Weeds with small sticker seeds

Seeds That Stick To Clothing: Different Types Of Hitchhiker Plants

Even now, they’re lingering along the roadside waiting for you to pick them up and take them wherever you’re going. Some will ride inside your car, others on the chassis and a few lucky ones will find their way into your clothing. Yes, weeds that spread by people, or hitchhiking, have certainly taken advantage of you this year. In fact, the average car carries two to four seeds for hitchhiker plants at any given time!

What are Hitchhiker Weeds?

Weed seeds spread in a variety of ways, whether traveling by water, by air, or on animals. The group of weeds nicknamed the “hitchhikers” are seeds that stick to clothing and fur, making it difficult to dislodge them immediately. Their variously barbed adaptations ensure that the seeds will travel far and wide via animal locomotion, and most can be eventually shaken off down the road somewhere.

Although it might sound like all fun and games, the weeds spread by people are not only difficult to contain, they’re costly for everyone. Farmers lose an estimated $7.4 billion each year in productivity to eradicate these pest plants. Humans are spreading these seeds at a rate of 500 million to one billion seeds a year in cars alone!

Although the weeds within crop stands are annoying, those that appear in fields can be downright dangerous for grazing animals like horses and cattle.

Types of Hitchhiker Plants

There are at least 600 weed species that travel by hitchhiking with humans or on machines, 248 of which are considered noxious or invasive plants in North America. They come from every kind of plant, from herbaceous annuals to woody shrubs, and occupy every corner of the world. A few plants you might be familiar with include the following:

  • “Stick-tight” Harpagonella (Harpagonella palmeri)
  • “Beggerticks” (Bidens) (Krameria grayi) (Tribulus terrestris) (Opuntia bigelovii) (Torilis arvensis) (Symphyotrichum lateriflorum) (Arctium minus) (Cynoglossum officinale) (Cenchrus)

You can help slow the spread of these hitchhikers by carefully inspecting your clothing and pets before emerging from a wild area full of seeding plants, making sure to leave those unwanted weeds behind. Also, reseeding disturbed areas like your garden plot with a cover crop can ensure that there’s too much competition for hitchhikers to thrive.

Once those weeds emerge, digging them out is the only cure. Make sure to get three to four inches (7.5 to 10 cm.) of root when the plant is young, or else it’ll grow back from root fragments. If your problem plant is already flowering or going to seed, you can clip it at the ground and carefully bag it for disposal – composting will not destroy many of these types of weeds.

Last, but not least, check your car any time you’ve been driving on unpaved roads or through muddy areas. Even if you don’t see any weed seeds, it wouldn’t hurt to clean your wheel wells, undercarriage and any other location where seeds might be hitching a ride.

Cleavers

Cleavers (Galium aparine), with its characteristic ‘sticky’ seeds, is easily introduced to gardens from uncultivated land and can become a nuisance in beds and borders.

Quick facts

Common name Cleavers, goosegrass, sticky willie
Botanical name Galium aparine
Areas affected Beds and borders, hedgerows and uncultivated ground
Main causes Easily distributed seed produced in large quantities
Timing Seen spring-autumn; treat during growing season

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What is cleavers?

Cleavers is a common annual weed native to hedgerows, scrub and arable land, which can spread to gardens on the fur of animals and clothing of passers-by. Although seedlings usually appear singly, rather than en masse like many other common weeds, the numerous and easily distributed seeds mean the weed can quickly establish in gardens if not controlled promptly.

Cleavers can be a good addition to a wildlife garden, as it provides food for the caterpillars of many butterfly and moth species, including the impressive hummingbird hawk moth.

Butterflies in your garden

Moths in your garden

This page looks at options for gardeners when cleavers are becoming a problem.

Appearance

Weak, sprawling stems, up to 1m (39in) long bear whorls of 6-8 long, slender green leaves with a prominent central vein. Tiny greenish-white flowers are borne in branching clusters from May to August and develop into round, green or purple fruits 3-5mm in diameter. Stems, leaves and seed have stiff hooked hairs.

The problem

Control

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.

Cultural control

  1. Hand-pulling or hoeing of weed seedlings is the easiest way to control this weed, but is time consuming and needs doing promptly – before plants flower and set seed – to be effective. Use gloves if grasping stems directly. As seeds can lie dormant in the soil for long periods of time, this task will be on-going.
  2. To help reduce the number of seeds introduced to the garden, brush down clothing and pet fur following walks on arable or uncultivated land where the weed is most commonly found. It is also important to avoid adding any mature weeds, which have set seed, to a home compost bin.
  3. To prevent germination of weed seedlings, apply an opaque mulching film or layer of bulky organic mulch, such as woodchips, to the soil at a depth of at least 8cm (3in).

Weedkiller control

In beds and borders
Non-selective contact herbicides containing acetic acid (eg. Weedol Gun! Fast Acting, Roundup Speed Ultra or Spot On Fast Acting Weedkiller), fatty acids (eg. SBM Job Done Garden Ultrafast Weedkiller) or pelargonic acid (Doff 24/7 Fast Acting Weedkiller, Resolva Xpress Weedkiller or Roundup NL Weed Control) 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.

The systemic non-selective herbicide glyphosate can be used in the same way, but it is particularly important to avoid spray or spray drift coming into contact with garden plants. If treating weeds in the immediate vicinity of garden plants, apply carefully using a ready-to-use spray in cool, calm weather. Protect branches and shoots by tying them aside, or by using covers or screens. Make sure weed foliage has dried before releasing branches or removing coverings.

Around established trees and shrubs
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.

Inclusion of a weedkiller product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.

Download

Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see sections 3a and 5).