Despite information posted on the internet, the scientific name Philodendron hastatum was never changed, collectors have simply chosen not to read beyond the title of the published paper which is in and of itself misleading. 

This is the exact quote written by botanist George S. Bunting (formerly of Cornell University) in his 1966 published paper entitled Philodendron domesticum, A New Name for P. hastatum Hort.  "The spade-leaf philodendron is a popular foliage plant with glossy bright green leaf blades to about 6 dm. long borne on equally long petioles. Its spathes are pale green outside but beautifully colored inside with cherry-red on the blade and wine-red on the tube. This taxon is commonly designated as Philodendron hastatum.   Such usage, however, is untenable, for the name properly belongs to a very different species.  Philodendron hastatum C. Koch & Sellow was first published in 1854"   Please read once again what Dr. Bunting was attempting to explain in his paper!

Dr. Bunting clearly stated he was not attempting to change the name of a scientifically known species.  Bunting also stated the common usage of a published scientific name for a non-related hybrid is "untenable" since the name Philodendron hastatum "properly belongs to a very different species.  Philodendron hastatum C. Koch & Sello" which was first published in 1854".    The "C. Koch" is taken directly from Bunting's paper (apparently published in error) since the name is correctly K. Koch. 

Horticulturalists and plant collectors simply misunderstood what Dr. Bunting was attempting to explain in his description, especially the title.  What he was saying was he was giving a horticultural name to a plant that had only the common name "Philodendron hastatum" but further explained that name should have never been in use.

Plant and garden discussion websites have also stated the name Philodendron hastatum is a synonym of Philodendron domesticum, but scientifically that is also incorrect.   In the horticultural sense the two names may be "synonymous" but they are not synonyms in the scientific form. 

In all published scientific material Philodendron hastatum K. Koch and Sellow is not listed as a synonym of any plant species known to science and is certainly not a synonym of Philodendron domesticum.  You may check the sources yourself to verify there are no synonyms for Philodendron domesticum on the The International Plant Names Index - Philodendron domesticum or the Missouri Botanical Garden's TROPICOS  

In fact, no site indicates where Philodendron domesticum has ever been observed in the wild.  Most indicate it is a hybrid rather than a species and none reference it to be the same species or even closely related to the hybrid now known as Philodendron domesticum.  If you would like to check for yourself here are the direct links to all the major sources:  International Plant Names Index  World Index of Selected Plant Families  CATE Araceae  TROPICOS

Based on the Linnean rules of nomenclature used by science such a name change would not possible due to the original date of publication.  Carl Linnaeus (1707– 1778) was a Swedish physician, zoologist and botanist who established the foundations for the scheme of binomial nomenclature used by science.   Linnaeus is considered the father of modern taxonomy, the system which defines the kingdom, phylum, class, genus, and species of any living organism.  

One of the most basic rules of taxonomy is the earliest published scientific name correct to genus becomes the accepted name.  Attempts to rename a species at a later date become invalid unless a major error can be demonstrated in the original publication.  No such error can be found in the publication of the species Philodendron hastatum.

There are beliefs posted on internet plant discussion groups that botanists are perpetually changing the scientific names of species.  The fact is if a name change is required that change will be done in accordance with the rules of science and botany as outlined by Linnaeus as a result of a demonstrated error.  Sometimes a factual error in the naming of a plant species may be discovered by a qualified botanist which requires that error to be corrected.  However, botanists do not simply grant new names to plant species to increase their own stature in science ot publish another paper. 

According to personal email exchanges with botanist Dr. Thomas B. Croat Ph.D., P.A. Schulze Curator of Botany of the Missouri Botanical Garden in St. Louis, MO. as well as with aroid botanist Dr. Eduardo Gonçalves science knows exactly where Philodendron hastatum originated in nature Brazil.  However no scientist can tell you where Philodendron domesticum can be found in the wild since it has never been observed!  To be a species a plant should have been observed in its native habitat.

To the Aroid l discussion group sponsored by the International Aroid Society Dr. Croat also stated, "I am not familiar with what Bunting was calling Philodendron elongatum (and commonly referred to as P. hastatum in horticulture) but P. elongatum was described in 1966 many years after Engler described P. hastatum so P. hastatum cannot be a synonym of P. domesticum."   Please refer back up a few paragraphs to the explanation of the use of "Engler".

In a personal email from Dr. Croat received March 3, 2007, Tom wrote, ""I have never seen the type of P. domesticum and doubt if I would know any more if I had seen it.  Just looking at the illustration I could imagine that it could be a dozen different species.  The reason why it is confused with P. hastatum K. Koch is that the plant he described had commonly been called P. hastatum.  Naturally it had nothing to do with P. hastatum.  It was just another cultivated plant of unknown origin.  He accomplished nothing by describing it and instead just created another plant likely never to be understood.   The paper by Sakuragui listed below just deals with the real P. hastatum and has nothing to do with the plant that Bunting described." 

Plant collectors often incorrectly use the name "Philodendron glaucophyllum" in place of the scientific name Philodendron hastatum.  The name "Philodendron glaucophyllum" is a fictitious name and is one some unknown person simply made up to sound as if it were scientific!  The name "Philodendron glaucophyllum" appears to be sourced in the plant collector's guide Tropica by A. B. Graf but has no basis in science and cannot be found on any of the scientific sources given earlier in this article.   The name Philodendron elongatum is also used in place of Philodendron hastatum but that name has been determined to be only a synonym of the species (same species, other name) that was published after the original name.

 America's top aroid botanist Dr. Tom Croat responded with this information while answering a question regarding the name "glaucophyllum" posted on the forum Aroid l, "That was a made up but unpublished name for P. hastatum Engler, a species from the area of Rio de Janeiro".  He went on to add, "According to my records P. elongatum is a synonym of P. hastatum Engler and the images I have look identical to those of P. hastatum."