🌿 Draba

What it looks like

Draba is a genus that does its growing at the edge of the possible. It is a large genus — 433 species accepted by Plants of the World Online — in the mustard family (Brassicaceae), commonly called whitlow-grasses, though they are not related to the true grasses at all. The plants are typically small: basal rosettes or cushions of often hairy little leaves, wiry stems a few inches tall, and clusters of small four-petaled flowers in white or yellow, the mustard family’s cross-shaped calling card, followed by small flattened seed pods. Nothing about a Draba shouts for attention from across the garden, which is the point — these are plants you notice at knee height, on a rock, doing something quietly heroic: flowering in a six-week Arctic summer, on a scree slope, in a wind that never stops.

The butterfly context for the genus name is the Northern Marble guide, which lists its Host plants as mustards of the Arctic and subarctic, including rock cresses (Arabis and Boechera) and draba (Draba species) — the tough little crucifers that survive where almost nothing else flowers. The caterpillar is a mustard-feeder, green and striped, eating the buds, flowers, and fruits of Arctic mustards, and its season is the few weeks those plants are in bloom. A genus-level host list is an honest description of a butterfly that uses the Arctic mustard flora broadly, and a genus guide is the honest unit for it. The guide also says the Northern Marble is a wilderness butterfly of the far north, not a garden species, met on Arctic and subarctic tundra in summer and not attracted to any planting — a stance this guide repeats, because planting a Draba in Florida in hopes of a Northern Marble would be a category error in two directions at once.

One plain-text disambiguation, because the whitlow-grass name causes real confusion and this genus guide must not swallow the plants around it. This guide claims Draba species as a genus only. Rock cresses (Arabis and Boechera) are the other mustards named alongside draba in the Northern Marble guide’s host list; they are different genera with their own growing guide, and they are not covered here. Alpine whitlow-grass is a name shared by Draba alpina and Draba densifolia, so buy by Latin name, not by the shared common name. None of the species named in this guide’s Species section is covered in particular by this genus guide, and this genus guide does not replace any of them. Buy and plant by Latin name, species by species, and let this guide be the map of the genus, not a substitute for any one of its members.

How to grow

Growing Draba starts with the only decision that matters: do you actually live where a Draba wants to live? The genus spans Arctic tundra, alpine fell-fields, rocky slopes, scree, and dry meadows from the far north to high mountains, and the growing advice for an Arctic cushion plant and a garden rockery plant are related but not identical, so this section gives the genus pattern and names the species differences where they change the plan. The pattern is: a small plant for an open, sunny, sharply drained position; gritty, mineral soil, often alkaline, with no rich compost and no waterlogging; and a position where it can form a cushion or a tuft without being crowded by bigger plants, because drabas are at their best in the open, at rock level, with sky above them.

For the Arctic and alpine members — alpine draba is the type specimen of this group, a perennial subshrub reaching about 10 inches that prefers alkaline soils and is native across the Arctic and subarctic from Iceland and Svalbard through Siberia to Alaska and Greenland, and pointedly not found in the Alps despite its name — the pattern is a rock-garden or trough planting: full sun, a gritty mix of stone chips and lean soil, and winter cold that the plant expects rather than fears. For the lower, weedier members, the pattern shifts: spring whitlowgrass (Draba verna) is an annual of fields and open ground that emerges in fall or early spring and completes its life cycle by mid-May, with a basal rosette of hairy oblong leaves and tiny white flowers so deeply lobed they look eight-petaled. Same genus, same flower design, different addresses — check the species before you buy, and buy by Latin name.

Propagation follows the mustard pattern: seed, which drabas produce readily in their little pods, sown fresh or stored dry, and division of cushions for the perennial mat-formers. Several species recruit readily from seed in gritty open ground, so a draba cushion can become a draba colony without much help, and a gardener who wants a tidy trough should deadhead or site accordingly. Transplant young plants rather than mature cushions where the species is a taprooted alpine, give every new planting a season to establish before you judge it, and mulch with stone chips rather than bark: the genus is a child of mineral ground, and a rich, damp, mulched bed is the one place most drabas will sulk.

Florida note, stated plainly rather than hopefully. Draba is not a Florida genus. Its members are cold-climate plants of the Arctic, the subarctic, and high mountains, and no Draba is a sensible Florida garden plant. A Florida gardener who loves the look should admire it on a trip north, or grow a warm-climate mustard relative, and leave the Arctic cushions to the Arctic. The Northern Marble’s host list is a description of a far-northern food web, not a planting list for a subtropical garden, and this guide says so rather than pretending otherwise.

Water & feeding

Water, for the garden drabas, is a question of drainage first and moisture second, with the exact answer depending on which species you planted. The alpine and Arctic members want soil that drains instantly — scree moist, rock-crevice moist, the kind of moisture that comes from snowmelt and then leaves — and in a genuinely gritty site with normal rainfall they largely water themselves once established, while in a wet winter they want a roof of stone chips and a slope that sheds water, because a wet crown rots a cushion faster than any drought. The lowland annual members are more forgiving: spring whitlowgrass grows in fields and open ground on ordinary rainfall and finishes before summer heat arrives, which is its whole strategy — grow fast, flower small, set seed, and get out before the weather turns.

Feeding: lean, across the genus. Drabas prefer gritty, mineral, often alkaline soil, and no fertilizer program at all is the right scale of feeding — not a spring feed, which mostly produces soft, leggy growth that flops and rots in a cushion plant. In a rock-garden site, the nutrients arriving with stone dust and leaf litter are often plenty on their own. The soil science here is the alpine story: thin, mineral soils with little organic matter, where nutrients cycle slowly in cold conditions and plants grow slowly by design. A draba’s roots live in that community, storing energy in a caudex and sending up new growth through it, and its yearly leaf fall returns little to the soil because there is little to return. Planting a draba in a rich bed is therefore not generosity — it is a mismatch, and the plant will tell you so by rotting.

Common problems

• Wrong climate, wrong plant. The most consequential problem in the genus. An Arctic cushion in a subtropical bed, or an alpine plant in a wet lowland winter, is a plant out of place. Check the species’ native habitat before you buy, and buy by Latin name.
• Wet crowns. The alpine members want drainage above all. A rotting crown usually means the soil stayed wet. Mulch with stone chips, site it on a slope or in a trough, and keep winter water moving away from the plant.
• Rich soil. Drabas want lean, mineral soil. Heavy compost and fertilizer produce soft growth that rots. Starve them, politely, the way a scree slope does.
• Crowding. Cushion plants lose to bigger neighbors. Site drabas in the open, at rock level, where nothing taller shades them.
• Genus-species confusion. A genus guide does not cover any single species, and a species guide does not cover the genus. Rock cresses have their own guide; this guide is the map, not a substitute for it, and wiring or planting decisions should respect that boundary.
• Caterpillar nibbling. Northern Marble caterpillars eat buds, flowers, and fruits of Arctic mustards, and that is the point of a host plant in the wild. In a garden trough, a chewed draba is a badge of honor, not a problem — do not spray the caterpillars.
• Shared common names. Alpine whitlow-grass names both Draba alpina and Draba densifolia. Whitlowgrass without a qualifier can mean Draba verna or any of dozens of others. Buy by Latin name, always.

Harvest

Draba’s harvest is seed and admiration — in that order, and with no medicinal or food claims attached, because none is documented for this genus in the sources this guide draws on and inventing one would be exactly the kind of padding this library refuses. If you want seed, collect the small pods as they ripen from green to straw, and sow fresh or store dry; drabas recruit readily in gritty open ground, and a gardener with one healthy cushion can soon have a drift. If you want more plants, divide mat-forming perennials in spring, and transplant young plants into gritty, mineral soil in full sun.

The simplest harvest, though, is a summer walk on northern ground with no agenda at all: tiny four-petaled flowers at ankle height, a marbled white working the mustard patches, and the knowledge that the cushion at your feet is part of a genus of more than four hundred species that flowers where almost nothing else dares. Leave most plants standing through the season for the caterpillars, let a few pods ripen for next year’s cushions, and let the drabas do what they have always done — grow small in the cold, flower in the brief summer, and feed the butterflies that time their whole year to that bloom. That is the crop, and it arrives without a single spray, because spraying it would kill the very thing that makes it worth growing.

Saving seeds

One label first, because this is a genus guide: the method below is genus-level, drawn from how drabas as a group behave, not a promise about one particular species in a genus of hundreds. Drabas are the mountaineers of the mustard family — tiny cushions and rosettes that flower where almost nothing else dares — and their seed-saving logic is mountain logic: small seed, cold winters, and a plant that would rather wait out a bad season than gamble on it.

Collecting draba seed is an exercise in patience and good eyesight. The fruits are small, dry pods — the mustard family’s silicles — that ripen from green to tan and begin to split when mature, usually in late summer. The seeds inside are dust-small, so do not try to pick them out one by one like peas. Snip whole fruiting stems into a paper bag while the pods are tan but before they have fully shattered, let the bag sit indoors until the pods are crisp, then crush the dried material gently and sieve away the chaff. Work over a tray, indoors, with no fan running, because a sneeze at the wrong moment is the end of your seed collection. Label the bag immediately with the species name and the year — draba seed all looks alike, and an unlabelled envelope of mustard dust is a riddle, not a collection.

The step that separates draba from the easy mustards is cold. Many draba seeds carry a dormancy that only winter breaks, and sowing them straight into warm soil is how you get a tray of nothing and a crisis of confidence. Mix the seed with a little damp sand or vermiculite, seal it in a bag or small container, and refrigerate it for roughly four to eight weeks — sources disagree on the exact length, and the honest range is the point, because different species and different seed lots want different winters. Some lots want a shorter chill of about a month; others want a long, outdoor-style cold of several months. If your first batch sulks, a longer chill on the next batch is the first thing to try, not more fertilizer. After chilling, surface-sow: scatter the seed thinly over a gritty, free-draining seed mix, press it gently into contact, and do not bury it. Draba seed generally wants light to germinate, and a seed the size of a dust mote buried under a centimetre of compost is a seed buried alive.

Germination is erratic, and that is normal, not failure. Keep the tray bright but out of harsh direct sun, consistently moist but never waterlogged, and cool rather than warm — these are alpine plants, and a tray baking on a hot windowsill is the opposite of a mountainside. Sprouts may arrive in a few weeks, or they may take a couple of months, and a tray that looks empty in week three may be busy in week eight. Move seedlings on only once they have a couple of true leaves and can be handled without crushing the rosette, and give them the gritty, sharply drained home they evolved for. Division and cuttings are the backup routes when you want an exact copy of a good plant, but seed is the route that keeps a genus going. For storage, dry the seed thoroughly and keep it cool, dark, and airtight with a desiccant — and in Florida, say the plain truth: most drabas are cold-climate mountaineers, and a humid, hot Florida summer is the wrong climate for both the plant and its stored seed.

Species

Draba is a genus of 433 accepted species, and no guide can list them all, so this section names the species a North American gardener or butterfly-watcher is most likely to meet, in plain text, and states plainly that none is covered in particular by this genus guide. Alpine draba (Draba alpina) is the Arctic and subarctic perennial subshrub of the Northern Marble’s country, native from Iceland and Svalbard through Siberia to Alaska and Greenland, and not found in the Alps. Yellow whitlow-grass (Draba aizoides) is the European yellow-flowered cushion species. Spring whitlowgrass (Draba verna) is the lowland annual of fields and open ground. Denseleaf draba (Draba densifolia) is the western North American mountain cushion species that shares the alpine whitlow-grass name with Draba alpina. Snow whitlowgrass (Draba nivalis) is the circumpolar snowbed species. Slender draba (Draba albertina) is the high-elevation western North American species. Rock cresses (Arabis and Boechera) are different genera named alongside draba in the Northern Marble guide’s host list, and they are not covered here. This guide covers Draba species as a genus only.