Harrisburg Tomato Calendar

Start Seeds Indoors

March 1 - March 15

6-8 weeks before last frost (April 15-25)

Transplant Outside

May 10 - May 20

After last frost, soil temp >60°F

First Harvest

July 15 - Aug 15

65-85 days after transplanting

Pro Tip for Harrisburg

Start seeds indoors in early March to get a head start on our relatively short growing season. Our average last frost is April 20, but wait until mid-May for safe transplanting.

Choosing Your Tomato Varieties

Select varieties suited for Harrisburg's climate (hot summers, humid conditions):

Early Girl Better Boy Brandywine Sun Gold Roma Cherokee Purple Sweet 100 Celebrity

Determinate (Bush)

Grow to fixed height, fruit all at once. Perfect for canning. Examples: Roma, Celebrity.

Indeterminate (Vining)

Grow continuously, fruit throughout season. Need staking. Examples: Better Boy, Brandywine.

Days to Maturity

Choose early varieties (55-70 days) for best results in Harrisburg's season. Late varieties may not mature before frost.

Starting Seeds Indoors

1 Timing is Everything

Start seeds 6-8 weeks before last frost (March 1-15). Use seed starting mix, not garden soil.

  • Sow ¼ inch deep
  • Keep at 70-80°F for germination
  • Use heat mat if needed

2 Light & Water

Seedlings need 14-16 hours of light daily. Use grow lights 2-3 inches above plants.

  • Water from bottom
  • Keep soil moist, not soggy
  • Use fan for air circulation

3 Transplanting Seedlings

When first true leaves appear, transplant to 3-4 inch pots. Bury stems deep for stronger roots.

  • Handle by leaves, not stem
  • Use diluted fertilizer weekly
  • Harden off before planting out

Soil Preparation & Planting

Soil Requirements

  • pH: 6.0-6.8 (test soil in early spring)
  • Texture: Well-draining, rich in organic matter
  • Amendments: Add 2-3 inches of compost before planting
  • Location: Full sun (8+ hours daily), protected from wind

Planting Instructions

  1. Harden off plants: 7-10 days before transplanting
  2. Plant deep: Bury ⅔ of stem for stronger roots
  3. Spacing: 24-36 inches apart, rows 3-4 feet apart
  4. Add support: Install cages/stakes at planting time
  5. Water well: Soak soil immediately after planting

Soil Tip for Harrisburg

Our clay soil benefits from raised beds. Add gypsum to improve drainage and calcium to prevent blossom end rot.

Care During Growing Season

1

Watering Schedule

1-2 inches per week. Water deeply 2-3 times weekly rather than daily. Use drip irrigation or soaker hoses to keep leaves dry.

2

Fertilizing

At planting: balanced fertilizer (10-10-10). When fruits form: switch to low-nitrogen, high-potassium. Avoid over-fertilizing!

3

Mulching

Apply 2-3 inches of straw or shredded leaves after soil warms. Conserves moisture, prevents diseases, keeps soil temperature even.

4

Pruning & Support

Indeterminate varieties: remove suckers below first flower cluster. Keep plants staked/caged. Remove yellowing leaves.

Harrisburg Pest & Disease Control

Common Pests Common Diseases Prevention

Common Issues in Our Area

  • Early Blight: Remove affected leaves, improve air circulation
  • Blossom End Rot: Consistent watering, add calcium
  • Tomato Hornworms: Hand pick, use Bt (Bacillus thuringiensis)
  • Aphids: Spray with water, use insecticidal soap
  • Septoria Leaf Spot: Remove infected leaves, avoid overhead watering

Harrisburg-specific: Our humid summers favor fungal diseases. Choose resistant varieties (marked VFN), space plants properly, and water in morning.

Harvesting & Storage

When to Harvest

  • Color: Harvest when fully colored but still firm
  • Timing: Pick in morning when cool
  • Method: Twist gently or use pruning shears
  • Green tomatoes: Harvest before first frost, ripen indoors

Extending the Season

  • Use season extenders in early fall
  • Protect from early frost with row covers
  • Prune late-season flowers to focus energy on existing fruits
  • Harvest green tomatoes before killing frost

First Frost Dates

Average first frost in Harrisburg: October 15-25. Watch forecasts and protect plants when temperatures drop below 40°F.

End of Season & Saving Seeds

End of Season Cleanup

  • Remove all plant debris to prevent disease carryover
  • Add healthy plants to compost (remove diseased plants)
  • Test soil and add amendments for next year
  • Consider cover crops for winter

Saving Seeds for Next Year

Only save seeds from heirloom varieties (not hybrids):

  1. Choose perfect fruits from healthy plants
  2. Ferment seeds in water for 2-3 days
  3. Rinse and dry completely on paper towels
  4. Store in cool, dry place in labeled envelopes