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.
In the southern counties, many such kinds as Double Deutzias, Spiraeas, Dwarf Lilacs, Veronicas, Prunuses, Abuti-lons, etc., are frequently hardened off, cut back, and when breaking afresh are planted on a well-prepared, sheltered border, having first had their balls of soil considerably reduced and the roots trimmed. In this manner the majority of the plants recruit their strength sufficiently to admit of being forced the following season. Many err in not hard-pruning these forced shrubs, forgetting that the weakly growth that has resulted in many instances will not flower. Cut back hard, and if the locality be warm, plant out, or if the reverse is the case, shake out the roots, trim them, and repot into good rich soil. "When well established, plunge in the open borders, and encourage to root through into the soil. When plunged in pots, they will of course require to be watered occasionally.