Growing Atlantic White Cedars for Wetland Restoration Sites
Designing Atlantic white cedar planting trials at Marstons Mills
Living Observatory is developing an Atlantic white cedar (AWC) planting study at the Marstons Mills Comprehensive Study Area with Barnstable Clean Water Coalition and the restoration team. We will plant three hundred young AWC trees (4 - 7 ft tall) monitor them for vigor, mortality, growth. The trees will be placed at six upland "islands" or outcroppings within cell A, B, and the upper portion of cell C.
In addition to tree plantings, there is a sphagnum transplanting effort and we are considering a study of AWC seed germinated on location. The AWC planting, sphagnum transplanting, seed germination pilots area presented here together. In future posts plans and results of each trial will be presented separately.
See supporting files AWC_plant_layout draft (last image below) and AWC_plant_count. Supporting photos at end of post. This post was initially drafted after a site visit on 10/7, and has been revised to reflect key developments. Notes appear in blue quote blocks throughout.
Revised on: 10/15/26 by Adrian Wiegman [AW]; 10/17 by Glorianna Davenport; 10/22 [AW]
A call was held on Monday 10/19 planting plans, on Tuesday 10/20 Duke Bitsko visited the LO AWC nursery, and on 10/21 Adrian attended the construction meeting and Duke and Adrian did a site walk.
10/22 [AW]: the lower portion of cell C will be inundated periodically cranberry operations downstream, so it is not suitable for cedar plantings.
- Mound areas in the upper cells will be built with a loamy engineered soil generated by mixing excavated growing surface and underlying peat.
- The construction team is collecting Sphagnum moss from ditches and preserving these plants in kiddy pools. This sphagnum will be placed near around AWC plantings, and/or to will be tested as a germination medium AWC recruitment.
- Areas treated with microtopography (scoop and dump, pit and mound) will also be available in the flood plain portion of each cell for control planting.
We are using this opportunity to investigate how strategic preservation and re-use of site material can enhance growth / survival / recruitment of AWC. Specifically we plan to compare growth/survival of AWC planted on intentionally mixed and graded soils with those planted on microtopography with no amendments. We also plan to evaluate whether AWC seed that has been stratified will germinate and survive when introduced to areas of redistributed preserved Sphagnum moss. We will use a split plot block design to incorporate site environmental variability into the design.
Tree planting
- How much suitable planting area is available (e.g. design between 6" and 18" above design water table.), and what tree density fits it?
10/22 [AW]: approximately 6' spacing, corresponding to 1 tree per 36 sqft or ~1200 trees per acre, with 300 trees our planting will cover a 1/4 acre.
- Will microtopography be co-occuring adjacent to each graded mound (islands).
10/22 [AW]: Yes, microtopography can be placed near the islands. Micro-topography will be present in the floodplain area of each cell.
- What planting amendments should be used and how should they be combined/tested?
10/22 [AW]: The amendments to consider are mycorrhizae dip, fertilizer (7:7:7), top dressing of leaf mulch, and possibly biochar. The question is whether to compare the amendments as a separate treatments or to apply some or all as part of a treatment package. The latter is simpler to coordinate, and may result in a larger effect size. If there is an effect we can follow up with future plantings to discern which amendments are most important, and which do not enhance survival/growth. Hypotheses: The amendment package will have a larger effect / variance, in the micro-topography trees, and those trees planted adverse environmental conditions (extreme sun, wind, wet or dry), since the amendments help buffer moisture variation and help trees to obtain nutrients. Furthermore I would expect a larger response in younger trees (although we will not be planting young trees this year).
Sphagnum
- How much live Sphagnum can we allocate to the pilot?
10/22 Answer: There will be approximately 10 kiddy pools of sphagnum available for transplant.
- What moss coverage, and number of monitoring quadrats are practical?
- Within what size quadrat should we monitor for sphagnum, the standard 3m by 3m or smaller?
Seed sprouting
- How much viable seed can we dedicate to pilot, what area should seed be spread into?
- How often can we revisit the quadrats, and what recruitment and survival would make seed spreading worth expanding?
Education
- How can we incorporate citizen science / outdoor classroom monitoring into these trials?
For this planting we will place trees approximately ~6"- 18" inches above the estimated design water table elevation to avoid inundation and to account for settling. Previous monitoring at Tidmarsh by C. Hatch suggests that AWC can survive and grow, and recruit new trees when the water table is within 10cm (4") of the ground surface. For spacing, we will use the contractors design spec, of trees haphazardly planted, spaced roughly 6 feet apart on average. We will place trees in designated graded mounds (treatment) as well as in adjacent microtopography areas (control), and compare growth.
Treatments
- Surface preparation:
- micro-topography (control)
- graded mix (treatment)
- Planting amendments:
- bare surface (control),
- amended (one or both of inocculation with mycorrhizae dip + organic top dressing)
10/22 AW: The mico dip could be applied to both bare surface and organic top dressing
Replication
We will examine between 4 and 6 blocks that compare surface preparation and planting amendments.
10/22 [AW]: The exact planting locations and numbers will be finalized once construction is finished and the trees will be planted in spring 2027.
All trees:
- Each tree will be fitted with a rodent collar, a support stake, and a numbered aluminum tag.
- Before planting each tree will be unpacked from its pot, roots will be separated /cut to enable spreading.
- Holes will be dug/augared 12 - 18" in width and depth, roots will be spread out and the hole will be back filled.
- Each tree will be measured for height, diameter, vigor, soil moisture, and the specific treatment area will be recorded in a data sheet.
Amended plantings:
10/22 [AW]: Exact units and specs to be determined.
Half of the trees will have roots dipped in a mycorrhizae culture [insert specification for myco-dip]. Myco-dipped trees will receive a colored flagging and then be distributed to planting zones. Myco-dipped trees should be clustered together in separate plots. In case the inoculation of one tree has an effect on nearby trees.
After planting half of the trees will receive an organic top dressing of a premixed combination of leaf mold, organic fertilizer, and biochar.
Organic top dressing recipe:
- X [units] of organic fertilizer ([N:P:K, brand/source])
- X [units] of leaf mulch ([brand / source])
- X [units] of biochar ([brand source])
The main question for this trial is whether sphagnum can serve as a nurse medium to support the germination and recruitment of AWC plantings at a restored site.
10/22 [AW]: The seed spreading test I think would be best if replicated at multiple sites. We could pick existing veg plots with sphagnum cover, and those without]. Those near mother tree or without. Then we could establish new plots with and without transplanted Spagnum (perhaps at both century and at Marston mills).
Four Quadrats between 1 and 3 square-meter depending on available Sphagnum will be set out randomly. At each selected location, we could compare four combinations: seed with Sphagnum, seed without added Sphagnum, Sphagnum without added seed, and neither addition. The unseeded quadrats would help distinguish the response to spreading seed from background recruitment. Quadrats could be placed both within an AWC planting area and outside of AWC.
Further details will be determined in conversations with the design team. The key limitations are time, logistics, availability of sphagnum, and seed.
At each quadrat, we would count newly emerged seedlings and follow their survival, alongside observations of Sphagnum cover, competing vegetation, moisture, flooding and light. Repeat photographs would help document changes. The pilot’s purpose is to assess whether seed spreading produces additional seedlings that persist, and whether the results justify a larger trial.
Example treatments (A. Graded Loam - sand and peat mix, B. Microtopography).
Image of BCWC staff, borrow pit, spoil, with loamy mixture excavated from bed.
Plan view (areal) of example graded loam and microtopography surface treatments with sphagnum and AWC transplant.
Example level surface treatments for seed trial with/ without sphagnum.
Example microtopography with 12 - 24" amplitude pit and mound.
Example mark out of an AWC tree island with pin flags between 45 and 46.5 ft (Credit Becca McCue). This area contains the graded loamy mix of sand and peat (Note this doesn't contain actual loam surface cover, but the surface texture would likely be similar).
Cedars will be planted above the anticipated water line at 45'. (Credit Becca McCue)
October 9, 2026
