Should You Fertilize Your Lavender Plants This Season?
Trying to figure out if you should fertilize your lavender plants? This hardy shrub can handle quite a bit of neglect, but what about fertilizer? In this article, organic gardening expert and former lavender farmer Logan Hailey examines if it's a good idea to fertilize this season, or if you should skip it.
Lavender is a Mediterranean native herb that requires very little maintenance in the garden. Once established, most varieties are beginner friendly, drought-tolerant, and long lived perennials that flower for years to come.
But this herb does not enjoy the same conditions as most garden crops. Lavender’s preference for dry, gravelly, nutrient-poor soil sets it apart from other loam-loving vegetables and flowers. It even thrives on a bit of neglect.
If you want to grow lavender with an abundance of fragrant, beautiful blooms, you may be surprised by its soil and fertilizer preferences. Let’s dig into whether or not you should fertilize your lavender plants.
The Short Answer
No fertilizer is needed to grow lavender except for some optional trace minerals. Contrary to most assumptions, fertilizing can actually do more harm than good. Lavender naturally prefers poor soil with very few nutrients. An excess of nitrogen can cause too much foliage and few flowers. This extra leafy growth can lead to reduced airflow and disease issues.
Fertilized plants tend to grow large and unruly, with low fragrance flowers or no flowers at all. Too much fertility can even kill a lavender plant, which is why products like quick-release synthetic nitrogen fertilizers are particularly dangerous for this herb. The only safe form of fertilizer is a small amount of compost that can slowly release minerals and nutrients over time.
The Long Answer
One mistake lavender gardeners make is over-fertilizing it. Many beginners dump on fertilizer at the time of planting in hopes that it will make their new plants spring up more quickly.
While it may seem like you’re promoting a lot of healthy new growth, heavily feeding this herb with nutrients can lead to lots of leaves and no flowers.
Lavender Thrives With Low Nutrients
In its native Mediterranean habitat, it grows on sunny, exposed slopes in soil that resembles rocks and gravel. In spite of the harsh appearance of the environment, these native plants bloom with great abundance and thrive in hot, dry soils. When it rains, the soil drains water very quickly and takes many nutrients along with it.
Still, lavender enjoys low fertility and gets all that it needs from the rock minerals, scarce water, and abundant sunlight. Microorganisms in these dry conditions “mine” away at the minerals in the rocks and slowly make them available to the plant. In our gardens, the best thing we can do is try to replicate these conditions. You can mimic them by doing the following:
- Extremely well-drained soils.
- Trace minerals (from rocks or amendments).
- Low amounts of water (allow the soil to dry out before watering again).
- No nitrogen fertilizer.
- Optionally, small amounts of compost for a little potassium and phosphorus.
It may seem strange, but this is one of those plants that really prefers you let it grow naturally. A hands-off approach is the best thing you can do. As long as you properly prepared soil at the time of planting, it doesn’t need much else. Using fertilizer can disrupt its growth cycles and can send the plant into shock.
Signs of Over-Fertilization
Unlike most garden plants, additional nutrients cause undue stress to this lavender. When this herb is exposed to too much fertility in the soil, it may show these symptoms:
- Yellowing leaves
- Wilted lower leaves
- Droopy appearance
- Lavender that won’t bloom
- Flowers with very little fragrance
- Stunted growth
- Excessive leaf production
- Weak or drying plants
In addition, too much fertilizer can make the plant more susceptible to pests and diseases. Sap-sucking whiteflies and aphids can smell the nitrogen flush in the plant tissues and will come in swarms to suck up the nutrient-rich leaf juices. These bugs are particularly problematic when they spread diseases like Alfalfa Mosaic Virus or Xylella.
At the same time, the excessive foliage growth reduces the amount of airflow through the plant. Rainwater can sit for longer on the leaves and the inner portions (near the base and crown) can become stuffy and trap humidity.
This lack of aeration in their branches leads to major fungal issues like Botrytis, Shab, and Septoria Leaf Spot.
Optional Soil Amendments
If your plant is struggling to grow as quickly as you’d like, you may want to add some soil amendments instead of standard fertilizers. These amendments work by slowly releasing minerals to the roots for uptake. They are best supplied at the time of planting, but you can also use them as mulches.
Amendments help create the proper soil conditions for this perennial herb to thrive. Some amendments are primarily used to improve the drainage and aeration of the soil, but they can also provide trace nutrients.
The most beneficial soil amendments are:
- Coarse sand
- Fine pea gravel (excellent for drainage)
- Crushed limestone (also adds calcium and helps raise pH, as described below)
- Peat moss (only if your soil isn’t acidic)
- Vermiculite (can add trace minerals)
- Shredded wood bark
- Coconut coir
- Bark or leaf-based compost (not manure based)
In certain soils, lavender can often be lacking in calcium. Calcium is an essential plant nutrient for holding plant tissues and cell walls together.
Their native Mediterranean soils are naturally calcareous, which means they are calcium-rich because of the presence of limestone. This is the one mineral that is often missing in garden soils with high clay content or an acidic pH.
Most people think of fertilizer as NPK, or Nitrogen, Phosphorus, and Potassium. Lavender doesn’t usually need any of these supplemental nutrients. However, it may need a mineral fertilizer that adds calcium to the soil.
The best calcium amendments are:
- Crushed eggshells
- Oyster shell
- Clam shell
- Bone meal (in small amounts)
- Gypsum (calcium sulfate)
- Dolomitic lime (also raises pH)
Use Lime For Acidic Soil
Lavender naturally prefers a soil pH between 6.5 and 7.5. Acidic soils with a pH below 6.5 can cause major problems. If your soil is high in clay or comes back as acidic on a soil test, you may need to raise the pH for your plant to thrive.
Agricultural lime or dolomite lime increases the soil pH and makes it more alkaline. You can sidedress your lavender with lime powder per the package instructions. You can also mulch with limestone and rainwater will naturally filter the alkalizing compounds into the soil.
A hands-off approach is the best thing you can do for lavender, especially regarding fertilizer. This herb truly thrives in low-nutrient, poor soils. Too much fertilizer can cause a range of issues, from yellow leaves to excessive foliage to fragrance-free flowers to stunted growth.
Fortunately, home gardeners can easily avoid these issues by simply leaving your plant to its own devices. Avoid fertilizing, especially fertilizers with high amounts of nitrogen. If you feel that your plant is lacking in vitality, it may benefit from amendments like limestone, oyster shell, gravel, bone meal, or a low-nutrient compost (without manure). You should also check the soil pH and ensure that it is at least 6.5 or higher.