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August Gardening Tips and To-Dos for the Pacific Northwest

Looking for ways to keep your summer garden productive and healthy while starting to prepare for the fall season? I’ll show you some August gardening tips and to-dos for your Pacific Northwest garden that will give you the best results for setting your garden up for success.

The PNW gardens are in full bloom in August, thriving from the sunny days and warm weather. It’s a good month to take in the summer flowers and lush greenery. However, with the excessive heat, it’s important to pay close attention to the garden’s needs and plan ahead for the coming months.

I’ll be sharing best practices and gardening to-dos for the month of August in the Pacific Northwest (PNW) region. Use these tips for a beautiful and healthy garden through early fall and to prepare for the next year’s garden.

August gardening tips and to dos

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I’m a self-taught hobby gardener, not a Master Gardener. Everything I share with you on my blog is my personal opinion and things that have worked for me.

cottage garden and greenhouse in August

The summer garden is in full swing at the start of August so it’s time to start fall crops, continue to water plants deeply, and continue trying to control weeds, pests, and diseases.

Whether you’re a seasoned gardener or just starting out, these August “gardening by month” tips will help your garden thrive into the fall season. My tips are based on hardiness zone 8b so be sure to check your own gardening zone and make the necessary adjustments to this month’s timeline.

August gardening tips and to dos  - blue hydrangeas

As the heat continues this time of year, it’s crucial to keep watering your garden properly. With the dry weather, be sure to water both the flower beds and vegetable patches deeply to reach the roots of the plant.

The best time to water plants is in the early morning or late evening to minimize water evaporation. Make sure your garden receives the moisture it needs for the flowering season, especially for perennial plants, tomato plants, and newly added summer flowers.

bike basket full of flowers

If you have to water in the evening, try to water directly into the roots and keep from getting any foliage wet to avoid fungus or powdery mildew.

Flower containers, window boxes, and hanging baskets tend to dry out quickly in the summer months. Be sure to water them daily to keep your flowers hydrated, and twice a day when it’s hotter and windier than usual.

August gardening tips and to dos  -  au lait dahlias

Divide Perennial Plants

August is the perfect time to divide daylilies and other perennial plants. Dividing daylilies helps rejuvenate the plants, promotes healthier growth, and encourages more abundant blooms next year.

Deadhead Your Spent Blooms

Trim back spent blooms from annual and perennial flowering plants regularly and remove lower leaves affected by powdery mildew, such as dahlias.

Deadheading is the removal of dead flower heads from a plant to encourage growth by putting more energy into blooms for the remainder of summer.

orange daylilies

Cut back daylilies after they have gone dormant. If the lilies are pruned to the ground in the summer they can usually grow back once the temperatures cool and bloom again during the fall season.

You should divide your daylilies at least every 4-5 years.

August gardening tips and to dos 
 - dahlias in cottage garden

Support Tall Garden Flowers

If you haven’t already, support any tall flowers such as dahlias, snapdragons, and sedum autumn joy to protect them from damage due to…

  • heavy rains
  • winds
  • their own heavy blooms

Keep Weeds Under Control

Continue to keep up on weeds in the garden in August so they don’t steal water and nutrients from other plants in your garden.

It can be much easier to pull weeds if they are wet, after a rain storm, or by watering them deeply before the task. If you can’t get to weeding right away, cut off the heads of the weeds to keep them from going to seed.

cottage garden in August

Prune & Cut Back Garden Shrubs and Plants

August is a good time to prune back any dead growth or diseased areas to help prevent further disease from spreading to the plant.

August gardening tips and to dos  -  fir elise dahlias

As late summer approaches, it’s the right time to plan for the first frost.

Keep an eye on the weather forecast and determine the average time of year when the first frost typically occurs in your area. Use this information to gauge when to start transitioning your garden for the fall.

Harvest any remaining summer crops at their peak ripeness to enjoy the best results.

harvested tomatoes

August always brings an abundance of ripe fruits and vegetables, as well as beautiful blooms to harvest. The morning is the perfect time to harvest your ripe fruits and vegetables, and your garden flowers when the temperatures are cooler.

Picking fruits, vegetables, and flowers benefits your garden by…

  • helping to prevent disease
  • promoting new growth
  • keeping your garden looking neat and tidy
  • preventing ripe veggies from losing their flavor and texture

Harvest leaf vegetables before they bolt and become bitter.

Pick onions when the tops start to fall over. Be sure to stop watering onions when the stems turn yellow to force them into dormancy.

August gardening tips and to dos 
 - cottage garden

Take Advantage of Summer Plant Sales to Fill in Bare Spots

The end of August is an excellent time to visit garden centers and nurseries in your area. They often offer discounts on summer plants, making it a great way to find bargains on new plants for your garden.

Look for plants that will thrive in your hardiness zone and that will thrive in the PNW climate throughout the following year.

Take a look at your flower beds and evaluate areas with bare spots. Consider planting new perennials to fill in these gaps. By planting now, you give the new plants ample time to establish their root systems before the onset of early fall.

Direct Sow Cool-Season Veggies

For the vegetable garden, consider planting cool-season vegetables in August that thrive in the early fall, such as leafy greens and certain root vegetables.

August gardening tips and to dos 
 - spring bulbs

It’s not too early to order your spring bulbs in August. Many of the favorite varieties are sold out quickly and the bulbs will be delivered at the time they should be planted in your hardiness zone.

green pest on leave of sunflowers


Pests can be their worst in August.

Slugs thrive in moist areas of the garden. Some places I look for these pests are under rocks and flower containers, in overgrown vegetation, and even under large leaves. They generally hide out during the day but come out full force in the dark evening hours.

Continue applying slug bait to areas in the garden where the slug’s favorite flowers are such as dahlias, zinnias, and marigolds. I use Sluggo which is safe for pets and wildlife.

Other slug-killing methods include a small container of beer, an evening of slug hunting with a flashlight, and your favorite slug-killing tool,

Use the water spray from a hose or insecticidal soap spray to keep aphids, spider mites, and other sap-sucking pests from your favorite flowers.

August gardening tips and to dos 
 - diseased plant foliage


Plants are much more prone to diseases in the hot weather and humid summer months so be sure to inspect your plants regularly. Remove any diseased foliage and dispose of it (never compost) so it doesn’t spread to the rest of the plant.

Always wash and disinfect pruners and other tools that have been in contact to avoid spreading diseases.

copper hanging birdbath

You can save seeds from many types of plants you grew this summer to sow for next year’s garden.

This has worked out well for me because there have been a few times when I’ve loved a certain cut flower and the variety was no longer available.

The best plants for saving seeds are open-pollinated plants and heirlooms because the seeds usually grow into plants that look just like the parent plants.

My friends and I often swap seeds with one another which cuts down the cost of buying seed packets each year.

August gardening tips and to dos  - bird house in the cottage garden

With the warm weather in August, many garden birds and wildlife will frequent your garden. Create a welcoming environment by providing bird feeders, bird baths, and native plants that attract local wildlife.

Clean Water Features

Standing water allows mosquitos to breed so be sure to take some time to clean those dirty bird baths and fountains this month.

In August, it’s important to water your garden regularly, divide daylilies and perennials, plan for the first frost, and prepare for the fall harvest.

Yes, you can plant new perennials and cool-season crops that thrive in the early fall. Planting now gives them time to establish before the colder months.

To combat powdery mildew, remove affected leaves promptly, increase air circulation around plants, and avoid overhead watering. Applying fungicidal sprays may also help prevent further spread.

Yes, you can attract garden birds by planting native plants that produce berries or seeds, and by providing bird feeders and bird baths filled with fresh water.

rose and orange colored dahlias in the August garden

Regular deadheading of spent blooms, removing faded foliage, and filling bare spots with new perennials will help maintain a vibrant garden appearance throughout late summer.

Yes, excessive heat can stress plants and lead to wilting or scorching. Provide shade for more sensitive plants, mulch to retain soil moisture, and water adequately to counter the effects of extreme heat.

August gardening tips and to dos 
 - sunflower

A lot is happening in the garden during August in the Pacific Northwest. With the right care, your garden can flourish through the summer months and into early fall.

Keep an eye on water needs during hot weather, divide daylilies and other perennials, plan for the first frost and fall harvest, and take advantage of garden centers to add new plants to your collection.

By being aware of your garden’s needs in August, you’ll be rewarded with a beautiful and bountiful garden that continues to thrive in the following year.

If you have any questions or additional suggestions, feel free to share them in the comments below. And be sure to share this blog post link with anyone who may find these gardening tips useful.

Until next time,

Happy Gardening

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August gardening tips and to dos

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  1. Yes, it’s so hot here too and not enough rain! My flowers are doing OK but my veggies are lousy this year…cold in June and now so hot and dry! My poor puny pepper plants are gonna fall over from the weight of the teeny peppers growing!!!

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