This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
When at Mr William Chater's Nursery, at Saffron Walden, in the early part of January, inspecting his collection of Hollyhocks, I saw the stock of the fine new dwarf blue Ageratum Mr Chater is to distribute in the spring, and I was reminded that I saw it bedded out in August last, and I was so struck with its beauty that I have come to regard it as a "perfect gem " for the flower-garden; and it should be in the hands of every one requiring that great want - a thoroughly good blue bedding-plant. In point of colour it differs but little from the old form of A. mexicanum or coelestinum, but its great recommendation consists in its dwarf habit, only 6 inches in height, and the plants literally covered with lavender blue flowers, thrown 3 inches above the foliage. It is also of value as a winter blooming plant, for the old plants that were taken up from the beds at the end of the summer were in flower on the occasion of my visit. William Plester.