Herbicides seem to be difficult to understand for the novice gardener. There are two phrases that are used to describe how an herbicide works: pre-emergence and post-emergence.
A pre-emergent herbicide is used to control weeds before they emerge from the soil. This is the type of herbicide that is normally used to control annual weeds such as crabgrass. Pre-emergent herbicides do not control weeds once they have established themselves.
Post-emergent herbicides work when the target weed is in a stage after the emergence of the weed in the garden.
The names that describe how an herbicide works may sound elementary, but understanding them is important. For instance, you can buy a product that is called 'crabgrass control,' but does it control the weed be-fore or after the plant has reared its ugly head in your lawn? If you apply it at the wrong time for the product's mode of action to work appropriately, you've wasted your time and money.
Other terms that may sound simple are also confusing to new gardeners. Annuals and perennials are confusing terms to many greenhorns, and it makes sense if you think about it.
The term annual plants could be construed as plants that return from the soil on an annual basis. Perennial plants could be thought of as plants that perennially need to be replanted from year to year. However, the phrases mean just the opposite. A comparison I give to gardeners who are having trouble with the terms is that annual plants are like annual tax returns. We all know that our taxes need to be filed each year.
Biennial plants really throw a wrench in the works for those struggling with the former terms. Just when we've figured out which plants need to be replanted each year and which ones don't, along comes a group that lasts for two years - the first year growing foliage, and the second year flowering and sowing its seed. Hollyhocks are a good example of this group of plants.
The pH of the soil is perhaps the most confusing item a new gardener has to deal with. People often get lost in the technical side of this issue. In simple terms, the pH of the soil tells you if the soil is acidic like vinegar or alkaline like baking soda.
The terms sweet and sour have been used to describe low pH or acidic soils and high pH or alkaline soils respectively. I like these terms to remember what's good for the garden. Food that is too sweet or too sour is not near as good as food that has the perfect combination of both. Likewise, most plants like to be near that midpoint to grow best. Most plants prefer a bit of a sour pucker and do not have a sweet tooth.