You can already replant conifers from the end of August. You can dig out conifers with a sufficiently large root ball which have not stood where they are for more than three or four years and replant them at the new location.
In warm, dry weather conditions, prepare the plant for replanting approximately fourteen days beforehand. Water the plant every three or four days with ten to twenty litres of water, depending on the size of the plant, so that it can supply itself with water reserves prior to the re-planting phase. This measure is also beneficial to you: the well moistened soil can be dug much more easily than dry soil.
If, on the other hand, the conifers have been standing where they are for a longer period and you are then to replant them, you must first prepare them for this by allowing them to produce a sufficient number of new fine roots, without which your re-planting work will otherwise not be very successful.
And this is how to do it: determine the size of the root bale required later. Its diameter is approximately a quarter of that of the conifers. Dig one half of the root bale free with a spade from the end of August. Also prick the underside of this root bale half. Now fill up with abundant wet peat, wet peat substitute or a mixture thereof with sand (mixing ratio 1:1) in front of the later root bale and from now on keep this filler material evenly moist. The conifers take root in this in the following vegetation period with many new fine roots. At the end of August of the coming year, proceed in the same way with the left-over root bale. Now dig this free and encourage it to sprout copious roots with rooting substrate. At the end of the second year, the conifer is now equipped with many new fine roots around the planned root bale – now you can re-plant them with every chance of success.
Tip: As described here for conifers, you can also proceed in the same way with larger deciduous shrubs in order to replant them safely.