Cosmos "Apricotta" 6 pack

Cosmos Growing Guide

Cosmos are an easygoing, cheerful addition to any cutting garden, producing delicate, daisy-like blooms on tall, airy stems. These fast-growing plants thrive with minimal fuss, making them a favorite for home gardeners and flower farmers alike.

Quick Overview

• Common Name: Cosmos, Garden Cosmos, Mexican Asters

• Genus/Species: Cosmos bipinnatus

• Family: Asteraceae

• Life Cycle: Tender Annual

• Height: 3-5 feet

• Spacing: 9-12”

• Bloom Time: 45-60 days after planting

When to Plant

Cosmos can’t handle frost at any stage, so wait until all danger of frost has passed before planting. They thrive in summer heat and can grow in most zones. For continuous blooms, succession sow every 4 weeks, planting 2-3 rounds per season.

Soil & Light

• Soil: Cosmos actually prefer poor soil! Too much fertility will give you tall, bushy plants with very few flowers. Loose, well-draining soil is ideal.

• Light: Full sun is best for strong plants and abundant blooms.

• Day Length Sensitivity: Cosmos are short-day plants, meaning they naturally bloom more as days get shorter in late summer. If they get stressed (by becoming rootbound or too dry), they may start flowering prematurely. If growing in a greenhouse during winter, additional lighting will be needed to extend the vegetative stage.

Plant Care

• Spacing: 9-12” apart to allow for good airflow and strong growth.

• Pinching: When plants reach about 6” tall, pinch them back to a few sets of leaves. This will encourage branching and better flower production. If plants start blooming too soon, keep pinching off flower buds until they produce longer stems.

• Support: In windy areas, one or two layers of netting can help prevent the tall stems from flopping.

• Watering: Cosmos are drought-tolerant but bloom better with regular moisture. Be sure not to overwater, as soggy soil can lead to disease issues.

Harvesting Cosmos

Cosmos bloom quickly, usually within 45-60 days after planting. Harvest when flowers are just beginning to open for the best vase life. Side buds will continue to open after cutting. Always cut deeply into the plant—this encourages more branching and extended flower production. Fully open flowers will get pollinated, reducing vase life significantly.

Post-Harvest Care

• Immediately place stems in cool water after cutting.

• Use a floral preservative to extend vase life (expect about a week).

• Can be stored in a cooler for a short time but don’t keep them too cold.

Common Pests & Diseases

Cosmos are generally trouble-free but can develop powdery mildew and bacterial wilt in hot, humid conditions. Watch for pests like aphids, thrips, and Japanese beetles. Regular airflow and keeping plants spaced properly will help minimize disease risk.

Final Tips

• Keep Cutting! Don’t let cosmos go to seed—once they start setting seed, the plants will slow down or stop blooming altogether.

• Foliage for Bouquets? Some growers use cosmos stems as filler foliage, reporting decent vase life. It’s worth experimenting to see if it works for your arrangements!

Cosmos are the ultimate "cut-and-come-again" flower—easy to grow, quick to bloom, and endlessly rewarding. With regular harvesting and a little attention, you’ll have armfuls of delicate, fluttering flowers all season long.

Need Extra Support? Stay tuned for my new Garden Club on Facebook

If you want step-by-step guidance throughout the season, I’ve got you covered. My upcoming Garden Club Facebook Group will walk you through everything from planting to harvesting, plus tips on seed saving so you can grow again next year.

Important Details:

Local Pick-Up Only – Select LOCAL PICK-UP at checkout

Pick-up available the weekend of Mother’s Day – No early pick-ups

⚠️ No guarantees – I provide the healthiest plants possible and the best info, but nature has its own plans. Pests, weather, and the occasional garden mystery are all part of the adventure. But don’t worry—I’m here to help if you need it!