Question
Hi
I recently bought two mini standard roses.  I planted them into large sandstone pots, they had lots of flowers and buds, which quickly went brown and had what looked like a powdery grey/white substance on them, the leaves starting getting black spots on them, then went yellow and all fell off.  They are in a patio area with filtered light.  Is this because of the lack of full sunlight?  I live in Perth, Western Australia, and we have had approximately 9 weeks of very hot weather (35C - 45C).  I have watered them every second day.  I also used some water retaining crystals around them, because of the extreme hot weather.
Regards
Vanessa

Answer
Some roses you can get away with less sunshine on them but most require at least 5 hours of full sunshine directly on them. The grey powdery substance is caused by a fungal infection called Botrytis and this is caused when they can't dry out due to of lack of sun. Roses can withstand heat even high temperature but as you know, thy need extra water. However the water must be allowed to dry out or the pot should have good drainage. If the roots sit in water for too long then they will die and so finally will the rose. Hopefully your sandstone pots did have enough drainage holes. Don't be afraid to place them outside as that will be better for them then sitting in a shaded place. Put them anywhere they will get a minimum or 4 hours of full sunshine. But for now buy a rose spray for black spot as that will also kill the other fungal problem, and then only water when the soil is dry because they may not need to be watered so often.