NPS, no rights reserved (CC0) · Wikimedia Commons
Platystemon spp.
creamcups
Overview
Platystemon is a genus in the poppy family Papaveraceae represented by the single annual species Platystemon californicus, known as creamcups, native to western North America. Plants are low, soft-hairy annuals 4-12 inches (10-30 cm) tall, branching from the base into a loose mound of slender stems clothed in long, spreading hairs. The narrow, untoothed leaves are mostly opposite or whorled toward the stem base. Each stem ends in a single long-stalked, cup-shaped flower 0.5-1 inch (1.3-2.5 cm) across, with six petals in cream to pale yellow, sometimes tipped or tinged with deeper yellow. Numerous stamens fill the center, and the fruit breaks into separate one-seeded segments at maturity. Flowering occurs in spring after winter rains, often forming sheets of bloom in open grassland. Platystemon grows on open, sandy or gravelly soils in grassland, fields, burns, and disturbed ground, completing its cycle before summer drought. As a cool-season annual it dies after seeding and is grown from fresh seed each year, with no tolerance for hot, dry conditions during growth.
Native Range
Platystemon californicus is native to western North America, from Oregon and California through the Southwest into northern Mexico. It grows in open grassland, fields, sandy flats, and recently burned or disturbed ground.Suggested Uses
Used in wildflower meadows, native plantings, and seasonal containers in mild-winter regions. Sown in drifts for spring color on open, sunny ground before summer heat arrives.How to Identify
Appearance
Size & Dimensions
Height4" - 1'
Width/Spread6" - 1'
Bloom Information
Flowering occurs in spring, mainly March through May, following winter and early-spring rains, with plants blooming over several weeks. In favorable years large stands flower together in open ground. The segmenting fruits ripen and break apart as soils dry.
Detailed Descriptions
Flower Description
Cream to pale yellowFoliage Description
Gray-greenGrowing Conditions
Sun Requirements
Requires 6-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Water & Climate
Water Needs
Care & Maintenance
Care Guide
Platystemon is grown from seed sown in autumn or late winter where plants are to flower, in full sun on light, sandy or gravelly, freely drained soil. It germinates and grows during cool, moist weather and needs regular moisture through flowering, then sets seed and dies as conditions warm. Crowded sowings produce the characteristic sheets of bloom. Rich soil and summer irrigation give lax growth and serve no purpose once flowering ends. Plants self-sow where soil is left open and undisturbed. No feeding is needed on average soils.Pruning
No pruning is required. Spent plants are cleared after they set seed and die back in early summer. Some seed is left to ripen and self-sow for the following year.Container Growing
Suitable for container growing
Minimum container size: 1 gallons
Toxicity: Not assessed
UnknownPlanting Guide
Planting Methods & Timing
Planting Method
direct sow
Direct Sow Timing
Autumn to late winter in mild-winter climates
Days to Maturity
60–120 days
Plant Spacing
4 inches
Companion Planting
Good Companions