Vol. 15—1961 - NorthEastern Weed Science Society

339.
Summaryof Root, Stem, and Flo~r Studies
No rhizome production was observed in any of the Horse nettle plants
studied. New shoots, developing from the underground parts of the plant,
appeared to start from adventitious buds produced at irregular intervals and
at unpredictable locations along the roots.
Tap roots, grOWing at a depth down to 112 centimeters in the field, when .. '
excavated, cut into sections, and planted in soil, produced new shoots from
adventitious buds.
Horse nettle was capable of reproducing vegetatively from very small root
cuttings less than one inch long and 3/l6ths of an inch in diameter.
Under greenhouse conditions in: woodenf'lats, Horse nettle plants grown
from root cuttings and 'seed thepre\rious year, produced 9.3 and 10.1 new shoots,
respectively. Established Horse nettle plants, grown from seed the previous
year, produced an average of 2.5 new shoots per plant in outdoor 2 x 2 foot
concrete frames having no artificial depth restrictions on root development.
These observations suggest that Horse nettle plants grown in soils which restrict
normal root development may produce a larger number of plal ts from
buds than roots in soils permitting deep root penetration.
No significant differences were observed in the growth habit of plants
g l'.cMnin the greenhouse from root cuttings obtained from several different
locations 1n NewYork State.
Root cuttings of Horse nettle plants produced new shoots when planted
as deep as 18 inches in well drained, friable silt loam soil. Therefore, no
appreciable reduction in Horse nettle production could be expected as a result
of deep tillage operations.
Root cuttings exposed to drying on the soil surface for three days or
longer, did not develop shoots when planted at two-inch depths in soil. Thus,
Horse nettle roots lose their viability after being exposed to relatively
short periods of drying on the soil surface.
Of 92 root cuttings planted at 1-1/2 to 2-inch depths, 91 (99 per cent)
produced at least one plant and averaged 1.2 plants per cutting. This illustrates
the high reproductive capacity of this plant from vegetative parts.
There was no mortality among Horse nettle plants grown from root cuttings
that were clipped at a 2-1/2-inch height, at 5- to 8-day intervals throughout
a single grOWing season. Seed production was almost entire.ly prevented.
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Based on these results) the most appropriate time to clip Horse nettle
plants to prevent the production of viable seed, is in mid-July and again in
mid-August. It would be desirable to make further germination studies of seed
harvested during the various stages of growth of plants grown from seed and from
roots so that more reliable clipping schedules could be made.