Krameria bicolor, white ratany
Brahmsteadt, Taryn R., compiler. 2026. Species Brief: Krameria bicolor, white ratany. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-briefs/krabic
This Species Brief is a concise summary of the biological, ecological, and fire‑related characteristics of an individual species derived from a Fire Effects Information System (FEIS) Species Review.
| Attribute | Characteristic | Justification | Source |
|---|---|---|---|
| Biological characteristics | |||
| Life form | Shrub | White ratany is a thorny and intricately branched perennial shrub. Individuals typically grow to 60 cm, but may occasionally grow to 120 cm, and are generally wider than tall. | FEIS: Botanical Description [1] |
| Typical lifespan | 51-100 years* | White ratany is classified as a long-lived species. MoreOn a site in the northern Sonoran Desert, its estimated average maximum lifespan was 184 years, with estimates ranging from 34 to 404 years. Half of individuals there lived for at least 50 years. | FEIS: Population Structure; Plant Growth and Mortality [1] |
| Life cycle | Perennial | White ratany is a long-lived perennial shrub. | FEIS: Botanical Description; Plant Growth and Mortality [1] |
| Drought tolerance | High | White ratany is drought-tolerant. However, extended drought may cause high mortality rates. | FEIS: Site Characteristics [1] |
| Rooting depth | Shallow* | White ratany's root system is generally comprised of a short taproot and radiating, shallow lateral roots. MoreYoung plants grow a pronounced taproot, but later its lower portion dies and lateral roots grow as far as 2 m from the main axis. | FEIS: Botanical Description [1] |
| Bark thickness at maturity | N/A | This attribute applies to trees. | FEIS: Botanical Description [1] |
| Sheds low branches | N/A | This attribute applies to trees. | FEIS: Botanical Description [1] |
| Reproduction and Regeneration | |||
| Adventitious buds | Yes, unspecified | White ratany can resprout after top-kill or damage from disturbances such as fire. MoreHowever, information about the location of its adventitious buds was lacking. One source states that it may reproduce vegetatively but does not provide details. | FEIS: Regeneration Processes; Vegetative Reproduction and Regeneration [1] |
| Time to reproductive maturity | Insufficient information | The source does not provide explicit information about the time to reproductive maturity for white ratany. | FEIS [1] |
| Soil seed bank longevity | Insufficient information | The source does not provide explicit information about white ratany's soil seed bank longevity, stating that no information is available on this topic. | FEIS: Seed Banking [1] |
| Month(s) when seeds typically ripen | March; April; May; June*; July*; August*; September*; October* | Flowering and fruiting occur March to May, sometimes extending into June, and may occur again from August, or sometimes July, to October if there is adequate summer precipitation. MoreThe source did not specify the length of time it takes for fruits to first appear after flowering. | FEIS: Seasonal Development [1] |
| Serotinous cones | N/A | This attribute applies to conifers. White ratany produces roughly spherical fruits covered in barbed spines. Each viable fruit contains one large seed. | FEIS: Botanical Description; Seed Production and Predation [1] |
| Seed dispersal mechanism | Animal; Gravity | The fruit's barbed spines likely aid dispersal by animals. Gravity is implied because old fruits are often found beneath the plant's canopy. | FEIS: Seed Dispersal; Botanical Description [1] |
| Seed dispersal distance | Mostly under parent plant; <100 m* | Old fruits may often be found under white ratany's canopy. The spines of the fruit apparently aid in dispersal by animals, though dispersal distances are not reported. | FEIS: Seed Dispersal [1] |
| Optimal conditions for seedling establishment | Nurse plant/object* | White ratany is a root hemiparasite on a variety of shrubs. MoreAlthough seedlings can establish independently, they may require a host plant to persist. Rather than typical nurse-plant facilitation, white ratany requires a hemiparasitic attachment to a host. Establishment seems to require specific climatic or site conditions, such as relatively wet winters and protection from herbivores. | FEIS: Seedling Establishment [1] |
| Successional Status | |||
| Shade tolerance | Insufficient information | The source does not provide explicit information about white ratany's shade tolerance, although white ratany typically grows in open (i.e. sunny) communities. | FEIS: Entire; Plant Communities [1] |
| Successional status | Early*; Late | White ratany is often associated with late successional communities and is typically a larger component of undisturbed than disturbed vegetation. MoreIts ability to resprout may allow it to be present in early successional communities after disturbances, though it likely requires prior establishment of a host plant. | FEIS: Successional Status [1] |
| Fire | |||
| Primary fire response(s) or adaptation(s) | Recover/Resprout*; Fire Sensitive | Fire typically kills or top-kills white ratany. It may resprout after top-kill, but is often a poor resprouter, though it may be moderate or strong under some conditions. | FEIS: Immediate Fire Effects; Plant Response to Fire [1] |
| Germination is fire stimulated | Insufficient information | The source does not provide explicit information about fire-stimulated germination in white ratany, stating that information on the effects of heating or burning on its seeds was not available. | FEIS: Immediate Fire Effects [1] |
| Flowering/fruiting is fire stimulated | Rarely/No* | It is unlikely that fire stimulates flowering and fruiting of white ratany. MoreOne study found that individuals produced an average of 37 fruits/plant in burned edge areas and 56 fruits/plant in unburned areas, although differences were not significant. | FEIS: Plant Response to Fire [1] |
| Season when it is most sensitive to fire | Fire sensitivity does not vary by season* | White ratany is killed or top-killed whenever it burns, and its low growth habit and compact crown mean it is often partially to completely incinerated regardless of season. MorePostfire resprouting, however, may be more frequent under wetter conditions, including in more mesic microhabitats, times when postfire soil moisture is higher, and in the wetter Sonoran Desert compared with the drier Mojave Desert. | FEIS: Immediate Fire Effects; Plant Response to Fire [1] |
| Plant flammability | High | Aboveground parts of white ratany are often consumed by fire due to their receptive fuel structure: low-statured plants with compact crowns in close proximity to surface fuels and finely divided branching habits. MoreWhen it burns, it is often partially to completely incinerated. | FEIS: Fuel Characteristics; Immediate Fire Effects [1] |
| Early colonizer/recolonizer of burned or disturbed sites | Rarely/No* | White ratany is typically a larger component of undisturbed than disturbed vegetation, and postfire seedling establishment is apparently uncommon. MoreAlthough its abundance typically declines following fire, plants may resprout, allowing its abundance to remain stable after fire. | FEIS: Successional Status; Plant Response to Fire; Fire Management Considerations [1] |
| Effect of fire exclusion on population | N/A* | Fire intervals are estimated to exceed several centuries in most communities where white ratany occurs, so fire exclusion has not occurred on a time scale relevant to these communities. MoreHowever, as fires become more frequent, fire exclusion in contemporary communities may help to restore historic fire return intervals and preserve white ratany populations, which often decline after fire. | FEIS: Fire Regimes [1] |
| Is this species typically managed with prescribed fire? | Rarely/No | Fire is generally considered harmful to desert scrub communities where white ratany occurs, and fire prevention is the primary fire management strategy. | FEIS: Fire Management Considerations [1] |
| Predominant historical fire frequency where it most commonly occurs | Infrequent* | Historically, fires were probably rare to infrequent in most communities where white ratany is common, with modeled fire intervals estimated to exceed several centuries. MoreHowever, it also grows in perennial graminoid communities where fires may have been more frequent. | FEIS: Fire Regimes [1]; LANDFIRE Biophysical Settings (below) |
| Predominant historical fire severity where it most commonly occurs | Replacement | Historically, fires were likely replacement severity where white ratany is most common. MoreDesert scrub communities were fuel-limited in most years, with sparse, discontinuous vegetation and bare ground that impeded fire spread, so fires were probably rare and limited in extent. | FEIS: Fuel Characteristics; Fire Regimes [1]; LANDFIRE Biophysical Settings (below) |
| Predominant historical fire regime group where it most commonly occurs | 5 | Modeled historical fire intervals exceed several centuries in most communities where white ratany is most common, with predominantly replacement-severity fire—consistent with fire regime group 5. | FEIS: Fire Regimes [1]; LANDFIRE Biophysical Settings (below) |
| Alters historical fuel characteristics of ecosystems where it occurs | Rarely/No* | White ratany is native and does not alter fuels directly, but it may indirectly support higher densities of flammable invasive annual grasses such as bromes beneath its canopy. | FEIS: Fuel Characteristics; Value for Restoration of Disturbed Sites [1] |
| Biophysical Setting | Mean Fire Interval (years) | Fire Severity Percent (%) | ||||||
|---|---|---|---|---|---|---|---|---|
| Code | Fire Regime Group | Low | Mixed | Replacement | All | Low | Mixed | Replacement |
| Series 10820 - Mojave Mid-Elevation Mixed Desert Scrub | ||||||||
| 10820_12_15_16_17_23_24 | V-B | 815 | 815 | 0 | 0 | 100 | ||
| 10820_14 | V-A | 406 | 406 | 0 | 0 | 100 | ||
| 10820_4_13 | V-A | 399 | 399 | 0 | 0 | 100 | ||
| Series 11552 - North American Warm Desert Riparian Systems - Stringers | ||||||||
| 11552_13_14_15 | V-B | 735 | 735 | 0 | 0 | 100 | ||
| Series 10870 - Sonora-Mojave Creosotebush-White Bursage Desert Scrub | ||||||||
| 10870_4_6_12_13_14_15_17_24_25 | V-A | 329 | 329 | 0 | 0 | 100 | ||
| Series 10740 - Chihuahuan Creosotebush Desert Scrub | ||||||||
| 10740_25_26 | ||||||||
| Series 11350 - Inter-Mountain Basins Semi-Desert Grassland | ||||||||
| 11350_13_14 | IV-B | 119 | 119 | 0 | 0 | 100 | ||
| Series 11090 - Sonoran Paloverde-Mixed Cacti Desert Scrub | ||||||||
| 11090_14 | V-B | 1056 | 1056 | 0 | 0 | 100 | ||
| 11090_15_25 | V-B | 1049 | 1049 | 0 | 0 | 100 | ||
| 11090_4_13 | V-B | 1284 | 1284 | 0 | 0 | 100 | ||
| Series 10910 - Sonoran Mid-Elevation Desert Scrub | ||||||||
| 10910_13_14 | IV-B | 104 | 104 | 0 | 0 | 100 | ||
| Summary | ||||||||
| Minimum | 104 | 104 | 0 | 0 | 100 | |||
| Maximum | 1284 | 1284 | 0 | 0 | 100 | |||
| Mean | 630 | 630 | 0 | 0 | 100 | |||
| Median | 571 | 571 | 0 | 0 | 100 | |||
| Percentage of fires in 3 fire severity classes, derived from LANDFIRE succession modeling. Replacement-severity fires cause >75% kill or top-kill of the upper canopy layer; mixed-severity fires cause 26%-75%; low-severity fires cause <26%. | ||||||||
| LANDFIRE. 2020. Biophysical settings models and descriptions, [Online]. Washington, DC: U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior; U.S. Geological Survey; Arlington, VA: The Nature Conservancy, (Producers). Available: https://www.landfirereview.org/search.php [96496] | ||||||||
- Brahmsteadt, Taryn R. 2026. Krameria bicolor, white ratany. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/krabic