Invasive weeds form a common battlefield for the gardener. Herb Robert is in the geranium family and produces the characteristic crane-shaped seed pod that all members of the family bear. The seeds eject forcefully from the pod and can travel up to 20 feet (6 m.) away from the plant, making it a virtual nuisance. The seeds are not the only problem because Herb Robert growing conditions are flexible such that the weed is adaptable to most soil and site conditions.
What is Herb Robert?
It is unclear as to whether Herb Robert geranium is native to North America or if it was delivered here by settlers and colonizers. Either way, the plant is now widely spread across the Northwest and B.C. but present only lightly down into California. The rapid spread and ease of establishment are a threat to the local flora.
Herb Robert Identification
Forests, ditches, disturbed soil, garden beds, low mountain terrain, and almost any other location provide ideal Herb Robert growing conditions. It prefers well-drained soil but can survive in slightly boggy areas as well. The weed has a very short and branching root system. This means hand pulling is easy and effective.
The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.
SBM Job done Tough Weedkiller (ready-to-use only), SBM Job done Path Weedkiller (ready-to-use only) and Weedol Pathclear products containing glyphosate/diflufenican and can be applied once a season to natural surfaces where no plants are to be grown, and can also be applied under and around established woody trees and shrubs. This product kills off existing small green growth and prevents or checks developing growth. Check manufacturer’s recommendations before use to avoid damaging sensitive plants
The non-selective contact herbicides acetic acid (Weedol Gun! Fast Acting, Ecofective Spot On Fast Acting Weedkiller, Vitax Garden Weedkiller) and fatty acids (SBM Solabiol Super Fast Weedkiller), or the systemic non-selective herbicide glyphosate can be used in such situations to scorch off foliage. Take care if applying such herbicides between ornamental plants by covering them with plastic sheeting whilst spraying. The covers can be removed once the spray has dried onto the weed foliage.
Wildlife in gardens
The pink flowers 8-12mm across are produced throughout the spring, summer and autumn months on plants up to 30cm (1ft) in height.
Herb robert does not root deeply and can be readily controlled by cultural methods such as digging or pulling before flowering or seeding. Hoe off seedlings on a dry day.
First, consider whether this can be done using non-chemical means such as digging out or suppressing with mulch. Where these methods are not feasible, chemical controls may need to be used.