Planting Green Roofs: Sowing Seeds

With the installation of the green roof on Lang Performing Arts Center (our fifth green roof), we experimented with a new way of planting the vegetation: sowing seeds.  A year after the install, we are enjoying the initial success of this seed germination.

Sedum plugs laid out for planting. photo credit:R. Robert

As with our past roofs, we planted sedum and other green roof plants with small plugs and by spreading cuttings.  The install was completed by applying a slurry of seed. The seed mixture was combined with pourable fiber mulch and water. This slurry of seed was  applied with a hydro-spraying machine, similar to using a broadcast spreader to apply seed to your  lawn.

The slurry of seeds was applied with a hydro-spraying machine. photo credit: L. Kesterson

Sowing seeds is an effective and economic way to vegetate a green roof, but different seeds require different germination conditions. Thus various seed varieties will germinate throughout the growing season. We are enjoying some wonderful blooms a year after the install or planting of the roof.

Gypsophila repens in bloom on the roof of Lang Performing Arts Center. photo credit: J. Jabco

The most captivating this spring was the bloom of Gypsophila repens, creeping baby’s breath. As implied by the common name, this baby’s breath on reaches 15 cm in height. The diminutive white flowers created a carpet of white on the roof.

The brilliant pink blooms of Dianthus carthusianorum. photo credit: R. Robert

Another surprise delight from our seed mixture was Dianthus carthusianorum, Carthusian pink. This Dianthus was named in honor of the Carthusian order of monks  in the Chartreuse Valley in the French Alps. As an alpine plant, D. carthusianorum is ideal for growing in the harsh conditions on a roof top. The brilliant pink blooms add pops of color to the green roof.

Our seed mixture included:

Antennaria dioica

Armeria maritima

Camplanula rotundifolia

Cymbalaria muralis

Dianthus arenarius

Dianthus deltiodes rot

Hieracium aurantiacum

Hieracium pilosella

Petrorhagia saxifraga

Saponaria ocymoides

Saxifraga granulate

Sedum acre

Sedum aizoon

Sedum album

Sedum kamtschatium var. ellacombianum

Sedum hispanicum

Sedum hybridum ‘Czar’s Gold’

Sedum montanum

Sedum pulchellum

Sedum reflexum

Sedum sexangulare

Sedum spurium ‘Coccineum’

Sedum telephium subsp.  fabaria

Thymus pulegiodies

Thymus serphyllum

The Lang Performing Arts Center green roof in bloom one year after planting. photo credit: J. Jabco

Experience the green roofs for yourself on our guided tour on Tuesday, September 16 from 5 to 6:30 pm.