• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

GENERAL BOTANICAL CHARACTERISTICS :

Leafy spurge is an introduced perennial forb [105]. It generally grows in clumps, producing stems up to 3 feet (0.9 m) tall from caudices, rhizomes, and roots [35]. Stems are tough and woody with variable degrees of branching [94]. The alternate, sessile [11] leaves are broadly narrow with entire margins [35,103]. Leaf length is variable [11], usually 1 to 4 inches (2.5-10 cm) [105]. Leaves subtending the inflorescence are whorled. Flowers are borne in terminal, umbel-shaped cymes [103]. The fruit is a capsule with 3 seeds [5,105]. Seeds are oblong, 0.07 to 0.10 inch (2.0 - 2.5 mm) long and 0.05 to 0.06 inch (1.3 - 1.5 mm) wide, with a caruncle at one end [18,103].

Leafy spurge has an extensive underground rhizome and root system [11]. Roots can penetrate into the soil as far as 15 feet (4.6 m) to 30 feet (9 m) [86]. A large concentration of roots is typically seen at 8 feet (2.4 m) [87].  Underground organs consist of long and short rhizomes, and roots, that extend horizontally in the upper soil and vertically throughout the soil profile.  Deep rooting and thick, corky root bark help establish drought resistance [87,94]. The primary root shows vigorous indeterminate growth [87].  Large amounts of carbohydrates and nitrogen are stored within rhizomes and roots during fall and winter [40].  Reserves accumulate in the fall as top-growth dies.  Reserves are in low supply during the growing season [69].

Latex is present throughout the entire plant [10] at all life stages [94].

RAUNKIAER [88] LIFE FORM:

Hemicryptophyte
Geophyte

REGENERATION PROCESSES:

Leafy spurge reproduces vegetatively and by seed. [11,103,105]

Seed:  Leafy spurge has good seed regeneration, producing large numbers of viable seed [11].  Copious amounts of pollen and nectar [11,103] attract insects for pollination.  Self- and wind pollination is almost non-existent  [94,103]. Flowering shoots normally produce 10 to 50 fruits, with each flowering shoot able to produce and disperse over 200 seeds. The fruit has explosive dehiscence when dry, projecting seed up to 15 feet (4.6 m) [5,11,105]. Capsules erupt and eject seed during periods of high temperature and low humidity [94].

Successful dissemination occurs by water, animals, and self-propulsion [5]. Colonization of previously uninhabited streambeds and riverbanks is associated with the buoyant properties of the seed [11]. Domestic and wild animals including birds and insects, especially ants, act as agents of dispersal [84,94]. Ground-nesting mourning doves may aid in leafy spurge seed dispersal.  No viable seed is found in adult dove fecal matter; however, nestlings pass viable seed [13].

Once seed is disseminated, soil-stored seed may retain viability for 5 to 8 years [5,105]. Germination begins in  April, with most germination occurring in May.  Emergence is maximized within the first 0.5 to 2.4 inches (1.3-6 cm) of soil [87], but germination may occur within the first 4 inches (10 cm) of soil.

Vegetative reproduction:  Leafy spurge is a strong root, rhizome, and root crown sprouter [20]. An extensive rhizome and root system, and the ability to produce adventitious shoot buds on rhizomes and roots, support leafy spurge's vigorous persistence [87]. New shoots arise from numerous pink buds [105] located anywhere along rhizomes and roots [20,94]. The potential for underground buds to produce new shoots is unrelated to bud size or location underground [81].  Large amounts of carbohydrates and nitrogen are stored within rhizomes and roots and are utilized during shoot growth in the spring [69].  Vegetative shoots emerge earlier than leafy spurge seedlings [94]. 

Injury enhances production of vegetative buds on rhizomes and roots [86].  Tillage increases the formation of underground buds and subsequent shoot generation.  After a major portion of the leafy spurge rhizome and root system was removed, vegetative shoots emerged for 5 consecutive years from a depth of 3 feet (0.9 m) in Saskatchewan [94]. Roots at depths of 9.2 feet (2.8 m) have a regeneration capacity similar to those near the soil surface [87].

SITE CHARACTERISTICS:

Leafy spurge achieves greater vegetative reproduction, deeper root penetration, and a greater ability to withstand control treatments in coarse-textured soils than in fine-textured soils.  Soil type has no apparent effect on root biomass but does influence distribution within the soil profile. In coarse-textured soils a higher proportion of roots occurs in soil profiles from surface to 6-inch (0 -15 cm) depths and depths below 30 inches (76 cm) than in similar profiles in fine-textured soils [94].

Leafy spurge prefers disturbed soils. It commonly occupies fields, roadsides, stream valleys, open woodlands, and waste places. A 924-acre (374 ha) contained 83 colonies of leafy spurge, and 95% of the colonies were associated with anthropogenic disturbance.  The number of colonies within each disturbance area was:

49 - trails, fire-guards, and road construction
30 - disturbance caused by track vehicles
4   - no visible soil disturbance

No colonies were associated with natural disturbance from pocket gophers [8].

SUCCESSIONAL STATUS:

Leafy spurge can rapidly invade disturbed sites by establishing from seed and by sprouting from existing roots and root crowns [37,94,106]. Once established, leafy spurge tends to expand and persist. Patches of leafy spurge may expand throughout the growing season under favorable moisture conditions [94]. The mean rate of spread, in feet, for leafy spurge within different habitats was monitored in the Saskatchewan over 2 years.  Results were as follows [94]:

Location and Habitat	Radial increase 1957	Radial increase 1958
Native grassland, grazed	2.50	2.81
Native grassland, grazed	1.27	NA
Native grassland, grazed	0.78	2.31
Abandoned, naturally revegetated, grazed	2.90	-0.47
Cultivated, seeded to bromes in 1956	0.63	3.93
Mixed brome and crested wheatgrass	1.21	1.41
Cultivated (alternate crop and summer fallow)	2.57	NA

 

SEASONAL DEVELOPMENT:

Seedlings can appear as early as May, even when temperatures are freezing.  With adequate soil moisture seed germination may continue throughout the growing season.  Seedling top-growth begins to dry out towards the end of the growing season [78].  With little or no competition from other plant species, seedling shoots may persist until the end of the growing season; however, root growth is usually more vigorous than shoot growth [37].  Within a Saskatchewan mixed-grass prairie, 5% of 7-day-old seedlings severed 1 inch (2.5 cm) below the soil surface regrew [94]. 

The primary root is developed at an early stage of embryo development [86].  Seedlings develop extensive root systems in a relatively short period of time [94]. Spring growth begins with the production of adventitious shoots arising from the seedling root system. Mature leafy spurge fields are an accumulation of adventitious shoots produced from plants a year or more old. New adventitious shoots are from produced early in the growing season until the middle of June [94].  In Saskatchewan the first appearance of vegetative shoots occurred between April 17 and May 1, with vegetative buds appearing on plants as young as 7 days (4-leaf stage) [94]. 

In July a decrease in vegetative shoots corresponds with the increased production of flowering shoots. Flowering occurs throughout the growing season. Flowering shoots appear as early as late April to May, with obvious inflorescences by June.  Fruit matures after 4 to 6 weeks, usually late June or early July [20,37].  Late-season flowering shoots may form in August, with fruit maturing from September to October [37].  During late autumn (during the period of vegetative shoot senescence), root crown buds elongate to just below the soil surface, where they are winter hardened [32]. 

In Minnesota underground development is rapid and early.  Leafy spurge produces stems in late April. Fruit ripens and seeds are dispersed from late June to August [11].

Related categories for SPECIES: Euphorbia esula | Leafy Spurge