August is not the end of the garden in Zone 8b. It is the beginning of the cool-season garden—the one that gives you crisp radishes, sweet carrots, tender greens and sturdy brassicas after summer crops begin slowing down.
The short answer
In a Pacific Northwest Zone 8b garden, August is a good time to plant spinach, arugula, lettuce, radishes, turnips, Asian greens, kale, collards, carrots, peas and cover crops. Early in the month, you may also plant beets or set out transplants of broccoli, cabbage and cauliflower.
- Plant early August: carrots, beets, peas and brassica transplants.
- Plant throughout August: kale, collards, turnips, radishes, arugula and Asian greens.
- Plant late August: spinach, lettuce, cilantro and cover crops as temperatures cool.
This guide is written for the maritime Pacific Northwest, especially Kitsap County and similar western Washington Zone 8b climates. USDA zones describe winter minimum temperatures, not precise planting dates. If you garden in a hotter or drier Zone 8b region, shift cool-season planting later and use your local first-frost date.
Before you plant: prepare for warm soil and shorter days
August seeds face the opposite problem of spring seeds. The soil is warm enough, but the surface can dry before germination. Once seedlings emerge, every week brings shorter days and slower growth. That means you should choose quick-maturing varieties, seed a little more generously than usual and keep the top inch of soil evenly moist.
Soil and tools you will need
- Finished compost
- Balanced organic fertilizer, if indicated
- Hand cultivator or garden fork
- Trowel or hori-hori
- Rake for a fine seedbed
- Watering wand with a gentle setting
- Fine rose watering can
- Row cover or insect netting
- Plant labels
- Optional shade cloth
- Optional soil thermometer
- Slug protection for young greens
Loosen only the planting area and mix in about 1 inch of finished compost if the bed needs organic matter. Avoid piling rich fertilizer into root-crop rows; too much nitrogen can produce beautiful tops and disappointing roots. A soil test is better than guessing, especially in western Washington, where soils may be acidic.
August planting schedule at a glance
| Crop | Best August timing | Planting method | Estimated first harvest |
|---|---|---|---|
| Spinach | Mid-to-late August | Direct sow | 30–50 days; later sowings may overwinter |
| Lettuce | Throughout month; shade during heat | Direct sow or transplant | 25–55 days |
| Arugula | Mid-to-late August | Direct sow | 21–40 days |
| Radishes | Mid-to-late August | Direct sow | 22–35 days |
| Turnips | Early-to-mid August | Direct sow | 30–60 days |
| Carrots | As early in August as possible | Direct sow | 55–80 days; baby roots sooner |
| Beets | Very early August | Direct sow | 35 days for greens; 50–65 for roots |
| Peas | Early-to-mid August | Direct sow | 55–70 days |
| Kale and collards | Early August transplants; seeds early-to-mid month | Direct sow or transplant | 30 days for baby leaves; 55–75 for mature leaves |
| Asian greens | Mid-to-late August | Direct sow or transplant | 25–55 days |
| Broccoli, cabbage and cauliflower | Early August | Transplants preferred | 55–90 days after transplanting |
| Cover crops | August through early fall | Broadcast seed | Cut before seed set |
Harvest estimates vary by variety, temperature, daylight, soil and whether the crop is harvested young or mature. Read the seed packet and add extra time as autumn daylight decreases.
Plant spinach for fall leaves and possible overwintering
Spinach dislikes summer heat but thrives as temperatures fall. In western Washington, late July through September is a recognized fall planting window. Wait for a cooler stretch, or shade the row until germination.
Raised bed: Sow in a block or short rows where summer crops will not shade it completely.
Container: Use a pot at least 6–8 inches deep with drainage. A window box works well.
In ground: Choose loose, moisture-retentive soil and remove weeds before sowing.
Soil: Fertile, well-drained soil that stays evenly moist. A light compost top-dressing is usually enough in an established bed.
Sow lettuce in small batches instead of one giant row
Lettuce gives the fastest return when harvested as baby leaves. Sow a short row every 10–14 days. During a hot week, start seeds in a cool place or cover the seedbed with light shade cloth until seedlings emerge.
Raised bed: Plant along a reachable edge for frequent cutting.
Container: Use a container at least 6 inches deep; wide is more useful than deep.
In ground: Sow into finely raked soil and keep the shallow seed consistently damp.
Soil: Loose, compost-rich soil with steady moisture. Irregular watering can make leaves bitter.
Plant arugula when you want a harvest before patience runs out
Arugula germinates quickly and becomes milder as nights cool. Harvest individual outer leaves or cut baby leaves a few inches above the soil so the plant can regrow.
Raised bed: Sow a narrow band and reseed every two weeks.
Container: A pot 6–8 inches deep is sufficient.
In ground: Use row cover immediately if flea beetles are common.
Soil: Average fertile soil with reliable moisture.
Use radishes to fill the short gaps
Radishes are ideal between slower fall crops, but they need steady water. Dry soil followed by heavy watering can lead to split or overly hot roots.
Raised bed: Sow between young kale or broccoli plants and harvest before the larger plants fill in.
Container: Use at least 6 inches of soil for round varieties; use a deeper pot for daikon.
In ground: Remove stones and break crusted soil before sowing.
Soil: Loose, evenly moist soil without fresh high-nitrogen manure.
Grow turnips for two harvests from one row
Turnips provide edible greens before the roots mature. Japanese salad turnips are especially useful for an August planting because many mature quickly and remain tender when harvested small.
Raised bed: Plant in 4-inch-spaced rows or a carefully thinned block.
Container: Use a pot at least 8–10 inches deep.
In ground: Loosen compacted soil so roots can swell evenly.
Soil: Well-drained loam with moderate fertility and consistent moisture.
Plant carrots early and keep the seedbed from drying out
Carrots are worth planting in early August, but slow germination makes moisture management the entire game. Cover the row lightly with burlap, cardboard or a board to retain moisture, then check daily and remove it as soon as seeds germinate.
Raised bed: Deep, stone-free soil produces straighter roots. Nantes and Chantenay types tolerate heavier soil better.
Container: Use 12 inches or more of soil. Choose short-rooted cultivars if the pot is shallow.
In ground: Loosen the row deeply without adding fresh manure.
Soil: Fine-textured, well-drained soil. Avoid excess nitrogen, which encourages forked or hairy roots.
Plant beets at the beginning of August—or grow them for greens
For dependable roots in western Washington, early August is the safer cutoff. Later sowings may still produce useful beet greens even when roots do not fully size up.
Raised bed: Sow in rows 10–12 inches apart and thin clustered seedlings.
Container: Use at least 10–12 inches of soil.
In ground: Loosen compacted soil and remove stones.
Soil: Fertile, well-drained soil with even moisture. Beet “seeds” commonly produce multiple seedlings, so thinning matters.
Give fall peas a trellis and the fastest route to maturity
Fall peas can be less predictable than spring peas, but they are worth trying in a mild maritime climate. Plant early enough to flower before persistent cold and choose disease-resistant, quick-maturing snap or snow peas.
Raised bed: Install the trellis before sowing along the north side so vines do not shade smaller crops.
Container: Use a pot at least 12 inches deep with sturdy support. Dwarf varieties are easiest.
In ground: Choose well-drained soil and avoid a low, waterlogged winter pocket.
Soil: Well-drained soil with moderate fertility. Peas usually do not need heavy nitrogen fertilizer.
Plant hardy greens that improve after cool weather arrives
Kale and collards can be harvested as baby leaves, mature leaves or overwintered plants. Transplants provide the fastest route in August, but direct sowing can work early in the month.
Raised bed: Place full-size plants 18–24 inches apart or sow densely for baby leaves.
Container: Give each mature plant a container about 5 gallons or larger.
In ground: Add compost and protect young plants with insect netting.
Soil: Fertile, moisture-retentive but well-drained soil. Brassicas are heavier feeders than radishes or peas.
Plant bok choy, tatsoi and mizuna as temperatures ease
Asian greens are productive fall crops, ranging from quick baby mizuna to full-size bok choy. Row cover helps protect seedlings from flea beetles and cabbage moths.
Raised bed: Sow a baby-leaf band or transplant full-size heads.
Container: Use at least 8 inches of soil and allow airflow between plants.
In ground: Cover immediately after planting if pest pressure is high.
Soil: Fertile, evenly moist soil. Drought stress can make plants tough or trigger bolting.
Use healthy transplants for the best chance of a fall crop
By August, transplants are usually more dependable than starting full-size heading brassicas from seed. Choose compact, vigorous plants that are not root-bound, and transplant during an overcast stretch or late in the day.
Raised bed: Space generously and reserve the bed for fall. These plants eventually occupy more room than their nursery pots suggest.
Container: Use one compact plant per 5–7 gallon container.
In ground: Amend with compost, water deeply and protect with insect netting.
Soil: Fertile, well-drained soil with consistent moisture. Side-dress according to the fertilizer label and soil condition rather than automatically overfeeding.
Plant the empty bed instead of leaving winter weeds an invitation
A cover crop protects soil, competes with weeds and adds organic matter. West of the Cascades, crimson clover, red clover, oats and cereal rye are common choices, but timing and termination method matter.
Raised bed: Use an easy-to-cut crop and avoid anything difficult to terminate in a small space.
Container: Usually skip cover crops unless the container will rest for the season. Mulch is simpler.
In ground: Rake seed into the soil and keep it moist until established.
Soil: Cover crops improve rather than replace good soil management. Select the species based on drainage, planting date and what will follow next spring.
Raised bed, container or in-ground: which is best in August?
Raised beds
Raised beds are the easiest option when your native soil drains poorly. They are also easier to cover with insect netting or a low tunnel. The tradeoff is faster drying during August, so check moisture daily while seeds germinate.
Containers
Containers work especially well for lettuce, spinach, arugula, radishes and compact Asian greens. Use fresh, high-quality container mix rather than garden soil. Choose containers with drainage holes and enough depth for the crop’s roots.
In-ground beds
In-ground soil holds moisture longer and is ideal for larger fall plantings. Correct compaction and drainage before sowing. Do not work wet soil into hard clods—a problem you will rediscover all winter with considerably less enthusiasm.
Five mistakes that ruin an August planting
- Letting the seedbed dry out. Tiny seeds may need gentle watering more than once during a hot day.
- Planting long-season varieties too late. Choose short days-to-maturity cultivars and harvest some crops young.
- Ignoring summer pests. Flea beetles, cabbage moths, slugs and aphids can find new seedlings before you remember planting them.
- Failing to thin. Crowded carrots, beets and turnips produce leaves instead of well-sized roots.
- Following the zone without checking the weather. A USDA zone does not tell you next week’s heat, rainfall or first frost.
Frequently asked questions
Is August too late to plant vegetables in Zone 8b?
No. August is an important planting month for fall and winter vegetables in many Zone 8b climates. Focus on quick cool-season crops and established brassica transplants rather than starting long-season summer crops.
Can I plant tomatoes or cucumbers in August?
In western Washington Zone 8b, August is generally too late to start tomatoes or cucumbers for a dependable outdoor harvest. Continue caring for existing plants and use newly available space for fall vegetables.
What is the fastest vegetable to plant in August?
Baby arugula, radish greens, lettuce and mustard greens can provide harvests in roughly three to four weeks under favorable conditions.
Should I start fall vegetables indoors?
Full-size broccoli, cabbage and cauliflower are more dependable as transplants in August. Lettuce can also be started in a cooler protected location and transplanted after the hottest weather passes.
When should I plant garlic in Zone 8b?
Not yet. In western Washington, garlic is normally planted in fall, often October into November, for harvest the following summer.
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