Transcript Amenity Horticulture Hort 253

Amenity Horticulture
Hort 253
L. Atuah (Ph.D)
Outline
 Amenity horticulture- what it is and its
relevance
 Challenges in amenity horticulture and the
way forward
 Plants in the landscape
 Plant use – functional and aesthetic
 Maintaining amenity plants
 Some plant disorders and their treatments
Amenity Horticulture – what it is and
its relevance
 It can be referred to as landscape horticulture
or environmental horticulture.
 The term landscape commonly refers to the
appearance of the land, including its shapes,
texture and colours. It also reflects the way in
which their various components combine to
create specific patterns and pictures that are
distinctive to particular localities.
Amenity Horticulture – what it is and
its relevance
 The landscape or the natural environment has
gone through various modifications which are
man made.
 Amenity horticulture therefore refers to the use
of plants in the landscape to effect aesthetic
patterns, enhancing comfort and pleasantness.
 The plants may also serve other functional
purposes like checking erosion, screening etc.
Amenity Horticulture – what it is and
its relevance
 Amenity horticulture is therefore applied in
such a way that it reflects the set of priorities of
the users of a particular environ.
 Multi-professional collaboration is required to
produce the cohesion needed in our
landscapes/environs.
 Name professionals that will be needed for
such collaboration and briefly explain why?
Challenges in Amenity Horticulture
 General challenges: Vandalism, litter,
poisonous plants, hideouts for ‘bad people’,
timeliness in keeping maintenance schedule.
 Challenges peculiar to Ghana – name as many
as you can think of.
Amenity horticulture in Ghana- The
way forward
 Education
 Legislation
 More research on ornamental plants and the
environment (implying provision of funds)
 Re-organising the department of Parks and
Gardens
 Innovative ideas like an award for Ghana’s
most beautiful suburb etc.
Plants in the landscape
 The plants in the landscape can be categorised. They may be either
of the following;
Trees
Shrubs
Herbaceous perennials
Grasses and creeping plants/ground covers
Climbers
Bromeliads
Ferns
Cacti and succulents
Water plants
Plants in the landscape
 Plantings in the landscape may either be formal
or informal.
Trees: The four main groupings of trees are
namely, foliage trees, flowering trees, conifers and
palms.
Some examples are enlisted in later slides.
Foliage Trees
Scientific name
Common name
Some characteristics
Ficus benjamina
Azadirachta indica
Pithecellobium saman
Michelia champaca
Weeping fig
Neem
Rain Tree
Champac
Ravenala madagascariensis
Traveller’s Tree
Weeping spreading tree
Upright spreading tree
Spreading tree
Medium size erect and
Pyramidal tree
Erect fan shaped plant
Flowering Trees
Scientific name
Common name
Some characteristics
Cassia fistula
Cassia nodosa
Lagerstroemia speciosa
Poinciana regia
Plumeria alba
Golden shower
Pink shower tree
Queen flower
Flamboyante
Frangipani, Forget-me-not
Pendulous yellow flowers
Pink flowers
Showy purple flowers
Large scarlet flowers
White flowers
Conifers & Pines
Scientific name
Common name
Some characteristics
Araucaria heterophylla
Araucaria bidwilli
Cupressus Sp
Thuja orientalis
Casuarina equisetifolia
Norfolk Island Pine
Bunyan bunyan
Cupressus
Thuja
Whistling pine
Pyramidal evergreen
Spiny evergreen
Bushy and dense
Dense busy pyramidal tree
Needle-like leaves
Palms
Scientific name
Common name
Some characteristics
Roystonea regia
Royal palm
Cocos nucifera
Caryota urens
Coconut palm
Toddy Palm
There are both tall and
dwarf varieties
Tall and dwarf varieties
Erect tree with spiral
leaves
Washingtonia filifera
Shrubs
•
A shrub may be distinguished from a tree by
the fact that it is bushy and mostly multistemmed (i.e. woody, a plant smaller than a
tree and with several woody stems). Shrubs
are usually divided into two groups - flowering
and foliage. They are grown in the landscape
individually as specimen plants or in groups
for shelter belt, hedges, bedding plants or in
shrubberies.
Examples of shrubs
• Flowering shrub:
Scientific name
Common name
Some characteristics
Acalypha hispida
Allamanda cathartica
Monkey tail/red fingers
Allamanda
Bougainvillea glabra
Purple bougainvillea
Hibiscus rosa-sinensis
Hibiscus/Rose of China
Ixora duffi
Double red ixora
Slender long flowers
Yellow trumpet shape
flowers
Has thorns and is a
climber
Different kinds exists; red,
yellow, pink flowers
Large heads of crimson
flowers
Foliage shrubs
Scientific name
Common name
Some characteristics
Acalypha willinckii
Acalypha wilkesiana
Variegated acalypha
Acalypha tricolor
Breynia nivosa
Ice plant/snow plant
Pseuderanthemum
atropurpureum
Polyscias spp.
Purple eranthemum
Has heart-shaped leaves
Brown leaves blotched
with red
Terminal leaves are
variegated white
Has purple leaves
Panax
Several kinds exist
Herbaceous perennial
 These are perennial herbaceous plants which
are either grown for their flowers or foliage.
They include bulbous, tuberous and
rhizomatous plants.
Scientific name
Common name
Some characteristics
Anthurium andreanum
Anthurium lily
Canna spp
Canna lily
Gerbera jamesonii
Barberton daisy
Heliconia bihai
Pentas parviflora
Lobster claw
Red Pentas/flaming Katie
Bears large waxy scarlet
flower
Numerous varieties with
different colours
When well irrigated it
continue to flower
throughout the year
Bears yellow bracts
Cannot withstand drought
Climbers
 Climbing plants consist of both perennial
woody, herbaceous plants and annuals.
 These plants have various devices for climbing
which include tendrils, twining stem, root-like
holdfasts and drooping or rumbling over a
support.
 Since most climbing plants grow vigorously
and consequently carry a lot of vegetation,
stakes or supports used must be sufficiently
strong.
Climbers
Scientific name
Common name
Some characteristics
Monstera deliciosa
Scindapsus aureus
Thunbergia alata
Ceriman
Scindapsus
Black-eyed Susan
Ficus pumila
Creeping fig
Petrea volubilis
Purple wreath
Has perforated leaves
Quick growing
Yellow funnel shaped
flowers
Very useful for covering
bare walls
Has brittle papery
leaves
Grasses and ground covers
 Turf grasses perform the function of ground
cover plants. They are grown mainly in lawns,
playing fields etc.
 Ground cover plants are very useful on slopes,
irregular surfaces and in rocky areas where
mowing of grass is not possible.
Scientific name
Common name
Some characteristics
Chrysopogon aciculatus
Love grass/Tafo grass
Axonopus compressus
Cynodon dactylon
Setcreasea purpurea
Carpet grass
Bermuda grass
Purple heart
Tribulus cistoides
Tribulus
Grows in full sun and semishade
full sun and semi-shade
Does not thrive under shade
Violet flowers open in the
morning closes by afternoon
Very showy yellow flowers
Ferns
 Ferns belong to a group of plants which
produce pores instead of flowers and seeds.
 The spores are found on the fronds, usually
beneath.
 Suitable conditions for growth and
development; damp semi-shaded conditions
with protection from wind.
Scientific name
Common name
Some characteristics
Adiantum capillus-veneris
Nephrolepis exaltata
Asparagus plumosus
Maidenhair fern
Sword fern
Asparagus fern
Asparagus sprengeri
Asparagus fern
Cannot recover once wilted
Fronds are erect and stiff
Fern-like with need-like
branchlets
Can grow both in full sun and
semi-shade
Cacti and Succulents
 These plants can withstand a considerable amount of
neglect. This is possible because of their resistance to
drought, dry, hot and difficult conditions.
 Cacti has adaptive features to cut down on loss of
water through transpiration. These are thickened
stems and spines which are modified leaves.
 The fleshy nature of succulents allow for maximum
retention of moisture. Transpiration is further
reduced by a thin wax coating or woolly hairs plant
parts.
Cacti and succulents
Scientific name
Common name
Some characteristics
Agave americana
Century plant
Spreading plant with a large
rosette of thick and stiff leaves.
Euphorbia splendens
Christ’s Thorn
Sparsely foliaged with spiny stem.
Kalanchoe
blossfeldiana
Flaming Katy
Erect house plant bears clusters
of scarlet flowers.
Rhoeo discolor
Lady-in-boat/Moses in the
cradle
Succulent leaves which are glossy
purple beneath and green above.
Sansevieria trifasciata
laurentii
Mother-in-law tongue
Erect cylindrical pointed leaves.
Water plants
 Three general groups of water plants;
Those which grow entirely beneath water, those
which have their roots and stem beneath water
surface, those with their roots growing in water
and stems and leave above water surface.
Scientific name
Common name
Some characteristics
Nymphaea spp
Water lilies
Pistia stratiotes
Water lettuce
Thalia dealbata
Water Canna
Waxy leaf surface with
closely set minute hairs
Floating plant preferring
shallow waters
Floating and bears small
dull violet flowers
Plant use
 Avenue plants – Trees with clear trunks (allowing
for people to walk under) is ideal. The trees must
have aggressive root systems, should not have brittle
branches and not be messy (by way of leaf and seed
drop). The roots must have deep root system to
afford good anchorage.
 Specimen plants – Plants with unique characteristics.
They should be sufficiently attractive to stand alone.
 Hedge – Plants (especially shrubs) grown with close
spacing and trained in such a way to make a barrier
or mark a boundary.
 House plants – they are plants which can be
expected to live permanently under room
conditions.
Plant Use – functional and aesthetics
Trees
 Avenue plantings
 Provision of shade
 Specimen
 Noise control
 Pollution control
 Wind breaks
Plant use
Shrubs:
 Hedge
 Median planting to reduce headlamp glares
 Potted plant
 Bedding plant
 Border plant
Herbaceous perennial
 Beds
 Borders
Establishing an avenue:
 In avenue planting there should be a layout and
design and the following should be considered:
 Length

If an avenue leads from one definite point to
another, its length is automatically defined.

In other cases, the length should be decided in the
light of certain guiding factors including the following:
 If too long, an avenue tends to become monotonous.
 If very long, care must be taken to ensure that it is
not too narrow, in which case it will tend to shrink to
vanishing point before the end of it is seen.
 If a very long avenue is made too wide, in order to
avoid the last pitfall (shrinkage), the trees of which it
is composed will appear to be dwarfed.
 Avenues should not normally be more than one-half
to three-quarters of a mile in length if the above
points are to be avoided.
 It is difficult to lay down the exact width of an
avenue. The habit of the species planted: large crown
trees need more space than those with narrow crown.
The table below can be used as a guide
Length of avenue (m)
Width of avenue (m)
91
91-182
182-365
365-548
548-640
640-751
9
12
15
18
21
24
 The length of the avenue: long avenues should be
rather wider than those of shorter length.
 The number of rows of trees of which the avenue is
composed: an avenue of two single rows should be
rather narrower than one with two double rows.
 City conditions are often unfavourable for tree
growth and species must be selected which can
tolerate air pollution, dry conditions, glare from
pavements etc.
 Suitable trees should be planted far enough from the
kerb to allow them to spread without too much
pruning. They should be kept clear of overhead
wires and underground services.
 Discuss how a tree can be planted (Steps involved)
Trees in car parks
 The task of accommodating trees within a car park is not
always straightforward as it may seem. The challenge on
site a car park; are usually hard surface, dry conditions,
lack of air and the intensity of the light which is thrown
up from the ground to the tree.
 This can result in leaf scorch and abnormal transpiration
rate.
 Vehicles may damage trees by reversing into them and
tree roots can be poisoned if fuel run-off gets into the
water supply.
 To avoid the afore mentioned hazards it is
usually suggested trees in car parks be planted
between raised kerbs or in elevated boxes.
 Hazard fencing at bumper height can go some
way to meeting practicalities but the careful
siting of trees in relation to the overall car park
design gives the best solution.
 In tree selection, the tree should be able to
withstand pollution.
Hedges
 Essentials required are a shovel, rope/string, tape
measure, stakes/pegs, compost, spray paint
(optional).
 If a really dense and bushy hedge from ground
upwards, it is advisable to plant young small plants.
The result of using large plants can often be that the
hedge is rather gappy at the base.
Soil preparation:
 Prepare the ground by digging over a strip 60-90cm
wide and one spade blade deep.
 Remove all weeds if a weedkiller has not been used
before hand.
Hedges
 Add organic matter such as garden compost, spread
it over the soil and mix in top 25 cm of soil with a
fork.
 You may also mix in a general purpose fertilizer.
Planting
 Planting distances vary from 30-60 cm, depending on
the plants’ final size, the size of hedge required and
plant vigour. For hedges thicker than 90 plant a
staggered double row 45 cm apart with plants 90 cm
apart.
 Trim back damaged roots to healthy growth with a
sharp knife.
Hedges
 Spread out the roots, ensuring the planting depth is
correct (note that the previous soil mark on the stem
indicates how deeply the plants were grown in the
nursery).
 Work soil between the roots, firm plants in so that
soil is in close contact with the roots. Then water.
 Mulch to a depth of 7.5cm after planting to prevent
weeds.
Why will one plant a hedge?
What kind of plants are recommended for median
planting?
Planting beds and borders
 These are plants which are grown in beds and borders to
give color to a landscape environment. They include
annuals, biennials, herbaceous perennials, ferns, fern-like
plants, orchids, cacti and succulents and shrubs.
 Beds stand as an island of selected flowering plants.
 They could take any shape especially geometric shapes;
square, oval etc. If the bed is sited in a lawn you will have
to be careful your chosen shape will not hamper mowing
of the grass.
 If you plan a large bed you will have to make provision
for access in order to facilitate maintenance.
Beds and Borders
 Beds should be viewable from different angles.
Borders- They are planted against a wall or hedge.
 The plants in a border will therefore be affected by
shadow from the wall, possible reduced impact of
rain.
 Take into consideration the backdrop when planning
the colour scheme of the border.
 Be aware also of the fact that maintenance works on
the wall or hedge can affect the plantings in the
border.
How can you establish a bed; square and circular shape?
Lawn (Turf) establishment
 Lawn: A smooth layer of land covered with turf.
 Turf: A ground cover of grass which is kept mown
and which will stand a reasonable amount of traffic.
 Verge: A narrow strip of turf between beds, paths,
walls etc.
Preparations involved:
 Soil preparation is essential to ensure there is quick
establishment of uniform turf. The goal is to create a
fertile homogeneous root zone with acceptable
infiltration, aeration and drainage.
Lawn (turf) establishment
 Depending upon the scope of the project advance
planning may be of relatively little or of very great
importance.
 In general turf can be established from seeds or
vegetatively. This could be by sodding, plugging,
stolonizing and sprigging.
 Sodding: The process of installing mature turf in
large or small sheets, as opposed to spreading seed
or sprigs over a prepared area of bare soil.
 Sod is established turf that is harvested with roots
and soil attached and transplanted from its place of
origin and installed like carpeting to grow in another
place.
 Sodding is the most expensive method of turf
establishment but produces an established turf
within hours rather than weeks or months.
 The only maintenance required during the early
weeks of establishment is daily watering when there
are no rains.
 Sod is bought from a farm in the form of rectangular
pieces or as long rolled strips.
 Stolonizing: Every bud on a stolon can potentially
become a new plant.
 Many tropical turf-grass do not produce viable seeds.
Stolonizing is therefore one of the methods for
establishment of turf.
 Sprigging: The process of vegetatively establishing
turf grass by spreading rhizomes or stolon over a
prepared seed bed and pressing them into the soil.
 It is a modification of stolonizing. It involves placing
stolons in narrows spaced 15 to 20cm apart and
manually covered. 15 to 20% of the stolon should
extend above the surface.
 The advantage over stolonizing is less risk of
desiccation.
 The disadvantage is high labour cost.
 Plugging: Small (5 to 10 cm) diameter pieces of sod
are transplanted into a prepared area 15 to 35 cm
apart.
Site preparation
• This is the same irrespective of the method adapted
for establishment.
Steps: Debris removal
• Elimination of existing vegetation and preventive
weed control. An ideal herbicide/weedicide
translocates through and kills the entire plant without
leaving a harmful residue in the soil.
• Glyphosate known commonly as Kleenup or
Roundup will kill both annual and perennial
weeds.
• Weeds also can be removed by digging.
• Levelling – This involves changing the slope of
the area into an even gradient. This can be
adequately worked on from the subsoil before
spreading the top soil.
• Soil amending – Depending on the soil
condition of the topsoil soil amending may be
needed to improve drainage, fertility or pH.
• Surface preparation – The surface on which
the seed is to be sown should be free of clods
and form a tilth. A light raking will remove
remaining clods and provide the final surface.
• Information on seed germination rate and
purity must be noted.
• Seed rate – Generally package directions are
the best source of information on seeding
rate.
 For heavy seeding may be done but it have
some disadvantages. There will be quick
results but it will be under over crowded
conditions and weaker seedlings will be
weeded out by stronger ones which will
eventually form a stand of plants equal to that
which would have been formed naturally at a
lower rate.
 Seeding Techniques: For large areas
Mechanical methods should be adopted.
Maintaining amenity plants
 Trees
 Shrubs
 Grasses
This may involve the following:
 Pruning
 Watering
 Mulching
 Shading
 Removal of Competition/Weed Control.
 Staking
 Fertilization
Maintaining amenity plants
The general principles for pruning trees and shrubs will
be considered.
Pruning is the removal of plant parts on purpose to
enhance growth and maintain the usefulness of the plant.
Pruning tools:
 Examples of hand pruners – Pruning saw, hedge
shears, hand pruners, lopping shears.
Purpose for pruning:
 Size control
 Health improvement
 Appearance improvement
 Pruning young trees:
This implies pruning at transplanting and within the
first few years after transplanting.
(why may pruning be a requirement at transplanting)
 During the first few years of transplanting the plant
develops the main branches which will form the
support structure for the foliage.
 Pruning directs the growth of those branches in
order to create a strong tree.
What is a strong tree?
 Look out at the early stages of plant development for
double leaders and remove them.
 Most trees have a ‘central leader’ but a occasionally
two leaders develop causing a fork.
 If the weaker of the two lead branches is not
removed, it poses a potential cause for damaging of
the tree trunk with time.
 As each leader increases in diameter, it exerts
pressure against the other at the base and this can
cause eventual splitting.
 Selection of scaffold branching.
The lateral branches along the main stem is referred to
as scaffold branches.
 It is best to control the extent of branches in the
initial stages of development of a tree. It is best if
they are widely spaced and evenly along the trunk.
Pruning mature trees:
 A tree that was properly pruned when young should
need little pruning when mature.
 Three-cut pruning method is adopted for removing
large branches/limb
• Mature branches are usually heavy and easily break
and rip off tree back if being sawed off by one cut.
The three-cut pruning:
• 1st cut is made under the branch about 30 cm away
from the trunk and goes halfway through the branch.
• The 2nd cut is made about 8 cm away from the 1st cut
from the top of the branch. This is cut through.
• The 3rd cut removes the stub.
Note
• Some trees may naturally not have a central leader
and it will be a mistake to prune to have one.
• Pruning of such trees may involve only desuckering
and removal of crossing and inward-growing
branches.
Pruning shrubs:- This involves;
• Thinning
• Heading back
• Renewal Pruning
• Shrubs are multi-stemmed coming out from the basal
portions of the plant. With time as they grow by
increasing in height and number of stems there will
be the need to thin.
• This is because as the older stems age and lengthen,
they have the tendency to shade out the bottom
foliage.
• This results in the shrub becoming bare at the base.
• Thinning consists of removing the oldest stems at
ground level. This shortens the shrub and encourages
new shoots to grow from the roots and refoliate the
bottom.
Heading back:• This consist of cutting twigs or small branches to just
before/above an outward pointing bud.
• It encourages new growth to develop outward and
eliminate crossing branches.
Heading Back
Renewal pruning
• Used to rejuvenate and shorten over grown shrubs.
• Where branches are cut back they are reduced to
stubs 5 - 8 cm long.
• Renewal pruning involves thinning techniques as
well as cutting back.
• It a drastic measure which will make the plant
unsightly in the first two years.
Pruning hedges
• What is a hedge? (Recall)
• Hedges can be classified as formal and natural
(informal).
• Pruning of a natural hedge/shelter belt is same as
pruning a shrub i.e. thinning and heading back.
• Formal hedges require frequent pruning to
maintain a neat appearance.
• What is important is the selection of the correct
hedge shape.
Hedge shapes
Mowing
 Sound mowing is perhaps the single most important
factor contributing to the attractiveness and
longevity of any turf-grass area.
 The height of cut is important. The height to which a
given grass can be mowed is directly related to its
ability to produce enough leaves and to keep up with
production of carbohydrates.
 Some creeping grasses with fine leaves, such as
cynodon and zoysia, when properly fertilised and
watered, are able to produce adequate leaf surface at
very low mowing heights.
 It has been determined that removal of more
than one-third of total leaf area results in
severe physiological shock.
 With this in mind, only the growth rate will
determine the mowing frequency.
Mowing equipment:
 There are a number of mower types. The most
accurate are the reel mowers (cylinder mowers),
rotary mowers are intermediate and sickle-bar
mowers are the least.
 The proper choice of mowing equipment
depends on the type of grass and the
conditions of usage and maintenance.
 For high-quality sport or recreational areas,
reel mowers are recommended for cutting.
 They provide a clean even cut and leave the
turf looking the most attractive.
 Rotary mower should be used where perfect
appearance is not necessary. And where ease of
operation, maintenance and price are of
significant concern.
 Sickle bar mowers are the simplest and roughest.
They are used mainly across road side and other
areas where turf appearance is of secondary concern.
Reel mowers:
 A reel mower consists of a horizontal rotating
cylinder, the reel, with attached blade and stationary
bed knife, which is parallel to the ground.
 The reel usually bears between 3 and 7 blades, and
the width of the mower usually ranges from 50 to 80
cm depending on the model.
Rotary mowers:
 The blade of a rotary mower is usually a single
sharpened metal bar suspended parallel to the
ground at its centre point.
 It spins in a horizontal plane, striking and
severing vertically growing leaf blades.
 They do not provide an even cut and they
cause certain amount of mutilation at the point
of impact.
Mower operations
 Mowing should be done only when the grass is dry.
 This is because the mower is less likely to clog with
soggy clippings.
 Secondly grass blades are more susceptible to
disease invasion through the cut surface when wet.
 It is important to sharpen mower blades often. A
clean cut minimises the damaged area and reduces
tip browning of the blades.
 It also decreases moisture loss and eliminates
bruised blades which are a site for disease entry.
Some plant disorders
 A key to determining the kind of disorder is to know
the cause of it.
 The cause may be attributed to either a parasitic
organism or an environmental condition.
Examples of parasites:
 Rodents, insects and microorganisms such as
bacteria and fungi.
Examples of environmental conditions:
 Heat, drought, pollution etc.
 There are some disorders that may be as a result of deficiencies
or toxicities. This may result in manifest the manifestation of
certain symptoms depending on the nutrient element that is
lacking or in toxic levels.
 Note that symptoms are first seen in the oldest leaves when the
nutrient element can be easily moved about the plant.
 In deficiency, the small supply is shunted to areas of growth in
an attempt by the plant to complete the life cycle.
 Symptoms are first seen in the youngest leaves when the
element in poor supply is held firmly where it was first used.
 Deficiencies may often result in stunted growth
and off-colour leaves.
Other causes of stunted growth may be;
 Waterlogging, salinity, drought, disease eg root
rot, insects, viruses.
 Too much or too little light
 Wrong day-length
 Toxins in medium
 Problem
 Pests
 Caterpillars
 Borers
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Symptoms
Symptoms
Parts of leaves eaten away.
Borrow into stems, underneath
part of leaf eaten away whiles top
remains untouched.
Leaf miners
Scribble-like patterns on leaves.
Grasshoppers Large portions of leaves eaten.
Aphids
Disfigurement of leaves and buds.
Mealy bugs Raised spots or dots on leaves, leaves drop.
Nematodes Yellowing, general lack of vigour, roots
knotted. Death of irregular sections of
leaves and spotting.
 a. Fungi caused:
 Wilt
Entire or a section of plant wilts and
cannot recover even after watering.
 Leaf spot Spots (concentric rings with dark centre)
appear on foliage and sometimes on
stems and flowers spreading to cover all
other parts. Spots reduce photosynthetic
area of
leaves and plant may dies.
 Blight
Quick wilting and death of young and
growing tissues such as flowers and twig.
 Rust
Reddish-brown spots on foliage and
stems.
Virus caused:
 Curly top
 Mosaic
Twisting, distorted
foliage.
Mottled light and dark
areas on foliage.
Plant (disorder) disease control
 If the plant is diseased, the control may be both
cultural and chemical and understanding of both is
essential to restoring and maintaining plant health.
Cultural control:
 Watering
 Sanitation
 Pruning
 Roguing
 Crop Rotation
 Resistant Varieties and species