Bulletin of The Desert Legume Program of The Boyce Thompson Southwestern Arboretum and The University of Arizona

Volume 16, Number 2 August 2004

Effects of the December 2003 Freeze on in DELEP’s Tucson Fields

Matthew B. Johnson son. Consequently, the DELEP fields 18° F. Temperature readings at the Program Manager and Curator are excellent sites to evaluate cold CAC and WCAC are taken at Ari- Desert Legume Program tolerance in legume species. zona Meteorological Network Cold tolerance is difficult to (AZMET) recording stations. The DELEP maintains fields in the quantify. May factors can influence a minimum temperature reported at the Tucson area at the University of Ari- ’s ability to withstand freezing CAC in the December 2003 freeze zona Campus Agricultural Center temperatures including the duration was 16° F (-8.8° C). At the WCAC, (CAC) and West Campus Agricul- and intensity of the freeze, maturity of the lowest temperature recorded was tural Center (WCAC). Plants are the plant, whether the plant is actively 21° F (-6.1° C). The WCAC reading grown at these sites to increase seed growing or is dormant and hardened was recorded approximately ½ mile supplies, to provide plant material for off, protection provided by adjacent from DELEP’s field. Based on obser- research projects and to evaluate plants and buildings, and genetic char- vations of plant damage, it is likely survival and performance under local acteristics of individual plants. Usu- that temperatures in the WCAC field conditions. Initial plantings were made ally, several of these factors are in- were in the upper teens F. Due to the in 1989 and have continued as new volved in determining a plant’s re- lack of secure locations, thermom- species are acquired and propagated. sponse to freezing. eters were not present in the field The fields are located at two sites on The autumn of 2003 had plots for this freeze event so minimum the CAC and one site on the WCAC. above average rainfall with the re- low temperatures are estimates. Tem- Collectively, these fields encompass mains of three tropical storm systems peratures on both nights were below approximately 3.5 acres (1.4 ha.). As from the eastern Pacific Ocean cross- freezing for approximately 14-16 of December, 2003, there were about ing the area. Temperatures had fallen hours. 200 taxa of perennial legumes present into the low 20's F on several occa- The following report summa- in these fields. sions in late November and early De- rizes the effects of the December Freezing temperatures have cember, so most summer-growing 2003 freeze on plants in DELEP’s accounted for more plant deaths in plants had become dormant. No sig- Tucson fields. While precise informa- the Tucson fields than any other fac- nificant freeze damage was noted tion on minimum temperatures in the tor. The CAC fields are located along from these earlier freezes. On De- fields is not available, these observa- Rillito Creek and the WCAC field is cember 28th and 29th, 2003, the tions can provide a general idea of the immediately adjacent to the Santa Tucson area was subjected to a cold cold tolerance of many of the plants. Cruz River. These low-lying areas are air mass that resulted in temperatures As with past freezes, it was interesting subject to cold-air drainage at night that fell significantly below freezing at to observe the differences in the ef- and significant freezing temperatures night throughout the region. The offi- fects of the freeze between plants of occur each winter. On clear, dry, cial low temperature in Tucson fell to particular species from different ac- windless winter nights, the tempera- 19° F (-7.2° C). This is the lowest cessions and even within a single ac- ture in these fields can be over10° F temperature since December 1978 cession. colder than in warmer areas of Tuc- when the official reading dropped to 2 Aridus 16:2 2004

Notes: Damage to foliage is indicated stems at ground level were sufficiently craspedocarpa CAC (4) – only for those plants that typically protected that they escaped damage. 2 accessions: No freeze damage was remain evergreen through the winter in The plant is recovering. observed on these plants. Tucson. Where more than one acces- Acacia borleae CAC (2): A few Acacia crassifolia CAC (1): The sion is indicated, these are usually, stems froze back to 6" (15 cm) from were killed and many stems though not always located in separate the tips. froze back to 9" (23 cm) from tips. fields. Acacia brachybotrya CAC (1): Acacia davyi CAC (2): These This plant sustained some foliage plants froze back 6' (1.8 m) to the Acacia acuminata CAC (3) / damage only. base with stems 1" (2.5 cm) thick WCAC (1): None of these plants Acacia brachystachya CAC (1) / killed. They are recovering. exhibited freeze damage. WCAC (1) – 2 accessions: No freeze Acacia deanii CAC (1): This plant Acacia adsurgens CAC (1): The damage was observed on these did not exhibit any freeze damage. foliage was killed and stems froze to plants. Acacia difformis CAC (2): No 1" (2.5 cm) thick. Acacia brandegeeana WCAC (2): freeze damage was observed on these Acacia ampliceps CAC (2): This These plants did not exhibit any freeze plants. species freezes to the base at about damage. Acacia ehrenbergiana WCAC (1): 25° F (-3.8° C). A few root sprouts Acacia brevispica CAC (1): This This plant froze back 2.5' (0.75 m) to continue to grow despite removal of plant froze back 3.5' (1 m) to the the base with stems ¼" thick killed. It the parent plants several years ago. base with stems ½" thick killed. It is is recovering. Acacia aneura CAC (2) / WCAC recovering. Acacia erioloba WCAC (2): No (2): No freeze damage has been ob- Acacia cambagei WCAC (2): freeze damage has been observed on served on this species. These plants were planted in summer this species. Acacia angustissima var. 2003. They froze to the base with Acacia farnesiana CAC (5) / angustissima CAC (several plants): stems 1/8" thick killed. They are re- WCAC (2) – 2 accessions: These Most stems were frozen back to the covering. plants did not suffer any apparent base from 7' (2.1 m) tall. The plants Acacia cana CAC (1): This plant freeze damage. exhibit vigorous recovery. did not exhibit any freeze damage. Acacia fasciculifera CAC (2) / Acacia angustissima var. Acacia caven CAC (1) / WCAC WCAC (2): These plants froze to suffrutescens CAC (6): As is typi- (2) – 2 accessions: These plants did stems 1" (2.5 cm) thick and the foli- cal in most winters, these plants froze not suffer any apparent damage. age was killed. The plants are recov- back to the base. The plants exhibit Acacia citrinoviridis CAC (2): ering. vigorous recovery in the spring to a One plant froze back 6' (1.8 m) to the Acacia fleckii WCAC (1): Minor height of 3' (0.9 m). base with stems to 1" (2.5 cm) thick stem die-back to 3" (7.5 cm) from the Acacia aroma CAC (2) / WCAC killed, and is recovering. The other tips. (2) – 2 accessions: A few stems of plant had severe foliage damage but Acacia furcatispina CAC (3) – 2 CAC plants were frozen to 1' (30 did not sustain stem damage. accessions: A few stems died back to cm) from the tips. WCAC plants ex- Acacia constricta CAC (7) – 2 6" (15 cm) from the tips. hibited no damage. accessions: No freeze damage has Acacia galpinii CAC (2): Stems to Acacia ashbyae WCAC (2): No been observed on this species. ½" thick were killed. These plants are damage was observed on these Acacia coolgardiensis WCAC (1): 20' (6.1 m) tall and continue to grow plants. This plant had been planted in sum- larger despite sustaining freeze dam- Acacia atramentaria CAC (2) / mer 2003 and was killed by the age each year. WCAC (2): None of these plants freeze. Acacia gerrardii subsp. negevensis were damaged. Acacia coriacea CAC (2): The CAC (3) / WCAC (2): None of these Acacia berlandieri CAC (5) – 2 slender stems of this species froze plants exhibited any freeze damage. accessions: Some stems of some back to the base. These plants regu- Acacia grandicorniculata CAC plants suffered minor tip damage only. larly freeze at this site but recover (2): These plants froze back 6' (1.8 WCAC (1): This vigorously and grow to 7' (2.1 m) tall m) to the base with stems 1.5" (3.75 plant froze to the base with stems to the following summer. cm) thick killed. They are recovering. 2" (5 cm) thick being killed. A few Aridus 16:2 2004 3

Acacia grasbyi WCAC (1): Severe Acacia millefolia CAC (9) – 2 2.5' (0.75 m) to near the base and is damage to foliage and some stem tips accessions: Some stems on each plant recovering. were killed. froze back to 1' (30 cm) from the tips Acacia pravissima WCAC (1): Acacia greggii CAC (3) / WCAC while other stems were unaffected. Severe foliage damage and minor die- (2): No freeze damage has been ob- Acacia montana CAC (1): This back of some stem tips. served on this species. plant sustained minor foliage damage Acacia pruinocarpa CAC (3) / Acacia haematoxylon CAC (2): only. WCAC (2): The foliage of all plants No freeze damage was observed on Acacia montis-usti WCAC (2): was frozen. The WCAC plants suf- these plants. Both plants were killed by the freeze. fered no stem damage while the CAC WCAC (2): Acacia nebrownii CAC (2): Froze plants had surprisingly variable dam- No freeze damage was observed on to the base from a height of 9' (2.7 age with stems killed back several these plants. m) with stems to 3" (7.5 cm) in diam- feet to 3" (7.5 cm) thick on one plant Acacia harveyi CAC (1): The foli- eter killed. The plants are recovering while stems of another plant only age was frozen and some stem tips vigorously. froze to ¼" thick. were killed. Acacia neovernicosa CAC (3): No Acacia pyrifolia WCAC (2): These Acacia hebeclada subsp. freeze damage has been observed on plants froze to the base from a height hebeclada CAC (3) / WCAC (2) – this species. of 6' (0.9 m) with stems to 1" (2.5 2 accessions: Plants at both locations Acacia notabilis CAC (3) – 2 ac- cm) killed. They are recovering vigor- experienced die-back of some stems cessions: Some foliage damage on all ously. to 3' (0.9 m) from the tips. The CAC 3 plants and minor stem die-back on Acacia quornensis CAC (2): The plants suffered less damage overall 2 plants of one accession. foliage was killed and some stems than the WCAC plants. Acacia nyssophylla CAC (2): No froze back 3' (0.9 m) to the base Acacia hemiteles WCAC (2): Both freeze damage was observed on these while other stems had only minor tip plants were killed by the freeze. plants. die-back. The plants are recovering. Acacia hereroensis CAC (2): Most Acacia obtecta CAC (1 plant): The CAC (3) – 2 ac- stem froze back to 6" (15 cm) from foliage was killed but no stem damage cessions: The single plant of one ac- the tips. was noted. cession exhibited no damage while the Acacia jennerae CAC (3) / Acacia occidentalis CAC (1) / other plants suffered some foliage WCAC (2): No freeze damage has WCAC (2) – 2 accessions: No freeze damage and minor stem die-back. been observed on this species. damage has been observed on this Acacia reficiens WCAC (1 plant): Acacia karroo WCAC (2): No species. Minor die-back of some stem tips damage was observed on these Acacia oswaldii CAC (2): Severe only. plants. foliage damage occurred but the Acacia rehmanniana WCAC (2): Acacia kempeana CAC (3): No stems were undamaged. Some stems of one plant froze back freeze damage was observed on these CAC (1) / to 2' (0.6 m) to ¼" thick, while the plants. WCAC (2): No freeze damage was other plant froze to the base with Acacia kirkii WCAC (2): Most observed on these plants. stems to 1.5" (3.75 cm) thick killed. stems froze back to 2' (0.6 m) from Acacia patagiata CAC (3): Some Both plants are recovering. the tips. foliage damage was evident but the Acacia rigidula CAC (3) / WCAC Acacia leiocalyx WCAC (1): stems were undamaged. (2) – 2 accessions: None of these Froze to the base from a height of 4' CAC (1) / WCAC plants exhibited freeze damage. (1.1 m) with stems to 1" (2.5 cm) (2) – 2 accessions: The CAC plant Acacia rivalis CAC (2) / WCAC thick killed. The plant is recovering. suffered considerable foliage damage (2): No freeze damage has been ob- Acacia mellifera subsp. detinens while the WCAC plants had no ap- served on this species. CAC (1) / WCAC (1): No freeze parent damage. Acacia salicina CAC (2) / WCAC damage has been observed on this Acacia permixta CAC (2): Some (2) – 2 accessions: The foliage of the species. stems froze back to 2' (0.6 m) from CAC plants was killed up to a height Acacia microcarpa CAC (1): The the tips. of 15' (4.5 m). The foliage on the foliage was frozen and some stem tips Acacia prainii WCAC (2): One upper portion of the plants was un- were killed. plant was killed. The other froze back damaged, apparently as it was above 4 Aridus 16:2 2004

the layer of coldest air. The WCAC Acacia viscidula CAC (3): No Caesalpinia cacalaco CAC (1): plants were undamaged. freeze damage was observed on these This plant froze back to the base from Acacia saligna CAC (1) / WCAC plants. 8' (2.4 m) height but has vigorous (1): The plant at CAC was the last of Acacia visco WCAC (2): No freeze new growth. 12 originally planted in 1990 and was damage has been observed on this Caesalpinia gilliesii CAC (8): No senescent. This individual froze and species. freeze damage was observed on these subsequently died. The plant at Acacia wrightii CAC (2) / WCAC plants. WCAC was 9' (2.7 m) tall and froze (3): No freeze damage has been ob- Caesalpinia mexicana CAC (12) to the base with stems 3" (7.5 cm) in served on this species. – 2 accessions: Stems of some plants diameter killed. It is recovering. Acacia xanthina WCAC (1): The died back to 1' (30 cm) from the tips Acacia schaffneri CAC (3) / twigs froze back to 2' (0.6 m) from but otherwise appear undamaged WCAC (2): No freeze damage has the tips. while other plants had considerable been observed on this species. Albizia julibrissin WCAC (2): No stem damage with many stems killed Acacia schottii CAC (4): No freeze damage was observed on this to ½" thick. freeze damage has been observed on species. Caesalpinia palmeri CAC (5) – 2 this species. Albizia sinaloensis CAC (2): accessions: Some stems died back to Acacia sphaerocephala WCAC Froze to the base from 7' (2.1 m) tall 2' (0.6 m) from the tips while most (2): These plants froze back 3.5' (1 with healthy new growth apparent. stems remained undamaged. m) to the base to stems ¼" thick. One Amorpha fruticosa CAC (5) – 2 Caesalpinia paraguariensis CAC is recovering and the other appears to accessions: No freeze damage has (2) – 2 accessions: No freeze damage be dead. been observed on this species. was observed on these plants. CAC (1) / Anadenanthera colubrina WCAC Caesalpinia pulcherrima CAC WCAC (2) – 2 accessions: The CAC (1): Stems to ½" thick were killed. (6): All stems of these suffrutescent plant suffered significant foliage dam- Bauhinia forficata WCAC (2): plants froze to the base with rapid age and some stems froze back to 2' Stems to ½" thick were killed. recovery in the spring. This species (0.6 m) from the tips. The WCAC Bauhinia lunarioides CAC (5) – typically freezes at about 25° F (-3.8° plants were undamaged. 3 accessions: No freeze damage has C). Acacia tetragonophylla CAC (3) been observed on this species. Caesalpinia sessilifolia CAC (2): – 2 accessions: All 3 plants suffered Bauhinia macranthera CAC (3): Minor damage to some stems that foliage damage ranging from moder- No freeze damage was observed on died back to 2" (5 cm) from the tips. ate to severe. The single plant of one these plants. Calliandra californica CAC (7): accession experienced considerable Bauhinia natalensis CAC (3): Stems of this species were frozen to die-back of stems several feet from These plants froze back 2' (0.6 m) to near the base and exhibited rapid the tips, though a few stems had only the base. One was killed and the oth- recovery in the spring. The stems are minor die-back. The other 2 plants ers are recovering. typically killed at 22° F (-5.5° C). had no stem damage. Bolusanthus speciosus CAC (1) / Calliandra eriophylla CAC (12) – WCAC (1): No WCAC (1): The foliage was frozen 2 accessions: No freeze damage was freeze damage was observed on this and some stems died back to 1' (30 observed on these plants. plant. cm) from the tips while other stems Cercis canadensis var. mexicana Acacia victorieae CAC (1) / were undamaged. WCAC (2): No freeze damage has WCAC (14): None of these plants Brongniartia alamosana CAC been observed on this species. exhibited freeze damage. (1): This plant freezes to the base Cercis chingii CAC (2): No freeze Acacia villosa CAC (2): This spe- most years and exhibits vigorous re- damage has been observed on this cies typically freezes to the base each covery the following summer. The species. winter following temperatures of plant was 7' (2.1 m) tall with stems Cercis griffithsii WCAC (1): No about 25° F (-3.8° C). The plants ½" thick in December 2003. freeze damage has been observed on grow to 9' (2.7 m) tall the following Brongniartia minutifolia CAC this species. season. (1): No freeze damage was observed Cercis occidentalis CAC (1) / on this plant. WCAC (1) – 2 accessions: No freeze Aridus 16:2 2004 5

damage has been observed on this Havardia mexicana CAC (7) / Mimosa dysocarpa CAC (7): Many species. WCAC (2): No freeze damage has stems exhibited minor die-back to 1' Chamaecrista greggii var. greggii been observed on this species. (30 cm) from the tips. CAC (1): No freeze damage was Havardia pallens CAC (4) / Mimosa emoryana CAC (5): No observed on this plant. WCAC (2): Some stems of CAC freeze damage has been observed on Colutea istria CAC (3): No freeze plants were frozen back to 1' (30 cm) this species. damage has been observed on this from the tips. No stem damage was Mimosa ephedroides CAC (3): No species. observed on WCAC plants. freeze damage was observed on these Coursetia axilaris CAC (1): No Lebeckia sericea WCAC (1): This plants. freeze damage was observed on this plant was planted in summer 2003 Mimosa farinosa CAC (4): No plant. and was killed by the freeze. freeze damage has been observed on Coursetia glandulosa CAC (4): Leucaena greggii CAC (3) / this species. Most stems killed back to near the WCAC (1) – 2 accessions: No freeze Mimosa grahamii CAC (1): No base from 8' (2.4 m) tall with vigorous damage was observed on these freeze damage has been observed on recovery in the spring. plants. this species. Desmodium cinerascens CAC (5): Leucaena leucocephala CAC (2) / Mimosa malacophylla CAC (2): The stems were killed to the base. WCAC (2) – 2 accessions: These Most stems froze back 6' (1.8 m) to This species typically freezes at about plants froze to the base with stems to the base with vigorous recovery in the 25° F (-3.8° C) and grows vigorously 22' (6.7 m) tall and 3" (7.5 cm) thick spring. to 8' (2.4 m) tall the following sum- killed. This species suffers severe Mimosa strigillosa CAC (mass of mer. freeze damage below 25° F (-3.8° C) several plants): This trailing species Eysenhardtia orthocarpa CAC (6) but exhibits vigorous recovery the typically defoliates with freezing tem- – 3 accessions: No freeze damage following season. peratures but the stems have not suf- was observed on these plants. Leucaena pulverulenta CAC (1) / fered noticeable freeze damage. Eysenhardtia texana CAC (6): No WCAC (2): Stems to 2" (5 cm) in Nissolia schottii CAC (1): This freeze damage has been observed on diameter were frozen. vine froze to the base and recovered this species. Leucaena retusa CAC (2): No rapidly in the spring. Geoffroea decorticans CAC (2) / freeze damage was observed on these Olneya tesota CAC (1) / WCAC WCAC (1) – 2 accessions: No freeze plants. (2) – 2 accessions: These plants did damage has been observed on this Lysiloma watsonii CAC (5) / not exhibit apparent freeze damage. species. WCAC (2): Somewhat variable Parkinsonia africana WCAC (2): 1 Gleditsia amorphoides CAC (1): damage with many stems killed to /2" Many stems died back to 2' (0.6 m) No freeze damage has been observed in diameter. from the tips. on this species. Mimosa aculeaticarpa var. Parkinsonia florida subsp. florida Gleditsia caspica CAC (2): No biuncifera CAC (3): No freeze CAC (4) / WCAC (2) – 2 acces- freeze damage has been observed on damage has been observed on this sions: No freeze damage has been this species. species. observed on this species. Gleditsia triacanthos CAC (1) / Mimosa asperata CAC (3): These Parkinsonia microphylla WCAC WCAC (2) – 2 accessions: No freeze plants typically freeze to the base at (2): No freeze damage has been ob- damage has been observed on this about 25° F (-3.8° C) and recover served on this species. species. rapidly in the spring. Parkinsonia praecox subsp. Gymnocladus dioicus CAC (1) / Mimosa distachya var. laxiflora praecox CAC (2) / WCAC (2) – 2 WCAC (2) – 2 accessions: No freeze CAC (3) – 2 accessions: 2 plants of 1 accessions: The CAC plants sustained damage has been observed on this accession suffered major stem die- minor die-back to 6” (15 cm) from species. back, while the plant of the other ac- stem tips while the WCAC plants did Halimodendron halodendron cession had only minor stem die-back not exhibit any damage. WCAC (1): No freeze damage has to 1' (30 cm) from the tips. This spe- Parkinsonia texana var. macra been observed on this species. cies exhibits rapid recovery in the CAC (2) / WCAC (2): No freeze summer. damage has been observed on these plants. 6 Aridus 16:2 2004

Parkinsonia texana var. texana Psorothamnus spinosus CAC (3): CAC (2) / WCAC (2): No freeze These plants did not exhibit freeze damage has been observed on these damage. Delep Personnel plants. Retama raetam CAC (2): No William R. Feldman, Ph.D. Parkinsonia x Desert Museum freeze damage has been observed on Director CAC (2): No freeze damage has this species. been observed on these plants. Rhynchosia pyramidalis CAC (1): Matthew B. Johnson Parkinsonia xsonorae CAC (5): This herbaceous vine freezes to the Botanical Specialist Two plants were undamaged, while base each winter. Ken Coppola the others sustained some stem die- Rhynchosia texana CAC (1): This Horticulturist back up to 2' (0.6 m) from the tips. herbaceous vine freezes to the base Peltophorum africanum CAC (3) each winter. Margaret Norem, Ph.D. – 2 accessions: A plant of one Robinia pseudoacacia CAC (1): Editor Aridus accession froze back to the base and No freeze damage has been observed Gina Vance is recovering, while plants of the other on this species. Administrative Assistant accession had die-back on some Schotia afra var. afra WCAC (1): stems to 2' (0.6 m) from the tips while Severe foliage damage and stems to Volunteer Coordinators other stems were undamaged. ½" thick were killed. Prosopidastrum globosum CAC Schotia brachypetala WCAC (2): Glenn Branham (3): No freeze damage has been The foliage was killed and both plants Pamela Honaker observed on this species. froze to the base with stems to ½" Yuma Fields Prosopis chilensis WCAC (1): No thick killed. One plant died and the Dan Sims freeze damage has been observed on other is recovering. Greenhouses this species. Senna aphylla CAC (6) – 2 acces- Prosopis glandulosa var. sions: No freeze damage was ob- Advisory Board glandulosa WCAC (2): No freeze served on these plants. damage has been observed on these Senna artemisioides subsp. Rita Jo Anthony plants . xartemisioides CAC (3) – 2 acces- Elizabeth Davison Prosopis glandulosa var. sions: The upper foliage was frozen torreyana CAC (6) / WCAC (2) – and some stems died back to 6" (15 Stefanie Greene, Ph.D. 3 accessions: No freeze damage has cm) from the tips. been observed on these plants. Senna artemisioides subsp. Leslie Gunatilaka, Ph. D. Prosopis laevigata CAC (1) / filifolia CAC (3 ): These plants did Ryan Huxtable, Ph.D. WCAC (2): No freeze damage has not exhibit freeze damage. been observed on this species. Senna artemisioides subsp. Ken Morrow Prosopis nigra CAC (1): No freeze hamersleyensis CAC (1) – 2 ac- damage has been observed on this cessions: The single plant of one ac- Suzanne Nelson, Ph.D. plant. cession was killed. Plants of the other Kathleen C. Rice Prosopis pubescens CAC (3) / accession froze back 2' (0.6 m) to the WCAC (2) – 2 accessions: No freeze base and are recovering. Ursula Schuch, Ph. D. damage has been observed on this Senna artemisioides subsp. species. petiolaris CAC (5): Severe foliage Prosopis reptans var. cinerascens damage and some stems were killed CAC (numerous plants): No freeze back 3' (0.9 m) from the tips. damage has been observed on this Senna artemisioides subsp. xsturtii species. CAC (2): Most of the foliage was Prosopis velutina CAC (2) / frozen and many stems were killed WCAC (2): No freeze damage has back to 3' (0.9 m) from the tips. been observed on this species. Aridus 16:2 2004 7

Senna artemisioides subsp. Senna lindheimeriana CAC (nu- Sophora arizonica CAC (1): No zygophylla CAC (3): No freeze merous plants): This suffrutescent freeze damage has been observed on damage was observed on these species typically dies back to the base this species. plants. each winter following temperatures of Sophora secundiflora CAC (1): Senna confinis CAC (numerous about 25° F (-3.8° C). No freeze damage has been observed plants): This suffrutescent species Senna pallida CAC (8): This on this species. typically dies back to the base each species typically dies back to the base Tephrosia leiocarpa CAC (4): This winter following temperatures of each winter following temperatures of suffrutescent species typically dies about 25° F (-3.8° C). about 25° F (-3.8° C). The plants back to the base each winter follow- Senna costata CAC (4) – 2 grow to 6' (1.8 m) tall in the summer. ing temperatures of about 25° F (- accessions: This species typically dies Senna polyantha CAC (2): These 3.8° C). back to the base each winter plants sustained only minor die-back Zapoteca formosa var. schottii following temperatures of about 25° F to 3" (7.5 cm) from the tips of some CAC (5): The stems froze back to 3' (-3.8° C). The plants grow to 6' (1.8 stems. (0.9 m) to the base with vigorous m) tall in the summer. Senna roemeriana CAC (numer- recovery in the spring. Senna covesii CAC (numerous ous plants): This short-lived, plants): This short-lived, suffrutescent suffrutescent species did not appear species did not appear to have been to have been significantly damaged. significantly damaged. Senna wislizenii CAC (2): No Senna hirsuta var. glaberrima freeze damage has been observed on CAC (2): This suffrutescent species this species. typically dies back to the base each winter following temperatures of about 25° F (-3.8° C).

Tree Logo Opportunities for Participation Here

DELEP’s bulletin Aridus, is published Financial support for DELEP comes Dedicated volunteer work is an integral three times annually to stimulate interest from contracts, grants and contribu- component of DELEP. Our volunteers in desert legumes, to inform our readers tions from private industries, govern- come from many backgrounds and work of DELEP’s activities, and to encourage ment agencies and individuals. on a variety of projects including wild support for DELEP’s programs. Manu- seed collecting, seed processing, organi- scripts related to legumes are welcome To Contribute: Send a check, pay- zation of special events, and office work. and should be mailed to the editor for able to U of A Foundation/ DELEP, or review. Subscriptions are complimen- call the DELEP Office concerning a tary and are available by contacting the pledge, a restricted gift, or estate plan- To Volunteer: Or just to explore the DELEP office. Aridus is published by ning. possibilities, telephone our office (520) 318- The University of Arizona on behalf of The Desert Legume Program 7047) or drop us a note or email: The Desert Legume Program. 2120 E. Allen Road [email protected]. Tucson, Arizona 85719 8 Aridus 16:2 2004

Staff and Volunteers in Action

. Matt Johnson and volunteer photographic record of our fields. experience in providing weekend Bill Kendall made several seed While many photos and slides have nursery care for us. He is one of our collection trips in southeastern been taken during the past 15 years, newest volunteers and has been an Arizona this summer. Collecting pods we have not previously developed an active participant at many of the past at locations that are distant from image database. This database will be year’s sessions. earlier seed sources helps increase an important tool for use at DELEP Adam Ryan and I have spent genetic diversity within the collection. and Boyce Thompson Arboretum. additional time each week improving Our thanks to Bill Kendall for Margie Norem and I have and repairing the drip-irrigation accompanying Matt on those usually photographed many species in our system at our west campus field. long days into diverse territory. Tucson “West Campus” tree field, Many of those plants have become Matt and I have collected while Matt took several new images large specimens and we are pods from Acacia greggii and in the Yuma fields earlier this year. continuing to relocate their drip Prosopis velutina specimens at the Some pictures from our now seven emitters to improve their irrigation. UA main Campus Ag Center year old shrub field have been The summer has been relatively dry, location. These accessions will produced, with additional photos thus far, and we are irrigating our replenish the large seed numbers that being added as those specimens younger fields on a regular schedule. were used in growing plants for mature, flower, and produce pods. Our oldest fields are also being revegetation during the 1990’s. We These recent images are digital images converted to drip irrigation. had germinated hundreds of Prosopis and can be easily used in ARIDUS, Fall volunteer session dates velutina seedlings for varied grow Desert Plants Journal, and on the will be on the following Wednesdays: out projects during the 1990’s. Until web. September 8th, October 13th, now, many of those numbers had not Wayne MacGowan has November 10th, and December 8th. been replenished. provided important plant care in the Please call me during any month to During the past year we shadehouses, throughout the summer. verify that the date has not changed. continued devoting time to the Wayne uses his impressive plant care KC

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