Coreopsis 'Mercury Rising' (Mercury Rising Tickseed) care

Light

Coreopsis 'Mercury Rising' needs sun on the leaves, not just bright ambient room light. Full sun (6-8 hours per day) is essential for strong, upright growth and the richest flower colour. Partial shade reduces flower count and can cause legginess. A south or west-facing windowsill in the northern hemisphere is the default; anywhere else, expect the plant to stretch and pale out within a season.

Watering

Water coreopsis 'mercury rising' when the top 3-5 cm of soil is dry, roughly every 7-10 days. The actual day count varies with pot size, light, and season — the finger test (or lifting the pot to feel its weight) is more reliable than a fixed calendar. Empty any drainage saucer afterwards so the pot isn't sitting in water. Moderate drought tolerance once established. Water new plants regularly during the establishment period. Avoid waterlogged conditions at all times.

Soil and pot

Coreopsis 'Mercury Rising' grows best in average to lean, well-drained loam or sandy loam. Performs best in average or lean soils. Rich, fertile soils promote excessive leafy growth at the expense of flowering. Essential that drainage is good, especially over winter. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Coreopsis 'Mercury Rising' sits happiest at around 35-65% humidity and -15-30°C (5-86°F). Tolerates a range of humidity levels. Good air circulation helps prevent crown rot and foliar fungal diseases. If you keep the room above year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed coreopsis 'mercury rising' sparingly. Apply a balanced granular fertiliser once in early spring. Because the cultivar is sterile and already has a long bloom period, feeding should be light to avoid over-stimulating soft vegetative growth. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on coreopsis 'mercury rising' in the Growli community. Each is annotated with the most common cause so you know where to start.

• Crown rot in wet winters — Poorly drained soils over winter are the main threat. Improve drainage or mulch lightly around (not over) the crown.
• Aphids — May appear on new shoot tips. Control with a strong water spray or insecticidal soap.
• Aster yellows phytoplasma — Causes distorted, yellowed or virescent flowers. Remove and destroy affected plants immediately; no cure available.
• Powdery mildew — Occasional in humid, poorly ventilated spots. Treat with potassium bicarbonate and improve airflow.
• Clump decline without division — Divide every 3-4 years in spring to maintain vigorous flowering and prevent central die-out.

Companion plants

Coreopsis 'Mercury Rising' pairs well with Nepeta 'Walker's Low', Salvia nemorosa 'Ostfriesland', Geranium 'Rozanne', and Achillea 'Moonshine'. These are species with similar light and water needs, so you can group them in the same room or on the same shelf and water as a batch.

Propagation

Divide clumps in spring every 3-4 years. Because the plant is sterile, propagation is exclusively vegetative: division or stem cuttings from basal growth in late spring. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Coreopsis 'Mercury Rising' is pet-safe. Coreopsis is listed as non-toxic to dogs and cats by the ASPCA. 'Mercury Rising' is a cultivar within this non-toxic genus and is considered pet-safe. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Coreopsis 'Mercury Rising' deep-dive guides

Every aspect of coreopsis 'mercury rising' care, each with its own calibrated guide:

• Common coreopsis 'mercury rising' problems & fixes
• Coreopsis 'Mercury Rising' watering schedule
• Coreopsis 'Mercury Rising' light requirements
• Best soil mix for coreopsis 'mercury rising'
• Coreopsis 'Mercury Rising' fertilizing guide
• When to repot coreopsis 'mercury rising'
• How to propagate coreopsis 'mercury rising'
• How to prune coreopsis 'mercury rising'
• What's eating my coreopsis 'mercury rising'?
• Coreopsis 'Mercury Rising' growth rate & size
• Coreopsis 'Mercury Rising' cold hardiness
• Coreopsis 'Mercury Rising' temperature & humidity
• Is coreopsis 'mercury rising' toxic to cats & dogs?
• Is coreopsis 'mercury rising' toxic to cats?
• Is coreopsis 'mercury rising' toxic to dogs?
• All 24 Coreopsis varieties
• Getting coreopsis 'mercury rising' to bloom

Featured in these plant shortlists

Coreopsis 'Mercury Rising' qualifies for 10 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best pet-safe houseplants — Houseplants the ASPCA lists as non-toxic to cats and dogs — every one verified against the ASPCA toxic and non-toxic plant list.
• Best drought-tolerant houseplants — Houseplants that prefer to dry out — forgiving of forgotten watering and ideal for travel or busy weeks.
• Best flowering houseplants — Indoor plants grown for their blooms — selected from the flowering species in Growli’s plant-care library.
• Best pet-safe low-maintenance plants — Non-toxic to cats and dogs and forgiving of forgotten watering — the easiest safe choices for a busy pet household.
• Best pet-safe flowering plants — Flowering houseplants the ASPCA lists as non-toxic to cats and dogs — colour and blooms in a pet home, without the worry.
• Best pet-safe plants for bright light — Non-toxic to cats and dogs and happy in a bright, sunny spot — safe plants for your best-lit windowsill.
• Best houseplants for full sun — Houseplants that want direct sun — the species for a hot south or west-facing windowsill where shade-lovers scorch.
• Best houseplants for a cool room — Houseplants that tolerate cool conditions down to about 10°C — for an unheated spare room, hallway, porch or a home kept cool.
• Best cat-safe plants — Houseplants the ASPCA lists as non-toxic to cats (and dogs) — safe greenery for a home with a curious cat.
• Best dog-safe plants — Houseplants the ASPCA lists as non-toxic to dogs (and cats) — safe greenery for a home with a curious dog.
• Browse all 30 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Coreopsis 'Mercury Rising' is also commonly called Mercury Rising Tickseed or Big Bang Mercury Rising Coreopsis.

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