The Well-Tended Perennial Garden The Essential Guide to Planting and Pruning Techniques, Third Edition

Aconitum napellus

monkshood

ranunculaceae

Blue-violet spikes of hooded flowers;

deep green palmately divided foliage (lobed

or divided as in the shape of a fan)

3–4 ft. high; 1 ft. wide

Part shade

Blooms July–August

Zones 4–8

pruning Most parts of the plant are

toxic if ingested. When pruning or

handling do not get juice from the

plant into your mouth or open wounds,

and be certain to wash your hands

immediately after cutting back plants.

Deadhead to lateral buds for a smaller

second flowering. When secondary

flowering is finished, cut down to new

basal foliage if the old foliage declines,

and fertilize if plants are pale. Spo-

radic small flowering may occur from

the basal growth. Leave basal growth

over the winter, and prune off in the

spring. Plants can be cut back or

pinched to control height, although

this usually means removal of the

large terminal spike. This will produce

smaller but more numerous, and

possibly later, flowers on sturdier

plants. New plants can be cut back by

half at planting for a better branching,

slightly shorter first-year plant.

Established plants can be cut back by

half when 18 in. tall to increase

fullness. Some gardeners cut plants

back by 6 in. when plants are 2 1/2 ft. tall

and again by 6 in. when 3 1/2 ft. tall.

Staking may be necessary even with

any of these pruning techniques used

for height control, depending on

conditions. If plants are not pruned for

height control, side flower spikes can

be pinched out to increase the size of

the terminal spike if desired.

other maintenance Prefers a

rich, high-organic, moist soil. Avoid

hot locations and burning sun; water

during dry periods. Won’t tolerate tree

root competition. Division can be done

in early spring or fall, but plants are

slow to establish, so best left undis-

turbed for many years. Requires

staking.

related plantS Aconitum ×cam-

marum ‘Bressingham Spire’ is a 2 1/2- to

3-ft.-tall selection by Alan Bloom that

doesn’t require staking. A good choice

since pruning is not necessary.

Aconitum carmichaelii ‘Arendsii’ is a

late-flowering monkshood that doesn’t

require staking, thanks to its strong

stems, even though it reaches 3–4 ft. tall.

Aconitum henryi ‘Spark’s Variety’

grows 4–5 ft. tall. Plants cut back by

half when 15 in. tall, at planting,

flowered at 3 ft., as compared to

unpruned plants that flowered at 4 ft.

The flowers on pruned plants were

slightly smaller and bloomed 14 days

later. Pruned plants still require light

support from surrounding perennials.

Aconitum septentrionale ‘Ivorine’ is a

lovely cultivar with creamy flowers and

upright growth to 2 ft., not requiring

staking. Flowering usually starts in late

Aconitum napellus

Aconitum napellus