NAA - naphthaleneacetic acid (NAA) is a plant hormone that is often used during propagation by cuttings to encourage root growth.

See IAA and IBA
naked bud - having no bud scale to cover and protect the bud.

For example: Viburnums
narrowleaf evergreen - ornamental conifers with comparatively long, slender leaves that remain green throughout the year such as firs (Abies), junipers (Juniperus), spruces (Picea) and yews (Taxus). See broadleaf evergreen.
naturalistic garden or wild garden -  a garden developed with plantings that either add to an existing native, non-disturbed site or to completely create an area that is or appears to be populated by native species. Achieved in beds or gardens by use of plants with loose or broad growth habit or those which multiply by rhizomes. Naturalizing plants are often the same as those used to add unity and continuity to a landscape garden.
naturalizing - applied to planting areas where the number of plants expand and multiply in the setting. For examples, daffodils (Narcissus) will often increase from a few bulbs to a large number covering a wide area.
 
necrosis - the death of cells, tissues, or whole plants. Dead parts or plants are said to be necrotic and will generally turn black and rot. See chlorosis.
nematode - very small, (usually, but not always) microscopic roundworms, threadworms, or eelworms that may become pests of plants.

A common nematode is the root knot nematode. A less common type called the foliar nematode is found in hostas. They cause browning of tissue between the veins of hosta leaves late in the season.
nightshade family - members of the plant family, Solanaceae, including eggplant, tomatoes, potatoes, peppers plus petunias, nicotiana and nolana.  Several weed species are also included, one of which (Atropa belladonna) is known as belladonna or deadly nightshade because its berries are poisonous.
nitrogen - a chemical element represented by the letter N that is required for plant growth. It is part of the chlorophyll molecule and, when in deficiency, is one of the factors that may cause a leaf to turn yellow. With a few exceptions, plants use nitrogen in combination with oxygen as a compound called nitrate.

In fertilizers, it is indicated by the first of the three numbers i.e. 10-15-20 has 10% nitrogen in the form of elemental nitrogen.
nitrate - with the chemical formula, NO3, this is the form of nitrogen which is absorbed by most plants.
 
node - the segment of a stem where one or more leaves or axillary buds are attached. See internode.
non-selective herbicide - a herbicide that will indiscriminately kill or injure many different types of plants that come into contact with it. See selective pesticide.
nut - a dry, indehiscent, hard, one-seeded fruit.
nutrient availability - Due to the chemistry of the situation, nutrients in the soil are more or less available to a plant depending on the pH (acidity or alkalinity) of the soil.

Generally, most landscape plants do best in a slightly acid soil with a pH of about 6.0 to 7.0. Certain plants such as rhododendrons and azaleas, boxwood, pin oak and others are "acid loving" and need a pH of around 5.0 to thrive.

nutrient deficiency - Plants "talk" to us to tell us their needs if we only know how to listen. Nutrients or chemical elements are the building blocks of the plant tissue. If any of the necessary nutrients are missing from the soil, the plant will tell us by displaying certain nutrient deficiency symptoms.

For instance, a plant that has very dark veins surrounded by yellowish tissue in the leaf is often expressing an iron deficiency. Since nitrogen is one of the key components of chlorophyll, a deficiency shows up as a yellowing leaf. Lack (or in some cases, excess) of plant nutrients will result in fairly specific symptoms on the plant.

Note: Unfortunately, a particular symptom such as yellow leaves may be caused by many other things too. So, knowing nutrient deficiency symptoms is often just a part of the process of figuring out what is wrong with your plant.

nutrient toxicity - When fertilizing plants, there is such a situation as "too much of a good thing". Over-applying nutrients to a plant may actually kill it. Many fertilizer products are a form of chemical salt. Too much salt applied next to the root of a plant will cause the water to flow from the root into the salt causing a "burn". In other situations, the plant may actually absorb too much of the nutrient and cause problems within the plant.

The key is, of course, to take a soil test and follow the recommendations or, at least, follow general recommendations for fertilizing a particular type of plant in the absence of a soil test.
 

 

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