Origin and Habitat: Guairá and adjacent areas, Paraguay.
Type locality: Cerro Charará , Guairá, Paraguay.
Altitude range: Around 300 metres above sea level.

• Echinopsis paraguayensis Mundt ex F.Ritter

• Echinopsis oxygona (Link) Zucc. ex Pfeiff.
• Cereus oxygonus (Link) Otto
• Echinocactus oxygonus Link
• Echinonyctanthus oxygonus (Link) Lem.
• Echinopsis multiplex (Pfeiff.) Zucc. ex Pfeiff. & Otto
• Cereus multiplex Pfeiff.
• Echinonyctanthus multiplex Lem.
• Echinopsis paraguayensis Mundt ex F.Ritter
• Echinopsis schwantesii Frič

• Echinopsis oxygona f. monstruosa hort.
• Cereus multiplex var. monstrosus Pfeiff.
• Echinopsis multiplex var. monstrosa Gürke

Description: Echinopsis paraguayensisSN|8384]]SN|8384]] is is a local or morphological form of the widespread and variable Echinopsis oxygonaSN|8376]]SN|8376]]. It was briefly mentioned by Mundt (Monatsschr. Kakteenk. 13: 109. 1903) and described by Friedrich Ritter (Kakteen in Südamerika,Vol. 2, 1979). The key difference by which Echinopsis paraguayensisSN|8384]]SN|8384]] was separated, namely the thinner and longer stems (5-9 cm thick, 20-50 cm long), the very free clumping habit and the reduced number of ribs (8-12), seems entirely spurious. Echinopsis oxygonaSN|8376]]SN|8376]] is quite variable and has received numerous unnecessary names of no botanical value, representing no more than local phenotypes: Echinopsis paraguayensisSN|8384]]SN|8384]] is one of them, but it still has a value for a collector because they identify plants with particular characters.
Stems: Green, 5-9 cm thick, elongated (20-50 cm long), branching profusely from the base.
Rib: 8-12, slightly tuberculated, 1,5-3 cm in height, triangular in cross section, sides sligly convex, separating grooves very close at their base .
Areoles: Nearly orbicular, white woolly, 2-4 mm in diameter, slightly recessed in the rib, 1-2 cm apart.
Spines: Brown or black, becoming grey, variable (depending on specimens).
Marginal ribs: 3-11, 2-25 mm long, more or less acicular.
Central spines: 0-4, 3-30 mm long, thicker, acicular.
Flowers: ca 22 cm long , fragrant. Nectar camber about 5 cm long. Tube funnel-shaped up to 13 cm long with small, narrow pointed scales filled by brown woolly hairs. Inner perianth segments 5 cm long, 2 cm wide, mucronate, white. Outer perianth segments narrower, white with green midrib. stigma-lobes 14, yellow, 1 cm long.
Fruit: Green, 4 cm long, 2 cm thick.
Seeds: Helmet-shaped, dorsally slightly keeled, 1,6 mm long, 1,2 mm wide, 1,0 mm thick, testa opaque with thin tubercules.

Bibliography: Major references and further lectures
1) Friedrich Ritter "Kakteen in Südamerika: Ergebnisse meiner 20jährigen Volume 2, Brasilien / Uruguay / Paraguay", Friedrich Ritter Selbsverlag 1979

Cultivation and Propagation: Echinopsis paraguayensis is extremely resistant to cultivation errors and easily reproduced by offshoots. The only thing that can kill this plant is cold. Nevertheless, it is appropriate to provide adequate growing conditions in order to obtain abundant blooms. It has very large fragrant nocturnal flowers and many plant lovers are willing to take care of it all year for one or a few magical nights with exotic charm.
Growth rate: It is a relatively rapidly growing species that will make large clumps given the best conditions.
Soils: It likes very porous standard cactus mix soil, but it is extremely adaptable to various growing media. Prefer a low pH compost, avoid substrata rich in limestone.
Repotting: This plant needs plenty of space for its roots, repotting should be done every other year or when the it has outgrown its pot. Use pot with good drainage.
Watering: Needs moderate to copious waterings in summer (it is more demanding than other cactus), but do not overwater, keep dry in winter at a minimum temperature of 0°C.
Fertilization: Feed with a high potassium fertilizer in summer.
Hardiness: Reputedly resistant to light frost if kept on the dry side prior to, and during, cold weather (hardy to -2 C ° C, or less for short periods). However warmth throughout the year will increase the grower's success (5°-8° C during rest season).
Exposition: The plant tolerates bright situations which encourages flowering and heavy spine production, but is likely to suffer from sun scorch or stunted growth if over exposed to direct sunlight during the hottest part of the day in summer. It grows well with filtered sunlight or afternoon shade.
Uses: It is an excellent plant for container growing. It look fine in a cold greenhouse and frame or outdoor in a rockery. It is also used as a rootstock for grafting delicate and slow growing cactus species.
Pests & diseases: It may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for:
- Red spiders: Red spiders may be effectively rubbed up by watering the plants from above.
- Mealy bugs: Mealy bugs occasionally develop aerial into the new growth among the wool with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects.
- Scales: Scales are rarely a problem.
- Rot: This species is particularly easy and accommodating, seldom suffer of cryptogamic diseases. Rot it is only a minor problem with Echinopsis if the plants are watered and “aired” correctly.
Propagation: Division of larger clumps, direct sow after last frost. Seeds germinate in 7-14 days at 21-27° C in spring, remove gradually the glass cover as soon the plants will be well rooted (ca 1-2 weeks) and keep ventilated, no full sun for young plants! To make a cutting twist off a branch and permit it to dry out a couple of weeks, lay it on the soil and insert the stem end partially into the soil. Try to keep the cutting somewhat upright so that the roots are able to grow downward.