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Acer (macrophyllum)

Rae Watson
Forestry Technician
USDA FS - J Herbert Stone Nursery
2606 Old Stage Rd.
Central Point, Oregon 97537
541.858.6110 (fax)

Family Scientific Name: Aceraceae
Family Common Name: Maples
Scientific Name: Acer macrophyllum
Common Name: bigleaf maple
Species Code: ACMA3
Propagation Goal: plants
Propagation Method: seed
ProductType: Container (plug)
Stock Type: 1,2,3,4 gallon containers
Time To Grow: 1 Years
Target Specifications: Seedlings have reached target when roots have fully occupied the container but not to the amount where seedlings are root-bound.
Propagule Collection: Seedlings are started from fresh seed collected in the fall. The seed is brought to the nursery in plastic bags to avoid having the seed dry out. It is put in cold storage conditions until stratification.
Pre-Planting Treatments: Seed is placed in open trays and stored in stratification rooms for 2 to 3 months prior to the anticipated sowing date. The rooms are set at 33oF and equipped with foggers to maintain a very high humidity (surface moisture can be seen on the seed coat). If the seed is dry it is placed into cold running water for 48 hours prior to stratification, otherwise seed is not soaked.
Growing Area Preparation/
Annual Practices for Perennial Crops:
Containers used are TreepotsTM distributed through Stuewe & Sons, Inc. Sizes used are 1, 2, 3, 4 gallon capacity. Media is Grower's Gold Mix #1 (from SunGro Horticulture), which is composed of 40% composted pine/fir bark (fine 3/8" minus), 35% Canadian sphagnum peat moss (growers grade) and 25% screened volcanic pumice (3/8"minus). The media is pre-moistened and contains a starter fertilizer (6-10-6 with fritted trace elements). Containers are filled with media prior to planting and lightly tamped to reduce large pores spaces, then filled to 1" below the top of the container.

The containers are used more than once but pressure washed at 160 oF to remove media and clean containers between crops.

Most seedlings are grown outside without shade on drivable-gravel surfaced pads. The surface is graded and sloped to allow rain or irrigation water to not puddle.

Climate at the nursery is hot and dry in the summer with average maximum temperatures in July and August of 87.5oF. Spring temperatures are moderate with frost in the upper 20's uncommon. Fall temperatures are warm with average maximum highs in October of 67oF and maximum lows of 37.5oF. Frosts in the low 20's is uncommon in October.
Establishment Phase: Seed trays in the stratification rooms are regularly monitored for germination. When seeds begin to show a radical, they are removed from stratification and planted into large containers. One seed is planted in each container by placing the seed into the media and the directing the wing vertical position. This operation occurs from late winter through mid spring.

Containers are placed on transportable steel racks (6.5' by 3.5'). The racks include a hardware cloth for the bottom of the container to rest on and a wire mesh top with 4" by 4" openings to support the one-gallon containers. 8" by 8" openings are used for three and four-gallon containers. Eight-gallon containers are free standing and do not require support. Nearly all containers are placed so that there is a space or opening between every container. The lower density gives seedlings more light and space for growth.

Several weeks after seedlings have been transplanted, a isobutylidene diurea top dressing is applied to each container. Wil-Gro (Wilbur-Ellis), a 18-6-12 with Mg, S and Fe elements, is applied as follows: 1/16 cup for 1-gallon containers, 1/8 cup for 2, 3 and 4-gallon containers. Seedlings are only fertilized one time per year. If a seedling is held over for a second year, controlled-release fertilizer is again applied as a topdress in the spring.

During the establishment phase, seedlings are irrigated 1 to 2 times per week. Watering is accomplished through overhead fixed irrigation system. Sprinkler head nozzles are a Rainbird BR5 and are placed on 5 to 7 foot-high risers to accommodate tall seedlings. Risers are on a square grid pattern with a 20' by 30' spacing.
Length of Establishment Phase: one month
Active Growth Phase: Seedlings are irrigated in the early morning when the wind is at a minimum. Irrigation scheduling is based on the moisture content of the plug. Generally, the plug is not allowed to dry down much below field capacity. With maximum summer temperatures in the high 80's, seedlings are irrigated every 2 to 3 days for up to 4.5 hours an irrigation. Seedlings are not cooled in the afternoon with overhead irrigation.

Seedlings are monitored for pests but generally insects and diseases do not occur in this species and stocktype. Seedlings must be hand-weeded every 6 weeks.
Length of Active Growth Phase: 3 month
Hardening Phase: Hardening begins in the late summer with a reduction in the frequency of irrigations. Generally seedlings are hardy to any nighttime low temperatures that are encountered in the fall and winter months. For winter freezes where temperatures reach into the low teens, seedlings are either brought into unheated greenhouses or tree storage facilities until the event has passed. Roots will circle and amass at the bottom of the containers due to the container design. Per client request, the bottom inch of the root plug will be pruned during the hardening phase. This is accomplished by pulling the plug from the container and cutting off the end of the plug with an industrial-strength paper cutter. Clients with containers that will remain for two years will often chop the bottom inch of the container off using a chop saw with an abrasive blade. This leaves the bottom of the container completely open, which prevents spiraling the second year but makes the container unusable after extraction.
Length of Hardening Phase: 3 months
Harvesting, Storage and Shipping: Seedlings are not extracted from their container or stored prior to shipping. Containers are stood up in cardboard are transported in enclosed refrigerated and non-refrigerated trucks. Many orders are simply shipped on the transportable steel racks. Empty containers are returned in the summer after the seedlings have been planted.
Length of Storage: NA
References: Forest Nursery Notes Winter 2003


Steinfeld, David. 2003. Propagation protocol for production of Container (plug) Acer macrophyllum plants 1,2,3,4 gallon containers; USDA FS - J Herbert Stone Nursery Central Point, Oregon. In: Native Plant Network. URL: http://NativePlantNetwork.org (accessed 2021/05/08). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources.

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