It is one of the basic rules of gardening that the best time to plant shrubs and trees is autumn. There are several reasons for this. The soil is still warm and moist, the shrubs which are just entering dormancy, will have plenty of time for the soil to permeate their roots ready for spring growth and, traditionally, nurseries lifted their stock, ready to plant, in autumn.
When I was a teenager and worked at Nags Hall, autumn was a busy time and all the shrubs arrived, often from The Netherlands, bare-root or ‘rootballed’ and had to be plunged into beds of peat to keep the roots moist. When customers wanted shrubs we went and lifted them. At the end of the season, any not sold were potted for sale later.
How things have changed! We now expect plants in pots so we can plant them whenever we feel like it. This is very convenient and it is great to be able to spot a gap in the border and ponder on what to fill it with and then go and buy something and plant it on the same day.
The key to summer planting is to water. I will walk you through planting a hydrangea in my own garden but before I start I want to explain why summer plantings need careful watering.
If my hydrangea was left in its pot it would need watering almost daily. It is in leaf and is growing and all the water it needs has to be applied to the pot. Once planted, the roots cannot absorb water from the surrounding soil – the roots are still within the rootball – so it still needs watering every few days, especially in dry weather. If it was planted in October, when the leaves are dropping and growth has stopped, it probably won’t need any watering and once growth begins in spring, the roots will be moving into the surrounding soil. So plant now but be prepared to water often.
My hydrangea
Hydrangeas have not always done well in my garden and I think it is because I have been planting small plants. I have had more success with larger plants. This bed has slowly been developing and it gets morning sun but is shaded after midday. I put in a couple of yellow-leaved acers as an experiment but they have done quite well and show up against the dark hedge. It seemed the right spot for a white hydrangea. The shade will help the flowers remain white and not turn pink – white hydrangeas are best protected from fierce sun – if we ever get any.
Dunk your plant
While you are digging the hole you should dunk your plant in a bucket of water so it is thoroughly watered.
Prepare the hole
Dig a large hole. You should add some organic matter too. Dig the hole at least twice as deep and wide as it needs to be – ideally much more so you break up the soil. You can then replace the mixed up soil so the roots have an easier job growing into the soil.
Water the hole
So that all the water doesn’t disappear when you water the plant in, give the planting hole a good watering at this stage.
Plant
Take the plant out of the pot, take off the coir compost-cover if present, and plant at the correct depth. Work the soil around the rootball and gently firm as you refill the hole. Because the plant is in full leaf and the young roots are around the edge of the pot do not pull all the roots apart. You can do this if planting in autumn but you will damage all the sensitive roots if you do it now.
And water again
You then need to water again. This will make sure the roots are in contact with the surrounding soil and avoid air pockets around the roots which will kill the roots if they dry out. Direct the water at the roots and pour it on rather than sprinkle.
You then need to keep an eye on your plant and water every few days unless the weather is wet. Do not allow your plant to dry out and wilt.
Help: my plant is dying!
If your hydrangea appears limp, or worse, even though you have been watering it is because the rootball has dried out. As it dries it will shrink and when you water it the water will run round the roots and not actually do any good. If your plant has only been in the soil a few weeks it is best to dig it up, dunk it in water and replant to save it.