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| Hardfacing or hard surfacing
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Wear-resistant coating of one metal applied by weld overlay to another softer base metal. Alternately it can be applied by insertion of a section of the hardfacing material into a recess in the softer metal. Hardfacing is often used with devices in a high-pressure steam system. |
| Hardiness
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The ability of a plant to withstand low temperatures or frost, without artificial protection. |
| Hardiness zone
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U.S. Department of Agriculture classifications according to annual minimum temperatures and/or lengths of growing seasons. Also referred to as USDA zone. |
| Hardness
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Measure of a materials resistance to dents or scratches. |
| Hardpan
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The impervious layer of soil or clay lying beneath the topsoil. Water will run off and plant roots can not penetrate the layer.Ê Can be broken up. |
| Hardscape
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Includes any garden feature that is not a plant. Like birdbaths, deck, fences, trellises, benches, and patios. |
| Hardwood
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Generally, one of the botanical groups of deciduous trees that have broad leaves in contrast to the conifers or softwoods. The term has no reference to the actual hardness of the wood. |
| Hardwoods
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Wood from broad leaf, deciduous trees such as oak, walnut, ash, maple or birch, which are used commonly as flooring in homes. |
| Hardy
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A plant which can withstand prolonged exposure to temperatures at or below 45¡F. Compare half hardy and tender. |
| Harmonic(s)
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A sinusoidal quantity having a frequency that is an integral multiple of the frequency of a periodic quantity to which it is related. |
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