Getting it to bloom

Why won't my Rock Cress bloom? (and how to make it flower)

Also called Rock Cress, Aubrieta, Purple Rock Cress (Aubrieta deltoidea).

More about rock cress

About Rock Cress

Aubrieta deltoidea · also called Rock Cress, Aubrieta · flowering

A vigorous, mat-forming perennial producing masses of small cross-shaped flowers in shades of purple, lilac, mauve, and pink in spring. Native to stony habitats from south-eastern Europe to western Asia. Widely grown to cascade over walls, rock gardens, and raised beds. Thrives in poor, alkaline soils with full sun and sharp drainage.

Plant type: flowering

Watch for — Straggly, open growth after flowering: Plants become untidy and bare at the centre if not cut back after flowering. Trim back hard by about two-thirds immediately after flowering in late spring to encourage compact, fresh growth and a second flush of blooms.

The reasons rock cress isn't blooming

Almost every non-blooming rock cress traces back to one of these, roughly in order of how common they are:

Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
Too much nitrogen feed, driving lush foliage at the expense of flowers (very common with general or lawn feeds).
The plant has not been deadheaded, so it stops flowering once it sets seed.
Irregular watering — drought or waterlogging at the budding stage makes buds abort.
It is still too young or was checked by a transplant and is rebuilding before flowering.

Feeding rock cress a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.

The fix — how to get rock cress to flower

Maximise sun. Give rock cress the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers.
Switch the feed. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
Deadhead regularly. Remove spent flowers often to keep it producing more rather than stopping to set seed.
Water consistently. Keep moisture even through budding and flowering — drought-then-flood swings make buds drop.

Light and feeding do most of the heavy lifting here. Dial in the spot with the light guide for rock cress and get the feeding right with the rock cress fertilising schedule — the wrong feed (too much nitrogen) is one of the most common silent reasons a healthy plant makes leaves instead of flowers.

Bloom season and what to expect

Rock Cress flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.

Post-bloom care so it flowers again

Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.

For everything else this plant needs day to day, see the full rock cress care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Rock Cress blooming — frequently asked questions

Why won't my rock cress flower?

Rock Cress blooms on the season's growth given enough sun, warmth and the right feed — there is no cold or photoperiod trick, just good growing conditions and a bloom-leaning feed. The most common reason it is not happening: Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.

How do I make rock cress bloom?

Give rock cress the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.

When does rock cress normally bloom?