island’s name sounds familiar, it is named after Icarus, who in Greek legend escaped from King Minos by fabricated wings from feathers connected by wax. When he flew too close to the sun, the wax melted and he fell to earth. Legend has it he was buried on this island that bears his name! This species bears smaller pendant flowers to 1” long and a single green mark on the tips of the inner, bi-lobbed tepals (pictured at right). Often, this green mark will extend half way or further up these tepals. The foliage is glossy and more attractive than the mat-green forms, growing to 6-8” tall. Not ideal for plugging into turf since the reflective foliage does not blend well with turf grass. In the wild, the plant is often found in river valleys, growing with Cyclamen hederifolium in deep humus rich soils. It has also been found in upland gravely soils in scrubby growth. The plant is somewhat less winter hardy, but I have not had any issues in over 30 years of growing the plant. Unfortunately, it does not appear to naturalize as readily as other species.

Snowdrops are an easily grown bulb, providing your garden is zone 7 or colder, since they resent summer heat. The challenge is often getting them established. Due to their smaller size, some of the bulbs desiccate before they arrive on retail shelves. The most successful time to transplant is while the foliage is still green and they are in active growth! All the species enjoy well-drained soils and thrive in full sun or in locations beneath deciduous trees. Plant to a depth of three times their diameter or around 3” deep. They are best planted in random groups with 3-6 per hole to provide a more mature appearance. Consider interplanting among deciduous shrubs such as early blooming Quince (Chaenomeles) and Witch Hazel (Hamamelis), or at the base of Red Stemmed Willow (Salix alba ‘Britzensis’). Or plant in turf, providing you can wait until the second week of May to make the first cut, allowing for the foliage to go dormant before it is cut.

Snowdrops are a remarkably easy and rewarding bulb for your garden, typically the first bulb, or if I may, geophyte to awaken in the NJ garden. I should also mention the vast number of unusual Snowdrop selections available from specialty nurseries with unique green or yellow markings. These selections can drain the checking account, yet in moderation they will enhance your appreciation for this plant! Whether ordering bulbs next fall or plants this spring, Snowdrops will delight you for years to come as they start your spring symphony of garden color.
Snowdrops

Bruce Crawford
Program Coordinator for Home and Public Horticulture (NJAES)

Gardening Notes for February 2021

January 25, 2021 By Bruce Crawford

The month of January provided near average temperatures for the month, although the start of February is forecast to be colder as I write these notes. February is the month to finalize any design considerations for the year to come since March becomes busy with gardening activities. This month is also the time to complete the ordering of seeds, since many of the more popular varieties will soon become sold out. On warmer days, make it a point to walk through your garden, enjoying its beauty and giving thought to exciting new spring improvements. Reread your journals from last year, and focus upon how to improve those parts of the garden that performed poorly or on how to repeat last years’ success stories!

Things to do:

    gardening pruners

  • Sharpen pruners and handsaws in preparation of the many pruning tasks to come. If you own a by-pass pruner, like a Felco (pictured at right) or Corona, take the pruner apart to sharpen since the side of the blade without the beveled edge needs to be laid flat on a sharpening stone to sharpen.
  • If you own a saw with a tri-edge blade that is dull, they are notoriously difficult to sharpen and it is probably best to simple purchase a new blade.
  • Clean and sharpen the edge of spades, as well as make certain wheelbarrows and other tools are in good shape for the season to come.
  • Start to prune fruit trees, including apple, pear and quince as well as grapevines. For budded fruit trees, including Pawpaws (Asimina), make certain to remove root suckers, since they are actually the understock and are not the plant/fruit variety that you wanted.
  • Prune winter damaged branches if your garden experienced snow, ice or wind damage. When pruning back to a trunk, be certain not to remove the swelling where the branch meets the trunk, otherwise called the branch collar. The collar aids in the healing process.
  • Should it snow this month, knock the snow off of shrubs to reduce limb breakage.
  • Begin to prune multi-stemmed shrubs, such as Forsythia, Lilac, Deutzia and Weigela. These plants flower best on younger stems necessitating the removal of 1 to several of the oldest canes in order to provide light for the growth of new canes. For Lilac, if the plant only has one or two large trunks and it is not suckering, it is most likely grafted onto privet understock. In these cases, it is safer not to prune the plant back harshly, since it will not sucker from the base.
  • Bring Forsythia, Quince and Witch Hazel (Vernal Witch Hazel is pictured below right) branches into the house for forcing or to enjoy the flowers and fragrance should they be in bloom.
  • Witch hazel

  • Clean-up the greenhouse. Check on the heat mats and grow lights to make certain everything works and is clean. Check as well for sufficient potting soil, labels, fresh markers for labelling and pots for the seeding and potting tasks to come?
  • Near the end of the month, start to sow seeds indoors for cool season crops such as Broccoli, Cabbage and Leeks and for warmer season crops or ornamentals, such as Begonias, Eggplants and Hot Peppers.
  • Finish ordering seed for spring. Go through your stored seed and discard packages that are over 2 years old. Or, you can place some of the older seeds on a moist paper towel and place in a warm spot (like on top of the refrigerator) to evaluate the percentage of germination. If few seeds germinate, discard the package. Organize them by sowing time to make life easier for April and May!
  • Check on the bulbs that you have brought into the garage or placed in a protected spot outside for forcing. The Crocus and Snowdrops should be ready to bring inside soon for you to enjoy.
  • Check on stored tubers and corms, such as Canna or Elephant Ears. Discard any that are showing signs of decay.
  • With the days becoming longer towards the end of the month, begin to water indoor plants more frequently – but do not saturate, since that will encourage fungus gnats & root decay.
  • Lentel Rose foliage

  • Cut back Lenten Rose (Hellebore x hybridus) foliage (pictured at right) and other early bloomers, such that the foliage does not distract from the floral display. Watch areas where early spring bulbs are planted for some early color (and to avoid stepping on them!)
  • Cut back any matt forming perennials, such as Nepeta (Catmint). Often rodents will hide beneath the foliage and either eat the crowns or create homes. Leave behind any fallen leaves or lightly mulch to protect the crowns from freezing temperatures.
  • Do not remove any temporary winter mulch on Perennial beds, such as the boughs from the Christmas tree, unless it is around those early spring blooming bulbs. Late February and early March can still be bitterly cold.
  • Continue to apply anti-desiccant sprays to recently planted Rhododendrons, Hollies, Camellias or other evergreens that are in an exposed location on days with above freezing temperatures.
  • Watch for deer predation and set up fencing if needed.
  • When temperatures rise into the 40’s, get a head start on edging those bedlines and spreading mulch where possible. Every day that you can complete a springtime chore will relieve some of the burden of the April panic to get everything done.

Bruce Crawford
State Program Leader, Home and Public Horticulture (NJAES)

January 2021 Plant of the Month – Arum italicum: One Hot Flower!

January 25, 2021 By Bruce Crawford

italicumWith the chilly temperatures of winter well entrenched in our Gardens, evergreen foliage clearly plays an important role in providing interest at this time of the year. Conifers serve an important role in providing the bones for the garden, but there is still a need for detail plantings as we walk about our walkways and paths. One plant I have enjoyed using over the past 30 years for winter foliage and form, as well as for its ‘hot’ flowers come spring is the Italian Arum, Arum italicum.

Italian Arum is a member of its own family of Araceae – the Arum family – and is native to Southern Europe, Northern Africa and the Middle East. The genus name was crafted in 1753 by the Swedish Botanist Carl Linnaeus (1707-1778) from the Greek word Aron meaning poisonous. Plants within this genus contain calcium oxalates, which when ingested result in the swelling of the throat, tongue and eventually cause difficulty in breathing and even death for children. The species epithet was penned by the English botanist Philip Miller (1691-1771), meaning ‘of Italy’, giving homage to one of its native regions. The subspecies italicum is the most commonly cultivated form as the foliage has very distinctive and attractive white venation (pictured at right in November).

Italian ArumTypical to the genus, Italian Arum grows from a tuber, with the sagittate or arrow-shaped foliage beginning to emerge in late September or early October and typically remaining attractive until the following June (photo at right was taken on February 10th). During severe winters, the foliage can scorch if located in an exposed location, but fret not as it will be refreshed with new foliage come spring. The straight species features glossy, deep green foliage or foliage with white splotches while the previously mentioned subspecies is laced with white venation. The leaves usually grow to 12” tall by 6-8” wide, but can be larger if conditions are ideal. The foliage certainly provides great winter interest, but come spring, it is the flower that makes the plant all the more fascinating!

The flowers appear in May. They consist of a central club-like spadix, appearing in front of and slightly surrounded by a creamy white bract or modified leaf called a spathe. The spathe grows 8-10” tall while the spadix reaches a more demure 4-5” long. The urn-shaped base of the spathe wraps around the lower portion of the spadix and is called the spathe tube. This spathe tube encloses the fertile flowers which appear in whirls, encircling the spadix. The fertile pistillate or female flowers are located at the base of the spadix, with the pollen releasing staminate flowers perched above, with sterile female flowers called pistiloide florets separating the two. Atop the staminate flowers and located near the narrow neck of the urn-like spathe tube are the infertile staminode flowers that produce slightly downward oriented filaments that stretch outwards and nearly touch the neck of the spathe tube. flowresArum flowers are termed protogynous, whereby the female flowers mature first and are no longer receptive to pollen when the staminate flowers mature and begin to release pollen. This staged maturation prevents the flowers from self-pollinating, resulting in inbreeding depression. To further aid in pollination, the male flowers are thermogenic, whereby they actually go through periods of releasing heat and can become upwards of 50 degrees warmer than the ambient air! Initially, this makes little sense, until one realizes that the flowers are pollinated by flies and the heating of the flowers releases volatile chemicals that smell like rotting meat or even stale urine! None to worry though, since the odors are too faint to be noticed by the passing gardener. Attracted by the odor, small flies are able to push past the filaments of the staminode flowers in search of the source of the odor but, due the slightly downward orientation of the filaments, the flies are not able to escape. The filaments remain resilient against any attempts of escape for around 24 hours, allowing the incarcerated the flies to hopefully deposit pollen from a previously visited flower onto the stigmas. After one day passes, the stigmas become unreceptive to pollen while the staminate flowers begin to shed pollen and the staminode filaments become limp, allowing the pollinators to collect pollen as they move upward and out of the spathe tube. An incredible scenario!

Shortly after the flowers fade the foliage withers, leaving the fruit to develop. The peduncle or stem of the flower proceeds to elongate to 6-12” tall and is topped by an oblong cluster of developing fruit that is covered by a papery tunic. As the tunic dries, it splits open revealing the attractive cluster of red fruits that remain ornamental well into August (pictured below). In the southeastern and northwestern parts of North America, along with Australia, New Zealand and the UK, the dispersal of seeds by birds and even ants have caused this plant to be listed as an invasive, which outcompetes various native plants. I have always kept a watchful eye on this plant in garden settings and although I have seen seedlings produced around the mother plant, it has not proven to be a worrisome self-seeder in NJ. Of course, planting one plant or removing the fruit before it matures will negate any worries about invasiveness and allow the gardener to simply enjoy its winter and early spring beauty.

tunic flowers
Hardy from zones 5-8, the plants prefer to be located in a humus rich, shaded location where the soil does not become excessively dry throughout the growing season. They can even be located in fairly wet soils, as I witnessed at the Cornell Botanic Gardens where they are planted along a stream. The tubers readily produce offsets during the late fall, allowing an individual plant to gradually increase into a substantial clump with time. It is also interesting to note the tuber produce two types of roots: vertically oriented contractile roots during the early fall that help to pull the tubers ever deeper into the soil, followed by a mat of horizontal roots whose purpose is to absorb nutrients and water.

Available as a container plant or as tubers from bulb companies, Italian Arum is not any easy plant to find; most nurseries do not like to stock container plants since there is nothing to see following June. However, it is an amazing plant for the garden, providing nearly year-round interest with a flower that literally becomes warm to the touch during pollination. Truly one hot plant that needs to grace more mid-winter gardens!

Gardening Notes for January 2021

December 31, 2020 By Bruce Crawford

January always begins with the festivities of the Holiday Season, but reality soon returns as gardeners are looking at short and often cloudy days, cold temperatures and a sleeping garden. Looking on the positive side, we now have the leisure of working in the Garden when the time or the weather suits our schedule, since it is a time when the garden stands still. Continue taking notes in your journals on the temperatures, snowfall or rain amounts along with the sightings of visiting birds, all while enjoying your favorite winter beverage by a warm glow of a lamp.

Things to do:

  • Plain your vegetable and annual gardens! As seed catalogues continue to appear almost daily in the mailbox, keep your designs handy so you do not buy more seed than is needed.
  • Order your seeds early, as gardening is promising to be popular this year and certain varieties may sell out quickly!
  • If this is the first time you are planning on creating a vegetable garden, think small to start. A 10’x12’ or similar sized area is perfect for a start. Also consider starting with easy vegetables, such as Zucchini, Bush Beans, Beets or Lettuce. Tomatoes are great but are best when staked, so make certain you also have staking materials. As a reminder, tomatoes can grow to 6’ tall, so it is important to plant a crop on the North side of tomatoes that will tolerate partial shade.
  • Resist the urge to order too many of those vegetables that yield heavy amount of fruits. Three or four tomato plants is often all that is needed for a family of 4!
  • Reread your journal from the past year. Take note of some of the major problems you encountered in 2020 (or even 2019) that can be resolved in 2021. Some of these problems may have included starting seed to early or planting vegetables too closely.
  • Witch Hazel Jelena

  • Study the winter bones of the garden. During the calm of winter, give thought to improvements that can be made for a more colorful winter garden, such as the addition of colorful stems with Red Stemmed Dogwoods or Willows, the blooms of Winter Witch Hazels such as ‘Jelena’ pictured at right, views that need to be screened or new views that should be created, etc.
  • Take care of your tools! Sharpen, clean, oil and otherwise repair saws and pruners. Sharpen the cutting edge of spades and lawnmower blades, repair the handles of shovels and wheelbarrows or any other tool placed on the ‘to be fixed’ pile. Compose a list of tools to purchase that are beyond repair.
  • Start to evaluate pruning needs. Typically, most pruning is completed in January through late March, with the heaviest pruning reserved for late February and early March. January is the time to evaluate plants for heavy cuts, and to begin structural work, shaping and thinning of small trees and shrubs. All rubbing or potentially rubbing branches should be removed as well as any necessary shaping. All suckers (vigorous shoots originating from the roots) should be removed and water sprouts (vigorous shoots originating from branches) should be thinned.
  • Study your shade trees for potential problems as well. This is a great time to hire a tree service to tend to these problems and the woodchips produced from the trimmed branches makes a great mulch or a surface for woodland paths.
  • Helleborus niger

  • Cut some branches of winter blooming Witchhazels (Hamamelis hybrids), Winter Sweet (Chimonanthus praecox), Winter Jasmine (Jasminum nudiflorum) or Flowering Apricot (Prunus mume) to force and enjoy indoors.
  • If snow is absent, start cutting back Hellebore Hybrids (Helleborus x hybridus) towards the end of January. It is easier to remove the foliage when the buds are not present and the foliage often turns brown by bloom time. The foliage of Helleborus niger ‘Joseph Lemper’ (photo at right) often remains green throughout the winter and nicely compliments the flowers.
  • This past December I noticed a number of Hellebores breaking bud early. Helleborus niger ‘Joseph Lemper’ was blooming in early December and H. x ‘Royal Heritage’ were showing buds. Consider laying evergreen boughs of pine or even the Christmas tree on these plants, providing protection during cold days.
  • Cut Leaf Japanese Maples

  • Remove last year’s foliage of Cut Leaf Japanese Maples (Acer palmatum var. dissectum) that has accumulated on top of the plant branches, as it will hold snow and cause limb breakage. Pictured at right.
  • If we receive snow, remove heavy snow from hedges and tightly grown plants to prevent breakage!
  • Check any potted plants that you have in a lightly heated garage or basement for watering needs. Keep them on the dry side so they do not begin to push vigorous growth or start to decay. You may also wish to invest in a Min-max thermometer, which records the coldest and hottest temperatures. This will allow you to understand just how cold the garage is getting on those cold winter nights. For more tender plants, even though dormant, you may wish to put them on a table to keep them off the cold floor.
  • If you have Colocasia or Alocasia tubers stored in a peat, potting soil mix or shredded mulch for the winter, lightly water the mix periodically (around once a month) to prevent desiccation of the tuber. Or, if they were left in their containers and the foliage is still up, water them lightly and check for spider mites, especially in the case of any Alocasia that may serve as house plants for the winter. If you do have spider mites, wash the leaves thoroughly with regular tap water – obviously, this is more easily accomplished if you can bring the plant outside on a warmer day. If the temperatures remain cold, you can simply wipe down the leaves and stems with a moist rag.
  • By and large, most of your houseplants need to be kept on the dry side during winter, as too much water will cause root or crown decay. Put your Poinsettias, Amaryllis or Cyclamen in a sunny southern window and water when the top of the soil becomes dry.
  • Houseplants should be rotated 180 degrees every few weeks so that the plants receive equal light on all sides.
  • Jade Plant

  • Tillandsia or Air Plants should be soaked in warm tap water every 5-7 days. More frequently if they are located next to heat ducts. I have come to enjoy placing Tillandsia among the leaves of larger plants, such as the Jade Plant (picture at right). It provides great presentation and looks like the Jade Plant is flowering!
  • If you have Coleus, succulents or other easy to root annuals in containers, you may wish to start cuttings of new plants in late January, building up your supply for the summer garden. With succulents, you can often place a leaf or a cutting on a table and over a period of several weeks, it will sprout roots, after which, it can be potted.
  • Repair fences! Perennials, vegetables, vines or other plants whose roots resent foot traffic typically grow adjacent to fences and prevent access during the growing season.
  • Set-up and fill bird feeders. Place them near windows so the birds can be appreciated!
  • Most important – pour yourself a cup of good tea or a glass of wine to celebrate your garden accomplishments of 2020. It was a tough year for a number of reasons. Personal accomplishments deserve a personal reward and no one knows those accomplishments better than you!

January 2021 Plant of the Month – A Plant for Many Generations!

December 31, 2020 By Bruce Crawford

With its short days and cold temperatures, January is a good month to turn your focus to indoor gardening and expand upon your houseplant palate. It is a wonderful way to bring the garden indoors, so to speak. However, simply because the plant is labelled as a houseplant does not mean it cannot go outside come next summer! Haworthiopsis is a succulent that my mother propagated and distributed throughout the house and summer garden with great abandon, but it never garnered much of my attention. Having now ‘inherited’ all of these plants, I have come to discover its beauty, along with its wonderful care free nature!

Haworthiopsis was originally described and placed under the genus Aloe by Carl Linnaeus (1707-1778) in 1753 and was classified within the Liliaceae or Lily Family. It has recently been relocated under the Asphodelaceae or King’s Spear Family. The genus name was changed from Aloe to Haworthia in 1809 by the French physician and botanist Henri August Duval (1777-1814). The genus name honors the English Zebra Cactusbotanist and entomologist Adrian Hardy Haworth (1767-1833) who described 21 species of the genus throughout his career, although he too classified them as Aloe! In 2013, based upon genetic studies, the British botanist Gordon Douglas Rowley (1921-2019) split the genus creating the new genus of Haworthiopsis. The new ending for the name is from the Greek Ópsis for appearance, indicating these plants appear like Haworthia. The most noticeable physical difference is the thicker and harder epidermis or outer covering of the Haworthiopsis leaf when compared to Haworthia. Both Haworthia and Haworthiopsis are native to countries in the southern regions of Africa with the predominance of species found in South Africa, although Mozambique, Swaziland and Namibia are also home to numerous species. Both genera exhibit CAM or Crassulacean Acid Metabolism whereby the leaf stomata open only at night to reduce the loss of water during the day and allow for gas exchange. This allows the plant to be very efficient at conserving water, but also rather slow growing since it can only produce a limited amount of sugars per day based upon the amount of CO2 absorbed at night.

The most commonly grown species, and the plant my mother used with seemingly reckless abandon is the Zebra Cactus or Haworthiopsis attenuata (pictured at right). The species epithet is from the Latin Attenuatus meaning diminished or lessened and refers to the form of the leaf, which tapers or diminishes to a sharp point. The common name of Zebra Cactus comes from the ornamental bands of small white warty projections called tubercles on the back sides of the dark green leaves, which with a touch of imagination resemble the markings of a Zebra. The tubercles allow the expansion of the leaf during the moister summer months without imparting any tearing or damage to the stiff epidermis of the leaf. The plants are stemless and produce 3-6” diameter rosettes of foliage that develop offsets or pups over time and eventually develop into sizable colonies. White to soft pink flowers are occasionally produced during late fall and winter, which corresponds to the spring and summer months in the plants native homeland. The genetic clock does not change simply because the plants are now in North America! The flowers are located along slender stems that bend like fishing poles under the weight of the flowers. The flowers actually consist of tepals, whereby the petals and the leafy calyx look identical and they are displayed in a bilobate arrangement, with a very distinguished upper and lower lip, as seen above. The tip of the lips reflex back, giving the flower a very pronounce appearance similar to a set of puckered lips. Green or reddish brown stripes run down the inside and outside of the flower and most likely serve as nectar guides or visual cues for visiting pollinators.

Haworthiopsis limifoliaAnother very ornamental species is Haworthiopsis limifolia, commonly called the File Leafed Haworthia or Fairies Washboard. Herman Wilhelm Rudolf Marloth (1855-1931), a German born South African botanist and pharmacist, described the species in 1910, under the genus Haworthia. The epithet is from the Latin limo, meaning to diminish or file off, a reference to file-like appearance of the raised linear ridges of tubercles along the leaves. The common name of Fairies Washboard is also a reference to the raised ridges of tubercles. The leaves are arranged in stemless rosettes, although they are slightly broader, especially near the base when compared to its previously mentioned cousin. ‘Spider White’ (pictured above) is a relatively recent introduction with very white tubercles and is the recipient of the 2015 Dutch ‘Glass Tulip’ award for best new houseplant. The tubercles are a very showy white and give the foliage a very attractive creamy glow!

Not all the species form rosettes of foliage, as some have stems reaching up to several inches long. Haworthiopsis coarctata bears a central stem that grows to nearly 8” long with tightly clasping leaves appearing radially around the stem. The species was initially described by Haworth himself in 1824 and the epithet is from the Latin for crowded or close together, describing the densely overlapping nature of the foliage. The tubercles appear as linear dots along the length of the leaf and are not as distinctive as in the previous two species. In shade, the foliage is a dark green, although the foliage often turns to purplish-red in full sun, as seen in the image below at Chanticleer Garden. Interestingly, this species is the type species for the genus, although it looks quite different from those forms that create rosettes.

Haworthiopsis species are exceptionally easy plants to grow, providing you do not equate weekly watering with proper plant care! During the summer months, the plants are actively growing and are tolerant of our summer rainfalls, allowing them to be used in summer container arrangements or simply set outside for the summer. In the regions where they are native, they typically grow in the shadow of a rock and prefer a similar, lightly shaded location as an ornamental. Fertilize with a half dilute houseplant food that has a higher phosphorus content, such as 5-10-5. Come fall bring the plants inside and give them a windowsill with bright light or morning light. The key in winter is to let the soil dry out completely in-between watering, which can mean upwards of 2-4 weeks without the need for a watering can – something that may prove very difficult for some gardeners!

As you enjoy the warmth of your home this January, hopefully planning additions to your outdoor garden for 2021, it is always nice to enjoy and add some new houseplants to your indoor garden. There are many plants that ask for so very little, yet provide interest and joy throughout the season. Haworthiopsis is one such genus that will continue to provide joy not only throughout the year, but from one generation to the next!

Haworthiopsis

Bruce Crawford
Program Leader in Home and Public Horticulture, NJAES

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