Dear Sir or Madam:
I bought 3 summersweets from Humber,Hwy 50 3 weeks ago.
I planted as instructed.
The flowers look brown, the green leaves are looking dry.
Other than watering these plants, is there anything I can do to save them?
I know little about the growing conditions of your three Clethra alnifolia plants so it is a little hard to determine if they will survive.
You have planted your shrubs during a very hot period which makes their survival chances difficult.
Flowers browning off may not be surprising as nurseries tend to sell the plants on a slightly different cycle than what grows in our yards. Next year it will be on a natural cycle.
Do your plants get filtered light with some dappled shade? You said you followed the planting instructions so I assume you prepared a proper hole. Have you watered them freely? Water to a depth of 1 inch twice a week. Over watering is also hard on plants as the plant needs space to breath.
Is the soil you planted in fertile, humus rich, moist but well drained?
With sincere hope that you shrubs survive and get through the winter, here is a pruning tip. Don’t prune now as there would be sap bleeding but do prune while dormant in the winter or early Spring. Cut the dead stems off at the base, and remove any crossing branches. Generally they need little pruning except to maintain a good framework.
Here is a general gardening guide reference used by Toronto Master Gardeners which may be helpful.
and an article about growing summersweet