17. A farmer buys clover seeds or grass seeds that were grown in some state that never before grew seeds that went onto his farm and thus he may get some new weeds. Seeds of alfalfa or some other crop bring new kinds of weeds, especially those of dodder. As every kind of weed goes onto a farm to stay there it follows that as a country becomes older the greater the number of kinds of weeds. As a rule each farm is annually getting more sorts of weeds, and as each farmer is cultivating weeds, they are more freely distributed in every field and along every roadside and by exchanging they are carried to neighboring and distant farms.
A great many farmers buy and sow whatever the merchant offers them under the name mentioned. For example, the college has a sample of something called clover seed, sold by a dealer in this state. It contains about 40 per cent of narrow-leaved plantain.
To begin with, years and years ago no new farm in the wilderness of Michigan contained more than twenty to thirty-five kinds of weeds, as there were not more than thirty-five sorts in the entire state, while at present there are not far from 250 kinds. A large majority of weeds hail from older countries, more especially from Europe.
There are a few weeds, like Canada thistle and quack-grass, that may infest any crop of farm or garden, but in most cases, whether to call a weed very bad depends on the nature of the crop grown, the size of the weed-seeds and their time of ripening.
Some weeds have a very wide distribution, thriving all around the world in temperate climates, while others are more limited in range; some thrive only in dry, thin, sandy soil and others in wet soils. To some extent the presence of a few weed-seeds is almost as objectionable when once on the farm, as though there were more, because these few may thrive and seed freely.
In many respects the lists of weeds for New Jersey is different from the list in Michigan, while half the weeds of Nevada or Oregon are not known in our state.
Chess, cockle, red root and rye are liable to be troublesome in fields of winter wheat, because the seeds are more or less difficult to separate from this grain and for the reason that they require a portion of two years to come to maturity.
