Lecture 14
Creating food-safe gardens
make a chart of what you are exposed to - see FDA's "risk cup"
minimize risk of heavy metals in gardens
- heavy metals stay in soils
- be aware of local pollution that puts it there (soil, water, air)
- when plating in-ground, how the history of the local area
- GET A SOIL TEST
sources of lead: near roads, old paint, old pipes
Pesticides: arsenic-based pesticides were common for fruit trees
tires/rubber mulches, as they break down - zinc, lead, rubber and other heavy metals leach into soil
atmostpheric deposition - things like smelters that put toxins in air
landscaping timbers - if old can have heavy metals, old pesticides, etc
waste water/rain barrels - know what your roof is made out of since this water comes from there, zinc, etc can leach into it. filter it.
flooding can also bring toxic material inland, check EPA files for maps of known toxicities
iron, a macronutrient, is also a heavy metal
cereals and root veggies are primary sources of cadmium toxicities
heavy metals are found more in urban veggies than rural veggie gardens
you can always buy good soil
uptake of heavy metals from air depends on species, tissues and life stages
sand and silt dont bind nutrients of heavy metals [in soil]
earthworms increase heavy metal uptake
chealating fertilizers can solubilize heavy metals for uptake
phosphate fertilizer increases heavy metals in soil
organic matter will bind to heavy metals and increase uptake
- metal mobility in soils (no easy rule of thumb) - acidic conditions means the roots will trade for heavy metals and uptake them
- roots and mycorrhizae can acidify the root zone as normal process
order of contamination, in plants, for heavy metals
- roots (beets, carrots, etc)
- stems (rhubarb, etc)
- leaves (lettuce, etc)
- fruits (typically contain seeds) (excluding zuccini which tends to aggregate heavy metals in its fruit)
uncertified organic products have not been tested for any type of contamination
certified organic compost has been checked
have your soil tested for heavy metals
- not bad idea to wear dust mask and gloves when working with soil that may be contaminated
- use untreated wood when using for gardening/staking, etc
can replace soil or use raised beds when planting outdoors
use things like untreated timber or concrete/bricks which dont leach bad things into soil
herbs like conditions that drain well and are sunny - raised beds can recreate this environment
Lecture 15
Water-wise landscaping
- reduce evaporation of water (windbreaks, shading)
- direct flow of water (hardscape, pavers)
- create hydrozones (plants with same requirements, group together)
succulents can tend to use as much water as given, not as much as needed to thrive
dissected leaves - helps reduce evaporation
blue-green or waxy leaves - reduces evaporation
pubescence - hairs on leaves reduce evaporation thru heat/wind
packing plants together can reduce evaporation (creates more humid area)
turf uses the most water of any plant
[she talks about sustainable lawns]
she talks about a story of her replacing her lawn 3 different times;
tried it once then next time she wanted to save the roots, good stuff in the soil, etc so she flipped the sod over and put mulch on top and it worked well. 3rd time she mowed it back during fall and let it cook during summer, turf was gone and soil structure was undisturbed
[wow that seems like dedication to having a green lawn that I cant relate to...]
protect water quality as well as availability
- manage storm water (can wash soil away)
woodchip mulch can be used to propigate good fungus before transplanting into more woodchips to innoculate and help/grow to the root zone of nearby plants
be careful of the source of water - what is in your water?
just because it doesnt hurt your plants doesnt mean it wont hurt you
reduce contamination from phosphate fertilizers and reduce use of pesticides
using not at all or as little as possible means less exposure
limit use of rich organic soil (contaminants can aggregate when used a lot)
agriculture (usually monoculture) and growing lawn is easy to guage how much water is needed, everything else can be tough to guage - wilting often signals to water
- PLANTS DONT RECOVER FROM TERMINAL WILT, dont wait to water when plant wilts
- indicator plants wilt first, once they wilt water all the plants
- make sure wilt isnt caused by something else like overwatering
finger test = get your fingers in the soil,
- can you form a ball of soil in your hand and will it stay? enough water.
- falls apart, too much/little
Evapotranspiration Coefficient (ET Coefficient) = mathmatical model to predict how much water is used by each plant (often used by golf courses, etc) but wont work in a landscape
Physiology and biochemistry: why crabgrass stays green and why succulents need less water
photosynthesis involves carbon fixation (most important step), the only way you can get carbon is by ingesting something with carbon, plants can only get it from a gas (air). Photosynthesis takes light and CO2 and turns it into oxygen and sugar with help of chlorophyll.
RuBisCO fixes carbon into a solid form (oxygen poisions this process by more redilly binding to it than CO2)
Photorespiration - cuts photosynthesis off
[great chart in the lecture shows the whole process, try googling it]
Types of photosynthesis by example:
- beauty berry
- C3 pathway(photosynthesis) (all plants do C3 at some level)
- requres less energy to photosynthesize, when photorespiring they can lose weight by all the energy they use
- ornamental grass
- C4 pathway(same as C3 with one extra step - CO2 binds to PEP Carboxalase)
- great diagram of how Mesophyll cell takes this new step to the bundle sheath cell [see Krans anatomy] and RuBisCO then on to Vascular tissue for sugar conversion
- C4 uses more energy at beginning than C3 but overall uses less energy overall because of a reduction in photorespiration
- C4 loses a lot of water, may not do well in hot climates
- suculent ("fat plant") [lol]
- Can revert back to C3 if given enogh water
- can use more water than a lawn this way
- CAM (Crassulacean acid metabolism) plants = differnet method of photosynthesis - just like C4 except have a temporal (time) seporation - ie night time [dark light cycle]
- they close stomatas down when hot and dry outside (day time), although cant photosynthesize during this time but they open at night to start process
- PEPC can metabolize at any time (why they taste sour in morning time)
- again, a great diagram, google it
Lecture 16
She has traiing as a plant stress physiologist - they match symptoms to whats happening inside the plant
plants die most often from poor horticulture practices instead of pests and disease
its not just the plant, its the environment as well but you must see the entire plant too if diagnosing
root zone & leaves show problems the best
first decide if the plant even has a problem (or did you ID the plant wrong?)
- know what a plant of the same species looks like, needs to thrive and does throughout the seasons
look for symptoms of damage, pests or other biotic factors
- be able to describe the abnormality you find to get help with it
- hard or impossible to diagnose from a pic or a leaf, need whole environment to factor in
with trees and shrubs - soil problems from a few years ago may manifest later on, site history comes into play to find out what real problem is
know how the plant was installed
- planted properly?
- how site was prepared
- what happened during planting
roots should go out like spokes on a wheel, if root bound break up and spread out when transplanting
- surface roots are a problem (can grow and emerge from soil can be OK, circling roots above ground = bad)
- single-trunk species with multiple trunks can indicate problems below ground
[she shows how pruning can caues suckering in a tree and therefore lack of water gets to the top and it 'bonsais' itself by getting shorter and dieing back the part where water cant reach - the top] - could be root issue or water competition issue, etc
non-living stress factors on leaves:
- wilting - "leaf doesnt have enough water" (water related stress, notice "leaf" insted of "soil")
- chlorosis - yellowing of leaf, they do this before falling
- intervenal chlorosis (green veins and tissue between veins is yellow) -lack of iron/manganese, likely over-fertilized which limits uptake of these elements
- necrosis- tissue death - related to water usually or early dying (brown and crinkley tissue thats dried out)
- notice the pattern, it will be on tips and margin, water is lost from tips of leaf first (drought issue)
- tissue redening - out of season = water stress, sometimes tree leaves turn red before yellow when dying for fall
- surface damage (could also be just abrasion) can be from sun "frying" the leaf with too much light
- distortions (like leaf warped or cut) and can vary in what caused it
location of discolorations on leaf:
- tips/margins = water related
- surface = sun related
- uniform = nutrient related
leaf size
- if multiple plants look at leaf size in realtion to each plant
- smaller leaves = water related stress
Living stresses shown in leaf: (insects, diseases, etc)
- missing parts of the leaf (like its being eaten)
- line of dots or big dead spots = something munching on your leaf
- leaf skeletonization - pest eats everything but epidermis layer
- discoloration - like a bullseye pattern on a leaf (fungal spore growing)
- bacterial infections typically have angular shape, unable to grow past veins at first
- chlorotic pattern (like web or pathway) indicate virus infection
Things that cause a variety of symptoms:
- crappy location (water, sun, etc)
- poor plant selection
- bad soil management
- compacted soil (lack of oxygen)
- bare soil/no mulch - some plants die off with this
Causes of lack of root establishment:
- circling roots (pot bound) = bad, if not fixed will cause problems
- not planted at grade - lack of oxygen, early death
Staking can cause problems - lack of upkeep can kill plants and grow into it
Phosphate fertilizers and over fertilizations are most common problems
over use of organics can also cause this problem
bad pruning - overpruning will stress your plant and open it up to stress and pests
