Tomato Fertilizing and Soil Preparation for Santa Cruz County
Here's a truth that experienced tomato growers understand: good soil matters more than expensive fertilizer.
You can pour every tomato-specific product on the market onto poor soil and still get disappointing results. Conversely, tomatoes planted in well-prepared, organic-rich soil often thrive with minimal additional feeding. The foundation you build before planting determines most of your season's success.
In Santa Cruz County, our diverse soils—from sandy coastal loams to heavier inland clays—require different approaches. This guide covers soil preparation and fertilizing strategies tailored to local conditions, with emphasis on the moderate, well-timed feeding that produces healthy plants and abundant fruit.
Understanding Santa Cruz County Soils
Before you can improve your soil, you need to understand what you're working with.
Coastal Sandy Loams
Where: Westside Santa Cruz, Live Oak, Aptos, Capitola, coastal areas
Characteristics:
Light, well-draining texture
Warms quickly in spring
Dries out fast, especially in wind
Nutrients leach quickly with irrigation
Often slightly acidic
Challenges for tomatoes: Rapid drainage means more frequent watering and faster nutrient depletion. Organic matter disappears quickly.
Focus: Adding organic matter to improve water and nutrient retention.
Heavier Inland Clays
Where: Parts of Scotts Valley, some San Lorenzo Valley areas, Soquel hills
Characteristics:
Dense, slow-draining texture
Slow to warm in spring
Holds moisture well (sometimes too well)
Retains nutrients effectively
Can become compite and waterlogged
Challenges for tomatoes: Poor drainage can lead to root problems. Slow warming delays planting. Can be difficult to work when wet.
Focus: Improving drainage and soil structure; raised beds often help.
Redwood Soils
Where: Felton, Ben Lomond canyons, shaded areas throughout the county
Characteristics:
Often acidic from decomposing redwood duff
High organic matter but may be nutrient-poor
Variable drainage depending on location
Cool and moist
Challenges for tomatoes: Acidity may need correction. Limited sun is usually the bigger issue.
Focus: pH adjustment if needed; maximizing available sun.
Soil Testing: Know Before You Grow
A soil test removes guesswork from soil preparation and fertilizing. It reveals pH, nutrient levels, and organic matter content—information that guides your amendments.
Why Test?
Avoid over-fertilizing: Many gardens already have adequate nutrients. Adding more wastes money and can harm plants.
Identify deficiencies: Some soils lack specific nutrients that generic fertilizers don't address.
Check pH: Tomatoes prefer pH 6.2-6.8. Outside this range, nutrients become unavailable even when present in soil.
Establish a baseline: Testing every few years tracks how your soil management is working.
Where to Get Tested
UC Cooperative Extension: Offers soil testing through the UC Davis Analytical Laboratory
Private labs: Several serve California home gardeners
Home test kits: Less accurate but useful for basic pH and nutrient screening
What to Test For
Request a basic garden soil test that includes:
pH
Nitrogen, phosphorus, potassium (N-P-K)
Organic matter percentage
Micronutrients if you suspect deficiencies
Soil Preparation Before Planting
UC IPM emphasizes that tomatoes need well-drained soil and benefit from organic matter to hold moisture and nutrients without waterlogging. Preparation before planting is your best opportunity to create these conditions.
The Foundation: Loosen and Amend
1. Loosen soil deeply.
Tomato roots can extend 2-3 feet down in good conditions. At minimum, loosen soil 8-12 inches deep. Deeper is better if your soil is compacted.
Use a garden fork or broadfork rather than a rototiller if possible. Tilling can destroy soil structure over time and bring weed seeds to the surface.
2. Add organic matter.
Work 2-4 inches of compost or well-rotted manure across the entire planting bed, not just in planting holes. This:
Improves drainage in clay soils
Increases water retention in sandy soils
Adds slow-release nutrients
Supports beneficial soil organisms
Improves soil structure over time
3. Address pH if needed.
If soil test shows pH below 6.0, add garden lime according to test recommendations. If above 7.0 (less common here), add sulfur. These amendments take time to work, so apply in fall if possible.
Special Considerations by Soil Type
Sandy coastal soils:
Add extra compost (3-4 inches) since organic matter depletes quickly
Consider adding aged manure for additional nitrogen retention
Plan for more frequent irrigation and possible mid-season fertilizing
Heavy clay soils:
Focus on drainage; add coarse compost and consider raised beds
Avoid working soil when wet (compaction)
Don't overwater; clay holds moisture
Raised beds:
Excellent solution for poor drainage, contaminated soil, or rocky areas
Fill with quality garden soil/compost mix
Plan for faster drainage and more frequent watering than in-ground beds
Pre-Plant Fertilizing
With good compost incorporated, many gardens need minimal additional fertilizer at planting. However, a modest boost of phosphorus and potassium supports root establishment and early flowering.
What to Add at Planting
UC guidance favors modest, balanced fertilization rather than heavy nitrogen early on, which can produce lots of foliage but few flowers.
Recommended approach:
Work a balanced, slow-release fertilizer into the top 6 inches of soil according to label directions. Look for:
Moderate nitrogen (first number)
Higher phosphorus (second number) for roots and flowers
Good potassium (third number) for overall health
A ratio like 5-10-10 or similar vegetable fertilizer works well.
What to avoid:
High-nitrogen lawn fertilizers (promotes leaves, not fruit)
Excessive fertilizer of any kind (more isn't better)
Fertilizers with herbicides (obviously)
The Compost Question
If you've added 3-4 inches of quality compost to your bed, you may need little or no additional fertilizer at planting. Compost provides slow-release nutrition throughout the season.
Gardens that receive regular compost applications often reach a point where additional fertilizer becomes unnecessary. Pay attention to your plants and adjust accordingly.
In-Season Fertilizing
Once plants are established and fruiting, they may benefit from additional nutrition—but timing and amount matter.
When to Side-Dress
UC IPM suggests side-dressing nitrogen only if plants show poor vigor or pale foliage, and not until fruit has set, to avoid excessive vegetative growth.
Practical schedule for Santa Cruz County:
First side-dress: When first small fruits are forming (marble-sized or larger). This ensures the plant is in fruiting mode before adding nitrogen.
Second side-dress: 4-6 weeks later if plants are still actively growing and producing. Skip if plants look healthy and vigorous.
Don't side-dress:
Before fruit set (promotes leaves over fruit)
If plants are already growing vigorously
Late in the season when plants are winding down
How to Side-Dress
Apply fertilizer in a band around the plant, 4-6 inches from the stem
Scratch lightly into soil surface
Water deeply to move nutrients into root zone
Avoid getting fertilizer on stems or leaves
What to Use
Organic options:
Fish emulsion (quick-acting nitrogen)
Composted chicken manure (balanced)
Kelp meal (micronutrients and potassium)
Balanced organic vegetable fertilizer
Synthetic options:
Balanced vegetable fertilizer (follow label rates)
Tomato-specific formulas (often higher potassium)
Organic fertilizers release nutrients more slowly and build soil health over time. Synthetic fertilizers provide faster response but don't improve soil.
Calcium and Blossom End Rot
Blossom end rot—that frustrating black patch on the bottom of tomatoes—sends many gardeners rushing to buy calcium supplements. This is usually a waste of money.
- Adding calcium to soil (usually unnecessary)
- Foliar calcium sprays (doesn't reach fruit)
- Epsom salts (provides magnesium, not calcium)
- Eggshells in planting hole (too slow)
- Antacid tablets (folk remedy, no evidence)
- Consistent, deep watering
- Mulching to even soil moisture
- Avoiding excess nitrogen early
- Patience (later fruit often fine)
- Proper soil prep before planting
The Real Story
UC Master Gardeners explain that blossom end rot is usually caused by irregular watering and rapid growth, not a lack of calcium in the soil. Most Santa Cruz County soils contain adequate calcium. The problem is that inconsistent moisture prevents calcium from reaching developing fruit, even when it's plentiful in the soil.
What Actually Works
UC ANR emphasizes that prevention focuses on water management, not calcium addition:
Water consistently. This is the primary solution. Deep, regular watering prevents the moisture swings that interrupt calcium transport.
Mulch. Maintains even soil moisture between waterings.
Avoid over-fertilizing with nitrogen. Excess nitrogen promotes rapid growth that outpaces calcium uptake.
Don't over-fertilize early. Heavy early feeding causes rapid vegetative growth more prone to blossom end rot.
What Doesn't Work
Adding calcium to soil: Usually unnecessary; calcium is likely already present.
Foliar calcium sprays: Calcium doesn't move from leaves to fruit.
Epsom salts: Provides magnesium, not calcium, and can worsen the problem by interfering with calcium uptake.
Container Tomatoes: A Different Game
Container tomatoes live in an artificial environment entirely dependent on what you provide. The rules are different from in-ground growing.
Soil Mix
Use high-quality potting mix, not garden soil. Garden soil compacts in containers, drains poorly, and may harbor disease. Quality potting mixes:
Drain freely while retaining moisture
Are lightweight and well-aerated
Start relatively sterile
Fertilizing Containers
Nutrients leach from containers with every watering. Container tomatoes need regular fertilizing that in-ground plants don't require.
At planting:
Mix slow-release fertilizer into potting mix according to label directions
Ongoing:
Begin liquid fertilizing 3-4 weeks after transplanting
Feed every 1-2 weeks with diluted liquid fertilizer
Use balanced fertilizer or tomato-specific formula
Watch for deficiency signs:
Pale or yellowing leaves (nitrogen)
Purple tinge to leaves (phosphorus)
Brown leaf edges (potassium)
Container plants show nutrient stress more quickly than in-ground plants. Monitor closely and respond promptly.
Watering Containers
Container soil dries much faster than ground soil. In warm weather, daily watering may be necessary. Check soil moisture daily and water when the top inch feels dry.
Fertilizing Mistakes to Avoid
Too Much Nitrogen Early
High-nitrogen fertilizer applied before fruit set produces lush, leafy plants that flower poorly. The plant puts energy into vegetative growth instead of reproduction.
Fix: Wait until fruit is setting before any nitrogen-heavy feeding.
Over-Fertilizing in General
More fertilizer doesn't mean more tomatoes. Excess fertilizer:
Promotes leaves over fruit
Can burn roots
Contributes to blossom end rot
Wastes money and resources
May pollute groundwater
Fix: Start conservative. Add more only if plants show deficiency symptoms.
Ignoring Soil Preparation
No amount of fertilizer compensates for poor soil structure. Plants in compacted, poorly drained, or depleted soil struggle regardless of feeding.
Fix: Invest time in soil preparation before planting. It pays dividends all season.
Treating Blossom End Rot with Calcium
As discussed above, calcium supplements rarely fix blossom end rot because the problem is water management, not calcium deficiency.
Fix: Focus on consistent watering and mulching.
A Simple Approach
If all this seems complicated, here's a straightforward approach that works for most Santa Cruz County gardens:
Before planting: Add 3-4 inches of compost to your bed. Work it in 8-12 inches deep.
At planting: Add a small handful of balanced organic fertilizer to each planting hole. Mix with soil.
When fruit forms: Side-dress with compost or balanced organic fertilizer if plants seem to need it.
All season: Maintain consistent watering and mulch to keep soil evenly moist.
That's it. Many successful tomato growers use nothing more elaborate. The foundation matters more than the feeding.
Frequently Asked Questions
How do I know if my tomatoes need fertilizer?
Healthy tomatoes have deep green leaves and steady growth. Pale, yellowing leaves (especially lower leaves) may indicate nitrogen deficiency. Poor fruit set despite healthy foliage may indicate too much nitrogen. Purple-tinged leaves suggest phosphorus deficiency.
What's the best fertilizer for tomatoes?
Compost is arguably the best "fertilizer" because it provides balanced nutrition while improving soil. For supplemental feeding, balanced organic vegetable fertilizers work well. Avoid high-nitrogen formulas.
How often should I fertilize tomatoes?
In well-amended soil, you may only need to fertilize once or twice during the season—when fruit begins forming and again 4-6 weeks later. Container tomatoes need more frequent feeding (every 1-2 weeks).
Will Epsom salts help my tomatoes?
Probably not. Epsom salts provide magnesium, which is rarely deficient in Santa Cruz County soils. Magnesium excess can interfere with calcium uptake, potentially worsening blossom end rot.
Should I add eggshells for calcium?
Eggshells break down very slowly and rarely add significant calcium during a single growing season. They're fine in compost but won't fix blossom end rot. Consistent watering is the real solution.
Is organic fertilizer better than synthetic?
Organic fertilizers release nutrients more slowly, are less likely to burn plants, and build soil health over time. Synthetic fertilizers provide faster response and precise nutrient ratios. Both can grow good tomatoes; organic options better support long-term soil health.
The Bigger Picture
Fertilizing is important, but it's just one piece of tomato success. Variety selection, timing, watering, pest management, and support systems all matter at least as much.
If you focus on building healthy soil through regular compost additions, you'll find that fertilizing becomes simpler over time. Healthy soil grows healthy plants with less intervention. That's the goal worth working toward.
Free Gardening Resources
Know Your Microclimate Worksheet: Understand your specific Santa Cruz County growing conditions
Seasonal Planting Calendar: Month-by-month guidance for Santa Cruz County
Related Tomato Articles
Growing Tomatoes in Santa Cruz County
Growing Tomatoes in Containers
Heirloom Tomatoes for Santa Cruz
Determinate vs Indeterminate Tomatoes
Watering Tomatoes in Santa Cruz
Tomato Fertilizing + Soil Prep
Tomato Problems + Troubleshooting
