BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Helianthus maximiliani | Maximilian Sunflower 



GENERAL BOTANICAL CHARACTERISTICS : 
Maximilian sunflower is a warm-season, bunching, perennial native forb
[44].  It grows 1.6 to 8.2 feet (0.5-2.5 m) tall [17], with a spread of
1 to 3 feet (0.3-0.9 m) [21].  Stems grow singly or clustered from short
rhizomes [44].  The flowers occur in long, raceme-like inflorescences
[15].  The floral head is 1.5 to 3 inches (4-8 cm) wide [1].  The fruit
is an achene 0.12 to 0.16 (3-4 mm) long [17].  Maximilian sunflower has
short, thick, rhizomatous rootstocks [17] with crown-buds [15].


RAUNKIAER LIFE FORM : 
   Hemicryptophyte
   Geophyte


REGENERATION PROCESSES : 
Maximilian sunflower is a perennial which reproduces by seed [31,43].
It also spreads vegetatively by rhizomes, and can form large colonies
[44].

Maximilian sunflower cultivar "Aztec" seeds germinate within 1 to 3
weeks with a germination temperature regime of 12 hours each day at 86
degrees Fahrenheit (30 deg C) or lower [31].  With other seed sources,
germination can occur in 7 to 14 days, but nearly half can be dormant.
Seedling vigor is good [44].

Maximilian sunflower seeds from the soilbank at 22 typical habitats in
Kansas were collected in November, 1945, and stored in cool, dry
conditions until February, 1946.  Subsequent germination tests showed
two major periods of germination:  one between days 6 and 25, and another
between days 46 and 55 [26].


SITE CHARACTERISTICS : 
Maximilian sunflower occurs on dry to moist open prairie, often on sandy
sites [17].  It is best adapted to deep, sandy to clayey loam upland
soils of subhumid prairies [44].  Growth is poor on gravel and dense
clay, fair on sand and clay, and good on sandy to clayey loam.
Maximilian sunflower grows poorly on saline soils.  Its optimum soil
depth is 20 inches (50 cm) or more.  It is more common on heavier soils
[44].  It is also found on waste ground, roadsides, pastures [1], fence
rows [33], riverbanks [18], and other disturbed areas [29].

Maximilian sunflower generally occurs in areas with 10 to 50 inches
(250-1270 mm) annual precipitation [35], but it can occur on lowlands
with better moisture conditions in the semiaric zones [44].

Maximilian sunflower exhibits good growth on gentle slopes and poor
growth on moderate and steep slopes [10].

Maximilian sunflower occurs at the following elevations [10]:

                    Elevation (feet)    Elevation (m)

          CO          3,500-7,000        1,067-2,134        
          MT          2,300-3,900          700-1,190             
          WY          3,600-6,000        1,100-1,830              


SUCCESSIONAL STATUS : 
Facultative Seral Species

Maximilian sunflower thrives in sunlight and has only fair shade
tolerance [44].  Stand longevity can be 5 or more years [9].


SEASONAL DEVELOPMENT : 
Maximilian sunflower seeds germinate best when soil is warm [31],
generally in May throughout much of the area in which it occurs.  Stands
develop rather rapidly from seed.  Growth occurs in late spring and
summer [43], with some flowering possible by the end of the first
growing season in the South.  However, plants are not usually fully
developed until the second year [44].  Maximilian sunflower dies back to
the ground each year, and regenerates new growth from rhizomes or
root crown buds [43].  Plants continue to spread by rhizomes after
establishment [44].

Maximilian sunflower flowering times are:

                 Begin           Peak           End
               Flowering       Flowering     Flowering

    CO          June            August        September    [10]
    IL          July             ----         August       [29]
    KS          August          September     October      [21]
    MT          July            July          September    [10]
    NC          September        ----         October      [33]
    ND          July            August        September    [10]
    SD          July             ----         September    [22]
    WY          July            July          September    [10]
Great Plains    August           ----         October      [17]
New England     August           ----         September    [36]

Related categories for Species: Helianthus maximiliani | Maximilian Sunflower