Purple Asters for sale in Eugene Oregon at Johnson Brothers Greenhouses

Purple Asters at Johnson Brothers Greenhouses

September Gardening Tips

A great time for planting trees, shrubs,fall blooming perennials & bulbs!

September is one of the best planting times!  The weather starts to cool which is ideal for planting and growing strong healthy roots before the harsh winter weather sets in.

It is also a great time to start thinking about fall and tidying up the garden by cutting back already bloomed or unhealthy plants and filling in colorless spots with some new fall flavor.

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Don’t forget to check out the Oregon State University’s Gardening Extension for more great gardening tips!

Looking for what blooms this month? Download our monthly plant bloom calendar to help you decide!


Until it starts to frost be sure to keep after the weeds and the slugs!  It is a great time to mulch with a good bark or textured mulch which will help keep plant roots warm in winter and protect plants from deadly cold days, and a plus is it will help control weeds and slugs for you!  If you have never applied mulch to your garden be sure to add at least 2-3 inches the first time. If you are top coating then you will only need about an inch.

Helping The Birds

Many bird species will soon begin their winter migrations, this also includes hummingbirds who fly south to South America on a very long journey. Give them a helping hand by providing them with some food for their long journey whether it be suet, seed or sugar water.  Providing food may even allow many species to stick around for the winter!

Family Fun Ideas

September and fall is a great time for family fun and crafts.  From dried pumpkin and gourd flower arrangements boasting big textured seed pods, to pinecone peanut butter seed feeders be sure to enjoy all that nature has to offer and share it with your children and friends.  Check out these fun craft ideas.

Also, remember Johnson Brothers winter fundraiser forms are available starting September 1st.  It’s time to start thinking about beautiful lush wreaths and poinsettias!

Annuals Care

Remove spent annuals and compost them.  Winter pansies, flowering Kale, flowering Cabbage, and fall mums may be planted now, to give a little color to the garden when the summers flowers have faded away.  Some annuals such as Coleus and many tropical plants can be taken indoors as houseplants during cold winter months!

Cut growth back and pot into a clean, freshly soiled indoor house pot.  Not all annuals do well as houseplants, but feel free to experiment. Hey, you were going to let them die anyways right?  Be sure to make the transition easy on your plants by first bringing them indoors at night, and then for longer periods of time throughout the day and evenings until the weather no longer permits them outdoors.

Larger tropical plants should be cut back and brought indoors inside a garage or greenhouse for the winter once outdoor temperatures begin to drop at night, and then during the day.


As soil temperature drops below 60 degrees F., Spring flowering bulbs such as  tulips, daffodils, hyacinths, dwarf irises, Anemone, and crocus should be planted. Select healthy, disease free bulbs. Add Bone meal or Bulb fertilizer into the planting hole, as you prepare the soil.

Tender bulbs should be dug up and stored in a dry, cool, dark area after first frost. It is good to store bulbs in paper bags to prevent moisture.

Fruits & Veggies

Many fruits and Veggies are now ready to be harvested.  Check your edibles frequently for ripeness. Also be sure to read through our Oregon Edibles Harvest Calendar to help you in your harvest schedule.

Share your garden’s abundance with friends and neighbors, and don’t forget about your local food bank or food pantry! It is also a good idea to reap the benefits of your garden longer by freezing, drying, storing, or canning.

  • Plum trees should be pruned right after harvest, to ensure a bountiful crop next year.
  • Once the tops of onions have withered, the bulbs should be lifted and dried in a warm, dry, sunny location for about 10 days. They should then be stored in a cool, dark, dry place.
  • Some root crops, such as carrots, onions, and parsnips can be left in the ground in cold climates and dug up as needed.
  • Apply enough mulch to keep the ground from freezing, and the crop will be kept fresh until it is needed.

After you have finished harvesting your summer vegetables, plant a cover crop of clovers, cow peas, soybeans, or vetches for the purpose of plowing under next spring.  These nitrogen producing plants will add needed nitrogen and provide good organic matter into your soil for next year’s crop. They will also prevent weeds!


Gather the seeds from perennial plant seed pods and scatter them in rows or around the garden this month.  This new plant stock will appear as seedlings next spring ready to grow on and be transplanted to better areas.

Be sure to mark your perennials with permanent tags so you can find their placement this fall or next spring once they have died back.  This will prevent you from digging up plants or mistaking new growth as weeds next spring.  It will also help you identify plants that are your favorites or a plants’ characteristics which will help you further enhance your dream garden by shopping for complementary colors or textures.
September through October is a great time to take over-grown or multiplied perennial plants and divide them, or move them around the garden.  Due to the cooler days it is also a great time to replace any perennials that may have died due to summer drought or other circumstance.

Winter’s in our area are usually mild, but be sure to protect any above-ground potted perennial plants with a mulch of leaves or other warmth.  If temperatures hit freezing, everything above 3 inches below the ground will freeze, and this means a cold death for unprotected potted plants!

Trees & Shrubs

Fall is a good time to select, transport and plant trees and shrubs. Fall planting encourages good root development, allowing the plants to get established before spring. It is a good idea to help new plants get started with a root stimulating fertilizer that is higher in Phosphorus.  If weather is dry, provide deep watering, as needed, up until the ground freezes.

Stop fertilizing your established trees and flowering shrubs to allow this years growth to harden off before winter.  Water established trees and shrubs less often, unless the weather stays warm, allowing them to harden off before winter sets in.


Pot up some spring flowering bulbs for indoor color during the winter. Store the pots in a cool, dark place, until new growth emerges from the soil, and then move them to a bright window. Repot or top-coat any outdoor houseplants with fresh soil and wash the pots down as best you can. You may want to do this with any indoor houseplants as well to avoid getting dirt everywhere indoors.

Be sure to acclimate your houseplants slowly to the indoor environment again by first bringing them indoors overnight and then leaving them in longer each day until the weather no longer allows them outside.

Check to make sure you indoor plant placement is away from drying vents or heaters.  As the days get shorter and the sun gets lower you may need to take plants that were receiving enough light further from the window, and now move them closer to the window.

Begin conditioning your Poinsettias and Christmas cactus to get them ready for the upcoming holiday season.  Both of these plants are short day plants.  Although they will eventually bloom, if you want the plants in bloom in time for the holidays they must be kept at about 65 to 70 degrees.  They must also be subjected to at least six weeks of 14 hours of total darkness per day (mid to late September).This may be accomplished by placing the potted plant in a closet or unlighted room, or by covering the plant with black cloth, black plastic over a frame or a cardboard box. The plant must then be returned to the light each day and given a minimum of 4 hours of direct sun, or 10 hours of bright light.

The application of a 0-10-10 fertilizer this month and again next should help encourage the development of flower buds, then feed your plant every 2 weeks with a high nitrogen fertilizer once color has begun to show.

Christmas cactus needs the same general care, with the exception that they require cooler temperatures of about 50 to 60 degrees.