Yes, fertilizing plants in September is fine for most houseplants, but it should be your last month of feeding for the year. Use this time to taper off your fertilizer amounts before stopping for winter. Your plants are slowing down and need less food as the days get shorter outside.
I used to keep feeding my plants through October and November each year. They kept pushing out weak growth that couldn't survive the low light of winter. Once I started my final feeding in late September, my plants went into winter looking strong. They came back even stronger the next spring.
My friend learned the opposite lesson by stopping too early in August. Her plants looked pale and tired by October because she cut off food while they still had weeks of active growth left. The right fall fertilizer schedule catches that last growth push before dormancy sets in.
Shorter days trigger changes inside your plants that prepare them for rest. Even though your home stays warm all year, your plants sense the dropping light levels outside. Their roots slow down and can't absorb nutrients like they did in summer. Feeding during this shift just wastes fertilizer and can hurt roots.
Plan your end of growing season feeding as a gradual wind-down through the month. Give full strength fertilizer in early September when days are still long. Switch to half strength by mid-month as growth visibly slows. Make your last application by the end of September at quarter strength or skip it entirely.
Watch your plants for signs that they're ready to stop feeding. New leaf growth slowing down or stopping tells you dormancy is near. Existing leaves hold steady without getting bigger. These signals mean your plant has stopped building and started saving energy for winter. Autumn plant care means following their lead.
Some plants keep growing year-round under bright grow lights in your home. These can handle feeding into October or later since they don't experience the daylight drop. But plants near windows will follow natural light cycles no matter how warm you keep your home inside during winter.
Mark your calendar to start tapering your feeding in early September each year. Feed one more time at reduced strength, then put your fertilizer away until March or April. Your plants will thank you by staying healthy and strong through winter and bursting with new growth when spring arrives.
Read the full article: Fertilizing Indoor Plants for Healthy Growth
