The Perennial Ground-Cherry
Table of Contents
Smooth ground-cherry (Physalis virginiana Mill. var. subglabrata
(Mackenz. and Bush) U.T. Waterfall) and clammy ground-cherry (Physalis
heterophylla Nees) are perennial weeds native to Canada and the
United States. In southern Ontario clammy ground-cherry occurs in
cultivated fields and pastures, and along ditches, railway embankments
and roadsides. It is usually found growing in sandy light-textured
soils. Smooth ground-cherry grows in similar habitats but is most
often seen growing in cultivated fields, usually on heavier textured
soils. In soils of medium texture both species are often found growing
together. The two species have been increasing in importance as
weeds of cultivated fields in Ontario during the last five years.
Neither species constitutes a serious weed problem as yet, but there
are fields where large vigorous clumps of smooth ground-cherry interfere
with crop growth and impede the passage of farm implements.
Figure 1. Flowering and fruiting plant of smooth ground-cherry.
Figure 2. Young plant of clammy ground-cherry. The stems and petioles are densely covered with hair. (xo.15)
Smooth and clammy ground-cherry are perennial herbs propagating from root buds and reproducing by seeds. The stems are much branched; erect to 90 cm high and ridged, often with a greyish tint in smooth ground-cherry; spreading to erect, up to 60 cm high in clammy ground-cherry. The leaves are arranged alternately on the stems; oval or lance shaped; with toothed or entire margins in smooth ground-cherry and toothed margins in clammy ground-cherry. Both the leaves and stems of clammy ground-cherry are covered abundantly with hair, giving them a clammy touch.
Figure 3. Drawing of leaves, stem, buds and flower of clammy
Smooth ground-cherry is sparsely hairy to hairless.
Figure 4. Drawing of leaves, stem and flower buds of smooth ground-cherry. (xo.6) Drawn by Marguerite Kane
The flowers of both species are funnel shaped, drooping singly where three stems or leaves meet; yellow with a star-shaped dark purplish (lighter colour in clammy ground-cherry) centre; and measure about 2.7 cm wide. Flower pedicels measure about 1.5 cm long and elongate to 2.5 cm after fruit formation. Flowering begins about six weeks after emergence and continues up to September. The fruits, or berries, are loosely enclosed by the much enlarged calyx.
Figure 5. Four papery calyes of clammy ground-cherry, each enclosing one berry. (xo.9)
Berries are green at first and red or yellow at maturity.
Figure 6. Berries of clammy ground-cherry ranging from freshly ripe and smooth to older and wrinkled. (xo.9)
and contain about 255 and 155 seeds per berry in smooth ground-cherry and clammy ground-cherry, respectively. The seeds are white or brown depending on maturity; measure 2.0 mm x l.5 mm and 1.8 mm x 1.3 mm; and weigh 0.8 and 0.54 g per thousand in clammy ground-cherry and smooth ground-cherry, respectively. Establishment from seeds appears to be a rare occurrence in clammy ground-cherry because many developing seeds are destroyed by insects and young seedlings have rarely been seen. Percentage seed survival is often higher for smooth ground-cherry but seedlings of this species have not been noted in natural sites. A possible reason for the absence of seedling establishment is the lack of seed dormancy in samples we have tested.
In Southwestern Ontario, new shoots arise from overwintered root systems in mid-May. Through the initiation of daughter colonies, single plants are capable of covering wide patches in the field within two years. Tillage operations can spread these weeds into uninfested fields. It is through such tillage procedures that serious infestations, particularly of smooth ground-cherry, can be created.
Smooth ground-cherry and clammy ground-cherry are resistant to
commonly employed herbicides. The OMAF Publication 75, Guide to
Weed Control does not list any herbicide treatment for ground-cherries.
Resistance to herbicides, and reduced tillage apparently have helped
the ground-cherries spread at the expense of competing species.
Efficacy of selected herbicides on ground-cherries is currently
being evaluated at the Ridgetown College of Agricultural Technology.
The ability to regenerate from deeply buried root buds makes these
species difficult to control. However, repeated cultivations early
in the season, or spot treatment with glyphosate at the highest
recommended rate can be effective.
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