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Hoya lanceolata/bella Complex

HOYA LANCEOLATA/BELLA COMPLEX


(Hoya lanceolata Wall ex D. Don and similar species, subspecies, and forms).


Note: I would like to acknowledge that most of the information here are from an article written by Mr. Mark Randal. I just re-arranged the contents of the article to make it easier to understand for most of us Hoya collectors who do not have background in botany and who prefers to read blogs or write-ups of a trying hard non-expert Hoya fanatic. It is re-arranged to suit Hoya collectors/enthusiasts in New Zealand. I have seen only three of the species,subspecies and forms of the Hoya lanceolata complex in New Zealand and they are:


1. Hoya lanceolata

2. Hoya lanceolata ssp. bella and

3. Hoya lanceolata ssp. bella f. paxtonii.


Hoya lanceolata Wall ex D. Don


Hoya lanceolata is often sold as Hoya bella in New Zealand. According to the article I’ve read, Hoya lanceolata and Hoya bella were originally separate species but H. bella was erroneously placed as a subspecies to H. lanceolata by Douglas Kent in his 1981 paper. So perhaps this is why in our PBI list, Hoya bella and Hoya lanceolata are listed separately.


Hoya lanceolata is similar in appearance vegetatively to ssp. bella but it has smaller, closely set leaves. The stems are pendant and clothed in lance-shaped leaves that are 1.5 to 2.5 cm long and approximately 1cm wide. (“Lanceolata”= “lance shaped, broadest in the middle and tapering to both ends”, Latin).


The flowers of Hoya lanceolata are about 1.7cm in diameter, with a creamy white corolla and a translucent lavender corona. The corona scales are more linear in shape (when viewed from above) than those of ssp. bella, similar in structure to the corona scales of H. linearis, and lack the broad concave top of the corona scales of ssp. bella, f. paxtonii, H. engleriana, and H. dickasoniana. The flowers are terminal and occur in groups of six to ten, usually during the northern hemisphere’s spring.


Hoya lanceolata Wall ex D. Don ssp. bella Hook)


Hoya lanceolata ssp. bella is the most commonly found of the "bella complex" in cultivation. The leaves of this plant are larger than those of H. lanceolata, ranging in size from 2.5 to 3cm in length and 1 to 1.5cm in width, but are of a similar, lanceolate shape. Flowers of both species are similar in size and color, though the corona of ssp. bella is usually more infused with a reddish-violet than that of H. lanceolata, and the corona scales (in ssp. bella) are cymbiform (boat-shaped), being wider and having a broad shallow concavity on the top of each scale. Flowers are borne (in ssp. bella) terminally and all along the stems, and the flowers occur, in clusters of six to ten, more freely and often for a longer bloom period that in H. lanceolata. “Bella” is a latin word for “beautiful”.


VARIEGATED HOYA LANCEOLATA SSP. BELLA

There are two variegated forms of ssp. bella. The more common one has green leaves bordered in white and often is sold under the name ‘Lida Buis’. The other form has green margins with creamy yellow centers often sold under the name Lois Buis.’. The new growth is often flushed with pink in these two clones. These variegated ssp. bellas are notoriously fussy, slow growers. As with most variegated plants, flowering is greatly reduced, so these are most often grown for their colorful foliage.


Hoya lanceolata Wall ex D. Don ssp. bella (Hook.) D. H. Kent forma paxtonii


In commoner’s (non-expert) language this means it is a species of Hoya called lanceolata under the subspecies bella but it has a different form and the form is called “paxtonii”. The difference is in the form of the leaves.

D. H. Kent forma paxtonii has longer, wider leaves than ssp. bella, often with an undulate* leaf margin. The flowers have minute differences from ssp. bella, the most obvious difference being that the corona scales of forma paxtonii are more compact, resulting in a smaller corona than that of ssp. bella. The prime difference (to growers) between these two forms will be that forma paxtonii (abbreviated as f. paxtonii) is said to be a more vigorous, less culturally demanding plant. Forma paxtonii blooms, similar to ssp. bella, over an extended period in the northern hemisphere’s summer, also in flower clusters of six to ten.The form designation of this plant probably refers to Joseph Paxton, a 19th century architect, landscape architect, and editor of several botanical journals.


Illustration of the differences between Hoya lanceolata, Hoya lanceolata ssp. bella and Hoya lanceolata ssp. bella f. paxtonii


Although the overall appearance of these species is very similar there are notable differences between these three:



Hoya dicksoniana


The remaining species, ssp., and form- ssp. bella, f. paxtonii, Hoya engleriana, and Hoya dickasoniana all have similar coronas which can be difficult to distinguish from each other with the naked eye. There are minor differences in the floral structure of each species, however, with the possible exception of ssp. bella and Hoya dickasoniana. Since the flowers of these four species are so similar, identification is easier when considering leaf morphology, which is distinct for each species or form. Hoya lanceolata ssp. bella is the most commonly found of the "bella complex" in cultivation. The leaves of this plant are larger than those of H. lanceolata, ranging in size from 2.5 to 3cm in length and 1 to 1.5cm in width, but are of a similar, lanceolate shape. Flowers of both species are similar in size and color, though the corona of ssp. bella is usually more infused with a reddish-violet than that of H. lanceolata, and the corona scales (in ssp. bella) are cymbiform (boat-shaped), being wider and having a broad shallow


Hoya engleriana


Hoya engleriana Hosseus has, again, very similar flowers to those of ssp. bella, and the coronas closely resemble those of forma paxtonii. The prime distinction for this species is the very small leaves (1- 1.5cm) which are linear or slightly tapered and closely spaced along the stems. The flowers are borne terminally, usually in clusters of four. Hoya engleriana was collected near Chiang Mai in the mountains of northern Thailand by C. C. Hosseus. This is very close to the collection site of H. dickasoniana. It was published by Hosseus in Notizbaltt des Konigel Botanischen Gartens und Museums zu Berlin 40 in 1907. The name honors Dr. Adolph Engler, a German Botanist of the 19th and early 20th centuries and one time Director of the Berlin-Dahlem Botanical Garden, where Hoya linearis and Hoya engleriana were grown and displayed.


PROVENANCE


Note: There are other species not listed here because I do not have photos and more information about those species.


OTHER IMPORTANT INFORMATION ABOUT THESE SPECIES (INCLUDING HOYA LINEARIS AND HOYA SERPENS) - note: Copied from the article of Mr. Randall.


CULTIVATION

All of these small species are epiphytic plants that grow on the trunks or in the crotches of trees in the forests of SE Asia. The distribution of these species crosses several climate zones and thousands of micro-climates. Any notes on the cultivation of these species must necessarily be based on generalizations, but some broad assumptions may be drawn which may be of help in growing these demanding species.


TEMPERATURES

Most of these species are generally classified as cool growers, but some collections come from locales which are closer to semi-tropical or tropical. The collection climate of a species does not necessarily limit the temperature tolerance of a particular plant- some plants from tropical locales may adapt well to intermediate or cool growing conditions, and some plants from cool climates may perform quite well under warm greenhouse conditions. Some plants, like some people, are more adaptable than others. Much- often contradictory- information has been written about the temperature preferences of these small species over the years, especially regarding Hoya serpens. A safe place to start may be to grow these species in intermediate bordering on cool conditions and to experiment with plant preference gradually. Cool conditions are usually regarded as being in the range of 10’ to 25’C (50’ to 78’F), intermediate as approximately 15’ to 35’C (60’ to 95’F).


LIGHT


In nature these plants usually occur as epiphytes on forest trees, where they are generally shaded by their host tree's canopy from the intense mid-day sun, receiving some direct sun in morning or afternoon, unless neighboring trees block even those few hours of sunlight. This is why, with few exceptions, most hoyas are recommended to be grown in bright indirect light with only direct exposure to the sun in early morning or late afternoon. This applies to most of the species considered here, although Hoya linearis is said to prefer slightly more sun (and in one instance was reported to be found growing in full sun on a rocky slope), and H. serpens, probably coming from a more densely shaded environment, seems to prefer no direct sun at all.


WATER


All of these species require regular water and prefer for their potting medium to remain consistently moist, except for H. linearis, which seems to need to be kept on the drier side to avoid root-rot. Good drainage is important for all hoyas, but is of prime importance for all of these species. Soil needs to retain some moisture at all times, but any period in which the soil is kept constantly wet seems to lead inevitably to root loss and the plants demise. A very light mix and keen attention to watering is necessary to keep this group of hoyas happy and productive.


FORM


As all of these hoya species are pendant (or in the case of H. linearis, flacid), and seem to lack the ability to climb (except for H. serpens, which can climb weakly), they are best grown as hanging plants. Hoya serpens, which branches freely and has somewhat stiff stems, can make a rounded plant suitable for a 15 to 20cm (6" to 8”) pot. H. linearis develops quite long, mostly unbranched stems which hang straight down and develop flowers terminally, suggesting that this plant should be hung quite high to fully appreciate its unique form. H. linearis can become quite large, eventually requiring a 20 to 25cm (8 to 10") pot. Hoya lanceolata, ssp. bella, and f. paxtonii are some where in between these two species (H. linearis and H. serpens) in size and form, and are best kept to 20cm (8") pots maximum.


When these plants have grown into larger pots and become root-bound, they are often past their prime and might better be started over again with cuttings in a small pot.


H. linearis seems to be an exception to this rule, as many very large specimens in cultivation seem to thrive year after year.

H. engleriana and H. dickasoniana are much smaller plants which tend to produce long, unbranched stems which can trail down to several feet in length. Unfortunately, these branches are somewhat stiff, lacking the more graceful aspect of the larger H. lanceolata and ssp. bella, and can be challenging to display attractively as they mature. These two plants will probably never require larger than a 15cm (6") pot, and should be potted up slowly and cautiously, increasing pot size by only 2-3cm (1”) at each step.


PESTS & DISEASES


All of these species except for H. serpens show a marked susceptibility to spider mites. Mealy bugs may also trouble all of these plants. Root rot may also be a problem for this group of plants, suggesting a low level of resistance to soil-based fungal infections, although the stems and leaves of these species are rarely troubled by mildew or black spot. A weekly shower with a moderate force spray from a garden hose (from above and below) serves to keep populations of spider mites and mealys at bay.


For serious mealy infections a systemic insecticide like imidacloprid works very well. Spider mites are more difficult to deal with. Heavy infestations may require thrice weekly applications of neem oil or insecticidal soap or more toxic chemical interventions to bring under control.


I hope you learned something from this blog because I did.... I always thought Hoya bella and Hoya lanceolata are the same until I read the article.


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