How to Grow Chrysanthemums: Complete Fall Flower Guide

How to Grow Chrysanthemums: Complete Fall Flower Guide

When autumn arrives and most flowers are fading, chrysanthemums burst onto the scene with an explosion of color that carries the garden through frost. Mums are the undisputed queens of fall, and for good reason: they come in every warm color imaginable, bloom for weeks on end, and are remarkably easy to grow once you understand a few key techniques.

The single most important skill in growing chrysanthemums is pinching — a simple technique that transforms a spindly plant into a compact, bloom-covered mound. This guide will teach you exactly how and when to pinch, along with everything else you need for stunning fall flowers year after year.

Quick Facts

Garden Mums vs. Florist Mums: Which Do You Have?

This is the most important distinction in chrysanthemum growing, and confusing the two is the number one reason people fail with mums.

Garden Mums (Hardy Mums)

Bred for cold tolerance and garden performance. They are true perennials in Zones 5-9 and will come back year after year when planted properly. They have a spreading root system and produce suckers from the base. Flower forms are usually single, daisy-like, decorative, or pompon.

Buy these in spring for planting in the garden. They need a full season to establish roots before winter.

Florist Mums (Exhibition Mums)

Bred for greenhouse production and cut flower displays. They have larger, more elaborate flowers but are NOT reliably hardy below Zone 7. The ones sold at grocery stores and garden centers in fall are almost always florist mums — they are grown as disposable seasonal color and may not survive winter even with protection.

These are the fall impulse buys. Enjoy them as seasonal decoration, but do not expect them to perennialize in cold climates.

How to Tell the Difference

What You Will Need

• Chrysanthemum plants (spring divisions or nursery transplants for perennial growing; fall potted mums for seasonal display)
• Compost or aged manure for soil amendment
• Balanced fertilizer (10-10-10 or 5-10-10)
• Mulch (straw, shredded bark, or leaf mold)
• Pruning shears for pinching and deadheading
• Stakes or plant supports (for tall varieties)
• Containers with drainage holes (if growing in pots, minimum 12 inches in diameter)

Step-by-Step Growing Guide

1. When to Plant

For perennial garden mums: Plant in spring (April-May) as soon as the soil is workable and frost danger has passed. Spring planting is critical — it gives the roots an entire growing season to establish before facing their first winter. Fall-planted mums rarely survive winter because their roots have not had time to spread.

For seasonal fall color: Buy potted mums in September-October when they are in full bloom. Treat them as seasonal annuals and enjoy the display. If you want to try overwintering them, plant immediately after purchase and follow the overwintering guide below.

2. Choosing the Right Location

Mums need at least 6 hours of direct sunlight daily. In fact, they are photoperiod-sensitive — they set flower buds in response to the shortening days of late summer. Artificial light at night (from street lamps, porch lights, or security lights) can delay or prevent blooming.

• Full sun is non-negotiable for heavy flowering
• Good air circulation reduces fungal disease risk
• Avoid low spots where frost settles first — mums bloom late and need every frost-free day
• Sheltered from wind if possible, especially for tall varieties
• Away from night lighting that could interfere with bud set

3. Soil Preparation

Chrysanthemums need rich, well-draining soil. They are heavy feeders and heavy drinkers, but they absolutely cannot sit in waterlogged soil.

1. Work 3-4 inches of compost into the top 12 inches of soil
2. Add perlite or coarse sand to heavy clay soil for drainage
3. Test pH: Mums prefer 6.0-7.0 (slightly acidic to neutral)
4. Raised beds work well in areas with poor drainage

4. Planting

1. Space plants 18-24 inches apart (they spread significantly during the growing season)
2. Plant at the same depth as the nursery pot — not deeper
3. Water deeply after planting
4. Apply 2-3 inches of mulch around the plants, keeping it away from stems
5. Pinch the growing tips immediately after planting (see Pinching section below)

5. The Pinching Technique — The Key to Beautiful Mums

Pinching is what separates a straggly, top-heavy mum from a compact, bloom-covered mound. Without pinching, mums grow tall and lanky with flowers only at the tips. With pinching, they branch repeatedly and produce three to four times as many blooms.

How to pinch:

1. When new growth reaches 6 inches tall, pinch (snap or cut) the top 1 inch off each stem, just above a set of leaves
2. Each pinched stem will produce 2-3 new branches
3. When those new branches reach 6 inches, pinch again
4. Stop pinching by July 4th (in most zones) — any later and you risk removing flower buds that are already forming
5. In southern zones (8-9), you can pinch until mid-July

The July 4th rule is the most important date in mum growing. Pinch freely before it, stop completely after it.

What happens if you skip pinching? You get a tall plant with a few flowers at the top and bare stems below. The plant flops over and looks untidy. Pinching prevents all of this.

6. Watering

Mums need consistent moisture throughout the growing season. They have shallow root systems that dry out quickly.

• Water at the base, not overhead — wet foliage promotes leaf spot and other fungal diseases
• Provide about 1 inch per week, more during hot dry spells
• Morning watering is best — gives foliage time to dry before evening
• Container mums need daily watering in warm weather
• Avoid drought stress during bud formation (August-September) — this is when consistent water is most critical for flower quality

7. Fertilizing

Mums are heavy feeders that need consistent nutrition from spring through bud formation.

• At planting (spring): Work balanced granular fertilizer (10-10-10) into the soil
• Monthly through June: Apply balanced liquid fertilizer every 3-4 weeks
• July-August: Switch to a high-phosphorus fertilizer (like 5-10-10 or bloom booster) to encourage flower bud development
• Stop fertilizing once buds show color (usually September) — late feeding produces soft growth that is vulnerable to frost

Overwintering Garden Mums

Getting mums through winter is the biggest challenge for gardeners in Zones 5-6. Here is the proven method:

Step 1: Do NOT Cut Back in Fall

After flowering, let the stems and foliage remain. The dead stems help insulate the crown and trap snow, which acts as natural insulation. Cut back in spring, not fall.

Step 2: Apply Winter Mulch

After the ground freezes (not before — you want the ground to freeze first):

1. Apply 4-6 inches of loose mulch (straw, pine needles, or shredded leaves)
2. Cover the entire plant loosely — do not pack it down
3. The goal is insulation, not warmth — you are preventing freeze-thaw cycles that heave plants out of the ground

Step 3: Spring Cleanup

In early spring when you see new green growth emerging from the base:

1. Remove the winter mulch gradually
2. Cut last year's dead stems to ground level
3. Dig up the clump and divide it (see Division section)
4. Replant the healthiest divisions with fresh compost
5. Begin the pinching cycle when new growth reaches 6 inches

Dividing Chrysanthemums

Mums benefit from division every 2-3 years. Without division, the center of the clump becomes woody and dies out, producing a ring of growth around a dead center.

When to divide: Early spring, when new shoots are 1-3 inches tall.

How to divide:

1. Dig up the entire clump
2. Pull apart or cut into sections, each with several healthy shoots and good roots
3. Discard the woody center — it will not recover
4. Replant divisions immediately with fresh compost
5. Water deeply and begin pinching when growth reaches 6 inches

Division also gives you free plants to share with friends or expand your garden.

Growing Mums in Containers

Mums are outstanding container plants for fall patios, porches, and entries.

• Pot size: Minimum 12 inches diameter. One plant per 12-inch pot, or three in a 16-18 inch pot
• Soil: Quality potting mix with added perlite for drainage
• Watering: Daily in warm weather — containers dry out fast
• Fertilizing: Liquid feed every 2 weeks through August
• Placement: Full sun, sheltered from strong wind
• For spring-planted mums in containers: Follow the same pinching schedule as garden plants
• For fall-purchased mums: Keep soil moist, deadhead spent blooms, and enjoy the display. They may last 4-6 weeks.

Overwintering in containers: In cold climates, sink the pot into the ground in a protected spot and mulch heavily, or move to an unheated garage. Container roots freeze more easily than in-ground roots.

Common Problems and Solutions

Leggy, Sparse Growth

Almost always caused by not pinching. If you missed the pinching window, you can still stake tall plants for support, but next year, start pinching in spring and follow the July 4th rule.

No Flowers

Three common causes: (1) Too much artificial light at night — even nearby street lamps or porch lights can prevent bud formation. Move plants away from light sources. (2) Pinched too late — if you pinched after mid-July, you may have removed the forming flower buds. (3) Insufficient sunlight — mums need 6+ hours of direct sun.

Aphids

Small green or brown insects clustering on stems and buds. Spray with a strong jet of water to knock them off. For severe infestations, use insecticidal soap or neem oil. Encourage ladybugs and lacewings.

Leaf Spot (Septoria and Cercospora)

Brown or black spots on lower leaves that gradually move upward. Caused by fungal pathogens that splash up from the soil in rain. Remove and destroy affected leaves. Water at the base, not overhead. Apply mulch to prevent soil splash. Space plants for good air circulation.

Spider Mites

Tiny pests that cause stippled, yellowing foliage and fine webbing. Most common in hot, dry conditions. Increase humidity around plants, spray with water, or use miticide for severe infestations. Keep plants well-watered — stressed mums are more susceptible.

Powdery Mildew

White powdery coating on leaves. Improve air circulation, avoid overhead watering, and apply fungicide if severe. Some varieties are more resistant than others.

Chrysanthemum Flower Types

Mums produce an incredible range of flower forms:

Companion Planting

Mums pair beautifully with other fall performers:

• Ornamental grasses — provide height and texture contrast behind mums
• Asters — complementary fall bloomer in purple and blue shades
• Sedum (Autumn Joy) — succulent texture contrast, similar bloom timing
• Ornamental kale and cabbage — cool-season color partners
• Pansies — low border in front of mums, extend season into winter
• Pumpkins and gourds — the classic fall display combination

Frequently Asked Questions

Will my fall mums come back next year?

It depends on when you plant them and what type they are. Garden mums (hardy mums) planted in spring have the best chance of returning because their roots have all season to establish. Fall-planted mums from garden centers are usually florist types that lack cold hardiness, and even if they are garden varieties, their roots have not had time to establish before winter. If you want perennial mums, buy small plants in spring, plant them in well-drained soil, and follow the overwintering steps in this guide. In Zones 5-6, even properly established mums benefit from heavy winter mulch.

When should I pinch my mums?

Start pinching when new growth reaches 6 inches tall in spring, and continue pinching every time new branches reach 6 inches. Stop all pinching by July 4th (mid-July in Zones 8-9). This is the single most important rule in mum growing. Each pinch creates 2-3 new branches, which means 2-3 times more flowers. After July 4th, the plant begins forming flower buds on the branch tips, so any later pinching removes the buds you have been working all season to create.

Why are my mums blooming too early?

Early blooming (August instead of September-October) is usually caused by the plant being root-bound in a too-small pot, experiencing drought stress, or being a variety bred for earlier flowering. Some modern garden center varieties are selected to bloom early for fall sales. If you want classic October blooms, choose late-season varieties and ensure the plant has adequate root space, consistent water, and is not stressed by heat or drought during summer.

How do I keep my container mums looking good longer?

For fall-purchased potted mums: (1) Water daily — containers dry out fast and wilted mums decline rapidly. (2) Keep in bright light but move to a sheltered spot if a hard freeze threatens (below 28°F). Light frosts actually improve flower color. (3) Deadhead spent blooms regularly to redirect energy to remaining buds. (4) Do not fertilize fall mums — they are already in bloom and feeding just makes soft growth. (5) Choose plants with lots of unopened buds rather than fully open flowers for the longest display.

Are chrysanthemums toxic to cats and dogs?

Chrysanthemums are considered mildly toxic to dogs, cats, and horses by the ASPCA. The plant contains pyrethrins (natural insecticides) and sesquiterpene lactones that can cause vomiting, diarrhea, drooling, and skin irritation (dermatitis) if ingested or with prolonged skin contact. While unlikely to be fatal, keep mums out of reach of pets who chew on plants. If your pet ingests a significant amount, contact your veterinarian.