Tower Silver
Callistephus chinensis
Photo: Lgovindprakash · Wikimedia Commons · (CC BY-SA 3.0)
All the elegance and beauty of peonies and garden mums in an easy-to-grow annual. Bicolor blooms in frosted white with lavender avg. 2-3" with 13-20 stems per plant. Tower features uniform bloom time and plant height across the series and mix. Also known as summer aster.
Harvest
110-120d
Days to harvest
Sun
Full sun to partial shade
Zones
2–11
USDA hardiness
Height
1-3 feet
Planting Timeline
Showing dates for Tower Silver in USDA Zone 7
All Zone 7 flower →Zone Map
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Tower Silver · Zones 2–11
Growing Details
Zone-by-Zone Planting Calendar
| Zone | Indoor Start | Transplant | Direct Sow | Harvest |
|---|---|---|---|---|
| Zone 3 | April – May | June – July | June – August | — |
| Zone 4 | March – April | June – June | June – July | — |
| Zone 5 | March – April | May – June | May – July | — |
| Zone 6 | March – April | May – June | May – July | — |
| Zone 7 | February – March | April – May | April – June | — |
| Zone 8 | February – March | April – May | April – June | — |
| Zone 9 | January – February | March – April | March – May | — |
| Zone 10 | January – January | February – March | February – April | — |
| Zone 1 | May – June | July – August | July – September | — |
| Zone 2 | April – May | June – July | June – August | — |
| Zone 11 | January – January | January – February | January – March | — |
| Zone 12 | January – January | January – February | January – March | — |
| Zone 13 | January – January | January – February | January – March | — |
Succession Planting
Tower Silver runs 110-120 days to bloom, which makes tight succession less practical than it is with a cut-and-come-again crop — you're mostly managing one wave per bed. That said, you can stagger two sowings: start one batch indoors in late February, transplant in April, and start a second batch indoors in mid-March for a May transplant. That spreads your bloom window by 3-4 weeks without overlapping too badly.
Don't push direct sowing past early June in most climates. Asters need time to mature before hard frost, and germination stalls once daytime highs are consistently above 85°F. If you want late-season color, start the second round indoors under lights rather than trying to direct sow into hot soil.
Complete Growing Guide
All the elegance and beauty of peonies and garden mums in an easy-to-grow annual. Bicolor blooms in frosted white with lavender avg. 2-3" with 13-20 stems per plant. Tower features uniform bloom time and plant height across the series and mix. Also known as summer aster. According to Johnny's Selected Seeds, Tower Silver is 110 - 120 days to maturity, annual, open pollinated. Notable features: Use for Cut Flowers and Bouquets.
Light: Full sun (6 or more hours of direct sunlight a day), Partial Shade (Direct sunlight only part of the day, 2-6 hours). Soil: Clay, High Organic Matter, Loam (Silt), Sand. Soil pH: Acid (<6.0), Neutral (6.0-8.0). Drainage: Good Drainage, Moist. Height: 1 ft. 0 in. - 3 ft. 0 in.. Spread: 1 ft. 0 in. - 1 ft. 6 in.. Spacing: Less than 12 inches. Growth rate: Rapid. Maintenance: Medium. Regions: Coastal, Mountains, Piedmont.
Harvesting
Tower Silver reaches harvest at 110 - 120 days from sowing per Johnny's Selected Seeds. Expect 2-3" at peak. As an annual, harvest continues until frost ends the season.
The fruit is a rough-textured, glandular, purple-mottled cypsela that turns gray with age.
Storage & Preservation
Store fresh Tower Silver flowers in the refrigerator at 35-40°F with high humidity (90-95%) to extend vase life. Keep stems in fresh water and change daily; blooms typically last 7-10 days. For preservation, air-dry entire stems in a dark, well-ventilated space for 2-3 weeks to create long-lasting dried arrangements. Alternatively, press individual blooms between paper in a flower press for 3-4 weeks for pressed flower crafts. Freeze flowers in ice cubes with water for decorative use in beverages, which preserves color for several months when stored at 0°F.
History & Origin
Tower Silver is open-pollinated, meaning seed saved from healthy plants will produce true-to-type offspring. Listed in the Johnny's Selected Seeds catalog.
Origin: China and Southern Russia
Advantages
- +Bicolor frosted white and lavender blooms offer sophisticated garden aesthetics
- +Produces abundant 13-20 stems per plant for substantial cut flower yields
- +Uniform bloom time and height simplify garden design and succession planting
- +Easy annual growth requires minimal gardening experience or special care
- +110-120 day season fits most growing regions with adequate summer warmth
Considerations
- -Susceptible to powdery mildew in humid or poorly ventilated conditions
- -Requires consistent moisture; drought stress causes bud drop and smaller blooms
- -Tall stems may need staking in windy locations or heavy rain
- -Shorter vase life compared to garden mums and cut flower peonies
Companion Plants
Marigolds (Tagetes spp.) and alyssum are the two companions most worth planting near Tower Silver. Marigolds deter aphids and whiteflies through scent and are thought to suppress root-knot nematodes in the soil beneath them — plant them within 12-18 inches. Alyssum's tiny flowers draw parasitic wasps and hoverflies, which prey on the aphid colonies that China asters tend to attract. Chives pull similar duty; their sulfur compounds are genuinely off-putting to aphids. Lavender and catmint at the border add scent-based pest confusion without competing aggressively for water at the root zone.
Black walnut (Juglans nigra) is the companion to take seriously. It produces juglone, a compound that leaches through the soil and can stunt or kill many annuals — China asters included. The affected zone extends well past the visible drip line, so if there's a walnut on the property, site your asters on the opposite end of the garden. Fennel is a lesser but real concern; it's broadly allelopathic and tends to suppress neighbors regardless of what's planted alongside it.
Plant Together
Lavender
Repels aphids, moths, and other pests while attracting beneficial pollinators
Marigolds
Deters nematodes and aphids, acts as natural pest control
Catmint
Repels ants, aphids, and rodents while attracting beneficial insects
Alyssum
Attracts beneficial insects like hoverflies and parasitic wasps
Nasturtiums
Acts as trap crop for aphids and cucumber beetles
Chives
Repels aphids and Japanese beetles with strong sulfur compounds
Cosmos
Attracts beneficial predatory insects and provides habitat diversity
Sage
Deters cabbage moths, carrot flies, and other flying pests
Keep Apart
Black Walnut
Produces juglone toxin that inhibits growth of many plants
Eucalyptus
Releases allelopathic compounds that suppress nearby plant growth
Fennel
Inhibits growth of most garden plants through allelopathy
Pests & Disease Resistance
Common Pests
Aphids, spider mites, whiteflies
Diseases
Powdery mildew, aster yellows, root rot
Troubleshooting Tower Silver
What you'll see, why it happens, and what to do about it.
White powdery coating on upper leaf surfaces, spreading from older leaves inward, usually mid-to-late season
Likely Causes
- Powdery mildew (Erysiphe cichoracearum) — thrives in warm days with cool nights and poor airflow
- Plants spaced too close, blocking circulation
What to Do
- 1.Strip the worst-affected leaves and bin them — don't compost
- 2.Spray remaining foliage with a diluted baking soda solution (1 tablespoon per gallon of water) or a sulfur-based fungicide
- 3.Next planting, hold to the 18-24 inch spacing minimum and avoid overhead watering in the evening
Stunted plants with yellowed, mottled foliage and distorted or discolored blooms — flowers may turn greenish or fail to open properly
Likely Causes
- Aster yellows — a phytoplasma disease transmitted by the aster leafhopper (Macrosteles quadrilineatus)
- High leafhopper pressure, especially in open, weedy surroundings
What to Do
- 1.Pull and dispose of infected plants immediately — there is no cure, and they act as a reservoir for the pathogen
- 2.Control leafhoppers on surrounding plants with insecticidal soap or pyrethrin if pressure is heavy
- 3.Use floating row cover over young transplants for the first 3-4 weeks to block leafhopper feeding
Clusters of small soft-bodied insects on new growth and flower buds, sometimes with sticky residue or ants trailing up the stems
Likely Causes
- Aphids (commonly Myzus persicae or Aphis gossypii) — populations can double in a few days in warm weather
- Excess nitrogen from heavy fertilizing, which pushes lush soft growth aphids prefer
What to Do
- 1.Knock aphids off with a firm stream of water from a hose — do this in the morning so foliage dries quickly
- 2.Release or attract parasitic wasps and ladybird beetles; alyssum planted nearby draws them in
- 3.If colonies persist, apply insecticidal soap directly to the colonies, coating the undersides of leaves
Wilting that doesn't recover after watering, brown or black stem tissue at or just below the soil line, plant pulls up with rotted roots
Likely Causes
- Root rot (Pythium or Phytophthora spp.) — triggered by waterlogged or poorly draining soil
- Planting in a low spot that holds water after rain
- Overwatering seedlings before they're established
What to Do
- 1.Remove the plant — a rotted root system won't recover
- 2.Amend the bed with 2-3 inches of compost and coarse perlite before replanting to improve drainage
- 3.In future sowings, let the top inch of soil dry out slightly between waterings and avoid planting in compacted areas
Frequently Asked Questions
How long do Tower Silver flowers last in a vase?▼
Is Tower Silver a good choice for beginner gardeners?▼
Can you grow Tower Silver in containers?▼
When should I plant Tower Silver seeds?▼
What's the difference between Tower Silver and other summer asters?▼
How often should I water Tower Silver plants?▼
Growing Guides from Wind River Greens
Where to Buy Seeds
Sources & References
External authority sources used in compiling this guide.
- BreederJohnny's Selected Seeds
See the Methodology page for how this data is sourced, what's AI-assisted, and known limitations.