Beginning about now, as people move their houseplants inside for the winter, we start to get panicked calls and emails. During their “summer vacation” outside, their houseplants probably thrived in a balanced ecosystem. The plant attracted pests like mealy bugs, aphids and whitefly, but having the pests attracted hungry beneficial insects that ate them before they became a serious concern.
Moving those plants inside to protect them from the cold leaves them vulnerable to the pests that moved with them because the beneficial insects probably didn’t come inside for the winter. All of a sudden, they’re stressed out in an environment where it’s less likely that they’ll get as much natural sunlight while they’re coping with extra-low humidity in your heated home.
And worst-case scenario, you’re forced to spray toxic pesticides inside your home where your family and pets are exposed to them.
Once again, neem can come to the rescue, and we don’t even recommend that you spray your house with something that smells funny. Instead, try a soil drench – preferably before you bring them inside. Treating the soil rather than spraying the plant means that your plants can uptake neem’s active ingredients through their roots where they become systemic and make it impossible for critters like aphids and whitefly to live and reproduce.
Using neem as a soil drench also will eliminate those horrible fungus gnats that can swarm houseplants and lay eggs that hatch into hungry larva munching on your plant’s root system. (It’s actually good for earthworms if you should happen to have them in your pots.)
Here’s how to make a neem soil drench. You want to mix just enough because neem oil breaks down when it’s exposed to water and air, so we’ve included pot sizes too. Use very hot water and shake well. Allow to cool slightly and pour over the plant’s roots.
| RESULT | NEEM OIL |
| 4 cups (1 quart) | 1 tablespoon |
| 8 cups | 1.5 tablespoons |
| 16 cups (1 gallon) | 3 tablespoons |
You’ll want to pour about a cup of this mixture for every four to six inches of pot size. For instance, pour one cup in a pot that measures four to 10 inches across at the top. You’ll want to double that for plants in pots wider than 10 inches and up to 24 inches. Above 24 inches, use three cups.
| Pot size | Cups of neem mixture |
| 4 to 10 inches | 1 cup |
| 10 to 20 inches | 2 cups |
| Above 20 inches | 3 cups |
The good news is that a neem oil soil drench lasts for four to six weeks, depending upon the level of stress that your plants are under. If you’re facing severe infestations immediately, you may want to spray the plant with a neem oil mixture which works more quickly but doesn’t last as long. (Learn more about mixing neem spray here.)