Disorders Flashcards
What is meant by the term Plant Disorder?
Plant disorder = plant health problem caused, not by a pathogen, but by some problem in the environment. Caused by a non living factor.
What are the 9 examples of disorders which can affect plant health?
Frost Shade Drought Water logging High temperature Low temperature Soil PH Fasciation Rose Balling
When is frost most likely to affect plants?
Late Autumn (first frost) Early spring (last frost)
What plants are susceptible to frost damage?
Potatoes, Camellias, Apple blossom, tender bedding plants, Gunnera, Strawberries.
What are the symptoms of frost damage on a plant?
Blackened rapid knockdown.
Wilting or blackening of the new leaves, flowers, buds, or stems.
In extreme cases death.
What methods are there to avoid frost damage to susceptible plants?
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!
What problems can shade cause to plant growth?
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.
How can you avoid problems caused by growing in shade?
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.
When is the most likely to time for plants to be affected by shade?
Anytime for mature plants.
Seedlings in winter or early spring when light levels are low.
What plants are susceptible to shade problems?
Seedlings on windowsill.
Plants in the wrong place - sun lovers in a shady spot.
What time of year are plants most likely to be susceptible to drought?
Most likely time is spring or summer.
What plants are most susceptible to drought?
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.
What are the symptoms of drought?
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.
What methods can be used to avoid drought in your plants?
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.
When is the most likely time for Water logging to be an issue for plants?
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.
Which plants are susceptible to overwatering?
Houseplants in winter.
Containerised plants with no drainage.
Cacti and succulents. Drought loving plants.
What is the effect of waterlogging on the growth of plants?
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.
What methods can be used to avoid waterlogging of plants?
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
When are high temperatures most likely to be a problem?
Summer outdoors.
Late spring/early summer under glass.
What plants are susceptible to problems from high temperatures?
Tomatoes.
Tender young growth on acers, apples.
Acers are prone to sun scorch.
Pelargoniums - leaves may become bleached.
What is the effect of high temperatures on plant growth?
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.
What methods are there to avoid damage to plants from high temperatures?
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.
When are plants most susceptible to low temperatures?
Most likely time is winter, early spring and late Autumn.
What plants are most susceptible to problems from low temperatures?
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.
