Japanese magnolia trees (Magnolia x soulangiana), also called saucer magnolias, grow slowly to 25 to 30 feet tall with a 15- to 25-foot spread. Well-known for their colorful and fragrant, saucer-shaped flowers that are 4 to 12 inches in diameter, Japanese magnolia trees grow best in moist, well-drained soil and partial shade. Collect their bright-red seeds from the cones that drop in fall, and prepare them as soon as possible so you can plant new Japanese magnolias during the following spring. Japanese magnolias are hardy in U.S. Department of Agriculture plant hardiness zones 5 through 9a.
Remove the seeds from a Japanese magnolia cone that recently fell to the ground in fall. Place the seeds in a glass of water. Discard the seeds that float, and keep the seeds that sank in the water. Wipe the seeds that sank, removing their red coating.by using a paper towel. Scratch each seed gently with sandpaper to abrade its surface.
Fill a sealable plastic bag with seed-starting potting mix, and moisten the mix lightly with water. Bury the seeds in the mix, ensuing they're covered. Seal the bag, and place it in a 40- to 45-degrees Fahrenheit refrigerator for at least three months. Keep the mix moist but not soaking wet during that time.
Fill a 12-inch-diameter plant container, which has bottom drainage holes, with moist, standard potting mix. Plant 2 or 3 seeds at a depth of 1/2 inch and 3 inches apart in the container's potting mix. Keep the container's potting mix moist but not soaking wet, and keep the container in an area with temperatures above 70 degrees Fahrenheit and bright but indirect sunlight. Direct sunlight can burn the foliage of the seedlings that will grow from the seeds.
Select an outdoor planting site for each Japanese magnolia tree you plan to plant. Each site must receive partial sunlight but be sheltered from hot, afternoon sun exposure, and the magnolia trees should be spaced at least 30 feet from each other, other trees and other structures to allow for the trees' mature size. Wait for the soil temperature in the locations to reach 70 degrees Fahrenheit in early spring. Set a 2- to 3-inch-thick layer of aged compost, aged manure or other organic matter on the selected sites' soil, and till the organic matter into the soil to a depth of 6 inches with a tiller or shovel.
Transplant the Japanese magnolia seedlings into the selected outdoor site's prepared soil when they're about 12 inches tall. Dig a hole for each seedling, making the holes the same depth and width as the seedlings' container. Remove each seedling and its roots gently from the container, and place the seedling's lower portion in the plant's respective hole, adding soil to the hole's bottom as needed so the seedling sits at the same soil depth as it sat in its container. Take care not to disturb the roots or damage the plants while planting them. Tamp the soil around each plant's root ball and stem base.
Determine the amount of fertilizer to use for one of the trees by measuring in inches the diameter of its canopy, from one side's outer edge to the opposite side's outer edge. Divide that number of inches by 12, and round it to the nearest foot. Multiply that number by 3.14, and round it to the nearest foot to determine the square footage of soil surface under the canopy. Figure the amount of fertilizer to use for each tree by using the same method. Spread a slow-release, 16-4-8, slow-release fertilizer at a rate of 1 tablespoon for every 5 square feet of soil surface in an even layer under the trees' canopies. Avoid letting the fertilizer touch the base of the trees. Rake the fertilizer into the soil at a depth of 2 inches, and water the soil.
Apply a 2- to 3-inch-thick layer of wood-chip mulch on top of the soil in a 2-foot diameter around each seedling, but don't allow the mulch to touch the plants. Mulch conserves soil moisture and keeps the soil cool.
Water the seedlings regularly, keeping their soil moist at a depth of about 2 inches for the first year. Reduce watering in winter to about once each month. Water deeply about twice each month, or more often during periods of drought or hot, dry weather, in the following growing seasons. Japanese magnolias prefer moist soil, but don't overwater their soil.
Fertilize the Japanese magnolias once every year during spring when their new growth begins, using 16-4-8, slow-release fertilizer. Follow the same square footage calculation that you used during planting time to figure out how much fertilizer to apply to each tree's soil. Use the same fertilizer application method that you used at planting time, too.
Prune your Japanese magnolias only when necessary to remove dead or diseased branches, or to control the trees' height or branch width when they obstruct a pathway or other object. Prune in late summer when the trees finish flowering. Use pruning shears for branches under 1 1/2 inches in diameter and a pruning saw for larger branches. Select wayward, dead or unwanted branches, and trim them back to their base. Make each cut at a downward angle so water won't collect on the cuts. Avoid pruning more than absolutely necessary because Japanese magnolias don't heal quickly from pruning cuts.
Things You Will Need
- Paper towel
- Sealable plastic bag
- Seed-starting potting mix
- Watering device
- Refrigerator thermometer
- Plant container, 12 inches diameter and bottom drainage holes
- Standard potting mix
- Tape measure
- Room thermometer
- Soil thermometer
- Aged compost, aged manure or other organic matter
- Tiller (optional)
- 16-4-8, slow-release fertilizer
- Disposable tablespoon
- Wood-chip mulch
- Pruning shears
- Pruning saw
- Disinfect pruning tools before use by dipping them in 1 part bleach and 9 parts water in a bucket. Let them soak for five minutes. Rinse them with clean water, and then air-dry.
- Today's Homeowner with Danny Lipford: How to Grow Magnolia Trees from Seed
- University of Florida, Nassau County Extension: Japanese Magnolia
- Magnolia Society International: Getting Started with Magnolias
- University of Florida IFAS Extension: Japanese Magnolia
- Southern Living: Magnolia, Essential Southern Plant
- North Carolina State University: Fertilizer Conversions
- City of Santa Monica, California: Calculating the Square Footage of Your Landscape Area
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