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Crimson Sentry Norway maple with a narrow upright crown and large five-lobed leaves in very dark red-purple. Small yellow flowers tinged red and widely winged samaras add seasonal detail. The outline represents an 8 to 12 m by 4 to 8 m tree positioned well away from woodlands and shorelines.

Narrow deciduous tree Sapindaceae

Columnar Zone 4 maple with dark-purple foliage

Crimson Sentry Norway maple

Acer platanoides ‘Crimson Sentry’

Crimson Sentry is a narrow upright Norway maple reaching 8 to 12 m high and 4 to 8 m wide over time. Large five-lobed leaves remain very dark red-purple through the season. Yellow flowers tinged red may be followed by green and dark-red samaras. Hardy in Canadian Zone 4, it prefers sun and fertile, moist, well-drained soil. Acer platanoides is officially a high-risk invasive alien species in Québec: avoid natural habitat, monitor seedlings and favour a locally native alternative beside woodland or shoreline. Sale sizes from 7 to 15 gallons and measured-tree formats do not alter mature dimensions or dispersal responsibility.

7 gallons; 15 gallons; 200 cm; 250 cm; 50 mm

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Quantity: 7 gallons; 15 gallons; 200 cm; 250 cm; 50 mm
Exposure: Full sun; light partial shade tolerated
Hardiness: Canadian Zone 4

Common nameCrimson Sentry Norway maple

FamilySapindaceae

GenusAcer

Speciesplatanoides

CultivarCrimson Sentry

TypeNarrow deciduous tree

Botanical nameAcer platanoides ‘Crimson Sentry’

Crimson Sentry Norway maple (Acer platanoides ‘Crimson Sentry’) is a narrowly upright deciduous tree selected for very dark red-purple foliage. Opposite broad leaves divided into five pointed lobes retain a burgundy tone through the growing season, then may become brownish or bronzy purple in autumn. Small yellow flowers tinged dark red appear before or with the leaves in spring. They may be followed by green and dark-red winged fruit whose widely spreading wings mature in autumn. The RHS gives an ultimate height of 8 to 12 m and width of 4 to 8 m, so the cultivar is narrower than the species but not a permanently small patio tree.

Hardy in Canadian Zone 4, Crimson Sentry prefers full sun for strong dark colour but tolerates light partial shade. Plant it in fertile, moist, well-drained soil; loam, clay and sand are acceptable where water does not remain stagnant. Keep the root flare visible, maintain 5 to 8 cm of mulch without touching the trunk and water deeply through the first two growing seasons. Once established, Norway maple tolerates urban heat and short droughts. Avoid concentrated salt, compaction and repeated heavy pruning. Remove only problematic wood after leaves expand, inspect branch unions after ice events and preserve an open soil area around the expanding root system.

In Québec, Acer platanoides is officially classified as a high-risk invasive alien plant and a priority for control. Seed can colonize woodlands, edges, vacant land and shorelines, where dense shade reduces plant diversity. Do not install Crimson Sentry beside natural habitat or a green corridor. Inspect the property and downwind areas in spring and autumn, then pull seedlings before they fruit. For a new planting close to nature, favour a locally native tree matched to the site’s dimensions and drainage. Canadian customers outside Québec should also check provincial and municipal guidance because invasive-species status and planting restrictions vary by region. Sale formats change neither mature size nor ecological responsibility.

Planting guide

From planting to establishment.

Spacing / density Space 5 to 8 m (16 to 26 ft) apart and according to infrastructure

Best planting time Spring or early autumn, allowing enough time for rooting before freeze-up

Propagation Grafting to preserve cultivar identity

Soil and care

The right care,at the right time.

Soil pH

Acidic, neutral or alkaline

Minimum temperature

About -34 °C (-29 °F)

Care level

Moderate

Drought tolerance

Yes

Watering

Water slowly and deeply after planting, then keep the root ball and neighbouring soil evenly moist through the first two growing seasons. Check moisture beneath mulch before irrigating again. Once established, Norway maple tolerates short dry periods, but deep watering during prolonged drought limits leaf scorch. Avoid small daily applications beside the trunk and standing water around the root flare. Expand the irrigated area as roots extend and monitor more often beside heat-storing pavement.

Soil type

Choose fertile, moist, well-drained soil. Crimson Sentry accepts loam, clay and sand and a range of soil reactions, but roots suffer in standing water or compacted fill. Loosen a broad area, set the root flare at grade and preserve permeable soil beyond the root ball. Avoid concentrated salt and changes in grade around the trunk. Soil structure and drainage matter more than applying a precise pH target without testing the site.

Fertilization

In suitable soil, 5 to 8 cm of organic mulch and a thin surface layer of mature compost in spring are generally sufficient. If growth or colour appears weak, test the soil before adding a labelled tree fertilizer. Avoid heavy nitrogen, products placed against the trunk and late feeding, which extends soft growth before Canadian cold weather. Correct drainage and watering before assuming fertilizer will solve limited growth.

Moisture

Moist soil without standing water

Seasonal care

In spring, inspect the trunk, graft union, root flare and major branch unions after snowmelt. Restore 5 to 8 cm of mulch without covering bark, remove tight ties and water when rainfall is inadequate. Observe flowers and young samaras. In summer, check moisture, drainage and compaction when leaf margins brown. Watch for aphids, mites, scales, tar spot, cankers and Verticillium symptoms, then obtain a diagnosis before treating. Prune after leaves expand to remove only dead, broken, diseased or crossing wood and rootstock shoots. Never top the crown. In late summer and autumn, observe samara maturation and inspect beds, ditches, property boundaries and downwind areas. Pull seedlings before they fruit. Water before freeze-up when soil is dry and collect heavily spotted leaves. In winter, direct salt-laden snow elsewhere and protect a young trunk from rodents without tightening the guard. After ice, keep the area clear until inspection. Consult an arborist for a large limb or crack. Report spread into natural habitat according to Québec guidance and record every inspected area each season. Reassess proximity to woodland, shoreline and green corridors as surrounding land use changes. Photograph the same downwind areas, record every removed seedling and inspect debris for fruit before disposal. Share the inspection map with every maintenance provider, and verify current regional guidance before each season begins. Keep records annually.

Bloom and dimensions

Its place,in your garden.

Mature height

8 to 10 m (26 to 33 ft)

Width / spread

2 m (6.5 ft)

Flower color

Yellow tinged dark red

Foliage color

Very dark red-purple; potentially bronzy purple to brown in autumn

Foliage type

Deciduous

Growth rate

Moderate

Growth habit

Narrow, upright and columnar

Bloom period

Small yellow flowers tinged dark red open in clusters in spring before or with the purple leaves. Their effect is subtle but visible on bare twigs. Some insects may visit them, so avoid non-targeted insecticides during bloom. They may be followed by green and dark-red winged samaras that mature in autumn. Quantity varies with maturity, weather and pollination, and the cultivar should not be assumed sterile. Monitor fruit development because seed dispersal drives the ecological risk associated with the species.

Fruiting

Paired green and dark-red samaras with widely spreading wings may follow the flowers and mature in autumn. Do not assume Crimson Sentry is sterile. Inspect the property and downwind areas in spring and autumn, then pull seedlings before they fruit. Do not discard fruiting branches in woodland, shoreline habitat or vacant land. Seed management is essential in Québec, where the species is officially classified as a high-risk invasive alien plant. Follow local disposal and reporting guidance when spread reaches natural habitat.

Garden associations

In goodcompany.

Companion plants

Pair Crimson Sentry with green conifers, sedges, ferns and non-invasive native perennials suited to the same drainage. Their foliage emphasizes purple without requiring the maple to be planted beside natural habitat. Establish them toward the future crown perimeter without cutting roots, covering the flare or obstructing inspection. Avoid invasive groundcovers and preserve open access for seedling detection. Beside woodland or shoreline, build the entire planting from locally native trees and shrubs instead. Match moisture needs so companions do not force drought or saturation around the maple.

Frequently asked questions

Your questions,answered.

How large does Crimson Sentry become?

The Royal Horticultural Society gives an ultimate height of 8 to 12 m and width of 4 to 8 m, reached over decades according to soil and climate. The habit is narrow compared with the species, but the cultivar does not remain a small patio tree. The 7- or 15-gallon, 200- or 250-cm and 50-mm formats describe sale stage only. Reserve mature width away from walls, overhead services and passages. Do not force an undersized site through topping or repeated shearing; those cuts deform the crown and create dense regrowth. Correct initial spacing reduces future intervention and preserves the upright outline.

Is Crimson Sentry invasive in Québec?

Crimson Sentry belongs to Acer platanoides, Norway maple, which the Québec government classifies as a high-risk invasive alien species and a priority for control. Do not assume this cultivar is sterile. Avoid planting beside woodland, shoreline, vacant land, a naturalized ditch or green corridor. Inspect the property and downwind areas in spring and autumn, then pull seedlings before they fruit. Do not move fruiting branches into natural habitat. Report spread beyond cultivation according to Québec guidance. When this annual monitoring is not realistic, choose a locally native tree matched to the site. Customers elsewhere in Canada should check current provincial and municipal guidance before planting.

How can Crimson Sentry retain dark-purple foliage?

Full sun generally supports the darkest red-purple colour, while heavier shade can make foliage less intense. Choose fertile, moist, well-drained soil and irrigate deeply during establishment. Prolonged drought, a saturated root ball, salt or compacted roots can scorch margins and reduce foliage quality. Check moisture beneath mulch before watering and keep the root flare visible. Do not add fertilizer simply to darken leaves without a soil test. Colour also changes with leaf age and season, so compare several branches before deciding that a deficiency or reversion is present. Healthy annual growth and intact margins are better indicators of site suitability than one exact shade.

Which native trees can replace Crimson Sentry?

The correct replacement depends on available width, drainage and exposure. In many Canadian regions, a native tree-form serviceberry provides flowers, fruit and fall colour at a smaller scale; suitable native hawthorns offer upright structure and fruit; red maple fits a much larger moist acidic site. Confirm local provenance, mature dimensions and municipal constraints before choosing. None is an automatic substitute for every property. A recommendation based on soil volume, overhead services, salt and proximity to natural habitat helps identify a genuinely suitable species. A diverse selection of regional trees also reduces the risk associated with uniform planting and provides more useful habitat than one invasive species.

How should Crimson Sentry be pruned?

Respect the narrow upright habit. After leaves expand, remove only dead, broken, diseased or crossing wood and every shoot arising from the rootstock. Gradually subordinate a competing branch instead of removing substantial foliage in one year. Use clean tools and cut just outside the branch collar without leaving a stub. Never top the crown or shear it into an artificial column, because dense regrowth increases maintenance. Correct planting distance naturally preserves the form. Hire a certified arborist for a large limb, crack or elevated work. Inspect samaras before disposing of pruning debris, and never move fruiting material into natural habitat. Minimal pruning also protects the cultivar’s architectural outline.

Wildlife and pets

Life,around your plants.

Supporting wildlife

Spring flowers may be visited by some insects and the crown can provide occasional shelter. This limited value does not offset the species’ ecological risk; it is officially classified as a high-risk invasive alien plant in Québec. Use several locally native flowering and fruiting plants to support wildlife, avoid non-targeted pesticides and prevent all spread toward natural habitat. Regional native plants provide stronger long-term habitat value.