Neem oil is a safe, organic alternative to using traditional pesticides in controlling harmful insect infestations, and to combat fungal diseases in most plants, including flowering plants.
Made from the neem tree, the active ingredient, Azadirachtin, works by disrupting the life cycle of harmful insects, hindering their ability to feed and reproduce. The pungent garlic/sulphur aroma of neem oil also becomes absorbed into the plant, rendering a taste downright unappealing to many insects.
Neem oil is biodegradable, non-toxic, and considered safe to use around people and pets, as well as safe for beneficial insects, such as pollinators, if applied correctly.
But what about flowers? Are there precautions to heed when using neem oil on flowering plants?
In this article, we’ll cover everything you need to know about using neem oil on flowering plants.
Is it Safe to Spray Neem Oil During a Plant’s Early Flowering Stage?
Neem oil is often used as a preventative, as well as to combat an ongoing bug problem. You can start spraying your plants (flowering and otherwise) once per month during late winter and early spring, when plants are emerging from dormancy. Often, gardeners will use a soil drench of the prepared neem oil mixture to pre-treat the soil and ensure that any larvae or eggs that have wintered over will not hatch.
During active growing months, preventative spraying should take place every 7 – 10 days.
If you’re battling a bug infestation, you can increase the applications to once every 3 – 4 days but watch your plants carefully for signs of burning. If you see any dry, white/tan patches on your leaves with curling edges, reduce the frequency of application.
It’s perfectly safe to use neem oil on plants containing flower buds that have not yet opened. Don’t concentrate the spray directly on the flower buds, as they are rather delicate, but on the leaves, stem, and soil around the plants.
Once the flowers have opened, avoid spraying anywhere near the blossoms. The safest bet is to forgo spraying at this stage and merely use a soil drench, if needed.
To prepare a soil drench of neem oil, start with cold pressed, pure neem oil. Use 1 teaspoon neem oil to one quart of water, and add a drop or two of liquid soap, as an emulsifier. Shake well and pour 1 – 3 cups of the solution into the soil at the base of each plant, depending on the individual plant’s size. Wait 2-3 weeks before reapplying, then repeat. It will take a little time to see results (usually about 10-14 days), but the plant will gradually absorb the neem oil solution and become unpalatable to most feeding insects.
What Can Happen if You Spray a Flowering Plant with Neem Oil?
The major risk of spraying a flowering plant with neem oil is that of potentially smothering pollinators with the wet oil. Although neem oil has been deemed safe for bees, ladybugs, and butterflies – since they don’t eat the leaves – they are still at risk of being smothered by the oil.
When you spray a flower – especially a bell-shaped flower – with neem oil, some of the oil gets trapped inside. As it’s then protected from airflow, it doesn’t dry as quickly as neem oil when applied to leaves (which takes roughly 45 minutes to dry – remember, the oil has been diluted with water).
Neem oil can block the airways of any insect, making it difficult to breathe. When bees crawl inside the flower to collect pollen, they may find themselves, and their airways, coated with neem oil and ultimately perish by suffocation.
By using a neem oil soil drench on flowering plants, in conjunction with spraying your non-flowering plants only in the evening hours or very early in the morning, bees are unlikely to get caught in the crossfire.
It’s also noteworthy that some flowers may react badly to neem oil and drop off before being pollinated, if sprayed.
How Late into Flowering Is it Safest to Use Neem Oil?
Once the flower petals have fully opened on a plant, stop using neem oil as a spray until the flowers drop. You can still use a neem oil soil drench.
Wondering about flowering fruits? Read our related post “Using Neem Oil on Fruit Trees” here.
Neem Oil Used on Cannabis
In areas where growing marijuana is legal, it is advisable to never use neem oil during any part of the flowering stage. Buds sprayed with neem oil, or neem oil used a soil drench for budding marijuana plants, is reported to affect the taste/aroma of the final product (buds) when smoked.
Other Neem Oil Tips to Keep Your Plants Safe:
1. Avoid Using Neem Oil in Hot Temperatures and Direct Sunlight – Not only will using neem oil during daylight hours put pollinators at risk, be aware that neem oil, when sprayed on leaves which are exposed to direct sunlight, may burn the foliage. Only use neem oil in the very early morning, or preferably, in the early evening, so the oil has a chance to dry before either the sun or pollinators return.
2. Do Not Use Neem Oil on Stressed Plants – If plants are newly transplanted, or already weakened by over or under watering, it’s best not to use neem oil as either a spray or soil drench until the plants are looking more hearty, to avoid shocking their systems.
3. Do Not Use Neem Oil on Thin/Delicate Plants – Any plants with thin, wispy, or delicate foliage may react badly to neem oil applications, resulting in the foliage burning and/or dying off. Please refer to this list of recommended plants to avoid using neem oil on.
Neem oil, when used properly, can be an organic gardener’s best friend! But, in order to be responsible gardeners, and enjoy our plants for years to come, we need to protect our pollinators. Avoid spraying neem oil at the wrong stages of flowering, and you’ll be helping to protect your local bee population.
Michelle Weaver is a former pastry chef of thirty years who reinvented herself during the pandemic, now happily earning a living through freelance writing and selling her art. She and her significant other live in an 1895 farmhouse in North Carolina, where they have several acres, allowing her to garden to her heart’s content. When she’s not playing in the dirt, she enjoys hiking in the nearby mountains, creating new vegetarian recipes, and photographing the wildlife that comes to visit.