Washington Association of Conservation Districts
Plant Materials Center
360-757-1094 * 16564 Bradley Road, Bow, WA  98232

EMAIL - pmcsales@gmx.com

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Ground Preparation
One of the first field activities in the spring is spreading chicken manure to the fields that were in production the previous year.  Chicken manure works as a natural fertilizer providing the soil with nutrients.
After the chicken manure is cultivated into the soil, Barley is sown as the cover crop helping with soil erosion and weed suppression.  Once mowed the barley gets tilled into the ground, which provides additional nutrients and organic matter. 


When the ground is converted from cover crop into our planting rotation, that field will get sub-soiled, disked, cultivated and then culti-mulched before planting.
Seeds for growing our plants are acquired from all different sources and we are able to provide our customers with source identified seed.  Western Washington shrubs and hardwoods are tracked by county.  Conifers are tracked according to the seed zone maps and elevation.  We also offer British Columbia, Eastern Washington, Idaho and Oregon seed sources depending on the species.

Once the berries are ripe and collected, they are lightly broken up in the blender. The blender is placed on a low setting making sure not to blend too vigorously so the seed coats are not damaged.  The seeds sink and the pulp is decanted, allowing the seeds at the bottom to be collected.

Air suction is used to complete the final cleaning for some seeds.   The chaff is separated from the seeds by a simple labyrinth of PVC pipes, complete with flow adjusters and a hopper that are attached to a small vacuum. The simple method of using duct tape to adjust the air flow on the PVC pipe will make sure the air suction is only removing the unwanted particles leaving the seed to fall into a bucket.  The seeds of a few species such as Paper Birch are lighter than some of the chaff, so the vacuum picks up the seeds and the chaff drops in to the bucket.

Some seeds need tumbling in order to be extracted. These species are placed in closed sacks and place in the dryer with multiple tennis balls. The light rotation of the seed with tennis balls separates the seed allowing the seed to be screened and ready for stratification.

Most tree and shrub seed are dormant when first collected. To break seed dormancy the seeds need a period of cold moist conditions. Native tree and shrub seeds sown in the fall will naturally receive this conditioning period through the winter and spring. 


Conifer seed sown in the spring needs artificial stratification. These seeds are mixed in with Perlite, which is inert, heat treated pumice that retains moisture. The mixture is placed in the cooler for 30, 60 or 90 days depending on the species.


A few species are more difficult germinate and need extended cold periods to break dormancy.  Some of these species are soaked in gibberellic acid, which is a plant hormone that reduces the amount of cold treatment needed.

Seed Sowing

The Love Oyjord seed drill is a great machine for sowing seed. Each seed lot is weighed and the machine is calibrated to disperse the seed so that the proper seedbed density is achieved.  It sows the seed to the correct depth in 8 rows.


The tree and shrub seedlings that receive the natural method of cold moist stratification are sown directly into the field in the fall. The seed beds are top dressed with a layer of clean Red Alder (Alnus rubra) shavings to protect the seed.

Spring seed sowing takes place in May when the ground temperatures are warm enough. Species that were artificially stratified and species that require light to germinate are sown in the spring. Flash tape is tied to the irrigation risers to discourage birds from eating the freshly sown seeds.

Plugs for transplanting are propagated in a greenhouse and are received at the PMC in mid March. Once the ground is tilled to perfection and the weather cooperates we can begin transplanting plugs for the following season's plug1 stock.


A seasonal crew of 9 is hired – seven are inside the transplanter and two walk behind for quality control.  Each year the amount of transplants we grow increases with demand. Species we offer as a P-1 include: Alaska Yellow Cedar, Douglas Fir, Noble Fir, Sitka Spruce, Western Hemlock, Western Larch, Western Red Cedar, and Western White Pine.  Ask us about contract growing options!


The PMC’s sixty acres is equipped with three wells that are all a part of irrigation system.  Most of the soil on the farm is a nice well drained sandy loam which is helpful during the rainy months. Irrigation is necessary during the summer when we can get warmer temperatures and periods without a great amount of precipitation.


Root wrenching is implemented during the growing months when the soil can become compacted, impeding root development. To reduce soil compaction a horizontal oscillating metal bar is pulled just under the root zone. This method of lightly lifting the seed bed to aerate the soil gives the roots more space to easily develop.


The same piece of equipment that is used for root wrenching is used for root pruning. The metal bar is replaced with a sharp thin blade.  The blade is pulled, oscillating horizontally at a set depth depending on the species root depth at the time of pruning. The sharp edge of the blade slices off the very bottom tip of the root, which causes the root to become more branched and fibrous, creating a new location for additional lateral feeder roots to develop.