Aloe polyphylla - Care & Cultivation
Congratulations, you have just purchased a very special plant which is threatened with extinction because of habitat deterioration due to the effects of overgrazing by cattle, sheep and goats. You may now participate in the salvation of an endangered species and enjoy its unique beauty. A.p. is also no longer able to reproduce itself because the bird which pollinates it is also endangered, the Malachite Sunbird. Viable seeds have few opportunities to find hospitable niches on the basalt slope because the flow of water regulated by the grasses, Themeda triandra-Festuca caprina, has dried up. The thick sod formed by these grasses functions like a sponge to regulate the flow of water downslope to the seedlings below, resulting in very few successful germinating seeds.
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Our new plant is grown from a seed produced by my pollination technique. This species is an obligate outcrosser. It does not self pollinate to produce viable seed. All natural progeny are hybrids. The species is dependent on hybrid vigor. Other growers are now producing clones by tissue culture methods.These plants will be slow to develop, and without hybrid vigor. Viewing a large block of 1gal plants is a good way to see the genetic variation which is preserved by hybridization, and which is the only acceptable way to save the gene pool of any endangered species. Cloning preserves only the genotype of the parent plant. A striking physical variance in the marginal dentation of the leaf in a block of seedlings illustrates this. The 1gal 35-40 leaf plants are about two years old and will grow to an adult plant 150-175 leaf and be 16" high and 32-36" diameter in about five years if all goes well.
There are five rows of leaf emanating from the center. A Left spiral is described by pointing your left thumb at the center and matching any one row(sequence) of leaf with the curl of your fingers. A Right spiral matches the curl of your right hand fingers in the same way. All plants I ship come labeled R & L with a diagram. As new leaf is produced the older leaves are shoved to the outside of the row sequentially, with the oldest leaf being appressed to the soil surface and shaded. These leaves are retired by the plant;the "goo" is conserved and used for other leaf and root tissue. Never attempt to remove any leaf just because it has some tip necrosis or looks bad. Remove only empty paper thin leaf from the underside. A.p. is bio-conservative and dynamic. The lifetime of a leaf on a mature plant is about two years. As new leaf appears in the center the plant twists clockwise or counter-clockwise to accommodate the spatial demands of the vertically oriented leaf. As the new leaf emerges a keel on the outside edge unequally divides it into a wide and a narrow section. The physical forces acting here produce a lateralization of the leaf, thus the spiral begins here. Right hand plants always have the narrow side on the right, and left hand plants al- ways have the narrow side on the left. If you have trouble seeing the spiral orientation in your juvenile plant it is because of the lower number of leaf, be patient. Almost every customer I've dealt with can see it at the 50 leaf stage. Many people have trouble recognizing the spiral pattern. Yes the plant is conducting the business of constructing the leaf sequence which will become manifest. The question is always, "Can your brain recognize the pattern your eye sees?" Almost all customers can recognize the 5 row spiral sequence of a 50 leaf plant. If you have trouble with this the number of leaf and the orientation of the leaf are variables in a young young plant (30-40 leaf) which are not present in an adult (150-175 leaf) plant.The spiral orientation is not genetically determined. Any individual may spontaneously change from R to L or L to R. These plants are very confusing to study. I have almost equal numbers of R and L plants in my inventory. My field studies of wild populations reveal the same.
Spiral phyllotaxy is a solution other plant species use to maximize photosynthetic capability(via leaf exposure) given their ability to mechanically support themselves. Acaulescence (without a stem) is a growth habit which imposes real challenges to plants in other Families,such as the Crassulaceae and Cactaceae. The biophysical solution is described by the Fibonacci equations. The maximum size of any acaulescent Aloe is related to the internal support the individual leaf get from the vascular strands and other fibers. A.p. leaf have virtually no internal support from fibers, only from vascular strands found just below the leaf surface. The rest of the leaf mass is "goo". Pressure from the roots inflates each leaf to a turgid state and this gives A.p. its form and drives new growth. A.p. biomass is about 98% water. Storage of starch (the fuel) is diffuse in A.p. leaf. In other woody plants starch is stored in parenchyma tissue. The translocation distance from leaf to root through the crown is short. A.p. can rapidly move "goo" to the roots and water from the roots to the leaf. The crown zone is a tightly packed mass of vascular stands, where leaf vessels connect with root tissue vessels. A.p. is a dynamic plant which reinvents itself continuously by retiring old leaf and roots, and using its "goo" to produce new tissue, almost in the same space. You cannot induce new leaf to form by adding fertilizer to an adult plant without witnessing the senescence of the oldest leaf.
One consequence of diffuse starch storage within the leaf is on flower production. To produce an inflorescence the size of deer antlers requires a lot of energy. A minimum leaf count required for flowering is about 90 leaf. This physiological feat requires the expenditure of several leaf. Plants may not repeat flower the next year and they rarely flower at all and then do not accept their own pollen.
I believe A.p. is very young species, only appearing in the Drakensberg and Malutis mountains of Lesotho in the last 25,000 years since the end of the Pleistocene glaciation. Populations are only found in a narrow altitude range 7500ft to 8500ft in the Malutis Mtns and the Drakensberg at 29-30 degrees South latitude on North facing slopes only which face the equator. Cold and dry Winters with nightly lows of 10-15 F alternate with daily highs 30-40 F. Light snow may come from cyclonic storms from the South. Plants flower in the Spring and the Malachite Sunbird returns to sip nectar and pollinate while the summer weather is mild with 30-40" rainfall from thunderstorms. When you take a plant species out of the environment it evolved in it may encounter conditions it never experienced before. Weather extremes may be a natural selection factor which at a minimum might restrict the plants performance and development. The temperate climate described will not have fungal pathogens found in more Tropical climes. The following recommendations for plant management are very broad. Specific site microclimates will always rule over regional advice. For USDA zones 1-9a juvenile plants should be brought inside and protected from hard freezes, the use of a Grolight on a timer to give 8hr/day extra light is essential to preserve good form. Without extra light the leaf width narrows and the leaf length increases.
The spiral form is dependent on shorter wavelengths of light, UVA and UVB which are plentiful at higher elevations. I suggest a small fan and never let your plant go dry. Cooler temperature are better, 40-60 F is OK. The adult plants are more tolerant of extreme temperatures than the juvenile plants. To cultivate A.p. in low desert areas with 100+ F summer temperatures do not use black plastic containers, ceramic is best to insulate the roots against high temperatures. Morning sun is OK but shade in the afternoon is necessary. I sometimes stretch 70% shade cloth over the plants. Use high quality water only, not salty or alkaline. Acidic soil mixes are beneficial. During high summer temperatures A.p. will not grow, withhold fertilizer until the Fall.
Understanding root physiology is important to successfully grow A.p. The bright yellow roots with white hairs have high oxygen demand. At high soil temperatures (90+F) the rate of respiration races beyond the soils ability to breath and deliver oxygen, so root tissue begins to die by suffocation. You can kill root tissue in two minutes by dropping it into 90F water. A physiology like this places A.p. just to the right of Cymbidium orchids on a scale which arranges plant root oxygen demand; with orchids on the left (highest O2 demand) and plants such as Bald Cypress (Taxodium) on the right. Proper combination of temperature, water availability and soil particle size enable the roots to function like a pump, to inflate the leaf fully. The first check on plant health is the turgidity of the leaf. A good soil mix for container A.p. will start with any good potting soil free of pest and diseases to which orchid bark chips are added to about 50% volume. These will be digested by actinomycete fungi in 3 years though. A longer lasting additive for permanent container plants will be pumice or red lava 5/16" or 3/8" grade. I use #3 or#4 perlite in the soil mix to about 30% volume. I use vermiculite also. Landscape A.p. will develop best on top of a sandy loam soil with free root run (i.e., no competition). The roots are very aggressive and will explore the soil volume wherever physical conditions permit. When in doubt select a larger container than you might suspect. An adult plant can be raised in a half-whiskey barrel. Confined roots which circle and girdle other woody plants are not a problem for A.p.
In the genus Aloe leaf propagation is not possible. You must have a stem section, seed, utilize tissue culture methods, or have offsets. Occasionally a plant splits growth centers. Wait for about two years before attempting to separate the plants. Let this happen naturally. Once separated you may clean the undercrown with a water jet, and use some root hormone to help new roots form. Place the plants in some shade and use compost for media. If the leaf collapse and the rosette close pull your plant up and jet wash the undercrown of all dead root tissue. To grow new roots place the plant on moist mini orchid bark or coif fiber in a shaded place. I about 4 weeks a new set of roots will enable you to replant it.
Aloes are attractive to Homopteran insects such as aphids, and mealy bugs, which may be farmed by ants. Aphids are able to tap a vein on the abaxial side of the leaf. Thrips, nematodes and some small beetles may chew roots and undercrown tissue. A preventive program of insecticide application will be a life insurance policy for A.p. The only soil borne pathogen which can kill A.p. is Fusarium oxysporum, primitive fungus which has a large host plant list and causes horticultural and agricultural businesses big headaches. If cloudy and cool weather stay for a week foliar infections are possible, with purple lesions anywhere on leaf resulting. This will not kill your plant, only mar its appearance, and not forever. When enough sun shines the UVA and UVB will kill the mycelium. If Fusarium infection occurs on the roots it will create a localized purple lesion which will not travel up through the vascular bundles. This infection will interfere with the root physiology at this locale only and does not kill the plant. If insects create a court of infection at the undercrown then Fusarium may kill the plant rapidly. Some fungicides which will stop or suppress Fusarium are Captan, Benlate, Cleary's 3336. The best strategy to manage the threat is to use "clean" soil, which is step 1. The next step is to inoculate the soil/plant with another microbe which will protect the plant from any infection. I now use Actinovate SP and Iron on all container soil. This contains the bacterium Streptomyces lydicum, which becomes an ectophyte on the surface of roots, aiding uptake of nutrients and disabling more pathogens than just Fusarium. All plants I ship are dipped in a solution of of Actinovate SP and have 1 tbspn of Actinovate Iron inoculate added to the sample soil below the plant. This should have a lasting value for plants shipped to new owners.
Here are some photos with captions showing essential parts of this discussion:
Greenhouse seedling at 5 leaf stage showing equitant leaf arrangement before first twist begins. Early plant development is an initial single leaf (monocot) indistinguishable from real leaf which come next. Subsequent leaf #2-7 are arranged in an equitant fashion. The next leaf #8 bears the keel on the abaxial (outside) edge and the first lateralization forces begin to twist the seedling into developing radial symmetry.
11 leaf stage seedling showing growing radial symmetry.
This plant is suffering an undercrown infection by Fusarium and will certainly perish in only a few days.
This plant has suffered the death of root tissue by suffocation, so the leaf has collapsed and is nearly devoid of"goo". This plant can be saved by pulling it out, cleaning all dead roots and replanting on moist coir fiber inside a greenhouse in shaded lighting. In about two weeks new root tissue will be witnessed.
If you have need for further consultation, send me a picture email and I can advise. My best advice is to tune into your plant and learn what it is telling you about current conditions of soil moisture and root aeration, light quality and quantity. Remember that the plant I ship to you is a starter plant which will re-morph into a form different from what you first see. A.p., like all plants, is very plastic and is in constant slow motion. We only notice this in cacti & succulent plants with a recognizable geometry, but the principle applies to all plants as well.
If you need more explicit information please contact me to describe the problem. Send a picture to id the problem.
Alan C. Beverly