Subtropical Plants

Subtropical plants offer home gardeners something that most temperate fruit trees simply cannot: extraordinary flavors, fragrant flowers, and lush, evergreen foliage that brings a sense of abundance to the garden year-round. The pineapple guava in full spring bloom — with its striking crimson stamens and petals that taste of cinnamon and cotton candy — is one of the most ornamentally remarkable plants a Pacific Northwest gardener can grow outdoors. A babaco papaya ripening on the windowsill in November is something you will not find at any grocery store. A bowl of freshly harvested Chilean guava, deeply sweet and complex, competes with anything from the berry garden.

The most important decision before selecting any subtropical plant is an honest assessment of your climate. In most of the US, true tropical and subtropical species require a greenhouse, conservatory, or at minimum a sheltered container culture that can be moved indoors before hard frost. In the warmer parts of the Pacific Northwest — protected urban settings in western Washington and Oregon, the southern Willamette Valley, coastal California — a surprising number of subtropical species can be grown outdoors year-round in the right microclimate. Pineapple guava (Acca sellowiana) is the standout example: hardy to 10–15°F, it grows and fruits reliably in Zone 7–8 PNW gardens given the right site.

The reward for choosing wisely and matching plant to climate is extraordinary. Unlike zone-pushing that ends in winter losses, a well-sited subtropical plant will reward you for decades — providing beauty, fragrance, and flavors unlike anything else in the temperate fruit garden.

Raintree's subtropical collection spans a range of cold-hardiness and growing requirements. Some — like pineapple guava — are reliable outdoor plants for Zone 7–8 and can be grown as landscape specimens. Others, like babaco papaya and lemon guava, are best suited to container culture in most of the US, with the container moved indoors before temperatures drop below the plant's cold threshold. Understanding each plant's requirements sets expectations accurately and leads to better growing outcomes.

The USDA Plant Hardiness Zone Map (2023 update) reflects the average annual extreme minimum temperature in a location — and it is the starting point for evaluating any subtropical plant. But the zone map is a minimum-temperature guide, not a complete climate picture. Two additional factors matter enormously for subtropical fruiting plants:

• Summer heat accumulation. Most subtropical fruit plants require a certain number of warm growing-degree days to ripen fruit. A site that rarely freezes in winter but stays cool throughout summer — such as a foggy coastal California location — may not ripen feijoa or loquat reliably. Sites with warm, sunny summers produce better fruit even at the same hardiness zone rating.
• Microclimate. A south-facing wall, a protected courtyard, or a slope that sheds cold air can create a microclimate a full zone warmer than the surrounding landscape. These microclimates are where subtropical plants succeed in marginal climates. A north-facing or low-lying frost-pocket location is the opposite — it will disappoint even when the zone rating appears sufficient.

Sun exposure

All subtropical plants in the Raintree catalog require a minimum of 8 hours of direct sunlight measured in early summer (late June through early August) for best fruit production. Sufficient sun exposure initiates flower buds for the following season and drives the carbohydrate production that ripens fruit and develops flavor. In cooler-summer climates like the Pacific Northwest, maximizing sun exposure — particularly from the south and southwest — is critically important. A site that receives adequate sun in June but is partially shaded in August will underperform.

For container plants grown indoors or in a greenhouse, an unobstructed south-facing window providing 6 or more hours of direct light is the minimum standard. Supplemental grow lighting dramatically improves outcomes for container babaco and lemon guava in darker indoor environments.

Soil preparation

Subtropical plants tolerate a range of soil types as long as drainage is excellent and the soil is moderately rich in organic matter. Poor drainage is the most common cause of subtropical plant failure in-ground — standing water around the root zone for even short periods will damage or kill roots. Test drainage before planting by digging a hole 12 inches deep, filling it with water, and observing how quickly it drains; a rate of 1 inch per hour or faster is acceptable.

Target a soil pH of 5.5–6.8 for most subtropical species (UC ANR; UF/IFAS Extension). Test before planting and amend if needed — elemental sulfur lowers pH in alkaline soils; agricultural lime raises it in acidic soils. Contact your local cooperative extension office for region-specific amendment rates and application timing.

Improve the planting area by working 1–2 inches of plant-based organic matter — compost, aged wood chips, or coconut coir — into an area 1.5 to 2 times the diameter of the planting hole and up to a foot deep. A 2–4 inch mulch layer applied after planting conserves moisture, moderates soil temperature, and builds long-term soil health. Keep mulch pulled back 4–6 inches from the crown of the plant to prevent rot and vole access.

Planting

Plant container-grown subtropical plants in spring after the last frost date has passed. Dig a hole twice as wide as the root ball and set the plant at the same depth as it was in the container — do not bury the crown. Backfill with amended native soil. Do not add concentrated fertilizer to the planting hole. Water thoroughly at planting and apply mulch immediately. Stake young trees in windy locations until the root system is established.

Most of the subtropical species in Raintree's catalog are self-fertile — a single plant can set fruit without a dedicated pollinizer. This is one of the practical advantages of subtropical plants over many temperate fruit trees that require matched pairs. However, "self-fertile" is not the same as "cross-pollination irrelevant." For virtually every self-fertile subtropical plant, planting a second plant (same or different named variety of the same species) nearby produces larger, more abundant fruit crops.

UF/IFAS Extension notes for feijoa specifically that "some self-fertile varieties have been described and are reported to present higher yields, especially when cross-pollinated with other varieties" and that "self-incompatible trees preferentially outcross to produce fruit." UC ANR Master Gardener documentation confirms that even self-fruitful feijoa varieties produce a "more bountiful crop" with a second plant present.

Pineapple guava varieties differ meaningfully in ripening timing, fruit size, flavor profile, and degree of self-fertility. For most Raintree customers, variety selection comes down to two questions: How long is your growing season? And do you want the earliest possible ripening, or the largest possible fruit?

In the Pacific Northwest, where the growing season is shorter and summer temperatures are moderate, early-ripening self-fertile varieties such as Ramsey are the practical choice — they produce reliable crops in Zone 7–8 where later-ripening varieties may not fully ripen before fall rains and cooling temperatures arrive.

Water requirements

Subtropical plants in the ground require consistent, deep watering through the growing season — approximately 1 inch of water per week over the root zone, equivalent to 7–10 gallons per week for a typical 3-foot-diameter root zone. Water deeply once or twice weekly rather than shallowly every day; this encourages deep root development and maintains moisture where roots actually are. The soil should remain moist to approximately 12 inches deep through the growing season.

Feijoa is notably drought-tolerant once established — UC ANR notes it "does well with minimal irrigation beyond normal rainfall" in many locations, but adds that it "might drop fruit and leaves" during extended droughts. For fruit quality and size, supplemental irrigation during dry summer periods improves outcomes even for established plants. Fruit sizing and sugar development in late summer through harvest requires consistent moisture; do not allow the root zone to dry significantly during this window.

In the Pacific Northwest, spring rainfall typically covers irrigation needs through June. Begin supplemental watering in July and continue through harvest. Drip irrigation at the base of the plant, keeping foliage dry, is ideal — it reduces fungal pressure while delivering water efficiently to the root zone.

Fertilizing

Apply a balanced all-purpose or fruit-tree fertilizer in early spring before growth begins, or top-dress with 2–3 inches of well-rotted compost over the root zone annually. Do not apply nitrogen-heavy fertilizers after early summer — late-season nitrogen drives soft new growth that is vulnerable to winter damage. If the plant is producing 12 or more inches of new growth annually and has healthy, deep-green foliage, it may not need supplemental fertilizer at all.

Maintain a 2–4 inch mulch layer over the root zone year-round (kept back from the crown) to conserve moisture, moderate root-zone temperature, and improve soil health progressively.

Container growing is the key that opens subtropical fruiting to home gardeners throughout most of the United States — including the Pacific Northwest, the Northeast, and the Midwest, where outdoor winters would kill tender subtropical species. The plants moved outdoors to a sunny patio in spring, ripened through summer, and brought back in before frost can produce surprising yields in relatively compact containers.

Use a quality potting mix with added compost — never garden soil in containers. Increase container size gradually as plants establish rather than starting in an oversized pot; excess soil volume around young roots can hold moisture that promotes root rot. Ensure every container has drainage holes and that saucers are emptied after watering — no subtropical species tolerates standing water.

Container plants require more frequent watering and somewhat more frequent fertilization than in-ground plants. Check soil moisture every 2–3 days in warm weather and water when the soil is dry to the touch 1–2 inches down. Saturate the container fully at each watering — water until it flows freely from the drainage holes — then allow it to partially dry before watering again.

Pineapple guava (Acca sellowiana)

Pineapple guava is highly adaptable to pruning and can be trained as a multi-stemmed shrub, a single-trunk small tree, a hedge, or an espalier against a wall (NC State Extension; UF/IFAS; UC ANR Master Gardener). Most home gardeners grow it as a shrub, which requires the least intervention — simply remove any dead, crossing, or inward-facing branches in late winter to maintain good air circulation and an open form.

For tree form, select 1–3 main leaders and gradually remove basal suckers and lower side branches over several seasons to develop a clear trunk. Ongoing sucker removal is necessary to maintain tree form — feijoa naturally wants to produce multiple stems from the base. Annual light pruning after harvest in late fall or early winter keeps the plant at a manageable size. Do not prune heavily in fall in Zone 7 locations — pruning encourages new growth that may be damaged by early frosts. Heavy structural pruning is better timed for late winter just before new growth begins.

For hedges, shear to the desired size and form in early spring and again in summer. UC ANR Master Gardener documents that feijoa can be maintained as low as 8×8 feet with "heavy pruning in early spring and later in summer."

Loquat (Eriobotrya japonica)

Loquat grows naturally as a dense, large shrub or small tree reaching up to 20 feet. In containers, prune annually to maintain a manageable size. In the ground, pruning is primarily for size control and to remove dead or crossing branches. Prune after harvest in spring; avoid heavy pruning in fall or winter, which removes next year's flower buds. Flowers form on terminals of the current season's growth — avoid heading cuts that remove shoot tips during the flowering period.

Babaco papaya (Vasconcellea ×)

Babaco produces fruit on a single central trunk and does not require pruning for fruiting. Remove lower leaves as they yellow to maintain good airflow around the trunk and reduce disease pressure. Plants naturally decline after 3–5 years; propagate from suckers or cuttings to renew your stock.

Chilean and lemon guava

Both species can be sheared to shape or pruned to maintain a compact form. Annual light pruning after harvest removes the oldest wood and encourages vigorous new fruiting growth. Lemon guava in containers benefits from tip-pruning during the growing season to maintain manageable size and encourage branching.

Pineapple guava

Feijoa fruit matures over an extended window — typically October through December in California; late summer to early fall for early-ripening PNW-adapted varieties like Ramsey. The most reliable harvest cue is "touch picking" — fruit that is ready to harvest detaches easily with a gentle twist or light upward pressure (UC ANR Cooperative Extension). Color is a secondary indicator: fruit transitions from bright green to a duller, slightly yellowed green at maturity. Cutting a fruit open and noting seed development and flesh translucency also aids timing judgment with experience.

Alternatively, spreading a tarp beneath the plant and gently shaking branches every few days catches naturally dropping ripe fruit — a traditional commercial harvest method for feijoa that works well in home gardens. Fruit that drops naturally is at or past peak ripeness and should be used promptly.

Freshly harvested feijoa is firm; it ripens at room temperature over several days to a week, softening slightly and developing full flavor. Eat by cutting in half and scooping out the creamy white flesh, which may show slight browning upon air exposure in some varieties — this is normal. Refrigerate ripe fruit for up to 2 weeks.

Loquat

Loquat fruit ripens in spring — typically March through May depending on location and climate. Harvest when fully colored (yellow-orange) and gives slightly to gentle pressure. Fruit clusters can be harvested when most fruits are ripe; individual fruits in a cluster may ripen at slightly different rates. Fresh loquat is best used immediately or within 1–2 weeks of harvest; it does not store well.

Babaco papaya

Individual babaco fruits ripen over many months — each 10-inch fruit turns progressively yellow as it ripens from the base upward. Harvest when at least half to fully yellow. Fruit can ripen at room temperature after picking or be eaten at any stage from firm (sharper flavor) to fully soft (sweeter, richer flavor). Refrigerate after cutting; fresh babaco is best used within a week of harvest.

Chilean guava and lemon guava

Chilean guava berries ripen in late summer to early fall, deepening from pink to red when fully ripe. Taste a few to judge sweetness before harvesting in volume. Lemon guava fruits turn yellow when ripe and have a pleasant aroma; the skin is thin and the interior is crisp and tart-sweet. Both species ripen fruit over an extended window — pick repeatedly as fruit matures rather than in a single harvest.