Do we need established shade from trees before planting?

One of the concerns we hear from customers is that they don’t have enough shade in their garden. Many customers plant trees in their gardens first and think that they will have to wait until the trees have provided shade before they can plant their rhododendrons. This is not the case – no waiting is required if you do it right. Rhododendrons thrive in an environment where their root ball is moist. The feeder roots of rhododendrons are near the surface, no more than 10cm from the base of the plant. It is these roots that need to be kept moist. There are any number of ways of doing this; if you provide one of the following you should do well.

1. A heavily mulched covering around the rhododendron. Leaf matter, bark, pea straw or pine needles are all options. Pine needles have the added advantage of keeping the weeds at bay and of offering acidity that rhododendrons love. The mulch helps to keep the moisture near the roots and ensures that the roots don’t dry out.

2. Shade overhead. Established trees will provide a canopy over rhododendrons which helps to keep their roots moist. This could be either deciduous or evergreen or a mixture. Rhododendrons do need the sun however, and many varieties flower better with sunlight.

3. Water, either by drip or sprinkler or any other system you have. If you don’t have shade or mulch then you will need to keep the moisture up to the roots through watering. However, be aware that rhododendrons like free-draining conditions so ensure that water doesn’t build up in their roots and that the plants are not sitting in pools of water. Note that if a plant dries out completely no amount of water will nurse it back to health.

As you travel around New Zealand you will notice rhododendrons growing in certain environments that you might not recognise as being particularly textbook conditions. Generally, the conditions will have one of the above three points going for it. On the West Coast of the South Island, you will find huge rhododendrons growing in random places, like in the middle of a paddock, or beside an old derelict house where no-one lives. The Rhododendron has thrived probably because of the high rainfall of the West Coast. A large established Cunningham’s white rhododendron grows in a cemetery in Canterbury: no-one looks after it and no-one waters it, but the mulch around it has created an environment where it can not only create enough moisture to survive – it has enough to thrive.