Plants are quite ingenious with their technology of exploitation of animals and people. Many get insects, birds, bats, spiders and anyone who is animated within their environment to disperse the plants’ pollen for them. Plants who prefer to not rely on wind, water or gravity to disperse their seed exploit a different range of animals to do so. They know how to compensate for their immobility.
This sort of exploitation is generally not as bad as it sounds. Many pollinators are rewarded for their service with nectar or surplus pollen. Dispersion of many types of seed is likewise rewarded with the fruit that surrounds the seed. Many types of nuts produce significant surpluses of seed to reward squirrels for burying them, and leaving just a few to germinate and grow into new plants.
However, there are many types of seed that are not so gracious, and several that are potentially dangerous because of the tactics they use to exploit those who disperse them. Mistletoe is an odd parasitic plant that makes very sticky berries. Those that do not get eaten by birds (for later ‘deposit’) can stick to the feet or feathers of unconsenting birds in order to catch a ride to other trees.
It is sneaky but effective. Most other plants that use this technique are small annual plants that rely on mammals instead of birds. Instead of sticking to feathers, their seed are designed to stick to fur. Such seed are not often a problem for wild animals who have short fur that the seed can stick to only for short distances before slipping out and onto the ground where seed really wants to be.
Domestic animals are not so fortunate. They have longer, shaggier and maybe curlier fur that weed seeds such as foxtail and burclover can get very entangled in. Because foxtail is designed to go into fur but not come out, it is seriously dangerous if it gets into the eyes, ears or noses of domestic animals. Because dogs and cats go wherever they want to, it is very important to eliminate such weeds from gardens where dogs and cats live, and to hopefully do so before they go to seed.
This is the opposite of the ‘right plant in the right place’. It is something that horticultural professionals should neither promote nor tolerate when feral plants appear in landscapes that they are getting payed to maintain. This example looks like it is more relevant to the topic of ‘Fat Hedges’ from 
Once it gets into a lawn, English daisy, Bellis perennis, can be very difficult to get rid of without leaving bald spots. The thin but tough rhizomes creep along the ground, producing rounded leaves that get no longer than two inches. Mowers barely scratch the surface. English daisy seems to prefer partly shaded areas to drier sunny spots. Although invasive, it can be pretty in informal lawns.
What an unappealing name! That is probably why so many of us know it simply as ‘wild onion’ or ‘allium’. Few of us bother to get sufficiently acquainted with it to know it by the species name of Allium triquetrum, which is actually not much more appealing than ‘onion weed’. It is not really wild, but has naturalized as an invasive exotic, or in other words, ‘weed’. At least it is a pretty weed.
Weeds always seem to have unfair advantages. While we pamper so many of our desirable plants to get them to grow and perform, weeds proliferate without help. They survive harsh conditions, inferior soil and some of the techniques we try to kill them with. They do not need much, if any water. They broadcast inordinate volumes of seed. They grow fast enough to overwhelm other plants.
This is one of those plants that many of us have strong feelings about. Many of us who remember it from when it was more popular in the 1970s might consider Algerian ivy, Hedera canariensis, to be an aggressively invasive weed. Those of us who are less familiar with it might appreciate it as a vigorous and resilient groundcover that gets dense enough to exclude most other weeds.
They are weeds for a reason. They grow like . . . well, weeds! By definition, they are unwanted. Yet, they typically proliferate and grow faster than desirable plants. They aggressively compete for space, sunlight and resources. Many weeds start to grow through winter, and get established while other seedlings are just beginning to germinate, or other plants are just waking from dormancy.
Every invasive exotic (non-native) species has a story of how it got here.
Tony Tomeo 