Fall: To Fertilize or Not to Fertilize. That is the Question

Manual fertilizing of the lawn in back yard in spring time | (c) Bakerette.com

With fall now in season, The days are turning shorter, the evenings cooler, sending a signal to plants to slow down. Now’s the time that plants concentrate on what is underground–their roots.

In the fall, plants’ needs are different than in the spring and summer. In warmer months plants are concentrating on leafing and blooming, but in the fall, their energy turns to the roots. They no longer need food (nitrogen) to stimulate upper growth. What they need is food low in nitrogen, which inspires upper growth, so that they can concentrate on a stronger root system. Trees, shrubs & perennials generally experience a burst of growth when they are fed with fertilizer high in nitrogen. For example, if the growth bursts in October, the new growth will get zapped by cold weather that can damage the entire plant.

Despite the hot weather you may still get in August and September, most hardy plants need to start slowing down. It’s best to stop fertilizing with high nitrogen the first of August in areas with freezing winters and in September in warmer areas. The exception is annuals. You can safely feed them until frost.
Different plants have different needs:
With perennials, what you want now is a fertilizer rich in phosphorus and potassium. Perennials actually do well if you feed them a high phosphate fertilizer with low nitrogen in the fall, which can produce stronger plants in the spring and help with producing more flowers.
When you look for fertilizer, look for the set of 3 numbers on the box or bag. These state the ratio of nitrogen, phosphorus, and potassium. Nitrogen is the first number, so for a fall fertilizer, make sure that number is low (i.e., between 2 and 5). A good ratio is around 3-12-12.

Spring Bulbs
Spring bulbs do well with an application of phosphorus applied at the root level to help them get established before winter sets. Mix this with a rich compost to give the bulbs plenty of food to help them through the winter.
You want to stop fertilizing your roses at least one month before your region’s first annual frost date. Fertilizing too long into the fall encourages roses to produce tender new growth that will damage the plant when frosts sets in. However, you can continue watering the roses until the ground freezes.
Fall is an ideal time to fertilize your yard. In early September your grass is recovering from a long, hot summer, so you’ll want to give your lawn a shot of nitrogen. A good ratio is around 20-8-8 to help get it growing again. An application of around 13-25-12 at the end of October or early November is essential to help stimulate root growth. This will help your lawn green up quicker in the spring and be more disease and draught resistant.

Shrubs and Trees
Trees and shrubs are often located in beds of mulch that use up nitrogen as they decompose. Fertilizing trees in late September and early October helps stimulate root growth.

Image credit: evgenyb / 123RF Stock Photo

About Jen

Jen is owner, author, and creative mind behind Bakerette. Jen eats a vegan diet and recently converted Bakerette to a plant-based website that offers a smattering of healthful recipes! Jen is author of the cookbook Festive Feasts: Meals and Memories from Halloween to Christmas, which can be purchased online at Amazon or Barnes & Noble.


  1. I really like your post on fall fertilizing. I did not study horticulture in college (communications instead). I just moved to a home with a yard so this is the first time I have been able to grow something other than annuals in containers. I'm so thrilled to have a "real" garden and I have been babying my plants since the day I moved in. I have been toying with when and what to fertilize my newly planted perenials and shrubs with for fall to enhance their health/roots over winter. The post was very helpful!

  2. I have been needing the motivation to apply another round of liquid fertilizer to my trees. I was going for monthly this summer. Your post was the little push I needed. Tomorrow morning, rain or shine! Thanks for the inspiration!

  3. Patsi 'Garden Endeavors' says:

    Good info on fertilizing. We don't always get it right but I know mid summer is not always the best time.
    We have phosphorus and potassium…maybe should use it.

  4. Susan Blossom says:

    Don't make the same mistake I did this year: I over fertilized my hydrangeas. I read in P. Allen Smith's newsletter to fertilize them in June & August but I failed to read the 3rd line that said don't over fertilize or you'll end up with big lush leaves instead of flowers. Now I'm suffering for it. And in my high desert Utah zone 6, it's not recommended to fertilize them in August at ALL. So lesson learned. But I DID get some lovely two toned heads in July: Lavender & pink in the same blossom!

  5. Rosey Pollen says:

    Hi Miss Daisy,
    Very timely post about fertlizing, thanks for addressing this, I am always confused, so I just do NOTHING to be on the safe side. Now I know, and maybe I can get a jump on spring.

  6. Autumn Belle says:

    This is a very informative post. I always seem to have this question of when to fertilize or to fertilize or not. I like the first photo very much because the leaves are reddish brown in colour, looks like gold. This colour always reminds me of autumn.

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