Botanical sources differ from each other on the definition of "herb". For instance, the Hunt Institute for Botanical Documentation includes the condition "when persisting over more than one growing season, the parts of the shoot dying back seasonally". Some orchids, such as species of Phalaenopsis, are described in some sources (including the authoritative Plants of the World Online) as "herbs" but with "leaves persistent or sometimes deciduous". In the glossary of Flora of the Sydney Region, Roger Charles Carolin defines "herb" as a "plant that does not produce a woody stem", and the adjective "herbaceous" as meaning "herb-like", referring to parts of the plant that are green and soft in texture".
Herbaceous plants include graminoids, forbs, and ferns. Forbs are generally defined as herbaceous broad-leafed plants, while graminoids are plants with grass-like appearance including true grasses, sedges, and rushes.
Some relatively fast-growing herbaceous plants (especially annuals) are pioneers, or early-successional species. Others form the main vegetation of many stable habitats, occurring for example in the ground layer of forests, or in naturally open habitats such as meadow, salt marsh or desert. Some habitats, like grasslands and prairies and savannas, are dominated by herbaceous plants along with aquatic environments like ponds, streams and lakes.
Herbaceous plants do not produce perennializing above-ground structures using lignin, which is a complex phenolic polymer deposited in the secondary cell wall of all vascular plants. The development of lignin during vascular plant evolution provided mechanical strength, rigidity, and hydrophobicity to secondary cell walls creating a woody stem, allowing plants to grow tall and transport water and nutrients over longer distances within the plant body. Since most woody plants are perennials with a longer life cycle because it takes more time and more resources (nutrients and water) to produce persistently living lignified woody stems, they are not as able to colonize open and dry ground as rapidly as herbs.
The surface of herbs is a catalyst for dew, which in arid climates and seasons is the main type of precipitation and is necessary for the survival of vegetation, i.e. in arid areas, herbaceous plants are a generator of precipitation and the basis of an ecosystem. Most of the water vapor that turns into dew comes from the air, not the soil or clouds. The taller the herb (surface area is the main factor though), the more dew it produces, so a short cut of the herbs necessitates watering. For example, if you frequently and shortly cut the grass without watering in an arid zone, then desertification occurs, as shown here.
Herbaceous plants include plants that have either an annual, biennial, or perennial life cycle. Annual herbaceous plants die completely at the end of the growing season or when they have flowered and fruited, and then new plants grow from seed. Herbaceous perennial and biennial plants may have stems that die at the end of the growing season, but parts of the plant survive under or close to the ground from season to season (for biennials, until the next growing season, when they grow and flower again, then die).
New growth can also develop from living tissues remaining on or under the ground, including roots, a caudex (a thickened portion of the stem at ground level) or various types of underground stems, such as bulbs, corms, stolons, rhizomes and tubers. Examples of herbaceous biennials include carrot, parsnip and common ragwort; herbaceous perennials include potato, peony, hosta, mint, most ferns and most grasses.
In botany, the word for a herbaceous plant is herb (from Latin herba, "grass") but it is common to use the word herb only for plants that are used in perfumes, medicines and for cooking, even if they are not herbaceous plants.
Herbaceous plants may be annuals, biennials or perennials. Most are annuals and die at the end of their growing season (the time when they produce flowers, fruits and seeds), leaving their seeds on the soil. Those seeds will produce new plants with good weather. Wheat and pea are annual herbaceous plants.
Biennial and perennial herbaceous plants will live for two or more years, but the stems that are in the air will die every year. The underground stems will form the new aerial stems (stems that are above the ground). Underground roots and stems can better resist bad weather (winter or a very dry season) than leaves and stems that are above the ground. Bulbs are biennial and peonies are perennial herbaceous plants.
Most herbaceous plants are small and their stems are not thick because they do not have much wood, but there are some big herbaceous plants. Bananas and papaya (a tropical fruit) are herbaceous plants but they look like trees. Papaya has a thick stem but without much wood.
Herbaceous plants are the first plants with flower that come to live in barren lands (lands without plant life), because they are small and produce many seeds. They are also found in places where the weather conditions are not good for most plants. They can use the little rain that falls in deserts. They can get enough heat to grow where the soil is covered with snow and ice most of the year, like in very high mountains.
Biennial plants go through two growing seasons before they complete their life cycle. What we observe in these plants, such as carrots, is that they accumulate food reserves in their first year so that they can grow seeds and flowers in the second year. Like annuals, the parent plant dies once seeds and flowers have been produced. In contrast to annuals, however, these plants have organs, for example roots, bulbs, or corms, which are adapted to remain under the soil and survive when unfavorable conditions arise. Once conditions become favorable for growth again, the underground structures start to produce different plant organs, beginning a new cycle.
The inhibition of linoleic acid peroxidation was observed to be significantlyhigher in PA and BA at both 25 and 50 μg/mL of plant extracts(Table 3). Furthermore, significantly higherpercentages of conjugated diene inhibition were detected in PA (79.31) and CA(77.61) compared to MA (70.31) at 100 μg/mL of the extract. Hence,each species showed significant differences in inhibition percentages ofconjugated dienes at various extract concentrations.
Compared to the inhibition percentage of conjugated diene formation in thelinoleic acid emulsion autoxidation system of tested samples, PA exhibitedrelatively higher effectiveness than the others at all extract concentrations(Table 3). The tested vegetables showed >70%inhibition of linoleic acid peroxidation in 100 μg/mL extracts, and PAin particular exhibited the highest inhibition of linoleic acid peroxidation, upto 79.31%. Therefore, all tested plants were effective inhibitors and exhibitedbetter inhibition efficacy at higher concentrations. Previously, we demonstratedthat water and methanolic extracts from PA both had higher antioxidant activity,and that the antioxidant activity of PA was equivalent to 10-4 Mof Trolox in preventing conjugated diene formation during linolic acidperoxidation at 62.5 μg/mL of methanolic extract . The polyphenol content of methanolic extracts was significantlycorrelated with the delay of the lag phase of low-density lipoprotein (LDL)treated with methanolic extracts. Moreover, the polyphenol content of themethanolic extract of herbaceous plants was significantly correlated withscavenging DPPH radical activity and ferric reducing power .
Deadheading, disbudding, pinching back, heading back, cutting back and thinning are all necessary pruning techniques. These chores will encourage plants to bloom for longer periods of time and improve overall plant appearance and health.
Annual plants will produce many flowers throughout the growing season without much maintenance, while perennial flowering plants only flower for a 2 to 3 week period. However, they will both bloom more profusely over a longer period of time if they are deadheaded regularly. Deadheading is removing old or spent flowers by cutting or pinching flowers off. This practice helps extend the flowering season by stimulating plants to continue flowering. Annual plants must complete their life cycle in one growing season, from seed germination and plant growth to flowering and seed production. Removing flowers from both annuals and perennials before seeds form, at least every five to seven days, will interrupt this natural progression, preventing them from setting seeds, and stimulating the plant to try again and complete the process. Be aware that only specific perennials will rebloom or have a prolonged bloom time when deadheaded and that sometimes the second flush will produce fewer, smaller blooms. Also, allowing a plant to go to seed, or form seeds, will drain energy from it, not only resulting in less flowers, but a decreased growth rate and smaller leaves.
Gardeners who want their plants to produce a limited number of large flowers rather than numerous small ones should disbud their plants. Instead of cutting off mature spent flowers, disbudding is the process of removing young side buds and leaving the one terminal bud. The purpose for this is to direct the plant's energy toward inducing one, or sometimes a few buds, to grow into very large flowers. This technique is often used for flowers entered into contests where flower size is judged such as Common Peonies (Paeonia officinalis) and Carnations (Dianthus caryophyllus), although it may be done in the home garden for a showy effect. Plants should be disbudded when lateral buds are large enough to handle, which is about the size of a pea.
No matter if the plants are started at home or grown by a professional, they should be pinched back. Pinching removes the terminal bud, or the tip of the vegetative shoot, along with the first set of leaves. It is only necessary to use fingers or a fingernail to remove this portion of the stem since it is often soft and fleshy. 041b061a72