Annual
Moss Rose
Portulaca grandiflora · Portulacaceae
Also called: Portulaca, Sun Rose, Rose Moss, Eleven O'Clock
Moss Rose (Portulaca grandiflora) is a very low-water annual well suited to Tucson and the low desert. It thrives in full sun, with a fast growth rate.
Moss Rose at a glance
- Water use
- Very Low (established)
- Sun
- Full sun; flowers only open in bright sun and close in shade/evening. Needs Tucson's intense sun to bloom well.
- Mature size
- 4-8 in tall, 6-12 in wide (low, spreading/trailing mat)
- Growth rate
- Fast
- Bloom
- Bright magenta, pink, red, orange, yellow, white (single or double, rose-like), Late spring through fall; profuse bloom through the hottest summer months. Flowers open midday in sun.
- Cold hardiness
- Frost-sensitive (USDA 9a-9b); tender warm-season annual killed by frost but extremely heat- and sun-loving.
- Soil
- Sandy, gritty, fast-draining soil is ideal; tolerates poor, rocky, alkaline desert soils. Sharp drainage prevents rot.
- Native range
- South America (Argentina, Brazil, Uruguay)
- Best used as
- Hot, dry color beds, Containers and hanging baskets, Edging and rock gardens, Groundcover in sunny spots, Reflected-heat areas where other plants struggle
- Wildlife
- Attracts bees and some butterflies when flowers are open in midday sun.
- Toxicity
- Considered toxic if ingested in quantity (contains soluble oxalates / oxalic acid); can cause digestive upset in pets and people. Keep children and pets from grazing on it.
How to grow Moss Rose in Tucson & the low desert
Watering
Highly drought- and heat-tolerant succulent annual; water once a week or less once established, allowing soil to dry between waterings. Overwatering causes rot. Warm-season annual in Tucson: plant after last frost (Mar-Apr) when soil is warm; excellent through summer heat and monsoon if drainage is good.
Fertilizer & nutrients
Very light feeder. A small amount of balanced fertilizer at planting is sufficient; too much produces foliage instead of flowers. Lean soil is preferred.
Pruning & care
No real pruning needed; pinch tips for fuller plants. Self-cleaning, so deadheading is largely unnecessary.
Notes
An ideal annual for Tucson's hottest, driest, full-sun spots and reflected-heat areas. Succulent leaves store water, making it one of the most drought-tolerant bedding annuals. Flowers close on cloudy days and in late afternoon.
Sources: University of Arizona Cooperative Extension (Pima County Master Gardeners); AMWUA low-desert plant lists; ASPCA Toxic Plant List (Portulaca)