GRO Landscape Care Guides
Learn proper landscape maintenance and care for landscapes installed in the SW Washington, Portland Metro, & Central Oregon Regions.
Landscape Care
Dear Readers,
Below you will find our GRO Care Guides; these are suggested care guidelines for landscapes installed by our team. Adjustments may be necessary for landscapes installed by other providers and for unusual sites. Please consult your GRO Experience Manager with any concerns.
Thank you,
Your Friends at GRO
GRO Care Guides
- Fertilize most trees once in early spring (March–April) before new growth flushes — avoid late-season fertilizing, which pushes tender growth before winter
- Use a slow-release balanced fertilizer (10-10-10) for ornamentals; fruit trees benefit from slightly higher nitrogen in spring
- Native trees (Douglas Fir, Oregon White Oak, Madrone) generally need no fertilizing — rich compost mulch is sufficient and won’t push unnatural growth
- Avoid fertilizing newly planted trees for the first year; let roots establish first
- Acidic PNW soils often lock out nutrients — test pH and add lime if below 5.5 for most non-native trees
- Prune deciduous trees in late winter (January–February) while dormant — wounds heal fast once spring growth begins
- Never prune Oregon White Oak or other oaks during wet months; dry summer pruning (July–August) drastically reduces Sudden Oak Death risk
- Remove the 3 D’s year-round: dead, damaged, and diseased branches — don’t wait for the dormant season for these
- Avoid topping trees — it creates weak regrowth, disease entry points, and long-term structural problems
- Thin interior branches for airflow rather than cutting back to stubs; make cuts just outside the branch collar
- Fruit trees should be pruned to an open-center or central-leader form each February before buds swell
- Newly planted trees need deep watering every 1–2 weeks through their first 2–3 summers, even drought-tolerant natives
- Established conifers and most natives can go without irrigation once roots are deep, but watch for wilting or needle drop during extended dry spells (3+ weeks)
- Water deeply and infrequently rather than shallow and often — this encourages deep root development
- Mulch the root zone (2–3 inches, kept away from the trunk) to dramatically reduce water loss and moderate soil temperature
- Reduce or stop irrigation in September as fall rains return — overwatering in fall promotes root rot in PNW clay soils
- Best time to plant is October — warm soil + incoming rain = strong root establishment before summer
- Avoid any major pruning or soil disturbance during the spring “sap run” (March–May) for maples — they’ll weep heavily
- Watch for slug damage on young trees in spring; iron phosphate bait around the base works well and is wildlife-safe
- Feed most perennials and annuals in early spring (March–April) as new growth emerges — a balanced slow-release granular fertilizer works well
- Vegetables and heavy feeders (tomatoes, squash, dahlias) benefit from a second feeding mid-summer
- Native plants like Sword Fern, Salal, and Oregon Grape rarely need fertilizer — top-dress with compost instead
- Acid-loving plants (rhododendrons, azaleas, blueberries) thrive in PNW soils naturally but benefit from a specialized acidic fertilizer in spring
- Avoid fertilizing any plant after August — late feeding encourages soft new growth that gets damaged by fall frosts
- Compost is always a safe, slow-release option and improves PNW clay soils over time
- Cut back dead perennial foliage in late winter (February–March) just before new growth pushes — leaving it through winter provides insect habitat
- Deadhead flowering plants regularly through summer to extend bloom time
- Prune spring-blooming shrubs (Red Flowering Currant, lilac) right after they finish blooming — pruning later removes next year’s flower buds
- Prune summer and fall bloomers in late winter or early spring before growth begins
- Remove any dead, diseased, or crossing stems year-round — don’t wait for a scheduled pruning window
- Rejuvenate overgrown shrubs by cutting 1/3 of the oldest stems to the ground each year over three years rather than shearing all at once
- PNW summers are essentially a drought — most plants need consistent watering June through September even if spring felt wet
- Drip irrigation or soaker hoses are ideal
- Established native plants (Sword Fern, Salal, Oregon Grape) can largely fend for themselves after year 3, needing only occasional deep watering during heat waves
- Reduce watering in September as rains return — overwatering in fall is a common cause of root rot in PNW clay soils
- Mulch around plants 2–3 inches deep (kept away from stems) to retain moisture and suppress weeds through the dry season
- Slugs are the #1 plant pest in the PNW — use iron phosphate bait starting in March and after every heavy rain
- Powdery mildew appears on many plants in late summer; improve airflow through pruning and avoid overhead watering to reduce it
- Aphids cluster on new growth in spring — a strong blast of water or insecticidal soap handles most infestations
- Root rot is common in poorly drained clay soils — if a plant suddenly collapses in fall or winter, drainage is usually the culprit
- Fall (September–October) is the best time to plant perennials and shrubs — soil is warm and rains do the watering work for you
- Apply a fresh layer of compost mulch each spring to feed soil life and suppress weeds
- Protect tender plants (dahlias, fuchsias, cannas) from frost — dig and store tubers after the first frost in colder inland areas like the Willamette Valley floor or east of the Cascades
- Most PNW lawns need little to no irrigation October through May — rainfall handles it naturally
- Begin irrigation in June or when dry season sets in; most lawns need about 1–1.5 inches of water per week in summer
- Water deeply 2–3 times per week rather than a little every day — this encourages deeper roots that handle drought better
- Water early in the morning (before 9am) to reduce evaporation and minimize fungal disease risk
- Reduce and stop irrigation in September as fall rains return — overwatering in fall promotes moss and fungal issues
- If your lawn goes dormant and brown in summer, that’s okay — cool-season grasses naturally do this and bounce back with fall rains
- The most important fertilizing window in the PNW is fall (September–October) — this is opposite to most of the US but suits cool-season grasses perfectly
- A second application in late spring (May) helps maintain color through early summer
- Avoid fertilizing in peak summer heat (July–August) — it can burn dormant or stressed grass
- Use a fertilizer with higher nitrogen for spring and a balanced or higher potassium formula in fall to harden grass for winter
- Apply lime every 2–3 years — PNW soils are naturally acidic and most lawn grasses prefer a pH of 6.0–7.0
- Have your soil tested before fertilizing if possible; over-fertilizing is a common and wasteful mistake
- Keep cool-season grasses (fescue, ryegrass, bluegrass — the PNW standard) at 2.5–3.5 inches tall; never cut more than 1/3 of the blade at once
- Mow higher in summer (3–4 inches) — taller grass shades roots, retains moisture, and
- crowds out weeds
- Keep mower blades sharp — dull blades tear grass rather than cutting it cleanly, leaving it vulnerable to disease
- Mow frequently in spring (every 5–7 days) when grass grows fastest in the PNW
- Reduce mowing frequency naturally in summer as growth slows, and again in fall
- Leave grass clippings on the lawn — they break down quickly and return nitrogen to the soil
- Moss is the #1 lawn problem in the PNW — it thrives in shade, compacted soil, poor drainage, and acidic conditions
- Apply iron sulfate or a moss-specific product in fall or early spring to kill existing moss; rake it out before overseeding
- Address the root cause of moss: improve drainage, overseed thin areas, add lime, or trim overhanging branches for more light
- Dandelions and clover are common PNW lawn weeds — spot treat with a broadleaf herbicide in spring or hand-dig before they seed
- Avoid weed-and-feed products in fall; the fertilizer timing is good but herbicides can harm nearby trees and shrubs through root uptake
- Aerate compacted PNW clay soils once a year — fall (September) is the ideal time
- Overseeding after aeration fills in thin or bare patches before winter rains establish new grass
- Use a fescue or perennial ryegrass blend suited to the PNW — they handle the wet winters and dry summers better than bluegrass alone
- Top-dress with a thin layer of compost after overseeding to improve germination and soil health over time
- Fall is your most important lawn care season in the PNW — aerate, overseed, fertilize, and lime all in September–October
- Spring is for cleanup — rake out dead moss, dethatch if needed, and apply a light fertilizer in May
- Summer is largely hands-off beyond mowing and watering; avoid aggressive treatments on heat-stressed grass
- Winter lawns in the PNW stay green but grow slowly — avoid heavy foot traffic on waterlogged soil to prevent compaction
- Rinse the turf with a garden hose every 1–2 weeks to remove dust, pollen, and light debris — especially important in the PNW where pollen and organic matter accumulate heavily in spring
- Remove leaves, twigs, and debris promptly with a plastic leaf rake or a blower — avoid metal rakes which can snag and damage fibers
- Spot clean spills immediately with water and mild dish soap; rinse thoroughly afterward
- For pet waste, remove solids promptly and rinse the area well with water; use an enzyme-based pet turf cleaner monthly to neutralize odors and bacteria
- Avoid using bleach, harsh chemicals, or acidic cleaners — they degrade the turf fibers and infill over time
- Brush the turf with a stiff-bristled power broom or turf rake every few months to keep fibers standing upright — high-traffic areas may need it more often
- Brush against the grain of the fibers to lift and restore them to an upright position
- Matted fibers in heavily used areas (play zones, pet runs, seating areas) need more frequent brushing to maintain appearance
- Avoid using metal-bristled brushes — synthetic or nylon bristles only
- Most synthetic turf has an infill material (crumb rubber, sand, or organic infill) that can shift or compact over time
- Rake or brush infill back toward thin or bare spots periodically
- Top up infill as needed — your turf installer can advise on the correct infill type and depth for your specific product
- Weeds can occasionally sprout through seams or edges — pull them by hand or use a water-based weed killer safe for synthetic turf
- Moss is a real issue in the PNW’s wet climate — it can grow on top of synthetic turf just as it does on real grass
- Apply a diluted iron sulfate solution or a moss killer labeled safe for artificial turf in fall and early spring
- Ensure good drainage under and around the turf — poor drainage accelerates moss growth significantly
- Keep edges trimmed and sealed to prevent weeds from creeping in from borders
- Synthetic turf can get significantly hotter than natural grass in direct sun — surface temperatures can reach 150°F+ on hot days
- In the PNW this is less of a concern than in hotter climates, but during summer heat waves (which are increasing in Oregon and Washington) lightly mist the turf with water to cool it before use
- Avoid placing grills, fire pits, or anything with open flame near synthetic turf — it can melt
- Keep cigarettes and fireworks away from the surface for the same reason
- Never use a metal rake, shovel, or sharp tools on the turf surface
- Avoid parking vehicles or heavy equipment on synthetic turf — it crushes fibers and compacts infill permanently
- Do not use pesticides, herbicides, or fertilizers on synthetic turf — they serve no purpose and can degrade the materials
- Avoid rubber-backed mats or furniture without turf-safe feet — they can trap moisture and cause mold underneath
- Fall — Clear fallen leaves frequently; they break down and create a layer of organic matter that encourages moss and weeds
- Winter — Synthetic turf drains well and handles PNW rain fine; avoid walking on it when topped with ice or frost as fibers become brittle in freezing temps
- Spring — Deep rinse and brush to refresh after the wet season; check for any moss growth and treat early
- Summer — Monitor for heat buildup during heat waves; mist as needed; this is the best time for any repairs or seam work
- Have the turf professionally cleaned and groomed every 1–2 years for best longevity
- Inspect seams and edges annually — re-secure any lifting edges promptly to prevent tripping hazards and further damage
- Most quality synthetic turf lasts 15–20 years with proper care; heavy pet or play use may shorten that lifespan
- Keep your installer’s warranty information — many warranties require documented routine maintenance to remain valid
- Turn the system on in late April or May, once the threat of hard frost has passed — open the main valve slowly to avoid pressure shock to pipes and heads
- Run each zone manually and check every head for clogs, tilted spray, or leaks; clean or replace nozzles as needed
- Program watering for early morning (before 9am) to reduce evaporation and fungal disease
- Lawns generally need 1–1.5 inches per week in summer; drip zones for beds and trees should run longer and less often
- Use a rain sensor or smart controller — PNW weather swings quickly and a skipped cycle after rain saves water and prevents root rot
- Adjust the schedule monthly: June is lighter, July–August is peak, and September should taper off as fall rains return
- Check drip lines monthly for kinks, chewed tubing (rodents and raccoons), and emitters that have popped off
- Flush drip line ends and clean inline filters every spring — clay and mineral buildup clogs emitters over time
- Keep spray heads clear of grass and mulch so the pattern isn’t blocked; trim turf around heads each season
- Avoid spraying directly on trunks, fences, and siding — constant moisture invites rot and moss
- Watch for soggy spots or unusually green patches, which usually mean a broken line or head
- Winterize by late October or before the first hard freeze (Portland-area freezes can arrive suddenly in November or December)
- Shut off the water supply, drain the mainline, and have the lines blown out with compressed air by a professional
- Open drain valves and insulate or cover exposed backflow preventers and above-ground pipes
- Turn the controller to “rain/off” mode rather than unplugging it so it keeps its programming
- Have the backflow preventer tested annually — many municipalities require it
- Most modern systems are low-voltage LED — efficient, long-lasting, and safe for DIY adjustment
- Wipe lenses every 2–3 months; PNW moisture, pollen, and moss film dim fixtures faster than you’d expect
- Trim plants away from fixtures as they grow so light isn’t blocked and heat doesn’t scorch foliage
- Check connections and wire runs each spring — moisture is the main cause of flickering and dead fixtures; use waterproof wire nuts or gel-filled connectors
- Re-aim uplights and path lights after mowing, mulching, or storms knock them out of position
- Reset timers or photocells after daylight saving changes and power outages
- Replace LED modules or bulbs as they fade; keep the transformer clear of debris and out of standing water
- Tighten stakes in saturated winter soil so fixtures don’t lean or fall
- Spring — Start up irrigation, test every zone, clean filters, and inspect lighting wiring
- Summer — Monitor for leaks and adjust watering during heat waves
- Fall — Taper off irrigation in September and schedule blowout in October
- Winter — Keep fixtures clear of fallen leaves and snow, and check lights after windstorms
- Sweep regularly and rinse with a hose; use a pressure washer (under 3,000 PSI, wide fan tip) once a year to remove moss and algae
- Moss and algae thrive on shaded, damp concrete — treat with a concrete-safe moss cleaner, then improve sunlight and drainage where possible
- Seal exposed concrete every 2–4 years with a penetrating or acrylic sealer to resist moisture and freeze-thaw damage
- Fill hairline cracks promptly with a flexible concrete crack filler — water entering cracks expands in freezing temperatures
- Avoid deicing salts, which cause scaling and spalling; use sand for traction instead
- Clean oil and rust stains right away with a degreaser or poultice
- Sweep polymeric sand back into joints annually and top up any gaps — it locks pavers in place and suppresses weeds
- Pull weeds from joints early; avoid harsh herbicides that can stain or harm nearby plants
- Treat moss and algae in fall and early spring with a paver-safe cleaner, then rinse well
- Re-level any sunken or heaved pavers — lift, add and compact base material, and reset
- Reseal every 3–5 years if you want color enhancement and stain protection; always re-sand joints after cleaning
- Keep downspouts and irrigation heads directed away from paver edges to prevent base erosion
- Inspect walls each spring and after heavy winter storms for bulging, leaning, cracking, or displaced blocks
- Keep weep holes and drainage pipes clear — water pressure behind a wall is the #1 cause of failure in PNW clay soils
- Don’t pile soil, mulch, or heavy planters against the top or base of the wall
- Plant shallow-rooted groundcovers near walls; keep large trees and aggressive roots well away
- Re-secure caps with masonry adhesive if they loosen
- Walls over 4 feet tall should be engineered — contact a professional about any movement or cracking in tall walls
- Sweep and rinse regularly; use a soft brush and pH-neutral cleaner for stains — avoid acidic cleaners on limestone, travertine, and sandstone
- Use low-pressure washing only; high pressure can pit and erode softer stones
- Re-set loose flagstone and re-fill joints with sand, polymeric sand, or soil with groundcover as originally designed
- Moss on shaded stone can be a slip hazard — treat with a stone-safe moss killer and scrub in fall
- Always clean and fully dry the surface (at least 24–48 hours of dry weather) before sealing
- Best sealing window is late spring through early fall when temperatures are 50°F or higher and rain is not forecast
- Test a small area first — some sealers darken or add gloss
- Apply thin, even coats; pooled sealer can leave a cloudy or sticky finish
- Penetrating sealers breathe better and suit most PNW applications; film-forming sealers can trap moisture and turn white
- Spring — Inspect for winter damage, clean, repair joints, and treat moss
- Summer — Best season for sealing and repairs
- Fall — Clear leaves promptly, since they stain stone and feed moss
- Winter — Avoid deicing salts and chipping ice with metal tools
- Sweep decks, fences, and pergolas regularly to prevent debris from holding moisture against the wood
- Wash once or twice a year (spring and early fall) with a wood-safe cleaner and soft brush; moss and mildew are constant in the PNW
- Use a pressure washer on low settings only (under 1,500 PSI, wide tip, moving with the grain) — high pressure gouges and fuzzes the wood
- Oxygen bleach cleaners are safer for plants than chlorine bleach; rinse nearby plantings before and after
- Re-stain or re-seal decks every 2–3 years and vertical surfaces like fences every 3–5 years; sooner on sun-exposed or high-traffic areas
- Test whether it’s time with the water test: if water beads, the finish is working; if it soaks in, it’s time to recoat
- Apply only in dry weather with temperatures between 50–90°F, with 24–48 hours of dry weather afterward; late spring through early fall is ideal
- Let wood dry fully (several days after cleaning) before applying finish
- Choose semi-transparent oil-based or quality water-based stains with UV and mildew protection — film-forming paints and solid stains can peel and trap moisture
- Wood in contact with soil or standing water will rot — keep a gap between wood and soil, and keep mulch and plants away from fence bases and posts
- Check posts, stair stringers, rail connections, and the underside of decks each spring by probing with a screwdriver; soft spots mean rot
- Replace rotted boards promptly and treat cut ends with preservative
- Clean out gaps between deck boards so leaves and needles don’t hold moisture
- Trim vegetation back for airflow and sunlight — shade and moisture are the main drivers of moss and rot
- Watch for carpenter ants, termites, and carpenter bees; sawdust piles or small round holes need prompt attention
- Check railings, stairs, and fasteners each spring; tighten loose screws and replace rusted ones with stainless or coated hardware
- Look for popped nails and raised screw heads that can cause injuries
- Inspect the ledger board connecting a deck to the house annually — failures here are serious
- Cedar and redwood — naturally rot-resistant; will silver gracefully if left unfinished, or can be stained to keep their color
- Pressure-treated lumber — let it dry for several months to a year before staining, and expect more cracking and warping
- Composite and PVC decking — never needs staining, but still needs regular cleaning, since mold can grow on the surface
- Spring — Inspect, clean, and make repairs
- Summer — Best time for staining and sealing
- Fall — Clear leaves and needles frequently
- Winter — Shovel snow with a plastic shovel and avoid metal tools or rock salt
- Maintain balance with a mix of aquatic plants, a good filter, and fish at a sustainable stocking level — a balanced pond stays clearer with less effort
- Cover 50–70% of the surface with water lilies and floating plants to shade water and reduce algae
- Skim leaves, needles, and debris regularly, especially in fall; decomposing debris fuels algae and harms water quality
- Use beneficial bacteria monthly in the warm season to break down waste
- Top up water with a hose as it evaporates in summer; use dechlorinator if fish are present
- Clean out accumulated sludge in late winter or early spring, but never completely drain an established pond — it removes beneficial bacteria
- Feed fish lightly and only when water is above 50°F; stop feeding in cold weather
- Check water levels weekly in summer — pumps running dry burn out quickly
- Clean pump intakes and prefilters every 2–4 weeks to keep flow strong
- Scrub basins and fountain surfaces with a soft brush and mild soap; avoid bleach and harsh chemicals if wildlife, fish, or plants use the water
- Descale mineral buildup with a vinegar solution, then rinse thoroughly
- Use a water treatment designed for fountains to reduce algae in warm months
- Make sure pumps are plugged into GFCI-protected outlets
- Clear debris from spillways and rocks so water doesn’t divert out of the system
- Check the liner edges and water loss; unexplained water loss over a few days usually means a leak or water diverting around the edges
- Pull algae by hand and trim aquatic plants as they overgrow
- Clean the skimmer basket and filter media weekly during leaf drop
- Algae is normal and mostly a sign of too much sunlight, nutrients, or debris; address the cause instead of repeatedly treating symptoms
- Keep water moving — still water breeds mosquitoes; use a pump, aerator, or mosquito dunks (BTI) in features without fish
- Avoid over-fertilizing nearby plants and lawns, since runoff feeds algae
- Keep pumps running in ponds with fish through winter when possible, or add a de-icer or aerator to maintain a gas exchange hole in the ice
- Never break ice with force — it can harm fish; melt an opening with warm water
- Drain and shut down fountains and shallow decorative features before freezing temperatures; store pumps indoors in a bucket of water
- Cover or net ponds in fall to keep out leaves
- Trim back dead plant material and move tender plants to deeper water or indoors
- Spring — Restart pumps, clean filters, and add beneficial bacteria once water warms
- Summer — Top off water, clean skimmers, and monitor algae and oxygen during heat waves
- Fall — Net the pond, trim plants, and reduce fish feeding as temperatures drop
- Winter — Keep ice openings, and drain features that can freeze
- Test water 2–3 times per week during swim season and after heavy rain or heavy use
- Target ranges: pH 7.2–7.6, free chlorine 1–3 ppm, total alkalinity 80–120 ppm, calcium hardness 200–400 ppm, and stabilizer (cyanuric acid) 30–50 ppm
- Balance alkalinity first, then pH, then sanitizer — alkalinity keeps pH stable
- PNW rain is slightly acidic and dilutes chemicals, so retest after storms
- Shock the pool weekly or after parties, storms, or heavy use to burn off contaminants
- Add chemicals with the pump running, and never mix different chemicals together
- Store chemicals in a cool, dry, ventilated place, away from children and from each other
- Run the pump 8–12 hours a day in summer to keep water circulating and filtered
- Empty skimmer and pump baskets several times a week — more often during leaf and pollen season
- Backwash sand and DE filters when pressure rises 8–10 PSI above clean level; rinse or replace cartridge filters on the same trigger
- Deep-clean filter media once or twice a season
- Ensure return jets point to promote circulation around the whole pool
- Skim the surface daily or as needed, especially with PNW pollen, needles, and fall leaves
- Brush walls, steps, and the floor weekly to prevent algae from taking hold, focusing on shaded corners and dead spots
- Vacuum weekly, or run a robotic cleaner on a schedule
- Clean the waterline with a pool-safe tile cleaner to remove oils and buildup
- Treat green or cloudy water right away: brush, shock, run the filter continuously, and retest before swimming
- Open in late April to May, when temperatures begin to warm
- Remove the cover, clean it, let it dry completely, and store it
- Reconnect equipment, refill to the proper water level, prime the pump, and check for leaks
- Test and balance water, then shock before swimming
- Inspect the liner, tile, coping, and ladders for winter damage
- Close in late September to October, once water temperatures stay consistently below 65°F
- Balance water, shock, and add winterizing chemicals before closing
- Clean the pool thoroughly and lower the water level as recommended for your pool type
- Drain equipment and blow out plumbing lines if freezing temperatures are expected
- Use a secure cover, and use a cover pump to remove standing rain and leaves through the wet winter
- Check the cover monthly and keep it free of heavy debris
- Keep fencing, self-latching gates, and covers in good working order — check latches and alarms regularly
- Keep rescue equipment (life ring, reach pole) and a phone near the pool
- Inspect drain covers and electrical equipment for wear; all outlets should be GFCI-protected
- Never leave children unattended near water
- Have equipment (pump, heater, filter) professionally serviced every 1–2 years
- Spring — Open, balance, shock, and inspect equipment
- Summer — Test often, clean regularly, and watch for algae during heat waves
- Fall — Keep leaves out, prepare for closing, and cover properly
- Winter — Monitor the cover, pump off standing water, and check water level
Your dream living space starts here.
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