When first I came here, and for a long time afterwards, "Erysimum cheiranthoides" was always among the kitchen garden weeds, and one year I found growing in a bed of onions its near relative "Erysimum orientale," which is quite a rare British plant.
Greater celandine, a rather handsome perennial with somewhat glaucous leaves and bright yellow flowers, used to be an abundant weed on the banks and among the bushes, and is still (1911) to be found in the garden, though in diminished quantity.
In 1889, a strange plant appeared which puzzled me a good deal at first. It was tall and straggling, but had no flowers. Next spring there were several of the same plants, very much branched with something of the habit of a mugwort, and long spikes of flowers at the end of every branch. I discovered it to be a species of "Ambrosia," a native of North America, but I soon discovered also that it increased by underground runners in every direction, and was only too thankful to get rid of it.
Two years before, I had found another visitor, this time from South America, with bright yellow flowers, evidently allied to forget-me-not, which proved to be an "Amsinckia" (intermedia ?). There were about 20 plants of this annual in one border and several others in other parts of the garden. With some consideration, but with no particular care on my part, it has maintained itself in more or less quantity in the same herbaceous border ever since.
In 1897, a single plant of an "Allium" appeared and grew to a height of more than five feet, straight up with very stout stems, one and a half inches in circumference, and handsome heads of reddish-green bell-shaped flowers on drooping stalks, which afterwards, in fruit, became quite straight and upright. I found it to be "Allium Dioscorides," a native of Sicily and Sardinia. There were many tubers at the root when I took it up, but none of them ever grew so tall and fine as the original.
One or two plants that I have introduced myself have proved very tiresome weeds. In 1875 or thereabouts, I brought back from the wild part of a large garden in the neighbourhood a balsam with rather a conspicuous yellow flower ("Impatiens noli-me-tangere," I think). It made itself at home at once, but as it would keep within no bounds, I have done all I could "to get without it," as they would say here, but it defies me to my face and in spite of relentless persecution, again and again every spring it comes up smiling in an abundant crop.
So indeed does a tall polygonum ("P. cuspidatum" I believe it is) that I brought back from the same garden about the same time. It absolutely refuses to budge from the place where I first allowed it to grow. It does not perpetuate itself by seed like the balsam, but from little odds and ends of rootlets and suckers that hide themselves in the soil.
What I take to be a variety of "Oxalis corniculata," a very pretty little thing with dark reddish-brown leaves and deep yellow flowers, is another uncontrollable subject. It is perennial and yet increases by seed as fast as a balsam.
A plant which on the top of a stone wall is very pretty, "Linaria vulgaris," has proved a veritable plague to me in the garden. I had it sent to me originally by a nurseryman for the "Peloria" variety, and as if the disappointment of that were not enough, it added insult to injury, or rather injury to insult, by running below the surface in a provoking and persevering manner and showing itself in most unexpected places. Although the normal "vulgaris" is so irrepressible, I have found "Peloria" quite the reverse, and have never been able to keep it above a year or two.
The double-flowered varieties of most plants are, as a rule, more difficult than the ordinary single, but a little potentilla ("reptans" ?) with a yellow ball of double flower has proved an exception here. No single-flowered plant could get over and under the ground faster than this has done.