Growing
Centaurea
Planting:
Centaurea love hot, dry conditions, but
most will
thrive in any normal garden soil. If your soil is claggy and poorly drained then
add plenty of grit to the soil when planting.
Most will benefit from the sunniest position you can
find, but in our experience many (e.g. montana) will grow well in light shade.
Care and Maintenance:
Most Centaurea will spread by underground runners so
they can easily be dug up and moved to a new location. Be aware though that they
can regrow from root left in the soil.
Whilst they are drought tolerant they will benefit
from a good soaking from time to time.
Cutting back the stems to new shoots after flowering
promotes repeat blooming throughout the season - don't be afraid to cut them
back hard. This is also the treatment if mildew is a problem - the new leaves
will be fresh and healthy provided you clear away all infected leaves.
Some species (e.g. macrocephalata, glastifolia) have
very attractive seed heads that last through the winter. The seeds are loved by
birds and small mammals (especially voles). Cut back these stems in early
spring.
Propagation:
Division is easy with most species - simply dig up and pull apart. Large
numbers of plants can be grown from root cuttings taken in winter. Most species
are easily raised from seed and do not seem to hybridise. Seed is best sown
fresh, straight after harvesting. If seed heads are left on the plants
over winter, seeds will often germinate inside the heads. These can be carefully
teased out and pricked out into trays or modules.
Using Centaurea:
Centaurea are ideal plants with species suitable for
the border, scree garden or rock garden. The tall species are largely self
supporting (the exception being perhaps dealbata which can flop a bit unless
supported with a few twigs) and compete well with other plants, holding their
own in the bed.
Try planting the tall yellow
glastifolia with Helenium, its branched stems and round heads contrast well with
the latter's flat heads of flower.
Many
Centaurea are meadow flowers (e.g. jacea, phrygia, nigra) and look great in a
cottage garden setting.
Remember that the buds of Centuarea can
provide interest and constrast as well as the flowers: glastifolia has silver
buds, macrocephala bronze and montana types have jewel-like black and emerald buds.