Don't Wait for the End of the World: Growing Rock Cress from Seed

Imagine a post-apocalyptic world that, instead of being a barren wasteland, is saturated with vivid groundcovers and climbing plants blooming in hues and densities only nuclear radiation could create. The designers of the video game Far Cry: New Dawn must have been inspired by rock cress as they dreamed up their in-world environment.

They almost nailed it.

Rock cress would easily grow in the crumbling rubble of civilization since it needs little soil, is drought-tolerant, and takes hold and thrives in the cracks and fissures of rock and concrete. Its masses of four-petaled blooms all but hide its fine, dense green evergreen leaves; in spring and early summer it "mutates" into waves of violet, pink, or white, forming cascades over walls and rock borders.

There are about 25 Aubrieta species, all with similar growth profiles. Our current favorite is purple rock cress (A. deltoidea), which is often considered the genus standard. Even if your past gardening attempts have ended in cataclysmic disaster, you'll manage to grow a carpet of spectacular color if you give this plant a try.

Native Range, History, and Medicinal Uses

Aubrieta (often mistakenly spelled "aubretia") is a member of the mustard (Brassicaceae) family. It's native to western Asia and southern Europe. While we often think of this region as having a "Mediterranean" climate, rock cress is more of an alpine plant, native to the Southern Alps and the Himalaya.

The genus is named for Claude Aubriet (1665-1742), the illustrator for the famed and scientifically important book Élémens de botanique by French botanist Joseph Pitton de Tournefort (1636-1708). Aubriet also illustrated birds, insects, and mammals, but it's his botanical work for which he was—and, in scientific circles, still is—most famous.

All parts of Aubrieta plants are edible. Given that it's known to grow in areas where food and herbs are scarce, we were surprised that we weren't able to find any reliable sources describing the genus' history as a medicinal or culinary plant. If you have any information, please fill us in!

Rock Cress in the Garden

This is the ideal plant for the imaginative gardener. Think of Aubrieta as being a sort of living, color-changing modeling clay. It's best-known as a rock garden specimen, and in this role, it shines. Where many plants require deeper soil and more consistent moisture, rock cress thrives in the nooks and crannies between stones and rocks, as well as behind retaining walls; all of these environments channel water away from roots, but drought-resistant rock cress is cool with that. This is especially good if you're planning to garden when nothing but acid rain is available for irrigation. Opinions vary on whether rock cress prefers acidic or alkaline soils, but if there's no water at all, it has an advantage over other plants with similarly lush foliage and abundant blooms.

Seeding tips for vertical surfaces

Google "Aubrieta" and you'll see examples of rock cress growing in gravity-defying plantings. One way to achieve this effect is to cram moist soil, sand, and Perlite mix into wall gaps, press in your Aubrieta seeds, and hope everything stays put. Or, you can dissolve a packet of Knox gelatin according to product instructions, make a paste with your substrate, and press it into any vertical hidey-hole you choose before you plant the seeds. The gelatin will serve as the perfect amount of nitrogen your young plants will need to get started, while at the same time, serving as a binding agent and a means of retaining moisture during the germination process.

Here's a cool seeding trick: First, go to the corner store and buy a Slushie-type drink. Be sure to get one of those straws with a spoon at the end. Mix some rock cress seeds with fine sand, scoop up a bit of the mix, and gently blow it into rock or wall fissures. Use a hand mister to keep the area moist until the plants emerge and quite literally take hold.

Ideas for container gardening

While you were online, you might have gone down the DIY gardening rabbit hole—on Pinterest, or just browsing an image search. Did you see all those wall-hanging planters filled with purple rock cress? Maybe the "pocket planters" used for living wall designs? Sedums, succulents, and air plants usually dominate those pictorials, but in most situations, you can use rock cress instead.

Aubrieta, when planted in small hanging baskets and wall sconces, can completely engulf the container and take on fascinating shapes as it cascades over the edges. Try globe-shaped "Kokedama" plantings or a creatively-angled "gutter garden" approach. How about a gallon-sized paint can with rock cress "pouring" out into a brightly-colored puddle? In the apocalypse, you make do with what you have.

Decorative gardening for doomsday preppers

We're certain you have a stockpile of our vegetable and herb seeds in your bunker, but what's the point in surviving if you can't have the nicest garden at your door—uh, hatchstep? After all, rebuilding civilization begins at home, and civilized folk always have nice front yards. (Or so they say.)

Go for the "Mass Effect" with Aubrieta. Terraform your yard with carefully-planned hillocks of color or blanket large, neglected areas of your garden. You can let your rock cress sprawl freely, or pinch and trim it to maintain unnaturally circular mounds. Create visual "bread crumbs" to draw attention to—or away—from a specific area, like your weapons cache, for example. Or, simply make your End of Days Easter Egg Hunt really, really challenging by camouflaging the search zone with cheerful spring hues.

Try interspersing rock cress with ground covers that bloom at different times of the season or have different foliage textures: Ice plant, mother-of-thyme, fescues, and alyssum are just a few. Just be sure to give each species visual and spatial breathing room. Plant Aubrieta around your spring bulb beds, or in sparse, low-maintenance schemes otherwise dominated by lonely juniper shrubs. Aubrieta doesn't handle foot traffic, but you can grow it between stepping stones and pavers. If a plant's damaged, you can always divide another to patch up the gaps.

There really isn't any "wrong" way to landscape with rock cress, as long as you respect its very basic cultivation requirements.

Environmental preferences

Rock cress is an evergreen herbaceous perennial in zones 4 through 9 (according to horticulture-savvy Oregon State University; other sources limit the zones to 4 to 7) preferring warm—but not blazing hot—coastal and subalpine climates. It's particularly popular in Colorado and Utah, thanks to its tolerance of temperatures as low as -40°F and preference for mountain climates. It's been a staple in traditional English cottage gardens for decades.

Aubrieta requires full sun for optimal bloom and foliage density. Partial afternoon shade in hot regions is fine, but too much shade will curtail flowering and produce bare, leggy stems. Provide it with well-drained, sandy to a loamy substrate; it does best in poor or medium soils. In fact, Aubrieta doesn't require much soil at all—it's evolved to take hold in rock dust and whatever dirt is trapped in fissures and crevices.

Aim for soil chemistry between 6.0 and 7.0 pH. Again, there are conflicting recommendations, with some reputable sources calling for acidic soil, and others swearing up and down that rock cress requires a bit of alkalinity. All agree that neutral soils are just fine, and you can experiment if you want to.

• Moisture Requirements: Once established, let the soil dry in between irrigation periods.
• Plant Height: 6" to 8" tall; upright, flowering stems may reach 12".
• Plant Width: 2' spread.
• Growth Habit: Mounding, spreading, cascading; some varieties are climbers.
• Bloom Period: April until early June.
• Flowers: 1/2" wide, sweetly fragrant; typically dark purple, with other species flowering in white pink, indigo, or lilac with yellow centers.
• Foliage: Narrow, spoon-shaped, deep green to blue-green leaves form opposite pairs on branching stems. In some species, the leaves are lobed or flat.

Rock cress is a hardy plant that rarely suffers from pests and diseases. Over-watering and poor drainage may cause fungal issues, particularly at the root base. Keep an eye out for the occasional aphid, but don't worry about deer!

Maintain your Aubrieta by cutting back the branching stems after the bloom period has ended to maintain the plant's shape. New spring growth will be tidy, with prolific blooms. Don't over-fertilize your rock cress, since too much nitrogen will cause it to become leggy. A diluted, phosphorus-rich solution at the beginning of the flowering period will enhance bloom vigor, but it isn't necessary.

Aubrieta tends to peter out after a few years, so plan on sowing new plants every third season. You can also divide your existing plants in late fall. It may also self-seed, so watch out for volunteers.

Growing rock cress from seed

Rock cress seeds are larger than most miniature ground covers, but they're still good candidates for scattering. Don't bury them too deeply, as they require some sunlight to germinate. Direct-sow Aubrieta seeds six weeks before your last frost, or press them into a fine, sand-amended seedling mix for indoor starts around this same period for a better head-start. We recommend growing rock cress from seed under fluorescent lights if you start them indoors.

• Seed Treatment: None required
• Seed Depth: 1/8" or surface-sow
• Seed Spacing: Plant, transplant, or thin to 18" intervals
• Days to Germination: 10 to 21 days at 65°F to 70°F

Cell trays work well for "plugs," which can either be transitioned into to 4" pots or transplanted directly outside. Be sure to keep the planting sites watered with a gentle mist until the seedlings have become established.

Seed Needs: Reliable support in uncertain times

The freshest seeds have the best shot at germination. If you're stocking up for the end of the world, remember the prepping motto: "Store what you use, and use what you store." That means you should be using your ornamentals, vegetables, and herb seed stash now, replenishing your supply as you go. That's how we do things here at Seed Needs! We only stock what we can sell in a single season, and we preserve our seeds in climate-controlled storage to maintain the highest germination rates possible.

We carry lots of "mutant" hybrids developed by traditional cultivation and open-pollination, but we leave genetic engineering to nuclear radiation and black-site shadow government laboratories. We also like to think that our standard of customer care is better than what you'd experience in Barter Town.