WateringTimesWatering plan, $19
Thunbergia alata, WUCOLS IV

How often to water black-eyed Susan vine in California

In July on the north-central coast, established black-eyed Susan vine in loam needs a deep watering about every 13 days: about 2.2 gallons each time for a plant 2 feet across, about 1.1 gallons a week. Black-eyed Susan vine is a twining tropical vine with soft, heart-shaped leaves and orange to yellow flowers with dark throats. It is unrelated to the black-eyed Susan daisy. Because it is frost tender, it is often grown as an annual and replaced each year. It flowers from summer through fall, with the best show after the hottest weeks.

VineRated for 5 of 6 zones

How often to water black-eyed Susan vine, month by month

Your city
Plant width
2 ft
Your soil

Type your city above and the days between waterings and the gallons appear here, worked out from your city's climate table. Or read the figures by climate zone further down.

Every month, on your water days. The personal plan prints this for black-eyed Susan vine and the rest of your yard, on the days your water supplier allows.Get the plan for $19

How this is worked out: established roots fill the top 1.5 feet of soil, and you water again when that soil has dried halfway. Loam soil holds about 1.5 inches of water per foot. Water the whole area the plant covers, and skip a watering after a good soaking rain.

Which soil do you have?

Dig down a few inches, take a handful of moist soil and squeeze it.

  • Sandy: gritty, falls apart when you open your hand, will not form a ball.
  • Loam: forms a soft ball that crumbles when you poke it.
  • Clay: forms a firm, sticky ball and squeezes out into a ribbon between thumb and finger.

Still not sure? Pick loam. Most garden beds sit between sand and clay.

How to measure plant width

A shrub with its width marked from one side to the other and the circle under it shaded blue

Measure across the plant, from the tips of the leaves on one side to the tips on the other.

Water the whole area the plant covers, shown in blue. The gallons here cover that area.

A wider plant means more gallons each watering, not more waterings. While it is young, measure again each spring.

How to tell it needs water

  • Soil dry an inch or two down around the base means black-eyed Susan vine is ready for a drink
  • Soft leaves that wilt in the afternoon and are still limp by evening point to a dry root zone
  • Few flowers during the hottest part of summer are normal, since blooms pick up as heat eases
  • Yellowing lower leaves over soggy soil suggest the roots are staying too wet
  • Fine webbing and speckled leaves on plants kept indoors point to spider mites

How to water it

  • Water black-eyed Susan vine at the base of the stems rather than over the leaves
  • Moisten the soil 6 to 8 inches deep, then let the top inch dry before watering again
  • Plant in rich, well-drained soil with full sun and some afternoon shade
  • Mulch around the base with compost to keep the root zone evenly moist
  • Widen the watered area as new stems and self-sown seedlings fill in around the trellis

Through the seasons

Water new plants or seedlings often enough to keep the soil lightly moist until they start climbing. Established vines need regular checks from late spring through fall, while they grow and flower. Bloom runs from summer into fall, and flowering often improves once the hottest weeks pass. Frost ends the season in most gardens, and many people simply replant each spring. WUCOLS rates black-eyed Susan vine moderate water on the north-central coast, on the south coast and in South Inland. It carries the same moderate water rating in the high desert and the low desert. WUCOLS marks it as not suited to the Central Valley.

In pots

Black-eyed Susan vine is a classic for hanging baskets and for pots with a small trellis. Containers dry fast, so check the mix daily in summer heat and water when the top inch is dry. Soak until water drips from the bottom, then empty any saucer. A basket in full afternoon sun may need water more than once on hot days. Before frost, move a potted plant indoors to a bright spot, and watch it for spider mites there.

1 Your climate zone six WUCOLS zones, each from its own reference city
Not ratedWUCOLS does not rate Black-Eyed Susan Vine for the Central Valley zone
A year
no figure
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses

WUCOLS lists Black-Eyed Susan Vine as not suited to this region for the Central Valley zone, so no monthly figure is computed here.

Monthly water need by climate zone

Black-Eyed Susan Vine: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.37–0.780.780.740.78
Feb0.53–0.810.870.930.93
Mar0.87–1.151.31.461.52
Apr1.18–1.41.611.891.95
May1.46–1.611.952.392.45
Jun1.61–1.742.292.852.79
Jul1.61–1.982.513.042.85
Aug1.49–1.862.332.792.6
Sep1.24–1.491.862.142.08
Oct0.87–1.151.331.461.49
Nov0.47–0.840.90.930.96
Dec0.31–0.650.680.650.68
Year12–15.518.4121.2721.08

How this is worked out: the WUCOLS water rating for each zone times that zone’s climate for the month. A dash means WUCOLS does not rate the plant there. The figures are what the plant uses, before sprinkler losses.

Plants with the same water needs 10

Rated not suited to this region in the Central Valley, like black-eyed Susan vine. Plants that drink alike can share one valve and one schedule.

Golden Trumpet VineAllamanda catharticanot rated, Central Valleyno Central Valley ratingPelican FlowerAristolochia giganteanot rated, Central Valleyno Central Valley ratingWax PlantHoya carnosanot rated, Central Valleyno Central Valley ratingFlame VinePyrostegia venustanot rated, Central Valleyno Central Valley ratingCup-of-Gold VineSolandra maximanot rated, Central Valleyno Central Valley ratingMadagascar JasmineStephanotis floribundanot rated, Central Valleyno Central Valley ratingSky Flower VineThunbergia grandifloranot rated, Central Valleyno Central Valley ratingCoral VineAntigonon leptopusnot rated, Central Valleyno Central Valley ratingQueen's WreathPetrea volubilisnot rated, Central Valleyno Central Valley ratingBeauverd's Widow's-ThrillKalanchoe beauverdiinot rated, Central Valleyno Central Valley rating
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes black-eyed Susan vine, your sprinkler type and the month, and gives the minutes per water day for that supplier's schedule. Or put it in a zone of the personal watering plan and get all twelve months printed.

Questions people ask

How often should I water black-eyed Susan vine in summer?

In July, established black-eyed Susan vine in loam needs a deep watering about every 11 days on the south coast and about every 9 days in the South Inland zone. Sandy soil holds less water, so waterings come closer together. Clay stretches them. Check the soil before each watering and skip one after a soaking rain.

How much water does black-eyed Susan vine need per day?

In July on the north-central coast, established black-eyed Susan vine needs about 0.2 gallons a day for a plant 2 feet across and about 0.7 gallons a day for a plant 4 feet across. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.

Does watering for black-eyed Susan vine change across California?

Yes. WUCOLS rates black-eyed Susan vine separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, not suited to this region in the Central Valley zone, moderate water in the South Coastal zone, moderate water in the South Inland zone, moderate water in the High and Intermediate Desert zone, moderate water in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

Is black-eyed Susan vine related to black-eyed Susan?

No. Despite the shared name, it has no botanical tie to the Rudbeckia daisy. This one is a twining vine that needs support and steady moisture.

Will black-eyed Susan vine come back next year?

It is frost tender, so a freeze usually ends it. It reseeds easily, and seedlings may appear the following spring. You can also root stem cuttings before cold weather or bring a pot indoors.

Why did my black-eyed Susan vine stop blooming in July?

Flowering often slows in the hottest part of summer. Blooms usually pick up as the heat eases. Keep the soil evenly moist rather than drenching it, since extra water does not bring flowers back faster.

Does black-eyed Susan vine need a trellis?

It twines and does best with support such as a trellis, fence or arbor. Without one, it sprawls as a groundcover or spills from a basket. Water at the base however you grow it.

Can you overwater black-eyed Susan vine?

Yes. It wants rich soil with medium moisture that drains well. Soggy ground around the base can yellow the leaves, so let the surface dry before watering again.

More plant watering guides

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Sources