Amateur Gardening – 29 June 2019

29 JUNE 2019AMATEUR GARDENING 13

Rose care in summer

Keep shrubs, climbers and ramblers healthy, says Ruth

Rose black spot is a common

disease caused by the fungal

infection Diplocarpon rosae.

It is the most serious to afflict the

plant and is thought to be the cause

of the drop in popularity of roses

over recent years.

It first presents in

spring as a dark

patch on foliage,

which may

slowly turn

yellow and

then drop. In

mild cases the

leaves remain

in place.

Scabby lesions also

appear on young stems and in the

worst cases plants lose almost all

their foliage and show a severe

decline in vigour.

The disease is spread by spores

carried by wind and rain and

splashed up from the soil by falling

water drops.

Non-chemical controls include

removing affected leaves and, in

autumn, removing and burning or

burying them under a generous

layer of mulch.

This may only offer temporary

respite as new spores are blown

in from elsewhere.

Alternatively, use a fungicide, if

possible avoiding any that also

contain an insecticide if pests are

not a problem.

Several new varieties of rose

have been bred to be black spot

resistant, but as the fungus mutates

their invulnerability is not always

long-lasting.

How to deal

with black spot

1

Nip pests in the bud before using

chemicals. Leaf notches are often

caused by leafcutter bees taking

material for their nests, and the loss is

cosmetic rather than destructive.

2

Deadhead spent blooms to

encourage more flowers. Suckers

growing from rootstock under the soil

should be pulled away before they

weaken the plant.

Remove suckers springing up

close to the main plant. They

look similar, but have paler

leaves and whippy stems

Remove and dispose of

black spot leaves

Avoid using systemic
weedkillers such as
Roundup around roses as
their roots grow close to
the surface and contact
with the chemical may
kill the plant.

Keep shrubs, climbers and ramblers healthy, saysKeep shrubs, climbers and ramblers healthy, saysRuth

3

Feed with a granular fertiliser for

a slow feed and then water it in.

Soluble and liquid feeds are good for

container-grown roses as they give an

instant hit of nutrients.

4

Tie in heavy-bloomed shrub

roses so they remain stable, and

secure climbers and ramblers to

keep them in place. Cut away brown

‘balled’ buds that are rotting.

weaken the plant.

Act fast to beat this fungal disease

over recent years.

It first presents in

patch on foliage,

Scabby lesions also

Treat with a fungicide

Remove aff ected foliage at

the fi rst sign of black spot