Marionberry Cultivation: How to Plant, Grow and Care Guide

The marionberry, with its blend of sweetness and tartness, is a charming and tasty addition to any garden. Expert gardener and berry cultivator Lindsay Miller shares her insights on how to successfully grow and care for these delicious berries.

While Vermont is known for its maple syrup and Florida for its oranges, Oregon is celebrated for its marionberries. This distinctive berry, named after Marion County where it was developed, is the result of crossing the ‘Chehalem’ and ‘Olallie’ blackberry varieties. Released in the 1950s by the University of Oregon and the U.S. Department of Agriculture, the marionberry combines a juicy, sweet, and slightly tart flavor, making it a beloved fruit of the region.

Oregon remains a strong supporter of the marionberry, which has become a favorite among both commercial growers and home gardeners. In 2008, the state’s blackberry production exceeded 39 million pounds, with marionberries making up two-thirds of that total. Recognizing its importance, Oregon officially declared marionberry pie as the state pie in 2017.

The great news is you don’t need to be in Oregon to grow and enjoy this cherished berry. With the right conditions, marionberries are easy to cultivate and can thrive in your home garden.

Marionberry Overview

What are Marionberries?

Marionberries are a type of perennial cane plant, similar to raspberries and other blackberry hybrids. They develop thorny, flexible canes from their base, which are responsible for producing leaves, flowers, and fruit.

Marionberries exhibit a distinct growth pattern. While the root system and crown remain perennial, the canes that produce leaves and fruit are biennial. In their first year, the canes, known as “primocanes,” survive through the winter. In their second year, these primocanes transform into “floricanes,” which then produce small white flowers and eventually the berries.

Floricanes bloom in late spring, and by mid-July, they bear plump, aromatic berries prized for their sweet and slightly earthy flavor. These berries are versatile and can be enjoyed fresh, or used to make jams, pies, tarts, salads, cocktails, and even as a savory ingredient in dishes like pork chops.

How to Plant Marionberries?

Marionberries are challenging to grow from seed and are typically started from transplants or bare roots. For either method, ensure you wait until spring, after the last frost has passed, and the soil is workable.

1. Transplanting

Planting a potted marionberry is not so hard. Start by digging a hole that is at least twice the size of the nursery pot. Gently remove the plant from its pot and place it in the hole, ensuring that the root ball is level with the surrounding soil. Avoid planting too high, as this can cause the plant to be displaced during winter frost heaves, and too deep, which may lead to stem girdling and suffocation.

Next, backfill the hole. I recommend filling about half of it with soil, watering deeply to eliminate any air pockets, and then adding the remaining soil.

Ensure marionberries have ample space to grow their canes. Space individual plants 3-5 feet apart within rows that are at least 6 feet apart.

2. Bare Root Planting

Bare root plants are exactly what they sound like: a small segment of stem or cane with a bundle of roots attached. While they may seem unimpressive at first, many plants thrive when started from bare roots, including fruit trees, roses, and marionberries.

If you’ve received bare root marionberries by mail, it’s essential to unpack and plant them right away. If planting isn’t possible within a few days, store them in a cool, slightly humid environment like a refrigerator or basement. Before planting, soak the bare roots in water for a few hours.

Next, dig a hole wide enough to spread out the roots. Place the bare root in the hole and backfill it, ensuring the roots are covered evenly with soil. Exposing roots to air and sunlight can harm them, so be sure to water deeply to settle the soil and eliminate air pockets.

How to Grow it ?

Marionberries can be somewhat particular about their growing conditions, but they are relatively low-maintenance once established, needing only annual pruning. When placed in the right environment, these hardy cane plants will yield fresh fruit for many years.

Light
With sprawling, thorny canes, marionberries boast bright green, lobed leaves and plump, glossy black berries. For the best results, position these plants in full sun. While they can tolerate some shade, placing them in full sun yields a better berry harvest.

Water
Marionberries need regular watering, about 1-2 inches per week. They are not drought-tolerant, so during hot, dry spells, increase watering. To prevent fungal issues, use drip irrigation rather than overhead watering to keep the foliage dry and reduce disease risk.

Soil
Marionberries thrive in loamy, well-drained soil enriched with organic matter. Incorporate compost or leaf mold into the soil before planting. They prefer slightly acidic soil with a pH range of 5.6–6.5. Raised beds are also a good option if your native soil lacks proper drainage.

Temperature and Humidity
Ideal for zones 6-9, marionberries flourish in mild climates with cool winters and sunny summers. They are not suited for extreme temperatures, whether too hot or too cold. These berries do best in regions with cool, wet winters and warm, dry summers.

Fertilizing
Feed marionberries annually with compost and a balanced fertilizer to promote healthy growth. Apply a granular fertilizer in early spring as new growth begins. If the plants show signs of nitrogen deficiency, such as slow growth or pale leaves, a nitrogen-rich fertilizer may be needed before harvest.

Trellising
Support marionberry canes with a trellis to prevent them from sprawling on the ground. Use a fence, pre-made trellis, or build a DIY structure to train the canes. This helps improve air circulation and keeps the canes off the ground, which is beneficial for both growth and protection from cold weather.

Pruning
In the initial planting year, marionberries require minimal pruning. Focus on removing any dead or diseased canes to help the plant establish itself. Allow the healthy canes to develop fully and leaf out, which will prepare them for future fruiting.

During the subsequent years, regular pruning becomes essential to maintain plant health and fruit quality. After the berry harvest, typically in late summer or early fall, remove the spent floricanes at ground level. These canes have already produced fruit and will not yield another crop. It’s crucial to avoid cutting the primocanes, as these are the new canes that will bear fruit in the next growing season.

Once you have pruned the old canes, you’ll have space to guide the current year’s primocanes onto the trellis or support structure. These primocanes will overwinter and produce fruit the following year. With each passing season, the cycle of pruning and training the canes will become more intuitive, ensuring a healthier and more productive marionberry plant.

Harvesting and Storing Marionberries

Marionberries typically reach their peak ripeness in mid-summer, around July to August. Unlike some fruits, marionberries will not continue to ripen once picked, so wait until they turn from a glossy black to a matte black before harvesting. It’s best to pick marionberries in the morning when they are firm. Avoid harvesting when the berries or plants are wet, as this can lead to mold and rot.

Enjoy the berries fresh from the garden, which is a delightful way to savor them! If you need to store them, marionberries will stay fresh on the counter for about 1-2 days. In the refrigerator, they can last 3-5 days. It’s important not to wash the berries until you’re ready to eat them; store them dry to prevent mold growth.

To keep marionberries available throughout the year, freezing is your best option. I recommend spreading the berries out on a cutting board and freezing them overnight. This method ensures each berry freezes individually, avoiding the common problem of clumped, freezer-burned fruit. Once frozen, transfer the berries to a freezer bag or container for long-term storage.

Common Issues

Marionberries are hardy plants, but they are not completely free from pests and diseases.

Pests

Birds and insects pose the greatest risks to ripening fruit.

Birds and Animals
Birds and deer are drawn to marionberries, making them significant threats to ripening fruit. To protect your harvest, use physical barriers like netting or fencing. These methods are effective and safe for both the berries and the wildlife.

Cane Borers
Cane borers are slender beetles with black bodies and long antennae. While the adult borers are moths with clear wings, their larvae cause most of the damage by tunneling through the canes and crown of the plant. To prevent serious harm, remove and discard infected canes immediately. Look out for sawdust-like frass as an indicator of their presence.

Japanese Beetles
Japanese beetles are metallic green insects with copper-colored wings that feed on leaves, leaving behind a skeletonized appearance. To manage these pests, either manually remove the beetles and drop them into soapy water or use row covers to shield your plants. For persistent issues, treat the soil with beneficial nematodes in early spring, applying twice a few weeks apart when temperatures are between 50-80°F (10-27°C).

Aphids
Aphids are small insects that cluster on the undersides of leaves, sucking out plant juices and causing leaf curl and death. They also produce a sticky substance that can attract ants and mold. Begin by rinsing the affected area with a strong water stream, then apply insecticidal soap. To naturally control aphid populations, encourage beneficial insects like ladybugs and predatory wasps by planting flowers such as bonesets, yarrow, dill, and fennel nearby.

Diseases

Marionberries can fall prey to various diseases, particularly in humid conditions with poor airflow.

Orange Rust
Orange rust manifests as bright orange, powdery spots on the underside of leaves, which eventually turn brown and fall off. This fungus thrives in cool, wet conditions and spreads through airborne spores. Since the fungus is systemic, it can persist in the plant’s crown and canes over winter. To combat orange rust, remove and discard infected plants. Ensure good air circulation by spacing plants 5-6 feet apart and thinning out floricanes right after harvest.

Cane Blight
Cane blight is identifiable by dark, sunken lesions or cankers on stems, often with a reddish-brown edge. Infected plants may exhibit wilting and dead shoots above the infection line. This fungal disease is more common in plants that have been damaged or poorly pruned. To prevent cane blight, maintain proper air circulation by regularly pruning and thinning plants, and ensure your soil is rich in nutrients. Weak canes are more vulnerable to disease, so keep plants well-fed and healthy.

Anthracnose
Anthracnose presents as dark, sunken lesions with purple edges on leaves, which can spread to stems and cause dieback. To prevent this fungal disease, remove all infected leaves and stems promptly. Avoid composting these prunings; instead, dispose of them to prevent the disease from lingering and spreading.

Botrytis
Commonly known as gray mold, botrytis causes a fuzzy, grayish-brown mold on berries. The disease is exacerbated by overhead watering and prolonged periods of warm, humid weather. To reduce the risk of botrytis, improve air circulation by training canes off the ground and pruning regularly. Harvest ripe berries frequently to prevent mold development and avoid letting the fruits remain damp.

Frequently Asked Questions

Is a marionberry a type of blackberry?
Yes, indeed! Marionberries are a specific variety of blackberry, often labeled as ‘Marion’ blackberry.

Are marionberries invasive?
No, they are not. Marionberries are intentionally grown and do not readily spread from seeds. This is different from the Himalayan blackberry (Rubus armeniacus), which is an invasive plant introduced from Europe and can spread aggressively.

Do you need more than one plant to get fruit?
Nope! Marionberries are self-pollinating, so you only need one plant to produce fruit.