Cultivars, varieties and hybrids in wildlife gardens
So, you go to your local nursery to look for native plants and find that they are mostly selling commercially mass-produced plants with wonderful sounding names. Can you put any of these plants in a native plant garden? With some understanding of the limitations, yes you can.
Terms to understand:
A cultivar is any plant that is cultured, in other words, produced en-masse by human intervention.
Some plants are produced by natural pollination methods from seeds collected from wild plants. These are called the straight species.
In a native plant nursery, you would expect to find only the straight species (from seed collected locally), but native plants can be cultivated by humans just like any exotic plant or hybrid. Even though it is not produced in a natural setting, a cultivar of a native plant is still native because it has the same set of genes.
A selection refers to a particular individual or group of plants that have been found in the wild or in a group of test plants which have desirable and distinguishing characteristics from other individuals of that species. A selection can be propagated by cloning to ensure the presence of the desirable characteristic.
A variety refers to a group of plants of a particular species that naturally produce offspring which inherit a set of distinguishing characteristics. Varieties do not have to be cloned and therefore are often not cultivars. Some Redbuds have white flowers. When these redbuds pollinate each other, their offspring are mostly white flowered too. The scientific name for this is Cercis canadensis var. alba. The word “variety” is sometimes used correctly as a botanical term and often not. Unless you see the acronym var in the name, it is likely to be a selection or a hybrid.
A forma is smaller group than a variety which contain one distinguishing characteristic that can be inherited. If you find one and want to know how it fits into the following discussion, treat it as a variety.
A hybrid is the result of cross-pollination between 2 species (for the sake of simplicity, we will ignore the intraspecific hybrids). This does not often occur in nature, so a hybrid that you buy will more than likely be due to human intervention.
Ecological and aesthetic considerations:
Other than the straight species, the most environmentally friendly option is a variety. Varieties are found in nature and therefore have ecological function. They are often produced by sexual reproduction and have some genetic diversity as well.
Selections of native plants have ecological function but have no genetic diversity. To guarantee that a distinguishing characteristic is present in all plants sold, a selection is reproduced by cloning techniques and each individual will have the same set of genes. A selection may have the advantage of being resistant to certain diseases, being more predictable in form and in some cases even being more attractive to pollinators. Phlox paniculata ‘Jeana’ is a known selection with smaller flowers that are more accessible to pollinators. On the other hand, a selection may be more difficult for insects to interact with. The difficulty with using selections in wildlife gardens is that you will have to use trial and error or use anecdotal evidence from online sources to find out if they support wildlife in the same way as the straight species. There simply isn’t enough research to know beforehand but the guidelines below will help you narrow down your choices.
Another question to ask yourselves is what happens if the cultivar in your garden escapes and changes the characteristics of the wild population in your area? Will a cultivar change the dormancy period or the blooming period or even the flower colour? If your garden is close to wild habitat, then the migration of genetic material might be a consideration. There is no research that answers this question or proves that it actually is happening to any significant extent; in a large wild population, it is evolution through natural selection that will determine phenotype frequency.
Hybrids tend to have less ecological function and they are typically produced by cloning. It is important to distinguish between fertile hybrids and infertile hybrids. Fertile hybrids are an environmentally dangerous option for gardeners because they could hybridise with wild plants and alter their genome. The genome of the Sundial Lupine is threatened by the escape of L. polyphyllus from gardens. Infertile hybrids pose less environmental danger than fertile hybrids because they cannot become invasive and cannot hybridise with native plants. They may be desirable in the garden if they are more manageable than the wild species. In my garden, I use Rudbeckia ‘Herbstonne’ and Helianthus ‘Lemon queen’. Both of these infertile hybrids have the advantage of clumping rather than spreading so they work better in smaller garden spaces. Hybrid plants typically will not support birds as much as native plants because birds need seed and insects for food. Infertile hybrids do not produce seed and may not be chemically similar enough to the straight species to support the same range of phytophagous insects. On the other hand, infertile hybrids often bloom profusely and for far longer periods of time, thus supporting pollinators.
How do you can you tell whether you are buying a hybrid, selection, variety or the straight species?
Look at the scientific name.
Both the genus and species name are written in italics. Nearly everything else is written in normal font.
Straight species – Genus and species name with no additional information
Variety - Genus and species name with var (in italics)
Cercis canadensis var. texensis
Chelone obliqua var. speciosa
Selection – Genus and species with selection name in inverted commas
Echinacea purpurea 'Kim's Knee High'
Echinacea purpurea 'Magnus'
Phlox paniculata 'Jeana'
Hybrids – Do not have a species name and may have an X (Ignore all the extra information)
Phlox × arendsii 'Hesperis'
Phlox PAPARAZZI MIX
Phlox 'Green Spring'
Echinacea 'Amber Mist'
Echinacea 'Balsomsolst' SOMBRERO SUMMER SOLSTICE
Should I buy a cultivar for a wildlife or native plant garden?
Purists will say no and may even deny that a cultivar, with the same set of genes, is a native plant. This is clearly not a scientific point of view. Cultivars lack genetic diversity, but if you are just planting a few individual specimens to support insects in your garden, then you really just need to consider whether the cultivar is close enough to the straight species.
Doug Tallamy has suggested that cultivars grown with different leaf colours may not support as many insects, especially if anthocyanins are involved. Excepting this characteristic, many cultivars were found to be just as good as the straight species at supporting herbivorous insects (https://mtcubacenter.org/do-leaf-eating-insects-eat-nativars/). I would also add that several dwarf cultivars I have tried did not turn out to attract pollinators. Choose plants that have the same leaf colour and are of similar height.
Avoid cultivars with double and semi-double flowers. Bloodroot sometimes produces double flowers naturally. These specimens are often considered more desirable by gardeners because infertility causes the blooms to last longer. However, the flowers remain unfertilised because they are not producing pollen and visiting insects are not getting the nutrition that they need. There are many other examples in which the double flowers produce more infertile petals and less pollen and less nectar. In more extreme cases of polyploidy, the flowers are so overdeveloped that the nectaries are not even accessible. Fancy flowers are not helping our insect pollinators. Choose cultivars with flowers that resemble the original plant in both size and colour.
Some native plants have several decent and commonly available cultivars that can be used in place of the straight species when the latter is not available to you. To make some decisions, read about climbing the native plant ladder. If you are starting a wildlife garden and do not have access to a native plant nursery, then the following plants are good starting choices: