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Stachytarpheta cayennensis Blue Porterweed

Edward F. Gilman

Introduction

Porterweed is a small perennial shrub that becomes woody toward the base of the stem as is grows to about one year old. Plants grow about 4 feet tall by 6 feet wide before stems droop and touch the ground. Blue or pink flowers are borne terminally on long, stringy spikes at the ends of the stems. They attract butterflies to the landscape. Rich, dark green foliage displayed on square, green stems makes porterweed a nice addition to any sunny landscape.

General Information

Scientific name: Stachytarpheta cayennensis
Pronunciation: stake-kee-tar-FEE-tuh 
Common name(s): blue porterweed
Family: Verbenaceae
Plant type: shrub; perennial; herbaceous
USDA hardiness zones: 10 through 11 (Figure 1)
Planting month for zone 10 and 11: year round
Origin: not native to North America
Uses: hedge; border; mass planting; attracts butterflies
Availability: somewhat available, may have to go out of the region to find the plant
Figure 1. Shaded area represents potential planting range.
Figure 1.  Shaded area represents potential planting range.

 

Description

Height: 4 to 8 feet
Spread: 4 to 8 feet
Plant habit: round
Plant density: dense
Growth rate: fast
Texture: medium

Foliage

Leaf arrangement: opposite/subopposite
Leaf type: simple
Leaf margin: serrate
Leaf shape: ovate
Leaf venation: pinnate; reticulate
Leaf type and persistence: semi-evergreen
Leaf blade length: less than 2 inches
Leaf color: green
Fall color: no fall color change
Fall characteristic: not showy

Flower

Flower color: pink; blue
Flower characteristic: summer flowering; fall flowering

Fruit

Fruit shape: unknown
Fruit length: unknown
Fruit cover: unknown
Fruit color: unknown
Fruit characteristic: inconspicuous and not showy

Trunk and Branches

Trunk/bark/branches: not particularly showy; typically multi-trunked or clumping stems
Current year stem/twig color: green
Current year stem/twig thickness: thin

Culture

Light requirement: plant grows in part shade/part sun
Soil tolerances: acidic; alkaline; sand; loam; clay
Drought tolerance: high
Soil salt tolerances: unknown
Plant spacing: 36 to 60 inches

Other

Roots: usually not a problem
Winter interest: no special winter interest
Outstanding plant: plant has outstanding ornamental features and could be planted more
Invasive potential: not known to be invasive
Pest resistance: long-term health usually not affected by pests

Use and Management

Porterweed is frequently used in a mass planting along a foundation, or as a clipped or natural unclipped hedge to provide continuous color to the landscape. Space plants about 3 to 4 feet apart. A row will maintain a nice uniform shape for 6 or more months without pruning. Regular clipping can maintain a uniform shape for more than a year before the plant needs to be cut back to thicken the growth. Unclipped plants begin to open up as stems droop to the ground. For this reason, they are usually cut back each year, or any time the plant becomes leggy. This allows new growth to fill in and thicken the plant.

Locate porterweed in a sunny location in any soil. Provide irrigation during establishment and then in extended drought in the summer. Fertilize about twice each year to maintain foliage color and provide for continuous growth.

Pest and Diseases

No serious pests or diseases are known to affect porterweed.

Publication #FPS-559

Date: 8/30/2021

    • Program Area: Plant Systems
    Fact Sheet
    General Public

    About this Publication

    This document is FPS-559, one of a series of the Environmental Horticulture Department, UF/IFAS Extension. Original publication date October 1999. Revised August 2021. Visit the EDIS website at https://edis.ifas.ufl.edu for the currently supported version of this publication.

    About the Authors

    Edward F. Gilman, professor, Environmental Horticulture Department; UF/IFAS Extension, Gainesville, FL 32611.

    Contacts

    • Gail Hansen de Chapman