When should I plant Alder hedging?
As Alder plants are generally sold as bare root, you can only plant from November - March, but only if the soil is not frozen. In general, late autumn is the best time to plant your Alder plants, with there being as little risk as possible with transplanting at that time.
How far apart should I plant Alder plants?
Bare root plants need to be planted quite close together to get the best results. This means planting at least 5 plants per metre (20cm spacing). You can go for as many as 7 per metre, for smaller 40/60cm sized plants, if you're keen on getting a dense hedge as quickly as possible.
How to plant Alder:
Planting your Alder plants is simple, but the trick with bare roots is ensuring they get plenty of water before going in the ground.
Begin with soaking the roots for at least 2 hours in a bucket of water. You can also spray the roots with a garden hose for a few minutes if you do not have a bucket to hand or you have too many to put into containers.
Whilst the roots are soaking, dig the trench/individual holes (if you haven't already). The hole will need to be at least twice as wide as the plant's root mass, but the same depth. Following this, place the soaked roots into the hole(s), and fill back in with the excess soil. Pat down the soil as you go along, to ensure as little air pockets are left as possible.
Water the plants very well and continue to regularly water for the next 1-2 years after planting (this is a very important step, as Alder particularly prefers wet soils).