10 Best Organic Slow Release Fertilizer 2026 in the United States

The GARDENWISE 10-10-10 Plant Fertilizer is a balanced all-purpose option featuring equal parts nitrogen, phosphorus, and potassium (10-10-10), which supports plant health by promoting strong roots, vibrant blooms, and lush growth. Its slow-release formula feeds plants continuously for up to 8 weeks, reducing the frequency of application—ideal for vegetables, fruit trees, shrubs, and flowers. It also contains a quick-release nitrogen portion for an immediate growth boost when plants need a fast nutrient pick-me-up.

The fertilizer comes as easy-to-spread granules suitable for outdoor gardens and some indoor plants, making application straightforward. It is versatile for many soil types and plant varieties. This fertilizer offers convenient, steady nutrition across a range of plants without complicated application, making it a practical choice for gardeners who want reliable feeding.

Burpee Natural Purpose Granular is an organic slow-release fertilizer designed to support a wide range of plants including vegetables, flowers, herbs, and seedlings. It provides a balanced supply of major nutrients along with calcium, trace minerals, and beneficial microbes, which help improve soil health and plant growth. Nutrients are released quickly and continue feeding plants for up to three months, making it convenient for gardeners who want longer-lasting nutrition without frequent applications.

The product comes in granule form, which is easy to spread over soil or mix into containers, fitting well with both indoor and outdoor gardening. It’s certified organic (OMRI listed), meaning it’s safe for organic gardening and reduces environmental impact compared to synthetic fertilizers. Its versatility makes it suitable for various soil types and garden setups.

This fertilizer is a solid choice for home gardeners looking for an easy-to-use, organic product that supports plant health and soil vitality. It works well as a natural option that covers a variety of garden plants without much fuss. However, if precise nutrient ratios or extremely long feeding intervals are required, other products might be more suitable.

The Burpee Organic Tomato & Vegetable Granular Plant Food is a solid choice for gardeners looking for an organic, slow-release fertilizer. Its NPK ratio of 3-6-4 provides a good balance of nutrients, especially with a bit more phosphorus to support strong root and fruit development, which is ideal for tomatoes and other vegetables. The fertilizer comes in easy-to-use granules that release nutrients right away and continue feeding plants for up to three months, reducing the need for frequent applications. Being OMRI listed means it’s approved for organic gardening, which is great if you want to keep your growing efforts eco-friendly.

It works well with most soil types and covers around 160 square feet per 4-pound bag, making it suitable for small to medium garden spaces. Compared to some other slow-release options, the NPK numbers are on the lower side, so it might not be enough for larger or more nutrient-hungry gardens without additional feeding. Also, while it’s organic and safer for the environment, some users might find the nutrient release less predictable than synthetic fertilizers.

For those who prefer a low-maintenance, organic fertilizer that supports healthy plant growth and fruit production over a season, this product fits well. However, very large gardens or those needing quick nutrient boosts may need to supplement it.