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Hot roof garden = dry pots!



Last year I moved to a house with a sunny but often windy roof terrace and I set about trying to make it more green and less concrete. Successes were sweet peas, tomatoes, two Clematis (that climbed up the chimney stack) and annual trailing plants such as Lobelia.

However, I was forever struggling with the weather and my small pots were either waterlogged with rain or baking dry come evening. In the heat of summer I watered twice a day (as they were all droopy by evening) and fed everything once a week. I just used miracle grow compost.


The big disappointment was my drought loving plants such as Lavender, Thyme and Rosemary... They all died by mid summer!


So my first question is - what did I do wrong?! Too much watering?


This year I invested in some troughs with water reservoirs at the bottom so I don't have to water so much. I have also bought some vermiculite to mix with my compost.


Second question - What ratios of compost/gravel/vermiculite/horse manure would you use for

Roses Alpines Lavender/Thyme/Rosemary Bedding plants (lobelia etc) Sweet peas Chilli plant

Also, would it help to top my pots with gravel to stop evaporation on hot days?


Any help or ideas on what I can do would be much appreciated as I have bought the plants but am holding off planting them until I know the right set up for them!







  • WelshonionWelshonion Posts: 3,114

    The bigger the pots, the less the evaporation will be.  Consolodate your planting so you have bigger pots and more plants in them.

    You will still have to do an awful lot of watering, that is inevitable.

  • ItalophileItalophile Posts: 1,731

    Welshonion is right about the size of the pots. The colour of the pots and even what they're made of will also contribute to their capacity to retain moisture.

    The darker the colour, the more heat they will absorb, the quicker they will dry out. Terra cotta pots will dry out quicker than plastic ones because the terra cotta "breathes". Plastic doesn't. I prefer terra cotta because its capacity to "breathe" is, I think, healthier for the plant inside. The downside is portability. Terra cotta pots can get mighty heavy.

    I hope you weren't fertilising your lavender and rosemary, Jessica, because it's the last thing they need. They thrive on controlled neglect in very very well drained soil.


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