References:

Photo Collections and Plant Databases:
• Aloe species pictured at Wikiwand
  
• Aloe cooperi notes and care at SANBI, South African National Biodiversity Institute
  
• Links to Aloe sites and care, courtesy San Marcos Growers
  
• Operation Wildflower / Operasie Veldblom
  
• Namauqaland photos aloe dichotoma and pachypodium
  
Plants of Southwestern United States:
• Claret cup cactus and others
  
• Dasylirion wheeleri, common sotol at Xera Plants
  More a cacti reference:
• Wildflower dot org - opuntia humifusa
  
• Agave rzedowshiana, article at Starr Nursery
  
• Agave petrophila
  2020-07-12
• agave pseudoferox bellville
  
• agave ovatispina "Blue Rapture"
  Found cerca 2012:
• Growing On The Edge - filifers and agave albipilosa
  
Plants of Pacific Northwest:
• Ashland Garden Club- calochortus tolmiei, Siskiyou onion, Western coral root orchid y mas
  
• coral root orchids
  
• lanceolatum
  
Aloe references:
• Viridis dot Net aloe polyphylla in England
  
• Maliba Lodge, Lesotho South Africa
  
• Aloe reitzii at PZA SANBI dot Org
  
• aloe broomii in article at Tucsan Cactus Society
  
• aloe nobilis
  
• aloe mitriformis
  

Nurseries

U.S. focus and also world wide:
• San Marcos Growers . . . California wholesale nursery, useful plant descriptions
  
• Edge Of The Woods Nursery
  
• Natura Greenhouse - Las Cruces, NM
  
• Rare Plants UK
  
Pacific Northwest nurseries:
• Portland Nursery . . . long standing Portland, Oregon nursery, great annual apple festival mid-October!
  
• Cistus Nursery . . . located on Sauvie Island, offering many Mediterranean-adapted and xeric plants
  
• Mount Pleasant Iris . . . local iris growers specializing in Japanese, bearded and select species iris
  
• Xera Plants . . . Portland area nursery focused on PNW adapted plants
  
• Sarracenia Northwest - pitcher plants
  
Seed sources:
• Silver Hill Seeds
  
• Klamath-Siskiyou Native Seeds - dodecatheon hendersonii
  

 
Gardens and plant societies

Botanic Gardens:
• Los Angeles County Botanic Garden
  
• Karoo Desert Garden, South Africa
  

 
 
 
Garden Materials:

• Get Chip Drop . . . arborists' wood chips for mulching
  

 
Weed and Invasive Plant Identifications:

• Penn State broadleaf weed identifier list
  
• GOERT Garry Oak restoration project, invasive species list of
  
• galium aparine - barweed, catchweed, goose grass
  

 
Plant Physiology and Morphology:

• Leaf Forms on Wikipedia - English version