Detailed Explanation of Cultivation Methods and Care Techniques for Nuphar

Nuphar, also known as golden lotus or Nuphar lotus, is a plant in the genus Nuphar of the family Nymphaeaceae. The genus contains about 25 species, with 4-5 species found in China. Nuphar blooms in early summer, with golden-yellow flowers rising above the water surface, brilliant as golden sunlight spread across the water, set off by shimmering ripples and fluttering butterflies - extremely beautiful. It is an extremely important ornamental plant in summer waterscape gardens. Its Latin species name pumilum means “dwarf”.

Main species in the same genus include: Nuphar bornetii Levl. et Vant. Nuphar sinensis Hand.-Mazz. Nuphar luteum Sm. Nuphar shimadai Hayata et Shimada.

(1) Morphological Characteristics

Nuphar is a perennial floating-leaved aquatic herbaceous plant. The rhizome is thick and block-like, lying horizontally. Leaves are dimorphic; floating leaves are papery or nearly leathery, round to ovate, 8-17 cm long, entire, with a deeply cordate base. The leaf surface is green and glossy, the underside is convex with soft hairs. Lateral veins are fine, with several dichotomous branches; the petiole is cylindrical. Submerged leaves are thin and soft. Flowers are solitary; the cylindrical peduncle rises above the water surface; flower buds are spherical and green. There are 5 sepals, obovate to cuneate, yellow, petal-like. There are 10-20 petals, narrowly cuneate, resembling sterile stamens, deciduous; stamens are numerous, borne on the receptacle at the base of the ovary inside the petals, deciduous. There are 12-15 carpels, fused into a superior ovary, with distinct carpel boundaries, each terminating in a stigma, making the stigma of the pistil radiate in a disc shape. The number of ovary chambers equals the number of carpels; ovules are numerous, borne on the septa. The berry is ovoid, 3 cm long, with persistent sepals, irregularly dehiscent. Seeds are oblong, yellow-brown, glossy. Flowering period is May-July, fruiting period is July-September.

Cultivation and Care Techniques for Nuphar

Nuphar Nuphar

Nuphar, also known as golden lotus or Nuphar lotus, is a plant in the genus Nuphar of the family Nymphaeaceae. The genus contains about 25 species, with 4-5 species in China. Nuphar blooms in early summer, with golden-yellow flowers rising above the water surface, brilliant as golden sunlight spread across the water, set off by shimmering ripples and fluttering butterflies - extremely beautiful. It is an extremely important ornamental plant in summer waterscape gardens. Its Latin species name pumilum means "dwarf". Nuphar is a perennial aquatic herb; the rhizome is thick and lies horizontally. Leaves are floating, ovate or broadly ovate, 6-17 cm long, 6-12 cm wide, with a deeply cordate base, with a sinus forming 2 distant rounded-obtuse lobes, glossy above, densely pubescent below, lateral veins pinnately arranged, branching dichotomously several times; petiole pubescent. Flowers are solitary at the tip of the peduncle, floating on the water surface, 3-4 cm in diameter; 5 sepals, leathery, yellow, petal-like; petals numerous, narrowly cuneate; stamens numerous; ovary superior, stigma disc-shaped, usually shallowly 10-lobed. Berry ovoid, 3 cm long, irregularly dehiscent, with persistent sepals and stigma.

Introduction to Nuphar

Nuphar is related to water lilies, with leaves that float nearly round on the water surface, with a V-shaped notch at the base. It was originally placed in the genus Nymphaea along with water lilies; however, Nuphar has a superior ovary and seeds without an aril, which differs greatly from the genus Nymphaea with its semi-inferior ovary and seeds with an aril. Nuphar flowers are much smaller than water lilies and lack the many beautiful floral structures, yet when a large patch of Nuphar's yellow flowers bloom in the water, it has its own attractive appeal. Because its fruit is shaped like a wine jug, it is called Brandy Bottle. Nuphar shimadai was collected by Japanese botanist Y. Shimada in 1915 in Xinpu, Hsinchu County, and described as a new species by Japanese botanist B. Hayata in 1916 in Icones Plantarum Formosanarum; the species name shimadai commemorates its collector Shimada. The type specimen (Isotype) is still preserved in the herbarium of the Taiwan Forestry Research Institute. This plant is characterized by nearly round leaves and many hairs on the leaf underside, though these are not easily seen with the naked eye and require a dissecting microscope to observe clearly. Additionally, the stigma tip is divided, with red on both sides of each lobe, making Nuphar shimadai more ornamental compared to other species of Nuphar.

Floral Characteristics

The most prominent outer part is the sepals, which are often green or dark red on the outside. The next whorl inward is the petals, which are very inconspicuous and closely resemble the stamens, making them hard to distinguish without careful observation. Further inward are the numerous stamens with prominent anthers that can be clearly distinguished from the petals. At the center is the pistil, whose stigma at the tip spreads out to form a plate-like shape. In some species the stigmas are completely fused, while Nuphar shimadai has stigmas divided into 6-10 lobes; the area below the stigma down to the ovary narrows like a bottleneck, though some species do not have this feature.

Nuphar is the only genus in Nymphaeaceae without tropical species, and the distribution of Nuphar shimadai represents the southern limit of the genus Nuphar's worldwide distribution. Early classifications of the genus Nuphar ranged from seven to twenty-five species, showing that this genus is quite troublesome within Nymphaeaceae and difficult to distinguish taxonomically. However, recent research may bring some adjustments; broadly, it can be divided into two sections: sect. Nuphar, distributed in the Old World (species of the Eurasian region), and sect. Astylus, distributed in the New World (species of the Americas). They can be distinguished by the structure of flowers and fruits: sect. Nuphar has five sepals, anther length approximately half or slightly less than the filament, and jug-shaped fruit with a narrowed neck; sect. Astylus has 6-12 sepals, anther length approximately 1-2 times the filament length, and ovoid fruit without an obvious neck. Based on various characteristics, Nuphar shimadai belongs without question to the Old World sect. Nuphar, though the author believes it may warrant subspecific or varietal status. Regarding the genus Nuphar, from the past recognition of seven to twenty-some species, many have now been merged or reduced to subspecies rank. The author examined some literature from Japan and the mainland and found that some species indeed share many similarities with Nuphar shimadai; furthermore, regarding aquatic plants, most are widely distributed species worldwide. Given Taiwan's geological age and geographical position, the likelihood of forming an endemic aquatic species is relatively low. Nuphar shimadai may have spread from the nearby mainland or Japan, and after a period of isolation formed the currently unique plant of Taiwan. However, lacking further data, the taxonomic status of Nuphar shimadai still requires more research before a conclusion can be drawn.

Plant Characteristics

Nuphar consists mainly of floating leaves, with a few submerged leaves in the water; submerged leaves are smaller and thin, with wavy margins; floating leaves are nearly round, about 10-12 cm long and 7-10 cm wide, with many short hairs on the lower surface; the petiole is triangular in cross-section, with a broad wing-like base, described in the Flora of China as having a swollen petiole base. The peduncle is round, with long white soft hairs; five sepals, about 1.6 cm long and 0.8-1.2 cm wide; 10 petals, linear, yellow, about 5-6 mm long and 1.5-2 mm wide; about 30 stamens, yellow, anthers about 3 mm long, filaments about 7 mm long; stigma flattened at the tip into a disc shape, 6-10 lobed, red. Fruit jug-shaped, about 2 cm long and 1.5 cm wide. Seeds ovoid, grass-green, like small mung beans, about 3-4 mm long and about 2 mm wide.

Perhaps you have never carefully examined the roots of Nuphar shimadai; the part that runs horizontally in the mud is the underground stem, with a diameter reaching 2 cm; the mature underground stem is white, about 3 cm in diameter, with obvious leaf scars remaining after leaves fall. Nuphar shimadai can continuously spread its colony, and its appearance resembles a spine, so the Japanese call it "kotsu" (river bone). Adventitious roots growing from the underground stem emerge in groups of two or three, a situation that also occurs in some species of the genus Nymphaea.

Comparison of Nuphar and Water Lily

Compared to water lilies, most people are less familiar with "Nuphar shimadai," for no other reason than that Nuphar shimadai was already relatively rare in Taiwan and is currently only distributed in a few ponds in Longtan, Taoyuan. Although there are collection records from Taoyuan, Hsinchu and Nantou in western Taiwan, the lack of more detailed information makes it difficult today to understand the past distribution and abundance of this plant. However, it can be imagined that Nuphar shimadai currently grows on private land, and people's land-use habits tend to favor converting farmland to building land for higher land prices. Facing the current situation of batches of farmland being converted to building land, some landowners resent it because it is a rare plant on the brink of extinction, adding a variable to future land development and use. The author once went to the Longtan area to look for other aquatic plants, but was stopped on the road by a local landowner who would not let me and my friend pass, speaking in a threatening tone. From this gentleman's tone, it was not hard to tell that he was referring to Nuphar shimadai. "Irrigation ponds" were once an important factor for Nuphar shimadai's survival in Taiwan, but today, with the irrigation function of these ponds lost, the fate of Nuphar shimadai hangs in the balance. Perhaps in the future we will only be able to see it in botanical gardens or in the ponds or water basins of specific aquatic plant enthusiasts.

Growth Habits of Nuphar

It prefers to grow in warm, humid environments with abundant sunlight.

It is not demanding about soil, preferring fertile soil that is slightly clayey. It is suitable for growing in water 30-60 cm deep, with a maximum depth not exceeding 1 m. The suitable growth temperature is 15-32°C; growth stops when the temperature drops below 12°C.

It is tolerant of low temperatures; south of the Yangtze River, it can overwinter in outdoor pools without cold protection; in the north, it needs protection to overwinter in winter, and the dormancy temperature should be maintained at 0-5°C.

Propagation Characteristics

In addition to the underground stem continuously producing new buds and shoots through vegetative reproduction, seeds play an even more important role in reproduction and dispersal. After the fruit matures and splits open, it reveals a white endocarp, within which the seeds are enclosed. This white endocarp is spongy and slightly sticky, which helps the seeds float on the water surface for a period of time before finally being completely released and sinking to the bottom. Seeds can germinate under appropriate temperatures without dormancy issues. Seeds are an important mechanism for the dispersal of Nuphar, while the underground stem is its most advantageous means of expanding territory and colonizing after reaching a new location.

Cultivation Methods for Nuphar

Sexual propagation: Seeds harvested and stored from the previous year are artificially germinated in the following spring. The sowing soil is clean mud with a pH between 6.5-7.0. Add fertilizer (decomposed sesame cake, bean cake, etc. are all suitable) and mix evenly. After soaking in water for 3-5 days (preferably spreading a layer of sand on the soil surface), add water to a depth of 3-5 cm. After the water has settled clear, scatter the pre-germinated seeds in it. Add water and change water promptly according to seedling growth conditions, until the seedlings grow small coin leaves (floating leaves) before transplanting.

When transplanting, use a row spacing of 10 cm and a plant spacing of 15-20 cm, and strengthen management during the seedling stage. Wait until the plants have grown to 4-6 floating leaves (over 8 cm wide) before planting in a permanent position. The planting method is one plant per tank (1 plant/sq m). If planting in a large ornamental area with fertile soil, plant at 1 plant per 2 m. The storage temperature for Nuphar seeds is best at 3-5°C, with a germination rate of over 80% the following year.

Asexual propagation: Asexual propagation is by underground stem propagation and division propagation. Propagation is carried out in March-April, cutting tubers with a main bud into 6-8 cm lengths, and lateral buds into 3-4 cm lengths, as propagation material. Division propagation is carried out in May-June, cutting tubers with a main bud into 6-8 cm lengths, then removing yellow leaves and some old leaves, retaining some adventitious roots for planting. The divided plants quickly enter the growth phase under conditions of adequate nutrition, and can bloom and set seed in the same year.

Tissue Culture

Materials and Methods

Materials and sterilization: In May, dig up Nuphar growing vigorously in the shallow water area of a pond, wash the entire plant repeatedly with tap water until clean, place the roots in 0.001% HgCl2 solution for preliminary sterilization for 48 h, then cut off the tender rhizomes, place them in a 500 ml ground-glass wide-mouth bottle, rinse with tap water for about 40 min, then shake-wash with 0.05% Amway detergent for 15 min, and transfer to a laminar flow hood for operation. Wash the treated tender rhizomes with sterile water until no foam remains, add 70% ethanol for sterilization for about 20 s, quickly shake-wash with sterile water 2 times, then shake-sterilize with 0.05% HgCl2 solution for 5 min, pour off the sterilizing solution, then pour in 0.025% HgCl2 solution, continue shake-sterilizing for 15 min, and finally wash with sterile water 5 times. Under sterile conditions, cut the sterilized tender rhizomes into 0.2-0.3 cm rhizome pieces, inoculate onto the corresponding solid medium, and culture and observe.

Culture Conditions

Using 1/2MS and 1/3MS as basic media, supplemented with different concentrations of cytokinins and auxins. When using 1/2MS as the basic medium, add 15 g/L sucrose; when using 1/3MS as the basic medium, add 10 g/L sucrose. The solid medium has a gel strength of 160 g/L, pH 5.8-6.0, culture temperature 18-26°C, light period about 12 h, light intensity 2000-3000 lx.

Results and Analysis

Effect of different concentrations of hormones on callus induction: On a laminar flow hood, inoculate sterile tender rhizome pieces of Nuphar into Erlenmeyer flasks containing MS as the basic medium supplemented with different concentrations of BA, 2,4-D, and IAA for callus induction culture. Inoculate 100 pieces per medium type, 10 pieces per Erlenmeyer flask. Observe and record after inoculation and culture. From Table 1, it can be seen that on medium without the hormone 2,4-D, callus cannot be induced from tender rhizomes; when different concentrations of BA are used in combination with 2,4-D at a concentration of 1.2 mg/L (units omitted hereafter), callus is induced from tender rhizomes to varying degrees, but the callus induction rate, growth rate and external morphology differ greatly among different BA concentrations. When BA at concentrations of 0.4 and 0.8 is used in combination with 2,4-D at concentration 1.2, not only does the callus induction rate reach over 97%, but the callus growth rate is fast, with a relatively loose texture and a light green granular appearance. This callus is callus with differentiation ability. Inoculate the above-induced callus onto the same medium and carry out subculture under unchanged culture conditions. Record the time required for each subculture generation. Continuous culture for 8 generations shows that the callus induced and formed on this medium, when continuously subcultured on the same medium, not only retains the ability to differentiate and form callus, but the callus culture cycle is shortened to 45 d, with a multiplication coefficient of 36 per subculture cycle. This indicates that MS + BA 0.4-0.8 + 2,4-D 1.2 is the ideal medium for inducing differentiation-competent callus from tender rhizomes of Nuphar.

Cultivation Management

(1) Temperature: Temperature has an extremely important relationship with the growth and development of Nuphar. The average temperature in Wuhan from April to July is 16.5-21.7°C, which is most suitable for seedling cultivation during the seedling stage; when the average temperature in August exceeds 29°C, it has a certain impact on the growth and development of the plant; when the temperature remains at 38°C for a long time, the plant stops growing or grows extremely slowly; when the temperature is above 42°C and the ground surface temperature is 53°C, the water temperature rises accordingly, causing leaf rot, and in severe cases causing plant death. Therefore, during this period, water flow must be maintained. The most suitable temperature for Nuphar plants: monthly average temperature range of 16.5-24-29-13°C. When the daily average temperature (late November or early December) is about 10°C, the plant stops growing.

(2) Light: Light has little effect on the growth and development of Nuphar. It can grow normally under the light conditions of Wuhan.

(3) Soil: Nuphar plants are not very strict about soil pH requirements, and can grow and develop normally under pH=5.5-7.5. However, fertility has a close relationship with it: fertile soil means more flowers, brilliant colors, a long flowering period, vigorous overall plant growth, and a long ornamental period; otherwise, it loses ornamental value.

(4) Selection of tanks and pools: We chose planting conditions with tank height 65 cm, tank inner diameter 65-80 cm, pool inner diameter 1x1 m or 2x2 m, and depth 60 cm.

(5) Pest and disease control: To control Spirogyra (algae), copper sulfate can be sprayed into the water; the concentration for spraying during the seedling stage is 3-5 mg/L, and 30-50 mg/L during the mature plant stage. For aphids, 1000-1200 times dilution of trichlorfon, dichlorvos, or 50% dimethoate emulsifiable concentrate at 2000 times dilution can all achieve insecticidal effects. For pests such as the tobacco cutworm, 1000-1500 times dilution of decamethrin sprayed on the leaf surface can achieve insecticidal effects. For snails, tea cake, quicklime, and yellow ginger powder can all achieve insecticidal effects. There is also the field management method, which is to continuously remove Spirogyra and weeds.

Construction and Planting

Select an environment with deep, loose and fertile subsoil and abundant sunlight for construction and planting. The construction methods for Nuphar are divided into direct planting and imported soil bag planting. Nuphar's rhizomes and petioles are slender; to improve survival rate, whole-plant transplanting is often carried out.

The direct planting method is suitable for construction environments with water depth below 80 cm and superior construction conditions. During construction, simply plant the Nuphar rhizomes directly into the soil layer. Nuphar has strong adaptability; when planted during the growing season, it generally recovers growth within 10 days after planting and can bloom in about 25 days.

For construction areas where the subsoil is too loose or too shallow for direct planting, or where the water level is too deep and fluctuates greatly, the imported soil bag planting method is often used for construction and planting. Imported soil bag planting uses non-woven bags or vegetation bags as carriers, with fertile loam or pond mud as substrate, tying the base of the Nuphar rhizome tightly inside the bag with the apical bud exposed. Place into the water area of the construction site according to construction requirements. The roots of Nuphar planted in imported soil bags can penetrate the bag body and take root in the subsoil layer; therefore, the survival rate after planting is higher than direct planting.

When growing Nuphar as a waterscape potted plant, use pond mud or decomposed organic matter mixed with garden soil as the cultivation substrate. After planting, place in a shallow water area for maintenance, and after growth recovers, move to the landscape area for routine care and management, which is extensive.

Pest and Disease Control

During the growth period, Nuphar often experiences large outbreaks of aphids, which can be controlled by spraying 1000-1200 times dilution of trichlorfon, dichlorvos, or 50% dimethoate emulsifiable concentrate at 200 times dilution. Snails can be controlled with tea cake, carbofuran, and quicklime.