Garlic and onions share a planting window that depends on root development before winter. Knowing exactly when to plant garlic and onions can mean the difference between a bountiful harvest and a disappointing one. This guide walks you through the timing, soil prep, and care needed for success.
Most gardeners plant these bulbs in fall for a summer harvest. But spring planting works too, depending on your climate. Let’s break down the best approach for your region.
When To Plant Garlic And Onions
Timing is everything for garlic and onions. These crops need cool weather to establish roots before the ground freezes. If you plant too early, they might sprout and get damaged. Too late, and roots won’t develop properly.
For fall planting, aim for 4-6 weeks before the first hard frost. This gives roots time to grow without top growth. In most areas, that means September to November. For spring planting, wait until soil is workable and temperatures stay above freezing.
Fall Planting Benefits
- Larger bulbs at harvest time
- Better flavor development
- Less pest pressure in spring
- Earlier harvest next season
Spring Planting Considerations
- Works for northern climates with harsh winters
- Requires cold treatment for garlic (vernalization)
- Smaller bulbs typically
- More watering needed in summer heat
Understanding Your Climate Zone
Your hardiness zone determines the exact planting window. Check your USDA zone before setting a date. Zones 3-5 need earlier planting than zones 7-9.
Cold Climates (Zones 3-5)
Plant in late September to early October. Soil temperatures should be around 50°F. Mulch heavily after planting to insulate bulbs. Spring planting works here if fall is missed, but use cold-treated seed garlic.
Moderate Climates (Zones 6-7)
October to November is ideal. Soil temperatures between 50-60°F work well. You can also plant in March for a later harvest. Onions do well with fall planting in these zones.
Warm Climates (Zones 8-10)
Plant from November to December. Avoid the hottest months. Some gardeners plant in January for a spring harvest. Onions need short-day varieties in these regions.
Soil Preparation For Garlic And Onions
Good soil makes healthy bulbs. Start preparing beds 2-3 weeks before planting. Remove weeds and rocks. Loosen soil to 8-10 inches deep.
Soil Requirements
- Well-draining loam or sandy loam
- pH between 6.0 and 7.0
- Rich in organic matter
- No fresh manure (use composted)
Fertilizer Basics
Add a balanced fertilizer like 10-10-10 at planting time. Work it into the top 4 inches of soil. Avoid high-nitrogen fertilizers, which encourage leaf growth over bulbs. Bone meal provides phosphorus for root development.
Choosing The Right Varieties
Garlic comes in two main types: hardneck and softneck. Onions are categorized by day length. Pick varieties suited to your region for best results.
Garlic Types
- Hardneck: Best for cold climates, produces scapes, larger cloves
- Softneck: Stores longer, better for warm climates, braidable
- Elephant garlic: Milder flavor, needs longer growing season
Onion Types By Day Length
- Short-day: For southern zones (8-10), bulbs form with 10-12 hours of light
- Long-day: For northern zones (3-6), needs 14-16 hours of daylight
- Day-neutral: Works in most zones, forms bulbs with 12-14 hours
Step-By-Step Planting Guide
Follow these steps for successful planting. Adjust timing based on your local frost dates.
Garlic Planting Steps
- Break apart garlic bulbs into individual cloves 24 hours before planting
- Keep the papery skin on each clove
- Plant cloves 2 inches deep, pointed end up
- Space cloves 6 inches apart in rows 12 inches apart
- Water thoroughly after planting
- Apply 4-6 inches of mulch (straw or leaves)
Onion Planting Steps
- Choose sets (small bulbs) or transplants for easier start
- Plant sets 1 inch deep, pointed end up
- Space sets 4 inches apart in rows 12 inches apart
- Water well after planting
- Mulch lightly with straw (1-2 inches)
- For spring planting, wait until soil is 50°F
Watering And Mulching Tips
Consistent moisture is key for bulb development. Overwatering causes rot. Underwatering stunts growth. Mulch helps regulate soil temperature and moisture.
Watering Schedule
- Fall: Water once after planting, then let rain do the work
- Spring: Water 1 inch per week if no rain
- Summer: Increase to 2 inches per week during bulb formation
- Stop watering 2 weeks before harvest
Mulch Benefits
- Prevents soil temperature fluctuations
- Suppresses weeds
- Retains moisture
- Protects bulbs from frost heave
Common Planting Mistakes
Avoid these errors to ensure a good harvest. Many gardeners plant too deep or too shallow. Others skip soil testing.
- Planting too early in fall (causes sprouting before winter)
- Using grocery store garlic (may carry diseases)
- Planting in compacted soil
- Overwatering after planting
- Ignoring day length requirements for onions
- Not hardening off transplants
Harvest Timing
Knowing when to harvest is as important as planting time. Garlic is ready when lower leaves turn brown. Onions are ready when tops fall over.
Garlic Harvest Signs
- 3-4 green leaves remain (for storage quality)
- Scapes have curled and straightened (for hardneck)
- Bulbs are plump and cloves separate easily
Onion Harvest Signs
- Tops flop over at the neck
- Bulbs are full size and papery
- Leaves start yellowing
Curing And Storage
Proper curing extends storage life. Cure in a warm, dry, well-ventilated area for 2-4 weeks. Trim roots and tops before storing.
Garlic Curing
- Hang in bunches or lay on screens
- Keep out of direct sunlight
- Maintain 80°F temperature for first week
- Reduce to 70°F for remaining time
Onion Curing
- Spread in single layer
- Keep in shade with good airflow
- Wait until necks are tight and dry
- Store in mesh bags or braids
Seasonal Care Calendar
Follow this monthly guide for garlic and onions. Adjust based on your local climate.
Fall (September-November)
- Prepare soil and plant bulbs
- Apply mulch after planting
- Water once if dry
Winter (December-February)
- Check mulch cover after snow melt
- Add more mulch if needed
- Order seeds for spring planting
Spring (March-May)
- Remove heavy mulch when soil warms
- Fertilize with balanced fertilizer
- Water regularly as growth accelerates
- Plant spring onions when soil is workable
Summer (June-August)
- Harvest garlic when leaves brown
- Harvest onions when tops fall
- Stop watering 2 weeks before harvest
- Cure and store bulbs
Pest And Disease Management
Common pests include onion maggots and thrips. Diseases like white rot and downy mildew can ruin crops. Prevention is better than cure.
Preventive Measures
- Rotate crops yearly (don’t plant alliums in same spot)
- Use disease-free seed stock
- Ensure good drainage
- Remove plant debris after harvest
- Use row covers to exclude pests
Organic Control Options
- Neem oil for thrips
- Diatomaceous earth for maggots
- Beneficial nematodes for soil pests
- Copper fungicide for fungal issues
Companion Planting Benefits
Garlic and onions repel many pests. Plant them near carrots, tomatoes, and roses. Avoid planting near beans and peas.
- Deters aphids and spider mites
- Discourages deer and rabbits
- Improves flavor of some vegetables
- Attracts beneficial insects when flowering
Frequently Asked Questions
Can I plant garlic and onions together?
Yes, they grow well together. Space them according to their individual needs. Garlic needs more space than onions. Both benefit from similar soil and watering conditions.
What happens if I plant garlic too late?
Late planting results in smaller bulbs. Roots won’t establish before winter. Spring planting is better if you miss the fall window. Use cold-treated garlic for spring.
How deep should I plant onion sets?
Plant sets 1 inch deep with the pointed end up. Cover with soil and water well. Deeper planting can cause stem rot. Shallower planting may dry out roots.
Do onions need full sun?
Yes, onions need 6-8 hours of direct sunlight daily. Less sun reduces bulb size. Plant in the sunniest part of your garden. Shade from trees or buildings will stunt growth.
Can I grow garlic from grocery store bulbs?
It’s possible but risky. Grocery store garlic may be treated to prevent sprouting. It can also carry diseases. Use certified seed garlic from a nursery for best results.
How do I know when to plant garlic in zone 7?
In zone 7, plant garlic from October to November. Soil temperatures should be around 60°F. Mulch lightly after planting. Harvest usually occurs in June or July.
Final Tips For Success
Start with quality seed stock. Test your soil pH and adjust if needed. Water consistently but don’t overdo it. Mulch helps regulate temperature and moisture. Rotate crops to prevent disease buildup.
Keep a garden journal to track planting dates and harvest times. Note weather patterns and pest issues. This helps you refine your timing each year. Share your experiences with other gardeners to learn more.
Garlic and onions are rewarding crops for any gardener. With proper timing and care, you’ll enjoy fresh bulbs for months. Start planning your planting schedule now for the best results. Happy growing.