Getting it to bloom

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

Also called Hairy Rock-cress, Hairy Rockcress, Mountain Rockcress (Arabis hirsuta).

More about hairy rock-cress

About Hairy Rock-cress

Arabis hirsuta · also called Hairy Rock-cress, Hairy Rockcress · flowering

Arabis hirsuta is a small biennial or short-lived perennial in the Brassicaceae family, native to calcareous grasslands, rocky outcrops, walls, and limestone pavements across Europe and North America. It forms a rosette of hairy, oblong leaves from which erect flowering stems carry small four-petalled white flowers from May to August. The most important care fact is that it is strictly a calcicole — it grows on base-rich, well-drained, alkaline or neutral substrates and will not persist on acid soils. No significant toxicity to pets has been reported.

Plant type: flowering

The reasons hairy rock-cress isn't blooming

Almost every non-blooming hairy 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 hairy 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 hairy rock-cress to flower

Maximise sun. Give hairy 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 hairy rock-cress and get the feeding right with the hairy 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

Hairy 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 hairy rock-cress care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Hairy Rock-cress blooming — frequently asked questions

Why won't my hairy rock-cress flower?

Hairy 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 hairy rock-cress bloom?

Give hairy 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 hairy rock-cress normally bloom?