Plant up containers with Hippeastrum (amaryllis) bulbs and plant prepared Hyacinths by 24 September to get flowers for Christmas.
Start to reduce watering of houseplants as light levels drop.
In the greenhouse
Damping down usually becomes unnecessary as the month progresses. It is best to do any watering or damping down earlier in the day, so that the greenhouse is dry by evening. Dampness during the cool nights could be a recipe for a fluffy grey mould (Botrytis) and damping off of seedlings.
Ventilate conservatories during warmer days but reduce ventilation once the cooler weather sets in. Use shading paint or blinds to help keep the area cool, but be ready to reduce shading towards the end of the month as light levels fall.
Pest and disease watch
September is an ideal time of the year to apply biological controls for use on vine weevil. Grubs will be starting to hatch, and soil and compost temperatures are now suitable for the nematodes to be effective. Target vulnerable plants, such as fuchsias, succulents and containerised plants.
When bringing plants indoors, check carefully for any pests and diseases they may have picked up outside, in particular red spider mite, mealybug and scale insect. Inspect rootballs and compost for vine weevil larvae and treat where necessary.