Ipomoea nil
Japanese morning glory
Tropical Asia and the Americas; original range disputed
Overview
Ipomoea nil is an annual twining vine climbing 6-15 feet (1.8-4.5 m) in a single season, with stems covered in stiff downward-pointing hairs. Leaves are broadly ovate to circular in outline, 3-6 inches (8-15 cm) long, usually cut into three lobes with a heart-shaped base, and hairy on both surfaces. Funnel-shaped flowers 2-4 inches (5-10 cm) across open from a twisted bud between 4 and 6 a.m. and close by late morning, earlier on hot days. Corolla colour runs blue, purple, magenta, pink, red, or white with a paler tube; cultivated forms carry white picotee margins, radial white stripes, and doubled or fringed petals. Sepals are narrow, 0.6-1 inch (1.5-2.5 cm) long, taper to a slender point, and are densely hairy in the lower third. Flowering runs from July until the first frost, with each vine opening 3 to 10 flowers daily at peak. Capsules 0.3-0.4 inch (8-10 mm) across split to release four to six black seeds. Vines need support within 2-3 weeks of germination and twine only around objects under 1 inch (2.5 cm) in diameter. Seeds contain ergoline alkaloids and cause vomiting, cramping, and disorientation if eaten.
Native Range
The native range of Ipomoea nil is not settled. The species occurs as a long-established weed of cultivation across tropical Asia, Africa, and the Americas, and morphological and molecular work points to a Mesoamerican origin followed by early dispersal to Asia. It reached Japan by the 8th or 9th century as a medicinal plant imported from China, and Edo-period breeding there produced several thousand named forms. It now grows on disturbed ground, field margins, and riverbanks from sea level to 5,900 feet (1,800 m) across the subtropics.Suggested Uses
Grown on trellises, fences, netting, and arbours at 6-12 inch (15-30 cm) spacing for a seasonal screen 6-15 feet (1.8-4.5 m) tall. Container culture uses pots of 5 gallons (19 L) or larger with a trellis, where vines reach 4-8 feet (1.2-2.4 m). Self-seeding produces 30 to 80 volunteer seedlings per plant in zones 7-11, and the species is listed as a weed of row crops in the southern United States and parts of Australia.How to Identify
Appearance
Size & Dimensions
Height6' - 15'
Width/Spread3' - 6'
Bloom Information
Flowering begins 60-90 days after sowing, from early July in zones 5-7 and from late June in zones 8-10, and continues until the first frost. Individual flowers open before dawn and close within 4-6 hours, and each vine carries 3 to 10 open flowers per day at peak. Overcast, cool days extend the open period to mid-afternoon. Flower numbers fall once capsules set in quantity, and vines carrying mature seed open 40-60% fewer flowers than vines cleared of developing capsules.
Detailed Descriptions
Flower Description
blue, purple, magenta, pink, red, or whiteFoliage Description
mid 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
Seeds germinate in 5-10 days at 70-85F (21-29C) after the coat is nicked or soaked 12-24 hours, and seedlings transplant poorly once the first true leaves expand. Plants take 1 inch (25 mm) of water weekly and wilt within 2-3 days of surface drying, recovering overnight without lasting damage. Soil of low to moderate fertility carries more flowers; nitrogen above 0.05 pound per 100 square feet (25 g per 10 square metres) pushes stem and leaf growth and delays flowering by 2-3 weeks. Support of netting, string, or wire under 1 inch (2.5 cm) across is set in place at planting, since stems will not twine around posts or trunks of greater girth. Leaf miners, spider mites, and rust occur in hot dry positions, and Ipomoea spp. is a host of sweet potato weevil in the southern United States. Frost at 32F (0C) kills the vine outright.Pruning
Pinching the growing tip above the third or fourth leaf produces two to four lateral stems and a denser screen, at the cost of delaying first bloom by 7-14 days. Stems that outgrow their support are cut back to a leaf node at any point in the season and regrow within 10-14 days. Removing developing capsules through August and September holds daily flower counts near peak and limits self-seeding. The whole vine is cut at ground level after frost, and roots are lifted in zones 9-11 where stems resprout.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
summer
Container Growing
✓ Suitable for container growing
Minimum container size: 5 gallons
⚠️ Toxicity Warning
Toxic to pets and humansPlanting Guide
Planting Methods & Timing
Planting Method
both
Indoor Start
4 weeks before last frost
Direct Sow Timing
After the last frost date, once soil reaches 65F (18C)
Days to Maturity
60–90 days
Plant Spacing
12 inches