The Gardens
The Physical Site
The UCR Botanic Gardens occupies 16 hectares (40 acres) of rugged, hilly terrain along the eastern boundary of the U.C. Riverside campus, in the foothills of the Box Springs Mountains. Natural features include two prominent arroyos with steep slopes and intermittent water flow in one - Chancellor's Canyon - and a spectacular assemblage of huge, weathered granite boulders in the upper reaches of the other - Alder Canyon. The elevation varies from 335 meters above sea level at the entrance to 442 meters in the southeast corner of the Gardens (1100 to 1450 feet).
The annual rainfall in this area has averaged only 271 mm (10.67 inches) over a 97-year period. From 1956 to 1986 the rainfall exceeded the long term average only ten times. The majority of this scant rainfall falls between November and May. With such low rainfall, especially during the hottest time of the year, the Gardens needs to be under irrigation most of the year to grow any but the most drought tolerant plants.
From a horticultural perspective, the Gardens is in USDA Hardiness Zone 9 and Sunset Western Garden Book
Climate Zone 19. The combination of this local subtropical climate and
the irregular terrain produce a range of "microclimates" that allow a
surprising variety of plants to be grown. The cold-air-drained upper
elevations are nearly frost free, while the lower canyon bottoms are
likely to receive light frosts in winter. The average maximum
temperature for the year is 26 degrees C (78 degrees F) while the
average minimum is 10 degrees C (50 degrees F). Over a 59 year period,
Riverside averaged 14 days with a minimum below 0 degrees C (32 degrees
F) per year. Over a 12 year period, the number of days with a maximum
over 32 degrees C (90 degrees F) has been 59 per year.
About one-third of the Gardens' 40 acres remains unplanted. This land consists of variably degraded Riverside Coastal Sage Scrub Community and grassland. Common plants native to the site include brittlebush (Encelia farinosa), California buckwheat (Eriogonum fasciculatum), California sagebrush (Artemisia californica) and deerweed (Lotus scoparius).
Native Plants found at the UCR Botanic Gardens
Perennial Plants
| Artemisia californica | California sagebrush |
| Baccharis salicifolius | Mule fat |
| Datura wrightii | Jimson Weed |
| Dichelostemma pulchellum | Blue dicks, wild hyacinth |
| Dudleya lanceolata | Live forever |
| Encelia farinosa | Brittlebush |
| Epilobium (Zauschneria) canum | California fuchsia |
| Eriogonum elongatum | Wild buckwheat |
| Eriogonum fasciculatum | California buckwheat |
| Galium angustifolium | Narrow-leaved bedstraw |
| Gutierrezia californica | California matchweed |
| Haplopappus (Ericameria) palmeri | Palmer's goldenbush |
| Lessingia filaginifolia | California-aster |
| Lotus scoparius | Deerweed |
| Marah macrocarpus | Wild cucumber |
| Melica imperfecta | Melic grass |
| Mimulus longiflorus | Monkeyflower |
| Mirabilis californica | Wishbone bush |
| Nothalaena newberryi | Cotton fern |
| Opuntia littoralis | Prickly pear |
| Opuntia parryi (O. californica) | Snake cholla, cane cholla |
| Phacelia ramosissima | |
| Salvia mellifera | Black sage |
| Sambucus mexicana | Elderberry |
| Salvia apiana | White sage |
| Sarcostemma cynanchoides | Climbing milkweed |
| Scrophularia californica | California figwort |
| Solanum xantii | Purple nightshade |
Annual Plants in Season
| Amsinckia menziesii | Fiddleneck, rancher's fireweed |
| Antirrhinum nuttallianum | |
| Calandrinia ciliata | Red maids |
| Camissonia bistorta | California sun cup |
| Camissonia micrantha | |
| Crassula connata | Pygmy-weed |
| Cryptantha intermedia | Popcorn flower |
| Eucrypta chrysanthemifolia | |
| Gilia angelensis | |
| Lasthenia glabrata | Goldfields |
| Lotus strigosus | |
| Lupinus truncatus | Collar lupine |
| Nemophila menziesii | Baby blue-eyes |
| Pectocarya penicillata | |
| Phacelia distans | |
| Phacelia minor | Wild Canterbury bells |
| Salvia columbariae | Chia |
| Tropidocarpum gracile |