Juicy, vine-ripened tomatoes are every gardener’s summer dream. But lush tomato plants and abundant harvests don’t happen on their own. Fertilization is key to success with this garden favorite. Tomatoes are heavy feeders and they require regular feedings of nutrient-rich supplements tailored to their needs.
One fertilizer that has long been a favorite for feeding tomatoes is bone meal. This organic source of phosphorus not only promotes strong roots and stems in tomato plants, but also abundant fruit production. The key question gardeners often have is how much bone meal per tomato plant is ideal.
So how much bone meal should you use per tomato plant?
The correct bone meal fertilization rate depends on several factors:
- Type of bone meal
- Application method
- Tomato variety
- Stage of growth
In this article, we’ll break down exactly how much bone meal to use per tomato plant. We’ll also discuss when and how to apply bone meal for optimal results.
An Overview of Bone Meal Fertilizer
First, what exactly is bone meal?
Bone meal is an organic fertilizer made from finely crushed animal bones that have been sterilized. Most bone meal comes from cow bones, but may also be sourced from other animals.
The bones undergo a process of steaming and crushing to create a fine, granular powder. This powder is rich in phosphorus and calcium which are slowly released into the soil.
Key Bone Meal Nutrients
- Phosphorus – The main nutrient supplied by bone meal, around 11-30%. Critical for root growth, flowering, and fruit production.
- Calcium – Bone meal contains around 20-34% calcium. Helps strengthen cell walls.
- Nitrogen – Usually 1-4% nitrogen to aid leafy growth.
Bone meal also contains traces of magnesium, potassium, iron, zinc, manganese, and other micronutrients.
Types of Bone Meal
There are a couple of different types of bone meal fertilizer to be aware of:
- Raw bone meal – Made from untreated, fresh bones that still contain fats and proteins. Has a faster nutrient release rate.
- Steamed bone meal – Bones are steamed at high pressures to remove organic compounds, fat, and proteins. Releases nutrients slowly over time.
Steamed bone meal is more commonly used as it resists compacting and doesn’t spoil or attract pests as readily. Either type can be used for tomatoes, but steamed bone meal is lower maintenance.
How Much Bone Meal Per Tomato Plant?
Now that we understand the basics of bone meal, let’s take a look at application rates.
The amount of bone meal to use per tomato plant depends on four main factors:
1. Bone Meal Type
Raw bone meal has a higher phosphorus percentage than steamed. On average:
- Raw bone meal contains 22-30% phosphorus
- Steamed bone meal contains 11-15% phosphorus
To supply equal amounts of phosphorus, you’ll need to apply more steamed bone meal.
Use these guidelines:
- Raw bone meal – 2.5-4 lbs per 100 sq ft
- Steamed bone meal – 5-7 lbs per 100 sq ft
And for tomatoes specifically:
- Raw bone meal – 1-2 tbsp per plant
- Steamed bone meal – 2-3 tbsp per plant
2. Application Method
Bone meal can be mixed into the soil before planting, side-dressed during the growing season, or used to fertilize seedlings.
Pre-plant and side-dress applications require more bone meal than fertigating seedlings since the nutrients are spread over a larger area.
- Mixed into soil – Use the high end of the per plant recommendations
- Side dressed – Use the mid-high end
- Seedlings – Use the low end
3. Tomato Variety
Indeterminate tomato varieties need more fertilizer than determinate types since they grow larger and produce fruit all season long.
Increase bone meal amounts by 1 tbsp per plant for indeterminate varieties.
4. Stage of Growth
Tomato plants need more phosphorus while flowering and setting fruit than during vegetative growth.
- Vegetative stage – Use the lower end of recommendations
- Flowering/fruiting – Use higher end of recommendations
Putting this all together:
- Raw bone meal
- Small determinate: 1 tbsp
- Large indeterminate: 2-3 tbsp
- Steamed bone meal
- Small determinate: 2 tbsp
- Large indeterminate: 3-4 tbsp
These are general guidelines per plant. Adjust as needed based on your soil, variety and growing conditions.
Now let’s look at exactly how and when to apply bone meal fertilizer.
How to Apply Bone Meal for Tomatoes
Bone meal can be applied at three stages of growth:
- Pre-plant
- Side dressing
- Fertilizing seedlings
Follow these tips at each stage to get the most out of this phosphorus fertilizer.
Pre-Plant Fertilization
Mixing bone meal into the soil before planting tomatoes is an excellent way to build up fertility. The nutrients will be in place for developing root systems.
How to apply:
- Loosen the top 4-6 inches of soil. Remove any large clumps.
- Sprinkle bone meal evenly over the bed. Use the high end of the recommended per-plant rate.
- Mix the bone meal into the top few inches of soil.
- Shape beds and rake the surface smooth.
- Transplant tomato seedlings or sow seeds.
Bone meal mixed into the soil before planting tomatoes
This pre-plant feeding will supply phosphorus and calcium for at least 6-8 weeks after planting.
Side-Dress Fertilizing
Even if you pre-fertilize, tomatoes will likely need an extra nutrient boost once flowering begins. This is where mid-season side-dressing comes in handy.
Side-dressing simply involves sprinkling fertilizer around the base of the plants and lightly working it into the top inch or two of soil.
When to side dress bone meal:
- Just before flowering begins
- Again when fruit sets and starts enlarging
How to side dress bone meal:
- Pull back mulch from around plants.
- Sprinkle bone meal in a ring around the base of each plant. Use the mid-high end of recommendations.
- Gently work into soil surface, being careful not to damage roots.
- Replace mulch.
- Water thoroughly.
Side dressing with bone meal when tomatoes start flowering
This will deliver vital phosphorus and calcium just when tomato plants need it most!
Fertilizing Seedlings
Bone meal can also be dissolved and used to fertilize young tomato transplants while they grow indoors or in a greenhouse.
Soaking bone meal releases nutrients into the water which can then be applied directly to seedlings. This is known as fertigation.
How to fertigate with bone meal:
- Place 1-2 tbsp bone meal in a gallon of water. Use the low end of recommendations.
- Allow to soak for 24 hours, stirring occasionally. The water will turn a tan, tea color.
- Fill a watering can or spray bottle with the bone meal tea.
- Apply directly to seedlings, being careful not to oversaturate the soil.
- Discard any leftover tea, as nutrients quickly degrade.
Watering tomato seedlings with diluted bone meal tea
Fertigating gives young plants an early boost of phosphorus for root and stem development.
When to Apply Bone Meal for Tomatoes
Now that we’ve covered how to apply bone meal at different stages, let’s discuss when it should be used over the course of a growing season.
Follow this timeline for fertilizing tomatoes with bone meal:
- Pre-plant – 2-4 weeks before transplanting seedlings or sowing seeds
- Side dress – When flowering begins, and again when fruits start developing
- Fertilize transplants – Every 2-3 weeks after germination until transplanting
Bone meal releases nutrients slowly over a period of several months. One early season application can support tomato plants for 6-8 weeks.
But side-dressing gives an extra dose of phosphorus when the plants need it most – during flowering and fruiting.
Bone Meal Fertilization Tips
Follow these tips to get the most out of bone meal:
- Always apply evenly and water thoroughly after application. This dissolves nutrients and makes them available to plants.
- Reapply if plants show signs of phosphorus deficiency like weak stems, poor flowering, or purple leaves.
- Use less bone meal in very alkaline soils, as phosphorus binds in high pH conditions.
- Combine with a nitrogen fertilizer to balance the low nitrogen in bone meal.
- Store sealed in a cool, dry place away from moisture.
Best Organic Bone Meal Options
When shopping for bone meal, look for pure organic bone meal from quality brands, such as:
- Espoma Organic Bone Meal – An all-purpose 3-15-0 fertilizer made from a blend of steamed bone meal and pasteurized bird guano. Provides phosphorus for blooms and fruiting.
- Down To Earth Bone Meal – A 4-12-0 natural fertilizer. Contains a diverse blend of ground animal bones for steady phosphorus release.
- Jobe’s Organic Bone Meal Fertilizer – A fast-acting 2-15-0 bone meal. Derived from organic bovine bones to stimulate blooms, fruit, and root growth.
- FoxFarm Soil Building Bone Meal – A rich 4-12-0 fertilizer made from steamed crushed bovine bones. Provides long-term phosphorus and calcium.
Avoid bone meal from unknown origins or chemically processed options. Always check labels and look for USDA-certified organic sources. These provide the purest nutrition and highest quality.
The Bottom Line
Bone meal provides an excellent slow-release source of phosphorus and calcium for tomatoes. By pre-fertilizing beds, side-dressing mid-season, and fertigating seedlings, you can supply tomatoes with abundant nutrition.
Factor in the type of bone meal, application method, variety, and growth stage. Then follow the recommended guidelines per plant:
- Raw bone meal – 1-3 tbsp per plant
- Steamed bone meal – 2-4 tbsp per plant.
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