Month-by-Month Seattle Landscape Care Guide

Most landscape maintenance calendars are written for “the Pacific Northwest” or “USDA Zone 8b” — which covers everything from coastal Oregon to the San Juan Islands. That’s too broad to be useful. What your landscape needs in Kirkland in October is different from what it needs in Portland or Bellingham, because your soil, your tree canopy, your microclimates, and your rainfall patterns are specific to the stretch between Seattle and the Eastside.

This calendar is built from what our maintenance team actually does on Eastside properties month by month — not what a textbook recommends. It reflects 40 years of observing how plants, lawns, hardscape, and irrigation systems behave across the seasons in Bellevue, Kirkland, Redmond, Woodinville, Sammamish, and surrounding cities. Use it as your baseline, and adjust for your specific property’s conditions.

January is Seattle’s coldest month — average highs around 46°F, lows around 36°F, with occasional hard freezes. The landscape is dormant, and the temptation is to ignore it until spring. That’s a mistake. January is when you notice what’s not working.

What to do:

• Walk your property after a heavy rain. This is the best month to evaluate drainage — if water pools against your foundation, in planting beds, or in lawn areas, you’re seeing the problem at its worst. Document it with photos.
• Inspect retaining walls and hardscape. Freeze-thaw cycles stress structural elements. Look for new cracks, leaning, or heaving in walls, steps, and patio surfaces.
• Check for storm damage. Windstorms in late December and January break branches, uproot shallow-rooted trees, and can damage fences and structures. Remove hanging branches promptly — they’re a safety hazard.
• Don’t prune yet. The urge to cut back deciduous plants is strong, but most pruning should wait until late February or March. The exceptions: damaged or hazardous branches, which should be removed any time of year.
• Plan. If you’re considering a landscape renovation, January is the ideal month to start the design conversation. Designers have more availability and your property is showing its honest face — bare branches, wet soil, drainage behavior you can’t see in July.

What our crews are doing: Dormant-season structural pruning on deciduous trees, storm damage cleanup, and winter bed maintenance on maintenance contract properties.

February is transitional — days are getting noticeably longer, soil temperatures begin to climb above 45°F toward the end of the month, and the first early-spring bulbs (snowdrops, crocuses) start appearing. The landscape is waking up, and your maintenance timing for the next several months is set by what you do now.

What to do:

• Prune summer-flowering shrubs. Hydrangeas (macrophylla and paniculata types — but NOT the oakleaf varieties, which bloom on old wood), butterfly bush, caryopteris, roses. These bloom on new wood, so pruning now directs energy into this year’s growth.
• Do NOT prune spring-flowering shrubs yet. Rhododendrons, azaleas, camellias, lilacs, forsythia, and viburnums bloom on last year’s wood. Pruning now removes the flower buds. Wait until immediately after they finish blooming.
• Apply first moss treatment to lawns. Iron-based moss control (ferrous sulfate) works well in February when moss is actively growing and the lawn hasn’t started competing yet. This is the most effective treatment window of the year.
• Clean and sharpen tools. Dull pruning cuts invite disease. Clean cuts heal faster.
• Begin bed cleanup. Remove winter debris, dead perennial stems, and fallen leaves that accumulated under evergreen shrubs. Avoid disturbing the soil surface — earthworms and soil organisms are already active.

What our crews are doing: Structural pruning on ornamental trees and large shrubs, first-round moss treatment on lawns, bed cleanup on maintenance properties.

By mid-March, soil temperatures are consistently above 45°F across most of the Eastside, and active growth is underway. This is the busiest month for landscape maintenance — and the month where timing matters most for several key tasks.

What to do:

• Apply pre-emergent weed control. The window is narrow: once soil temperatures reach 55°F consistently, annual weed seeds (including crabgrass) begin germinating. Pre-emergent herbicide must be down before that happens. In most years on the Eastside, the application window is mid-March through early April.
• First mowing of the season. Set the mower to 3-3.5 inches. Never cut more than one-third of the blade height in a single mowing. The first cut of the season is especially important — cutting too short exposes the root zone to late-season cold snaps and gives weeds an advantage.
• Fertilize lawns. First application of a slow-release nitrogen fertilizer. Timing matters: too early (February) and the roots aren’t active enough to absorb it; too late (May) and you’re pushing top growth during a period when the plant needs root development.
• Mulch beds. Apply 2-3 inches of arborist chips or fine bark mulch to planting beds. Mulch suppresses weeds, retains moisture for the coming dry season, and moderates soil temperature. Pull mulch 3 inches away from plant stems and tree trunks — mulch piled against bark creates a moisture trap that promotes rot and disease.
• Start dividing perennials. Hostas, daylilies, ornamental grasses, and other clumping perennials benefit from division every 3-4 years. March is ideal because the plants are just emerging and transplant shock is minimal.

What our crews are doing: Mulching, first fertilizer application, pre-emergent weed control, perennial division, spring cleanup across all maintenance properties.

April is when Seattle landscapes shift from dormancy to active growth almost overnight. Temperatures reach the mid-50s to low 60s, rain continues, and everything grows. This is the month that separates maintained landscapes from neglected ones — the growth rate is fast enough that two weeks of inattention creates noticeable problems.

What to do:

• Mow weekly. Growth rate accelerates in April. Maintain 3-3.5 inch height, mow when dry.
• Prune spring-flowering shrubs AFTER bloom. Rhododendrons, azaleas, camellias — prune within 2-3 weeks after flowers fade. This gives the plant maximum time to set next year’s buds. Deadhead spent rhododendron trusses by snapping them off at the base (don’t cut into the new growth buds just below).
• Monitor for aphids and other early pests. Aphids appear on new growth of roses, Japanese maples, and many ornamentals in April. A strong blast of water from the hose is often sufficient — pesticide intervention is rarely needed at this stage, and killing aphids eliminates food for beneficial insects that are also arriving.
• Check irrigation systems. Turn on the system and walk every zone. Check for broken heads, misdirected spray, and leaks at connections. Replace damaged components before the dry season begins. Most systems should be set to run 2-3 times per week by late April, depending on rainfall.
• Plant. April is an excellent planting month — the soil is warm, rain is still regular, and new plantings have 2-3 months to establish roots before the dry season stress of July and August.

What our crews are doing: Weekly mowing rotations begin, post-bloom pruning, irrigation startups, spring planting installations.

May is the hinge month — the last reliable month of regular rain before the dry season sets in. What you do in May determines how your landscape handles July and August.

What to do:

• Adjust irrigation. Increase watering frequency and duration as rain becomes less reliable. Most established lawns on Eastside clay soils need 1-1.5 inches of water per week. Deep, infrequent watering (2-3 times per week, 20-30 minutes per zone) is better than daily shallow watering, which encourages shallow root systems that can’t handle summer stress.
• Fertilize lawns — second application. Slow-release nitrogen again. Some programs add a potassium component in May to build stress resistance for summer.
• Edge beds. Clean, defined edges between lawn and planting beds make the entire landscape look sharper. May is when the growth makes this most impactful.
• Monitor for powdery mildew. Warm days and cool nights in May create conditions for powdery mildew on roses, dogwoods, and some hydrangeas. Good air circulation (don’t overcrowd plants) is the best prevention. Fungicide intervention is usually only needed on chronically susceptible varieties.
• Final weeding push. Pull weeds before they set seed. A weed that goes to seed in May becomes 500 weeds in June.

What our crews are doing: Irrigation adjustments, second fertilizer round, bed edging, weed management, final spring pruning.

June is when most Seattle homeowners realize their irrigation system matters. Rain drops off sharply — June averages only 1.5 inches, compared to 3-4 inches in winter months. The transition catches many landscapes off guard, especially newer plantings that haven’t developed deep root systems.

What to do:

• Verify irrigation is covering everything. Walk each zone while it runs. Look for dry spots, especially at the edges of spray patterns and under dense tree canopy where root competition is strongest.
• Water new plantings deeply. Anything installed in the last 12 months needs supplemental watering beyond what your irrigation system provides. Hand-water deeply (slow soak at the root zone) 2-3 times per week. A new tree needs 10-15 gallons per watering; new shrubs need 3-5 gallons.
• Mow higher. Consider raising the mower to 3.5-4 inches during the dry season. Taller grass shades the soil, reduces evaporation, and develops deeper roots. It also looks better than the stressed, yellow lawn that results from cutting short during heat.
• Deadhead roses and perennials. Removing spent flowers redirects energy to new blooms and prevents the plant from putting resources into seed production.
• Leave clippings on the lawn. Grass clippings decompose quickly and return nitrogen to the soil — roughly equivalent to one fertilizer application per season. Bag clippings only if the lawn is diseased.

What our crews are doing: Irrigation monitoring and adjustments, hand-watering on maintenance properties with new installations, mowing, deadheading, weed management.

July is the month that tests your landscape’s resilience. Average high temperatures reach the low-to-mid 70s, with occasional heat events pushing into the 90s. Rainfall is minimal — typically under 1 inch for the entire month. Plants that were marginal going in (wrong exposure, insufficient irrigation, poor root establishment) start showing stress.

What to do:

• Water consistently and deeply. Don’t skip irrigation days during heat events. Established landscapes need 1-1.5 inches per week; new plantings need more. Water in the early morning (4-6 AM) to minimize evaporation and disease risk.
• Watch for drought stress signs. Wilting, leaf curl, premature leaf drop, brown edges on broadleaf evergreens. Japanese maples are particularly expressive — leaf scorch on a maple that looked fine in June usually means insufficient deep watering or too much reflected heat from adjacent hardscape.
• Don’t fertilize lawns in July. Fertilizer during heat stress pushes growth the plant can’t support. Skip July entirely and resume in September.
• Prune hedges. Formal hedges (boxwood, laurel, privet) can be trimmed in July. Avoid heavy pruning on broadleaf evergreens — the new growth triggered by pruning in hot weather will scorch.
• Monitor pest pressure. Spider mites thrive in hot, dry conditions. Check the undersides of leaves on maples, hydrangeas, and roses. A strong water spray dislodges them; miticide is a last resort.

What our crews are doing: Irrigation management is the top priority. Mowing, hedge trimming, pest monitoring, hand-watering new installations.

August continues July’s dry pattern. The landscape is at its most stressed. The goal is survival and setting up for fall recovery, not pushing growth.

What to do:

• Continue consistent deep watering. Don’t reduce irrigation because you’re tired of the water bill. August is when plant losses happen if watering lapses. The investment in keeping established plants alive is always less than replacing them.
• Start planning fall projects. If you’re considering a landscape renovation, fall planting, or addressing drainage issues discovered last winter, August is when the planning should begin. Fall construction and planting produce excellent results.
• Avoid major pruning. Plants are stressed. Heavy pruning in August creates wounds that the plant doesn’t have the resources to heal efficiently.
• Seed bare lawn areas — prepare but don’t seed yet. If your lawn has bare spots from summer stress, prepare the areas (rake, amend soil) but wait until September to seed. Grass seed sown in August heat struggles to establish.

What our crews are doing: Irrigation management, light maintenance, planning fall installations, monitoring for tree stress.

September is arguably the most important month in the Seattle landscape calendar. It’s the beginning of what we consider the best planting window in our climate — better than spring in most cases.

What to do:

• Plant. Soil is still warm (60°F+), which promotes root growth. The rainy season is approaching, which handles watering naturally. New plantings installed in September have the entire fall, winter, and spring to establish root systems before facing their first summer drought. Plants installed in April have less than 3 months of root growth before July stress hits.
• Seed or overseed lawns. September through early October is the ideal lawn seeding window in the Seattle area. Cool nights, warm soil, and arriving moisture create perfect germination conditions. The new grass has 7-8 months to establish before next summer’s heat.
• Fertilize lawns — third application. This is the most important fertilizer application of the year. Fall fertilizer feeds root development through the winter, producing a stronger, denser lawn next spring. Use a formula with higher potassium and lower nitrogen than your spring applications.
• Reduce irrigation gradually. As rain returns, reduce irrigation frequency. By late September, most established landscapes can transition to rain-only watering. Keep irrigation active for new plantings until the rainy season is fully established (usually mid-October).
• Begin fall cleanup. Remove spent annual flowers, cut back perennials that have finished their season (leave ornamental grasses standing — they provide winter structure and bird habitat), and edge beds cleanly.

What our crews are doing: Major planting installations, lawn overseeding, fall fertilization, irrigation reduction, perennial cutback, bed cleanup.

October is the transition back to rain. Average rainfall increases from September’s 1.5 inches to October’s 3+ inches. The soil is cooling but still warm enough for root growth, which continues through November in most years.

What to do:

• Final planting window. Through mid-October, conditions are still excellent for planting trees, shrubs, and perennials. After October, success rates decrease as soil temperatures drop below the threshold for active root growth.
• Shut down irrigation. Most Eastside properties can turn off irrigation entirely by mid-October. Leaving the system charged risks freeze damage later — winterize by late October or early November.
• Fall aeration. Core aeration breaks up soil compaction and allows water, air, and nutrients to reach the root zone. Fall is better than spring because the lawn has the entire winter to recover and the aeration holes help rain percolate into compacted clay soils.
• Clean gutters and check drainage. Before the heavy rain arrives, clear gutters, verify downspouts are directing water away from the foundation, and check catch basins and French drains for debris.
• Leaf management. Leaves left on the lawn block light and trap moisture, promoting disease and moss. Remove them weekly through November. Leaves in planting beds can stay as mulch, but don’t let them mat into a thick, wet layer — a thin scattering is fine, a 4-inch pile smothers the plants beneath it.

What our crews are doing: Last planting installations, irrigation winterization, aeration, leaf management, gutter and drainage inspection.

November marks the beginning of Seattle’s heaviest rainfall period. Average rainfall exceeds 5 inches. Wind events become more frequent. The landscape is preparing for dormancy, and your job shifts from growth management to protection.

What to do:

• Complete leaf removal. The last major leaf drop happens in November for most deciduous trees on the Eastside. Get leaves off the lawn before December dormancy sets in.
• Winterize irrigation — if not done in October. Blow out the lines with compressed air. Water left in pipes will freeze and crack fittings. This is not optional.
• Stake newly planted trees. Trees installed in September and October should be staked to prevent wind-rocking during winter storms. Use flexible ties that allow some movement — rigid staking prevents the trunk from developing the taper and strength it needs.
• Check tree canopy for hazards. Dead branches, crossing branches, and weakly attached limbs are wind-storm liabilities. Have a certified arborist evaluate any mature trees you’re concerned about before storm season peaks.
• Apply lime to lawn if pH is low. King County soils tend toward acidity (pH 5.0-6.0). Lime raises the pH toward the 6.0-6.5 range that turf grass prefers. November application gives it the winter to work into the soil.

What our crews are doing: Final leaf cleanup, irrigation winterization, tree staking, hazard pruning assessment, storm prep on maintenance properties.

December is the least active month for landscape maintenance. Days are short, temperatures hover around 40-45°F, and most plants are fully dormant. Respect the rest — for your landscape and yourself.

What to do:

• Monitor for storm damage after wind events. Remove downed branches promptly. Check for hanging limbs (“widow makers”) that could fall on structures, vehicles, or walkways.
• Stay off wet lawn. Foot traffic on dormant, saturated lawn creates compaction damage that shows as bare patches in spring.
• Check for rodent damage. Voles and rabbits chew bark on young trees and shrubs during winter when other food is scarce. Protect vulnerable stems with hardware cloth cylinders.
• Plan for next year. December is an excellent month for landscape consultations — we see your property in its most revealing state, our schedule is most flexible, and there’s time to design for spring construction.
• Don’t prune. Resist the holiday-spirit urge to “clean up” the landscape. Most pruning is better left to February-March. Pruning in December stimulates growth that will be damaged by January cold.

What our crews are doing: Storm response, dormant-season tree pruning where appropriate, winter bed maintenance, drainage inspections after heavy rains.

This calendar covers what needs to happen. Whether you do it yourself or hire a professional depends on the complexity of your landscape, the time you’re willing to invest, and whether you have the knowledge to handle the timing-sensitive tasks correctly.

Where professional maintenance consistently outperforms DIY care:

• Pruning. Incorrect pruning causes more long-term plant damage than any other maintenance mistake. Each species has a specific timing and technique — our Master Pruner, Will Rak, can look at a hydrangea and tell you whether it blooms on old wood or new wood, which determines whether you prune in February or June. Most homeowners can’t make that distinction, and pruning at the wrong time eliminates an entire season of flowers.
• Fertilization timing. The difference between a lawn that looks great in June and one that browns out is often whether the fall fertilizer was applied in September (right) or November (too late for root uptake before dormancy).
• Pest and disease diagnosis. Many problems look similar — drought stress, nutrient deficiency, and root rot all produce yellowing leaves. The treatment for each is different, and treating the wrong cause makes the actual problem worse.

Most of the month-by-month tasks above can be DIY on a small property. For larger landscapes, or anyone juggling four-season timing across pruning windows, irrigation, and lawn renovation, Classic’s landscape maintenance program handles the full schedule with crews trained to take care of outdoor spaces in every season.

If you’re considering professional landscape maintenance — or want to evaluate whether your current approach is covering what matters — we’re happy to walk your property and assess what’s needed for your specific plantings, soil, and site conditions.