Bagging Flowers

Part of Seed Saving

Controlling which pollen reaches which flower is the foundation of reliable seed saving. Bagging is the most precise isolation method available without dedicated grow-out plots — a low-tech technique that guarantees genetic purity for any crop where cross-pollination would corrupt your seed stock.

Why Flowers Need Bagging

Many crops produce pollen that travels freely by wind or insects. Left uncontrolled, a squash vine 50 metres away can fertilize your carefully selected plants, and the seeds you save will grow offspring that combine traits from both parents unpredictably. For stable, true-breeding varieties, every seed-saving operation must decide: how do I prevent unwanted pollen from reaching my chosen flowers?

Bagging answers that question for a single plant or a handful of plants in a mixed garden. It replaces distance isolation when space is limited, and it allows two varieties of the same species to grow side by side without genetic mixing.

Types of Bags and Materials

Material	Breathability	Durability	Reusable	Best For
Spun polyester row cover	High	Moderate	Yes (2-3 seasons)	All crops, humid climates
Paper bags (glassine)	Moderate	Low (1 season)	No	Dry climates, small flowers
Organza fabric (fine mesh)	High	High	3-5 seasons	Pollinator-dependent crops
Lightweight cotton muslin	High	High	5+ seasons	Large flower clusters
Nylon tulle	High	High	5+ seasons	Wind-pollinated grains

Construction tips:

• Bags must be large enough to enclose the flower or flower cluster without compressing it against the fabric
• The open end needs a closure — tie with soft twine, use a clothespin, or sew a drawstring hem
• Avoid non-breathable plastic bags: they trap heat and moisture, causing flower abortion and fungal rot within 24 hours
• Minimum bag dimensions: 15 cm x 20 cm for individual flowers; 30 cm x 40 cm for compound clusters like brassica heads

How Pollination Works: The Timing Problem

Bagging is only effective if you understand the flower’s reproductive window. A bag applied after pollen has landed on the stigma accomplishes nothing.

Stages to manage:

1. Bud stage — the flower has not yet opened; this is the ideal time to bag
2. Anthesis — the moment the flower opens and the anthers release pollen; for self-pollinators, fertilization often occurs here
3. Stigma receptivity — the female surface is sticky and ready to receive pollen; duration varies from hours to days by species
4. Fertilization — pollen tube grows down the style; bag can be removed after this is complete

Important

Apply bags in the late afternoon or evening of the day before a flower is expected to open. Check bud tightness and color change — most flowers show petal color through the green bud casing within 12-24 hours of opening.

Step-by-Step Bagging Protocol

For Self-Pollinating Crops (Tomatoes, Peppers, Lettuce)

Self-pollinators fertilize themselves before or at the moment of opening. Bagging prevents outside pollen from reaching the stigma if you want to guarantee self-pollination rather than cross-pollination.

1. Identify buds 1-2 days from opening — firm, full-sized, showing color
2. Slip the bag over the bud without bending the stem
3. Secure the open end loosely below the flower node
4. Leave in place for 3-5 days (through flowering and early fruit set)
5. Mark the fruit with flagging tape or colored yarn for harvest tracking
6. Remove the bag once a small fruit is visible at the base of the withered flower

Labor estimate: 5 minutes per plant for initial bagging; 2 minutes per plant for monitoring and removal.

For Cross-Pollinating Crops Requiring Hand-Pollination (Squash, Corn, Brassicas)

When the goal is to create a specific cross — or to hand-pollinate an isolated flower that cannot self-fertilize — the bag must be opened at the exact right moment.

Squash protocol (applicable to cucumbers and melons):

1. The evening before a female flower opens, bag both the target female bud and one or more male buds from the same or chosen parent plant
2. In the morning (6:00-10:00 is peak receptivity), open the male bag, collect pollen by rubbing the anther column with a clean dry brush or by removing the male flower entirely
3. Open the female bag, brush pollen firmly onto the stigma lobes (central knob in squash female flowers)
4. Re-bag the female flower immediately
5. Leave the bag on for 48 hours, then remove and mark the fruit

Tip

Squash female flowers are identifiable by the small immature fruit visible behind the flower base. Male flowers have only a slender stem. In a seed-saving operation, bag both sexes the evening before anticipated opening — once opened unbagged, insects may have already visited.

Brassica protocol (cabbage, kale, broccoli):

Brassicas are obligate cross-pollinators — they are self-incompatible and will not set seed from their own pollen. You must bring compatible pollen from a second plant of the same variety.

1. Identify two plants of the same variety grown at least 10 metres from any other brassica
2. Enclose the entire flowering head of each plant in a large breathable bag (30 x 40 cm minimum)
3. On alternating days, swap bags between plants: remove bag from Plant A, shake the bagged head of Plant B vigorously over Plant A’s flowers, then re-bag Plant A
4. Repeat this exchange 3 times over 5-7 days as successive flowers open
5. Remove bags once the majority of flowers have set small seed pods

For Wind-Pollinated Crops (Corn, Spinach, Beet)

Wind-pollinated crops present the greatest challenge. Corn tassels release pollen in enormous quantities that can travel 400+ metres in a gentle breeze.

Corn isolation bagging:

1. Place large paper or fabric bags over individual ears (silk stage) before silks emerge — silks emerge 2-3 days after the ear bag is needed
2. Separately bag a tassel on the same or chosen parent plant while still enclosed in its sheath (before pollen shed)
3. Collect pollen by removing the tassel bag in the morning and holding it over the ear
4. Shake pollen from the bag onto the exposed silks of the target ear
5. Immediately re-bag the ear; leave in place for 5-7 days

Warning

Corn requires pollen from multiple plants for good seed set — single-plant pollen has reduced viability. Collect tassels from at least 5 plants of your chosen variety for hand-pollination.

Bag Management in Field Conditions

Heat management: Bag interiors can reach 10-15°C above ambient temperature on sunny days. In climates above 32°C, add shading with a second layer of reflective material over the bag, or bag in the evening and remove during the hottest part of the day if the flower has not yet opened.

Rain management: Paper bags disintegrate in rain. Switch to fabric bags if rain is forecast within the bagging window, or create a temporary cover from a larger plastic sheet suspended above without touching the bag.

Wind management: Secure bag ties firmly. A bag that blows off exposes the flower to uncontrolled pollination. In high wind areas, use a second tie wrapping around the stem 5 cm below the bag.

Pest management: Bag fabric can attract thrips and aphids that shelter inside. Inspect bags when you open them. If insects are present, gently brush them out before conducting hand-pollination.

Record-Keeping for Bagging Operations

Every bagged flower should generate a record. Without documentation, you cannot know which fruits to harvest for seed.

Minimum record per bagged plant:

• Date bagged
• Plant identification (row, position, or tag number)
• Parents involved in the cross (if hand-pollinating)
• Date hand-pollination conducted
• Date bag removed
• Fruit/seed harvest date

Tip

Color-coded yarn tied around the fruit stem is the simplest field marking system. Assign one color per variety or cross type. The yarn stays on through harvest and drying, giving you a direct link from seed packet back to plant.

Troubleshooting

Problem	Likely Cause	Solution
Flower drops without setting fruit	Bag applied too late; pollen already received	Re-bag fresh buds; check timing
Mold inside bag	Insufficient breathability; high humidity	Switch to spun polyester; open bags briefly in morning sun
Poor seed set in hand-pollinated squash	Pollen collected too early or late	Collect pollen when anthers are powdery yellow, not wet or dry
Silks emerge before tassel bag collected (corn)	Ear bagged too late	Monitor ear daily from first silk emergence; bag ears before silks appear
Bag falls off in wind	Inadequate closure	Add second tie; use clothespins on gathered fabric

Scaling Bagging Operations

For a community-scale seed saving operation producing 50+ bagged plants per season:

• Dedicate one person as “pollination manager” to track all bagging operations
• Batch bagging work: walk rows each evening to identify next-day candidates
• Prepare bags in bulk during non-peak times — pre-label with variety and date fields
• Aim for 3-5 confirmed fruits per variety per season for adequate seed quantity
• Store bagged materials by variety in labeled bins so bags can be reused systematically

Bagging Flowers Summary

Bagging is the most reliable isolation method for small-scale seed saving in mixed gardens. Apply breathable fabric or glassine paper bags to buds before flowers open, conduct hand-pollination at peak receptivity, and mark resulting fruits clearly. Self-pollinators need bags mainly to confirm genetic purity; cross-pollinators require active pollen transfer between bagged flowers. Proper timing, breathable materials, and detailed records are the three non-negotiable elements of a successful bagging program.