Why Your Lemon Tree is Dropping Flowers: 9 Causes and Cures
Lemon trees are must-have fruit trees! They’re great options for gardeners who want fresh lemons throughout the winter. Sometimes, lemon trees drop their blossoms instead of forming fruit. Join seasoned grower Jerad Bryant in curing these nine causes of premature blossom drop.
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Citrus trees—no matter their type—are icons for fresh fruit lovers worldwide. They conjure memories of key lime pie, freshly squeezed lemonade, and grapefruit halves with sugar dustings. Their delicious fruits develop from fragrant white and yellow blossoms that attract pollinators.
Since most North American gardeners grow plants in cold temperate regions, we must grow lemon trees in containers and bring them indoors for the winter. This transition is where most blossom drop issues begin, as citrus plants prefer to stay in one spot year-round.
Do not worry though, as there are simple methods for transitioning your tree indoors so you don’t disrupt its natural processes. Outdoor specimens also face these issues, although their flowers drop less often than indoor plants. Give your tree the cultural conditions it craves and it’ll reward you with aromatic blossoms and shiny yellow lemons.
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Lack of Pollination
One primary cause of blossom drop indoors is unsuccessful pollination and fertilization! Citrus flowers require pollinators to shake their male anthers and dust pollen onto receptive female stigmas. Without these pollinators, indoor blossoms wither and die before producing fruit.
Wind is another tool that helps flowers pollinate and fertilize themselves. It rumbles the anthers, shaking pollen out onto receptive flowers. Simulate wind and insects and you’ll pollinate your lemon tree to ensure proper fruit set.
The Cure
Lack of pollination infrequently occurs outdoors, unless the tree grows in a region with frosty winters. Cold temperatures prevent pollinators from flying freely, as they take the time to rest until spring. Avoid growing citrus outdoors where frosts are recurring. If pollination is low in a warm climate, consider planting another citrus tree nearby to attract more pollinating insects.
Indoors, use hand pollination to achieve the work of insects and wind. Use a paintbrush to dust pollen from one flower to the next, or gently shake your entire tree to emulate wind. These methods work on outdoor trees too, if you’d like to ensure they pollinate successfully.
Freezing Weather
Unlike deciduous fruit trees, lemons are frost-tender! These evergreen trees need warm temperatures year-round, although they appreciate some chill in winter. They’re hardy in USDA hardiness zones 9 through 11 and require protection from freezing weather below zone 9.
Cold temperatures cause blossom drop, as the trees decide to conserve their resources to survive the freeze. They can also damage fruit as it forms, ruining your precious harvests. Pay close attention to dropping temperatures, and bring your lemon indoors well before the first hard frost in your region.
The Cure
Avoid placing your lemon tree near cold windows indoors. Give them a heater and a humidifier if they reside in a cold room. The heater keeps the air warm, while the humidifier compensates for the dry air the heater produces.
If cold weather threatens your lemon flowers outdoors, use frost cloth over your entire tree to give it an extra protective layer. Frost cloth traps hot air from the lemon inside while blocking cold air from outside. Ensure it reaches around all sides of the tree, and weigh down the ends with rocks or containers.
A Change of Pace
The leading cause of blossom drop on indoor trees is the transition they must undergo! Citrus plants would prefer to sit in a single spot the whole year, but we must move them to save them from frost. Transition them slowly, monitor them the entire time, and they’ll have more defenses to protect themselves while they move.
A change of pace affects lemons on both sides of the spectrum. Whether transitioning them indoors or outdoors, give them a slow and gentle move so they can properly adapt.
The Cure
Prepare lemon trees for their indoor move by placing them in a semi-shady location outside for a week or two. Let them adapt to less light, then move them indoors to a bright location. The same goes for moving lemons from inside to your outdoor garden. Place them in a shady location outdoors for a week, then move them into a spot with full sun.
Soggy or Dry Soil
Watering infrequencies can lead to blossom drop, as citrus specimens are sensitive to abrupt moisture changes. Too much and too little water can cause issues. Too much moisture leads to soggy soil that drowns the roots, preventing them from accessing the necessary nutrients for flower and fruit formation.
Too little water also harms the tree, making it more difficult to pull up nutrients from the soil. Ensure you adjust your watering schedule to match your tree’s needs, and it’ll reward you with dozens of flowers and lemons come early spring.
The Cure
Maintain a moist soil culture for your lemon tree. Lemons prefer drier soil than other fruits like apples, plums, and pears. Ensure the top layer dries between waterings to help your sapling breathe. You want the soil to resemble a wrung-out sponge after watering.
A key component to consistent moisture is the type of soil your tree grows in. Lemons prefer well-drained soil with lots of organic matter. Use potting mix for container lemons or create a blend using individual ingredients.
Drafty Air Flow
As cold air affects lemon trees, so too does hot air! Heaters pose a challenge for potted plants, as they blow concentrated gusts of hot, dry air that zaps tender foliage. You’ll know this is an issue if your lemon tree has wilting, drooping leaves alongside dropping blossoms.
The Cure
The solution is simple—move your potted tree away from the heater. That way it enjoys the warmth without the negative effects. If dry air is a concern, consider adding a humidifier to the room to balance the humidity.
Outdoor trees may face this issue if they lie in the way of strong winds. Protect your tree with a windbreak like a fence or wall, or plant other tall plants in the way of the wind. If this doesn’t work, consider transplanting the lemon to a new location safe from harsh gusts of warm air.
Not Enough Light
Lemons need lots of light to perform their best! They’ll tolerate less light indoors, although they crave direct sunlight that’s abundant outside. Flowers may fall off the stems if your lemon receives less light than it prefers.
Lemons rarely have issues with too much light while they grow, except in the hottest regions of North America. Give them afternoon shade where droughts and excessive temperatures are frequent during the summer.
The Cure
It’s best to situate potted lemons within six feet of a sunny window so they have direct sunlight for part of the day. Consider adding grow lights to your indoor setup if your lemon craves more light. Set the lights on a timer so you don’t have to worry about turning them on and off every day.
Outdoors, give lemons full sun with at least six hours of direct sunlight daily. They’ll need partial shade during transition periods from inside to outside and vice versa. Otherwise, they’ll give you the most lemons when they grow under full sun.
Insufficient Nutrients
Plants use nutrients from the soil to grow, bloom, and fruit. Without the necessary nutrients, they struggle to complete their ordinary processes. Potassium and phosphorus are especially important for flower development, as they allow the tree to produce blossoms, fragrance, and pollen.
Too many nutrients can also cause issues, especially for outdoor specimens in fertile areas. Avoid overfertilizing your plants, and stick to a regular regimen.
The Cure
Fertilize lemons throughout the growing season, giving them several helpings of nitrogen-rich organic fertilizer. Ensure the ground is wet before you apply it, and water the powder, liquid, or pellets so they seep into the soil.
Avoid fertilizing during the middle and beginning winter months while your citrus trees are indoors. You may apply low doses of potassium-rich organic fertilizer as blooms appear in late winter and early spring. Watch for signs of nitrogen imbalances—too much causes dark green leaves with burned edges and too little causes yellow leaves throughout the tree.
If you’re unsure of the nutrient content in your soils, consider using a soil test kit. It’ll tell you exactly which nutrients you need to add or leach out, the pH level of your soil, and how much organic matter it contains.
Pest Damage
Pests target weak trees, wreaking havoc on susceptible specimens! Aphids, mealybugs, spider mites, and scale may infest your tree if it’s unhappy or unhealthy. Start by correcting the lemon’s cultural conditions and removing the pests. As your lemon tree grows and heals, it’ll thwart insect attacks with natural defenses.
The Cure
Remove pests from outdoor plants by spraying them with strong jets of water daily until the bugs disappear. The water knocks the insects off, and the moisture prevents them from returning. After a few days of daily spraying, most pests will disappear.
Indoors, lemon trees are especially susceptible to pest damage. They lack beneficial insect predators that eat pests. Give them a boost with horticultural oil, neem oil, or plant soap. Take care to spray these outdoors in the morning or afternoon. You want to avoid inhaling it indoors while minimizing damage to pollinators outdoors.
Weak Tree
Mature specimens with bound roots may experience blossom drop as they age. New transplants also may grow weak after repotting and struggle to hold onto their flowers. Let new transplants grow roots this year, and they should have normal growth in the following years.
Old trees in containers may need repotting. The best time to transition trees into new pots is during the growing season. Wait until long days and sunny temperatures return before moving them into a new home.
The Cure
Lemon trees need repotting every four to five years. Their roots grow too thick and abundant for their container and need treatment. Start by removing the tree from its container, taking care not to damage any branches.
Inspect the roots, noting any circling or upward-growing tendrils. Cut off the bottom layer of roots with a shovel or knife, and free any circling roots so they arrange downwards. Prepare a new container with fresh potting soil slightly larger than the last, and place the tree in its center.
Fill the edges with more potting soil, then water the tree well. If soil sinks below the trunk’s root flare, add more so that it sits level at the surface. Keep your plant in steady conditions without change while it adapts to its new container; it’ll grow strong for years!
