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Acid rain is measured through pH tests which determine the concentration of hydrogen ions. Pure water has a neutral pH of 7. When the pH is greater than 7, the material is said to be alkaline, or basic; acids have a pH less than 7. At a natural pH of 5.7, pure rain has a little bit of acid due to its mixture with naturally-evolving carbon dioxide in the atmosphere. However, when its pH is further reduced, the rain becomes pollution. In the worst cases, acid rain has shown a pH of 2.4, which is as acidic as vinegar. When pH levels are drastically skewed in soil and water, entire lakes and forests are jeopardized. Evergreen trees in high elevations are especially vulnerable. Although the acid rain itself does not kill the trees, it makes them more susceptible to other dangers and stresses. Plants and trees that are exposed to acid rain are less effective at photosynthesis and respiration. Also, high acid levels in soil cause leaching, or removal, of other valuable minerals such as calcium, magnesium, and potassium. According to the World Watch Institute in 1988, forest damage in Europe ranged from a low of 4% in Portugal, to a high of 71% in Czechoslovakia, averaging 35% overall.

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Approx. germination time: 3-12 days

Germination temp.: 45-90 degrees F

Sowing depth: 1/2 inch

Germination rates are simply the percentage of seedlings that sprout.

Ideally, you should test 10 to 20 seeds

Plant some seed in a pot. Make sure to record how many you are testing. Add water to moisten the soil. Place pots in a warm location in your house or on germination mats. After they sprout, count the seeds that sprouted and calculate the percentage that sprouted of the total.

A wing is a type of fin with a surface that produces aerodynamic force for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid. As such, wings have an airfoil shape, a streamlined cross-sectional shape producing a useful lift to drag ratio. The word "wing" from the Old Norse vængr[1] for many centuries referred mainly to the foremost limbs of birds (in addition to the architectural aisle.) But in recent centuries the word's meaning has extended to include lift producing appendages of insects, bats, pterosaurs, boomerangs, some sail boats and aircraft, or the inverted airfoil on a race car that generates a downward force to increase traction.

The various terms related to airfoils are defined below:[6] The suction surface (a.k.a. upper surface) is generally associated with higher velocity and lower static pressure. The pressure surface (a.k.a. lower surface) has a comparatively higher static pressure than the suction surface. The pressure gradient between these two surfaces contributes to the lift force generated for a given airfoil. The geometry of the airfoil is described with a variety of terms. A key characteristic of an airfoil is its chord. We thus define the following concepts: The leading edge is the point at the front of the airfoil that has maximum curvature.[7] The trailing edge is defined similarly as the point of maximum curvature at the rear of the airfoil. The chord line is a straight line connecting the leading and trailing edges of the airfoil. The chord length, or simply chord, , is the length of the chord line and is the characteristic dimension of the airfoil section.

if one or more of these factors is very low, then often plant growth is limited, or even halted

The three main factors that influence plant growth are temperature, the availability of water, and sunlight

Gathering plant material for dyeing: Blossoms should be in full bloom, berries ripe and nuts mature. Remember, never gather more than 2/3 of a stand of anything