Wall Rock Cress;
or, White Rockcress
Thou art an healing wind
That blowest over white flowers
A-tremble with dew."
The cultivar 'Snowcap' is also known as 'Alpina Snowcap' or 'Schneehaube,' shown first in a May (2003) portrait, & in an early April (2004) portrait. It is a strongly drought-hardy White Rock Cress or Wall Cress (Arabis caucasica, formerly A. albida), thriving in a full sun location with very little water.
It is cold-hardy to zone 4, though in the coldest areas it will need winter mulch protection for the root. It can be a somewhat shortlived perennial in zones 8 & 9, especially if it dislikes summer humidity, for it prefers cool dry sunny weather. It may need to be replaced every three to four years, or it can be refreshed by digging it up & dividing it every two to four years.
Ours was planted on the ledge of the stacking-stone wall of a low maintenance sun-garden. As it matured & spread, it cascaded over the stacked stones.
It fills much the same gardening niche as do Sun Roses, except Sun Roses ('Mrs. Mold' Sunrose for example) are even nicer with their longer blooming seasons & not as sensitive to heat &, being much more strongly evergreen, Sunroses lack Rockcress's periodic worn look.
Rock Cress, a native of Southern Europe, is in full bloom mainly for April & May. The flowers are fading out at some point during the first half of June. It's a good idea to sheer it back after it is finished blooming to regain fresh growth & compactness. If left untrimmed it will become rangy in summer heat.
Its attractive silvery-green evergreen leaves are matt-forming, about six or eight inches in height, occasionally humping up to ten inches or a foot. In our mild winters the leaves hold their looks pretty deep into winter, & does not invariably require a pre-spring sheering, the post-bloom sheering as summer begins being sufficient.
Though it does not require much water, I felt it fell short of an ideal xeriscape plant. For if it does not get periodic & timely sheering, it slowly turns quite ugly, nor does it swiftly recover from a sheering. Though it is gorgeous at the height of flower, for leafy groundcover it is simply not the equal of the above-mentioned sunroses, so at some point after its second year bloom, I dug out the rockcress to replace with something attractive even when not in flower.
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