After losing some leaves, our olive tree is taking a while to grow new ones. To help with this, we did some research. Here’s what we found.
Olive trees may not grow new leaves due to inadequate watering, nutrient deficiencies, pests and diseases, or unfavorable environmental factors. To promote new growth, ensure proper watering, provide balanced nutrition, monitor for pests and diseases, and create a suitable growing environment.
So, how can we tell which issue is causing our olive tree not to grow, and what are some ways we can fix it?
1. Improper Watering
Olive trees have specific watering needs to thrive and produce new leaves. The best way to water olive trees is to wait until the top 2-4 inches of soil is dry. You can check this by pushing your finger into the soil, up to the second knuckle.
However, there are times when we need to do more than watering.
Under-Watering
Under-watered olive trees are common when the soil is exposed to the hot and drying effects of the sun. In this case, the soil’s moisture dries out quickly, leading to the olive tree’s declining health in just days or hours.
To combat this, only water when the soil is dry and apply 2 inches of compost and 4 inches of mulch. Compost and mulch both dramatically retain soil moisture while promoting nutrients and beneficial soil life such as earthworms and mycorrhizal fungi.
Mycorrhizal fungi promote many aspects of plant life, in particular improved nutrition, better growth, stress tolerance, and disease resistance.
Department of Biology, University of Fribourg, Switzerland
Reapply compost on top of the olive tree’s soil every 1-2 months and mulch every 3-6 months. Some examples of mulches are wood chips, straw, leaves, or pine needles. Keep these amendments at least 3 inches from the tree’s trunk to prevent mold!
Over-Watering
Over-watered olive trees are often not caused by too frequent watering but by poorly draining soils. This leads to yellow leaves and reduced growth.
If your tree’s soil is sopping wet for more than 24 hours, it’s likely poorly draining. You can also test this by doing a soil percolation test.
To combat over-watering, apply 2 inches of compost on the top of the soil. Compost fixes both under-watering and over-watering as it increases the soil’s water retention while breaking up larger clumps of soil, such as compacted clay.
Avoid using mulch on olive trees until their soil is well-draining, as mulch can contribute to excess moisture and lead to root rot in poorly draining conditions.
2. Improper Nutrients
Lack of Nutrients
| Nutrient Deficiency | Leaf Symptom |
|---|---|
| Nitrogen | Entire leaf is pale or yellow |
| Iron | Dark green veins, rest of the leaf is yellowing |
| Zinc | Yellow blotches |
| Manganese | Broadly pale leaves, foliage color looks mottled or smeared |
When olive trees lack nutrients, they’re unable to maintain their health, and issues such as leaves yellowing, browning, and dropping begin. Poor nutrients can also cause flower and fruit drop.
A lack of nutrients in the soil is typically caused by:
- Degraded Soil
- Imbalanced Soil pH
- Sandy Soil
Fortunately, compost fixes all of the above three causes (more on compost and fertilizer soon).
Excess Nutrients
When olive trees have excess nutrients (usually caused by over-fertilizing), their roots get chemically burned, causing the plant stress. If not addressed, the stress begins to kill the plant, starting with leaves browning and dropping.
If you believe you’ve over-fertilized your olive tree, the best thing to do is flush the soil with lots of water.
This is called leaching, in which the water dilutes the nutrients/chemicals and pushes them further down into the soil (out of reach of the plant’s roots). Running your watering hose on low for 2-3 hours should do the trick.
How to Fertilize Olive Trees
The two main ways to fertilize olive trees are with fertilizer or compost. If you’re buying your fertilizer, I suggest avoiding chemical fertilizers if possible.
While chemical fertilizers work in the short-term, they often have long-term effects such as drying the soil. This not only causes issues with watering but kills the beneficial soil life, stopping benefits such as improved water retention, nutrients, and pest and disease resistance for the plant.
The good news is that the majority of organic fertilizers and compost provide sufficient nutrients. Ideally, this includes the three main nutrients, nitrogen, phosphorus, and potassium (abbreviated as NPK), as well as secondary nutrients such as iron, zinc, and magnesium.
To see which fertilizer I use and recommend, see my recommended fertilizer page.
If you opt for compost, I suggest going with the same recommendations above of 2 inches of compost every 1-2 months.
Imbalanced Soil pH
Olive trees also prefer a soil pH of 7.0-8.0.
Most plants prefer a slightly acidic to neutral pH, as it dissolves the nutrient solids in the soil and makes them accessible to the plant’s finer roots.
Fourteen of the seventeen essential plant nutrients are obtained from the soil. Before a nutrient can be used by plants it must be dissolved in the soil solution. Most minerals and nutrients are more soluble or available in acid soils than in neutral or slightly alkaline soils.
Donald Bickelhaupt, SUNY College of Environmental Science and Forestry
If the pH is outside of this range, olive trees aren’t able to absorb nutrients properly, leading to issues such as yellow, brown, and dropping leaves.
The best ways to check your soil’s pH are with pH strips or a meter. I prefer using a pH meter since they’re easy to use and affordable. To see which pH meter I use and recommend, check out my recommended tools page.
If you find your olive tree’s soil pH is too acidic (below 6.0), apply alkaline amendments such as wood ash, biochar, or lime.
For soil that’s too alkaline (above 7.5), apply acidic amendments such as sand, peat moss, and coffee grounds.
3. Environmental Factors
Olive trees are fairly hardy, but certain factors can stop or stunt their growth. Here’s a summary of these factors and what you can do to help:
- Temperature: Olive trees grow best in Mediterranean climates with mild winters and warm, dry summers. They can tolerate temperatures as low as 15°F (-9°C) but may suffer damage or reduced growth at lower temperatures. Ensure your olive tree is in a suitable climate, and protect it from frost and cold winds with frost cloths, windbreaks, or by planting it in a sheltered location.
- Light: Olive trees require full sun for optimal growth and leaf production. Ensure your tree receives at least 6-8 hours of direct sunlight daily. If your tree is in a shaded location, consider pruning surrounding trees or relocating the olive tree to a sunnier spot.
- Soil: Olive trees prefer well-draining, loamy soil with a pH of 6.0-7.5. They can tolerate some clay or sandy soils, but poor drainage or extreme soil conditions can stunt growth and reduce leaf production. Amend the soil with organic matter, such as compost, to improve its structure, drainage, and nutrient content.
- Pruning: Regular pruning is essential for maintaining the overall health and productivity of an olive tree. Prune your tree annually to remove dead, damaged, or diseased branches, as well as any branches that are crossing or rubbing against each other. This helps promote air circulation and sunlight penetration, encouraging healthy leaf growth.
- Transplant shock: If your olive tree has recently been transplanted or moved, it may experience transplant shock, which can lead to leaf drop and reduced growth. To help your tree recover, keep the root ball moist (but not waterlogged) and provide adequate nutrients. Be patient, as it may take some time for the tree to adjust to its new environment.
4. Pests and Diseases
Pests and diseases can also hinder the growth of new leaves on olive trees. It’s important to regularly check your tree for signs of infestations or infections and address them promptly to maintain the tree’s overall health.
Common Pests
- Olive fruit fly: These pests lay eggs in the fruit, which can lead to fruit drop and decreased leaf growth. You can manage them using traps, biological controls like parasitic wasps, or organic insecticides such as neem oil or spinosad.
- Scale insects: These tiny insects can cause leaf yellowing and drop. Control them by introducing beneficial insects like ladybugs or lacewings, or by applying horticultural oil or insecticidal soap.
- Aphids: These small insects feed on the sap of olive trees, causing leaf curling and reduced growth. Use insecticidal soaps or neem oil to control aphids, or introduce beneficial insects like ladybugs. For example, my lime tree recently had aphids and I used a garden hose to blast them off. They haven’t come back since!
Common Diseases
- Peacock spot: This fungal disease causes round, dark spots on leaves, leading to leaf drop and reduced growth. Prune affected branches and apply copper-based fungicides to control the disease.
- Verticillium wilt: This soil-borne fungus can cause wilting, yellowing, and browning of leaves, and even tree death. There’s no cure for infected trees, but you can prevent the disease by planting resistant varieties and maintaining good soil health.
- Olive knot: This bacterial disease causes swellings or knots on branches and trunks, which can stunt growth and reduce leaf production. Prune infected branches and apply copper-based bactericides to control the disease.
Regularly monitoring your olive tree for signs of pests and diseases can help you address problems early and prevent them from impacting new leaf growth. Also, maintaining overall tree health through proper watering, nutrition, and pruning reduces the risk of pests and diseases.
