Amateur Gardening – 10 July 2019

6 JULY 2019AMATEUR GARDENING 13

Chop, chop! Clematis such as montana and armandii keep

growing, and can become unruly and straggly. Keep them

in shape by regularly shearing off wayward growth.

Combat rusting and wilting

Ruth looks at the problems facing hollyhocks and clematis

C

LEMATIS and hollyhocks are
two summer garden delights:
one scrambling up walls, fences
and trellises; the other standing
tall and traditional in cottage-garden-
style borders.
Sadly, both are susceptible
to fairly common fungal
infections. In the column,
right, I look at how to beat
fast-striking clematis wilt,
and here I suggest ways
of combating unsightly
hollyhock rust.
This rust is spread by
windblown spores of Puccinia
malvacearum and, as its name
suggests, also affects members of the
mallow family such as hibiscus, abutilon,
lavatera, malvastrum and sidalcea.
It presents as bright-orange or yellow

spots on upper leaf surfaces, with

darker spore-producing pustules on the

underside. It tends to start low and work

up the plant, also contaminating stems.

Badly affected plants lose their leaves

and fail to thrive.

It is hard to control as

the spores can travel

long distances in the air.

However, it can be held

at bay by monitoring

new plants for symptoms,

checking existing plants

regularly, and removing

and destroying affected

plant material.

Although hollyhocks are

perennials, treat them as biennials or,

if you want them for more than one

season, cut them right back and

remove all plant matter in autumn.

CLEMATIS wilt is also a disease

caused by a fungus Calophoma

clematidina and is more likely

to affect large-flowered

varieties. It can survive

in soil and spreads

when spores are

splashed onto

plants by rain

or watering.

Symptoms include

blackening leaf stalks

followed rapidly by wilting

of the stem. The roots are rarely

affected and plants can regenerate

from below the ground.

However, C. clematidina isn’t the

sole cause of wilt, and if spores are

not present you may need to take

environmental problems such as

root stress and poor planting into

consideration when it occurs

(especially in resistant breeds).

Unfortunately, there is no chemical

control available, so careful planting

and good husbandry can help protect

plants from wilt.

Keep the roots happy by planting

deeply and mulching well. Keep

the plant well watered but not

waterlogged.

If you suspect a fungal attack,

cut away all wilted stems to healthy

growth and destroy the contaminated

material. Always sterilise tools

afterwards to contain the spread

of the disease.

Susceptible cultivars include C.

‘Henryi’, C. ‘Jacmanii’, C. ‘Nelly Moser’,

C. ‘Ernest Markham’, C. ‘Comtesse de

Bouchard’, C. ‘William Kennett’ and

C. ‘Marie Boisselot’.

Resistant varieties include ‘Avant

garde’, ‘Bonanza’, C.montana/alpine/

orientalis/integrifolia, macropetala

and C. tangutica.

Clematis viticella is tolerant of wilt

rather than completely resistant.

Clematis wilt

Clematis wilt is

fast-acting and

destructive,

though not fatal

1

Affected leaves and flowers should

be removed and binned or burned.

Never consign them to the compost

as it will be contaminated by the

spores. Sterilise tools after use.

Two ways of dealing with hollyhock rust

2

Fungicides can work but aren’t as

efficient. Provanto Fungus Fighter

Concentrate and Plus, Scotts Fungus

Clear Extra or Ultra Gun will work, but

with frequent applications.

I have planted dwarf hollyhocks

and will keep a sharp lookout

for the fi rst signs of rust

Sadly, both are susceptible

Puccinia

and, as its name

and fail to thrive.

It is hard to control as

the spores can travel

long distances in the air.

However, it can be held

at bay by monitoring

new plants for symptoms,

checking existing plants

regularly, and removing

and destroying affected

plant material.

Although hollyhocks are

Unsightly pustules

produce fungal spores

Keeping good airflow

around plants lowers

humidity and helps reduce

the risk of fungal diseases,

so leave plenty of

space between

each plant.

Reduce the risk with good planting

to affect large-flowered

varieties. It can survive

Symptoms include

blackening leaf stalks

followed rapidly by wilting

‘Nelly Moser’ is at

risk from wilt