Disorders

Question 1

What is meant by the term Plant Disorder?

Answer 1

Plant disorder = plant health problem caused, not by a pathogen, but by some problem in the environment. Caused by a non living factor.

Question 2

What are the 9 examples of disorders which can affect plant health?

Answer 2

Frost
Shade
Drought
Water logging
High temperature
Low temperature
Soil PH
Fasciation
Rose Balling

Question 3

When is frost most likely to affect plants?

Answer 3

Late Autumn (first frost)
Early spring (last frost)

Question 4

What plants are susceptible to frost damage?

Answer 4

Potatoes, Camellias, Apple blossom, tender bedding plants, Gunnera, Strawberries.

Question 5

What are the symptoms of frost damage on a plant?

Answer 5

Blackened rapid knockdown.
Wilting or blackening of the new leaves, flowers, buds, or stems.

In extreme cases death.

Question 6

What methods are there to avoid frost damage to susceptible plants?

Answer 6

Protection by fleece, mulch, plastic, grow undercover and plant out after frost risk. Eg. Potatoes/bedding plants.
Determine frost pockets, and don’t plant tender plants there.
Choose right plant for right situation - do not plant out HHA too early.
Do not over fertilise in late summer, as sappy growth more susceptible.
Do not plant Camellias in an east facing position as they thaw too quickly in early morning sun.
Listen to the weather forecast!

Question 7

What problems can shade cause to plant growth?

Answer 7

Can cause etiolation if severe shading. Stems are weak with long internodes as they try to grow towards the light.

Seedlings may bend in one direction.
Weak Spindly growth.
Poor yield if a crop.

Question 8

How can you avoid problems caused by growing in shade?

Answer 8

Don’t sow too early when light levels are low.
Use supplementary lighting in the greenhouse in the winter.
Turn seedlings regularly.
Cut back overshadowing plants/remove shade covering structures or move plant.
Select shade tolerant plants.

Question 9

When is the most likely to time for plants to be affected by shade?

Answer 9

Anytime for mature plants.

Seedlings in winter or early spring when light levels are low.

Question 10

What plants are susceptible to shade problems?

Answer 10

Seedlings on windowsill.

Plants in the wrong place - sun lovers in a shady spot.

Question 11

What time of year are plants most likely to be susceptible to drought?

Answer 11

Most likely time is spring or summer.

Question 12

What plants are most susceptible to drought?

Answer 12

Newly planted in their first year - especially trees as takes a long time for their root systems to establish.
Anything in the greenhouse or under cloches.
Containerised plants.

Question 13

What are the symptoms of drought?

Answer 13

Temporary wilting if minor and can be restored.
Prolonged periods of drought mean plants will have slower growth or not at all.
Young leaves may not fully expand.
Severe cases marginal leaf necrosis can appear on deciduous trees and needle necrosis on conifers.
Lower leaves drop off.
Leaves dull green or yellow colour.
Irregular watering shows signs of blossom end rot in tomatoes and peppers as calcium deficient.

Question 14

What methods can be used to avoid drought in your plants?

Answer 14

Monitoring and irrigation as required.
Pay particular attention to watering of newly planted trees in their first year.
Correct growing media if containerised.
Pot on regularly so pot is not too small.
Right plant for right situation.
Containerised add water retaining gel or moisture retentive organic matter.
Mulch to retain water at roots and prevent evaporation from soil surface.

Question 15

When is the most likely time for Water logging to be an issue for plants?

Answer 15

Any time for containerised if drainage is blocked.
When there is heavy rainfall and low transpiration. (winter)
Linked to soil type.
May be caused by overwatering.

Question 16

Which plants are susceptible to overwatering?

Answer 16

Houseplants in winter.
Containerised plants with no drainage.
Cacti and succulents. Drought loving plants.

Question 17

What is the effect of waterlogging on the growth of plants?

Answer 17

Roots rot due to lack of oxygen.

Upper parts wilt and are stunted.

Roots become weakened, underdeveloped and vulnerable to pathogens. (rotting)

Oedema or corky like blisters can appear on underside of leaves on certain plants growing in waterlogged conditions.

Can cause damping off diseases of young seedlings where patches die back after germination.

Question 18

What methods can be used to avoid waterlogging of plants?

Answer 18

Improve drainage by installing drains, soakaway or aeration.

Cultivate soil to remove pans.

Do not pick leaves off as this can make Oedema worse.

Right plant for situation

For containers adjust the growing media by adding perlite or grit sand.

Ensure containers have drainage holes. Raised beds for poorly drained borders.

Monitor irrigation and do not overwater

Question 19

When are high temperatures most likely to be a problem?

Answer 19

Summer outdoors.

Late spring/early summer under glass.

Question 20

What plants are susceptible to problems from high temperatures?

Answer 20

Tomatoes.
Tender young growth on acers, apples.
Acers are prone to sun scorch.
Pelargoniums - leaves may become bleached.

Question 21

What is the effect of high temperatures on plant growth?

Answer 21

Impact varies depending on plant species/age.
Tomatoes - hard green yellow areas on fruits. (greenback).
Papery brown patches on leaves.
Narrowing of roots in hot soil.
Apples develop a red brown burnt patch on exposed side.
Shoots and roots may stop growing if high temperatures prevail.
Transpiration will increase so plant may wilt.
If high temperatures are coupled with low soil moisture, plants may exhibit scorching on the margins of the leaves, premature leaf drop, and in severe cases entire plant death.

Question 22

What methods are there to avoid damage to plants from high temperatures?

Answer 22

Shading in greenhouse. (particularly for tomatoes)

Heater with thermostat control so that temperature does not get too high. Cooling fan.

Ventilation in protected structures.

Right plant for situation

Damping down of glasshouse structures to reduce temperature and raise humidity.

Question 23

When are plants most susceptible to low temperatures?

Answer 23

Most likely time is winter, early spring and late Autumn.

Question 24

What plants are most susceptible to problems from low temperatures?

Answer 24

Tender bedding and crops.
For example - tomatoes, runner beans, courgettes, half hardy annuals such as lobelia erinus ‘Sapphire’.
Any grown under protection, and then not hardened off before planting outside or planting out too early.

Question 25

Which plants can be affected by low temperatures?

Answer 25

Houseplants/tender plants can be moved outside in summer but if weather is unseasonal or left outside towards Autumn they can suffer from low temperature exposure.

Half hardy annuals and tender crops such as courgette and runner beans are not planted out until warm weather in June and can show signs of low temperature exposure if not hardened off or planted out when it is cold / too early.

Question 26

What are the symptoms seen on plants which have been exposed to low temperatures?

Answer 26

Symptoms are :

Growth stops for a while
Stunted growth
Discolouration of leaves
Premature leaf drop

Tomatoes show discoloured purple dull tinge to leaves as cannot absorb phosphorus at low temperatures

Question 27

What methods can be employed to avoid cold temperatures damaging plants?

Answer 27

Shelter from cold eg fleece structure or move into glasshouse / tunnel other protected structure.

Harden off young plants to prevent shock in a cold frame such as Cucurbita pepo and tomato

Replace with hardier species - Right plant for situation

Question 28

How can the soil PH affect plant health?

Answer 28

All extremes of PH, nutrients become unavailable.

High PH causes iron deficiency in Camellias, Azaleas and Rhododendrons.
Interveinal chlorosis is the main symptom, veins are green and rest of leaf is yellow. Stunted growth.

Low PH (extremely acid soil) will also show nutrient deficiency of NPK.

Iron deficiency on alkaline soils is the most common one.

Question 29

What methods can be employed to avoid soil PH problems with plant growth?

Answer 29

Test PH at appropriate intervals - every few years and amend as necessary.

Add ground limestone in the form of calcium carbonate to raise pH if acid.

Add sulphur chips or pine needles to lower pH if alkaline.

Right plant, right place.

Grow in ericaceous soil in containers.

Water with sequestered iron.

Question 30

What is Fasciation usually caused by and when?

Answer 30

Can be caused by many factors - bacterial, trauma, mutation, virus, insect damage.

Can happen at any time.

Question 31

Which plants can be affected by Fasciation?

Answer 31

Forsythia x intermedia
Saguero cactus
Delphinium and many more.

Question 32

What are the symptoms of Fasciation?

Answer 32

Symptoms – Oval curved distorted flowers. Crested growth at growing points
Flattened misshapen stems. Abnormal shape.
Can be undesirable and pruned out or may be desirable for propagating new cultivars eg Celosia ‘Cristata’ is a type of fasciation that is cultivated

Question 33

What methods can be used to avoid Fasciation problems with plants?

Answer 33

Damage to the plants by frost, animals (including insects), chemical or mechanical injury – even hoeing or forking around the plant have been implicated so avoiding these with susceptible plants is advised.
Otherwise not a lot you can do apart from prune it out.

Question 34

When can Rose balling be an issue?

Answer 34

Any time when blooms are in bud and it is wet. Spring/Summer.

Question 35

Which plants are susceptible to Rose balling?

Answer 35

Multi petalled rose.
Camellia
Peony

Question 36

How is Rose balling triggered and what does it look like?

Answer 36

Triggered by cool, damp conditions, often in a partially shady site, where water-saturated outer petals fail to dry out before being scorched by the sun. The outer mushy plant tissue dries to form a stiff straightjacket around the petals, preventing the flower from opening.
The bud initially feels mushy and then when it has dried out the outer layer is stiff and papery and brown. Buds fail to open and are wrapped in a brown sheath. When the outer layer is peeled back the inner petals appear normal.

Secondary infection of Botrytis may occur which looks grey and fuzzy. Buds fall from the plant.

Question 37

What methods can be used to avoid Rose balling?

Answer 37

Good air circulation to dry buds out.
Prune roses for good air flow, and stake peonies.
Plant in a sunny spot.
In extreme cases erect a shelter to keep rain off.
Water in the mornings at the base of the plant, and do not wet blooms.
Remove botrytis infected material immediately.