those grown in containers, which are entirely
dependent on the gardener to keep them
supplied with what they need. on the shelves
of garden centers are masses of products
devoted to the nutrition of plants.
numerous chemical elements are essential for plant growth, and these are divided into macronutrients and micronutrients. some of these the plant is able to source from the air (carbon and oxygen), while the great majority are sourced from the soil. deficiencies in any nutrient often show specific symptoms, and if noticed by the attentive gardener can often be remedied by treating with a specific fertilizer.
Camellias need a special ericaceous feed to provide the specific nutrients they require for healthy growth.
Like most ornamental trees and shrubs, Japanese maples (Acer spp.)
are best fed with a general, balanced fertilizer, as required.
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nitrogen
nitrogen (n) is a major plant nutrient. It is vital to plant growth as it is an essential component of all proteins and chlorophyll. If it is deficient, plants fail to grow strongly. In the soil, it is derived from organic matter, and it becomes slowly available to plant roots as this organic matter is decayed by soil micro- organisms into nitrates and ammonium salts. nitrogen-fixing bacteria living freely in the soil or in root nodules (see chapter 2) are able to shortcut this process by obtaining nitrogen directly from the air.
nitrates and ammonium salts are highly soluble, so available nitrogen is easily washed out of the soil by overwatering or high rainfall. flooding, drought, and low temperatures can also affect the availability of nitrogen. deficiency results in stunted or slow growth and pale, yellowish foliage (chlorosis). sources of nitrogen include well-rotted manure, blood, hoof and horn fertilizers, and ammonium nitrate fertilizers.
Phosphorus
Phosphorus (P) is another major nutrient needed for the conversion of light energy to atP during photosynthesis and is used by numerous enzymes. It is important for cell division and it is commonly associated with healthy root growth. Legumes have a high demand for phosphorus, but requirements vary between plants. Phosphorus deficiency is uncommon on well-cultivated soils as it is fairly immobile in the soil, but slow growth and dull, yellowish foliage are symptoms. sources of phosphorus include rock phosphate, triple super-phosphate, bonemeal, and fish, blood, and bone.
Potassium
Potassium (k) is the third major plant nutrient needed for photosynthesis, controlling water uptake by the roots and reducing water loss from the leaves. as it also promotes flowering and fruiting it is needed by plants that we specifically grow for their flowers and fruit, and it increases general hardiness. deficiency causes yellow fertilizers containing nitrogen will help produce plenty
of green, leafy growth on leaf vegetables, such as spinach.
High-potash feeds will improve the crop of fruiting plants, such as gooseberries.
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I n n e r W o r k I n G s
or purple leaf tints, and poor flowering and fruiting are symptoms. tomato fertilizers are probably the most commonly available potassium-rich feeds; sulfate of potash is another.
sulfur
sulfur (s) is a structural component of many cell proteins and is essential in the manufacture of chloroplasts, making it vital for photosynthesis. Its deficiency is rarely seen, especially in industrialized countries where sulfur dioxide is often rained down onto the soil from the atmosphere. flowers of sulfur can be used to lower the pH of soils (see p. 144).
Calcium
Calcium (Ca) regulates the transport of nutrients between cells and is involved in the activation of certain plant enzymes. Calcium deficiency is rare, resulting in stunted growth and blossom end rot— the softening and blackening of the bottom of the fruit. Its concentration in the soil determines acidity and alkalinity (see chapter 6). It can be added to the soil as chalk, limestone, or gypsum.
Magnesium
Magnesium (Mg) is essential for photosynthesis, and in the transport of phosphates. deficiency results in interveinal chlorosis (yellowing between the leaf veins) and it is aggravated by soil compaction and waterlog- ging. deficiency is often seen on sandy acidic soils. foliar sprays of magnesium sulfate or epsom salts are a useful remedy.
silicon
silicon (si) strengthens cell walls, so improves overall physical strength, health, and productivity. other benefits include improved drought, frost, and pest and disease resistance. Many grasses have a high silicon content, which is thought to be an adaptation to deter grazers. take, for example, the extremely sharp leaf edges
of the pampas grass (Cortaderia selloana); anybody who has cut their hands on these leaves will not be surprised to learn that silicon is also used to make glass.
Micronutrients
Micronutrients, sometimes referred to as trace minerals, are required in much smaller quantities. despite this, they are essential for good growth as they play vital parts in many biochemical activities. They include boron, chlorine, cobalt, copper, iron, manganese, molybdenum, nickel, sodium, and zinc.
B o t a N Y I N a C t I o N typical micronutrient deficiencies include lack of iron, which results in interveinal chlorosis; a shortage of manganese, which may result in coloration abnormalities, such as spots on the foliage; and lack of molybdenum, which can cause twisted growth—often seen in brassicas.
Potassium improves flowering and consequent fruiting in tomatoes.
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C
harles sprague sargent was an american botanist with a particular passion for dendrology— the study of trees. He did not receive any formal botany education or training, but possessed excellent botanical instincts.sargent’s father was a wealthy boston banker and merchant, and sargent grew up on his father’s Holm Lea
estate in brookline, Massachusetts. He went to Harvard College and after graduation enlisted in the Union army, and served during the american Civil War. after the war, he traveled throughout europe for three years.
on his return to america, sargent started his long horticultural career by taking over the manage- ment of the family’s brookline estate, much inspired by Horatio Hollis Hunnewell. Hunnewell was an amateur botanist and one of the most prominent horticulturists in america in the 19th century. With the help of Hunnewell and his unique instruction, Holm Lea estate was converted into a living landscape without geometric designs and flowerbeds, but with a more natural look, including mass plantings of trees and shrubs. It would soon develop a world-class collection of rhododendrons and majestic trees.
sargent concentrated much of his time on developing his arboretum. He worked with frederick Law olmsted, popularly considered to be the father of american landscape architecture, and was heavily involved with every aspect—from the overall master
planning to much smaller details, including selecting which individual trees to plant.
sargent soon became regarded as a leading dendrologist. He started to write about trees and shrubs and was widely published. He also became the linchpin in america’s rhododendron story. His skills and knowledge were sought nationally, especially with regards to the conservation of american forests, particularly the adirondack and Catskill forests in new york state. He was even elected chairman of a commission to help preserve the adirondacks.
In 1872, Harvard University decided to create an arboretum after James arnold left more than $100,000 to Harvard for “the promotion of agricultural or horticultural improvements.” Professor francis Parkman, then Professor of Horticulture at Harvard’s school of agriculture and horticulture, the bussey Institution, suggested that sargent should be heavily involved in its creation.
sargent, along with olmsted, undertook a massive job planning and designing the arboretum, as well as working on the funding to ensure its continuing success. by the end of that year, sargent was appointed the first director of what was named Harvard’s arnold arboretum, a position he held for fifty-four years until he died. during that time, it grew from the original 120 acres (50 ha) to 250
C h a r l e s S p r agu e S a r g e n t
1 8 4 1 – 1 9 2 7
Charles sargent published several works of botany and the abbreviation sarg. is attributed to plants he described.
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acres (100 ha). sargent also continued his own research and writing.
besides collecting plants and specimens, sargent also amassed a large collection of books and journals for the arnold arboretum Library. The collection grew from nothing to more than 40,000 books during his time. Most of these were purchased at sargent’s expense and by the time of his death he had donated his entire library to the arboretum as well as providing finance for the upkeep of the collection and the purchase of further materials.
Later he became Professor of arboriculture at Harvard. He was also appointed director of the botanic Garden in Cambridge, Massachusetts, a garden that has long since disappeared.
He regularly wrote about his passion for trees and published several works of botany. In 1888 he became editor and general manager of Garden and Forest, a weekly journal of horticulture and forestry. His publications include: Catalog of the Forest Trees of North America; Reports on the Forests of North America; The Woods of the United States, with an Account of their Structure, Qualities, and Uses; and the twelve-volume The Silva of North America.
after his death, Massachusetts Governor fuller commented: “Professor sargent knew more about trees than any other living person. It would be hard to find anyone who did more to protect trees from the vandalism of those who do not appreciate the contribution that they make to the beauty and wealth of our nation.”
Rhododendron ciliatum, rhododendron
Charles sargent amassed a world-class collection of rhododendrons at his Holm Lea estate and was important in establishing nonnative rhododendrons in america.
Picea sitchensis, sitka spruce
Charles sargent was famous for his work with trees and was instrumental in setting up the arnold arboretum.
sadly, after sargent’s death, his large plant collection had to be sold and was broken up and bought by individual
plant collectors and breeders. Plants named after him include Cupressus sargentii, Hydrangea
aspera subsp. sargentiana, Magnolia sargentiana, Sorbus sargentiana, Spiraea sargentiana,
and Viburnum sargentii. The standard author abbreviation sarg. is used to indicate him as the author
when citing botanical names of plants.
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b o t a n y f o r G a r d e n e r s