Advice
Prolonging the life of hanging baskets
Hanging baskets that become thin, straggly and lacking in flowers in late summer can be helped by improving plant growth to generate new flower buds.
Deadheading
Regular deadheading is important and if it has been neglected the developing seedheads will have seriously inhibited growth of new flower buds. It is too late to merely remove the seedheads; instead trim back plants to remove all seedy growth. Where shearing would be excessive consider removing all open flowers and also buds. The relief from reproduction will allow the plant to generate more leaves and shoots.
Then feed to induce growth and keep it healthy.
Fertilisers
Balanced liquid fertilisers, Miracle-Gro for example, used weekly, induce growth. When growth is satisfactory use potassium rich materials, such as tomato fertiliser to promote flowering.
Pests and diseases
Well fed, vigorous growth resists pests, red spider mites for example, or diseases such as powdery mildew, but some protection with approved pesticides may be necessary. Removing old, discoloured foliage also helps reduce troubles and improves growth.
Watering
Drying out is an increasing risk as foliage lengthens and days remain warm. Dunking dry hanging baskets in a bucket of water ensures they are fully wetted. Moving hanging baskets to a shadier spot can help where watering cannot keep pace.
Use cut-down plastic drinks bottles as funnels to direct water into the basket. These can be hidden in the foliage at the top of the basket.
Preventative action
Finally, look at causes of hanging baskets failing, and note preventative action for next year such as using larger baskets, adding controlled-release fertiliser and water-retention granules and going for plants that need less water and deadheading.