A guy on the roof next door shouted: “Nice plants. What’s your secret?”
“You have to water every day,” RP boomed back.
Yes, you totally need to water a roof garden every day in these hottest days. Even when it rains, we try to check and make sure all the pots got wet — remembering not to over-water the fussy geraniums.
Besides watering, we we do have one other way to keep our gardening going in the heat: succulents! Sempervivum (hens ‘n chicks), Portulaca grandiflora (moss rose) like a dry heat, so we sure have a spot for them right between our two Adirondack chairs on a small table right in the sun. I am surprised how few NYC gardeners plant sepmervivum and portulaca. Maybe that’s because these plants don’t look very fun in the garden center, when compared to annuals already in bloom.
Most of our plants are in plastic pots, which help to retain moisture, but we grow our succulents in low terra cotta bowls. This gives them the drainage they need and lets us highlight them on the tops of tables.
Last summer, my succulents sucked. This year I am having more luck. I figured out I could use portulaca, a faster growing annual, to fill in around my sempervivums (Hard-core gardening types call them “semps.”) The portulaca flowers add color too, but the flowers are only open during the day, so we don’t get to see them too often.
Brooklyn Roof Garden 