Pediocactus

Pediocactus (Greek: πεδίον (pedion) means "plain", "flat", "field") is a genus of cacti. The genus comprises between 6 and 11 species, depending upon the authority. Species of this genus are referred to as hedgehog cacti, though that name is also applied to plants from the genera Echinocereus and Echinopsis.^[1]

Synonyms

The genus has 3 synonyms:

• Navajoa Croizat
• Pilocanthus B.W.Benson & Backeb.
• Utahia Britton & Rose

Cultivation

Pediocactus are very difficult to maintain in cultivation unless they are grown grafted. Plants in this genus are cold adapted and have strict requirements for winter dormancy and temperature when grown on their own roots and are very fussy about soil composition. Pediocactus have a tendency to rot and lose their roots in cultivation and should never be grown in any type of organic soil. Plants in this genus require mineral based soils which are about ¹/₂ sand mixed with small diameter (¹/₄ to ¹/₂ inch / 6 mm to 12 mm) quartzite type rock in about equal volumes. In habitat, Pediocactus typically grow in dry, open areas receiving full sun on slopes and hillsides in mineral based, rocky soils and which experience deep cold for about 4 months of the year. Plants of this genus like to have their roots constrained to bloom well and the addition of small diameter quartzite helps to constrain the plants roots.

During the late fall Pediocactus will push water out of the plant body and through the roots back into the soil and shrink dramatically in size in preparation for winter and freezing temperatures. This is normal for all plants in this genus. It is vital this process not be interrupted. Subjecting the plants to high temperatures and watering during this period will usually result in the plants rotting or losing their roots. Plants which are allowed to freeze and enter dormancy respond in spring by producing healthy, robust growth and vigorous blooming.

Several of the Pediocactus species produce spectacular floral displays, and in particular, the offsetting varieties of P. simpsonii when grown on their own roots. Flower colors range from pink and magenta (most common), salmon, yellow, and rarely a white flowered form of P. simpsonsii. Both P. despanii and P. winklerii grow in very arid and cold desert areas and must be sparingly watered in the summer and grow more slowly than P. simpsonii. P. winklerii grows only in a very narrow band of elevation in the Castle Dale, Utah region with another population near Crescent Junction, Utah, and a third near Goblin Valley, Utah. P. despanii is only found along the slopes of the Price River south of Price, Utah with very limited populations. P. simpsonii is more water tolerant and widespread than most other Pediocactus species.

The key to growing Pediocactus successfully on their own roots depends on adherence to the following factors. The easiest approach in latitudes where it gets cold in the winter is to simply maintain the plants out of doors where they typically thrive:

• Soil - Soil must drain quickly and have a lot of surface area exposed to the air. Soil must be mineral based with no limestone cut with about ¹/₂ sand and then cut again with an equal amount of small diameter quartzite rock. Shallow wide clay pots are ideal for Pediocactus.
• Dormancy - In winter Pediocactus require at least two months with temperatures below 25 °F / -4 °C at night to complete dormancy and bloom profusely. Plants which are not subjected to deep cold produce weak, feeble growth, fail to bloom, and will collapse and rot when subjected to stress. In areas with cold winters, simply putting the plants somewhere dry with bright light where they will freeze is ideal. In summer Pediocactus have a very distinct secondary dormant period from about mid-June to mid-September when they need no water, just occasional light soil moisturizing (once a month) preferably when the weather is not too hot.
• Air Movement - Pediocactus will languish inside of a home environment and eventually rot unless grown grafted. Pediocactus experience constant air movement in habitat, and are best grown out of doors under the eaves of a house or porch to protect them from rain and excess watering.
• Light - Low light conditions will result in Pediocactus becoming infected with orange spot fungus and rotting then collapsing. Plants of this genus need bright light and preferably full sunlight.
• Pests - When grown indoors, Pediocactus can be attacked by spider mites. Spider mite damage which is only bothersome to some indoor plants is often fatal to Pediocactus and results in fungal infections (orange rot), which weaken then kill the plants. Mealybugs are another major threat.
• Watering - Watering P. despanii or P. winklerii during periods of high summer temperatures (over 90 °F / 32 °C) typically results in the plants rotting and collapsing. These species need to be watered sparingly in the summer when temperatures are high. This is generally true of most Pediocactus species but P. simpsonii is more tolerant of over watering than most of the other species in this genus. Pediocactus can take abundant water without harm when the temperatures are cool in the late winter to early spring, and can survive months buried under snowdrifts growing in saturated frozen soil. Providing Pediocactus water when the temperature is over 100 °F / 38 °C is likely to result in the plants rotting unless they have enough air movement to completely dry within a day or so.

Pediocactus seeds germinate easily and are benefited by cold stratification but the seedlings need bright light or they become spindly. The best method is to fill shallow trays of moist Pediocactus soil mix (described above) and place outside with a window screen over the trays in a protected area in the fall and allow to over winter. Some seedlings will germinate in the fall and a larger number the following spring. Keep the soil moist through the winter and spring. In the spring move the trays into direct sunlight and water heavily until summer, but allow the soil to dry completely between waterings.

References

1. ^ "Echinopsis (Hedgehog Cacti)". Cactus and Succulent Sosiety of Australia. Archived from the original on 2008-07-20. http://web.archive.org/web/20080720010527/http://cssaustralia.org.au/content/view/72/104/. Retrieved 2008-07-29.