By Jonathan O. C. Kubesch*,**, Frank Reith*, Dillon P. Golding*,***, Jake Sanne*, Forrest Brown*,  Derek Hilfiker*, Joseph D. House****, Jenna Beville*, and Peter Arnold*,***** 

*Virginia Tech School of Plant and Environmental Sciences, Blacksburg, VA 

**Country Home Farms, Pembroke, VA 

***Hoot Owl Hollow Farm, Woodlawn, VA 

****Indiana National Guard, West Lafayette, IN 

*****Arnold Classic Farms, Chestertown, MD 

The public is familiar with red (Trifolium pratense) and white clover (Trifolium repens) growing throughout the Kentucky Commonwealth. However, North America, from Oregon to Florida, is home to a plethora of native clover species. Buffalo clover (Trifolium reflexum) is one of several clover species native to the eastern U.S.A. (Kubesch et al., 2022; Kubesch, 2020). This species demonstrates annual to short-lived perennial life histories, and has potential as a horticultural or agronomic crop (Quesenberry et al., 2003; Kubesch, 2020).  

Current efforts to increase native clover populations involve laudable efforts regarding site management, as well as conservation horticulture (e.g Littlefield, 2022). After a site is prepared for planting, plugs are produced. Conservation horticulture work currently executes the following procedure: 

1. Germinate seeds on filter paper in petri dishes (Figure 1) 

2. Transfer seedlings to cell pack trays 

3. Pot up plants into small pots (Figure 2) 

4. Plug individuals into spaced nurseries or maintain on benches for seed production 

In restoration and agronomic contexts, seeding clover has a logistic and resource advantage over plugging clovers. Seeding clover can reduce the need for intensive planting efforts, reduce soil disturbance, and ease transportation of unique plant material. Seeding approaches require a basis for setting a seeding rate and dates. Often, clovers are timed for planting between Valentines’ Day and St. Patrick’s Day in the Upper South. Introduced red and white clovers are commonly frost seeded every several years into cool-season pastures (Kubesch et al., 2020). 

Seeding clovers can also take advantage of physiological mechanisms that improve seed establishment. In the field, frost seeding involves defoliation of an existing grassland stand, broadcasting clover seed onto the stand, and letting freeze-thaw cycles incorporate the seed into the soil surface. Compared to many native and introduced grasses, clover seed coats allow the seed to survive freeze-thaw incorporation into the soil surface. Quesenberry et al (2003) reports that buffalo clover has a similar seed weight to introduced clovers. A common rate of pasture frost seeding is 4 lb/A red clover and 2 lb/A white clover (Kubesch et al., 2020). 

Optimizing rather than maximizing seeding rate is desirable given the limited seed availability of buffalo clover as well as the desire to increase planting area in restoration attempts. Managers want to get a good stand with as little seed as necessary. In addition to generating stand densities that justify direct seeding over plugging, an optimal seeding rate should generate ground cover that conserves soil as well as meets existing criteria for composition.  

The present experiment sought to determine whether a 2 lb/A or a 4lb/A seeding rate can optimize buffalo clover establishment relative to white and red clover. This objective was measured through emergence as well as cover assessments. The hypothesis of this study was that the higher seeding rate will achieve the aforementioned targets comparable to, or greater than, red clover and white clover. 

Jake Sanne*, Dillon P. Golding**, Peter Arnold*, Jenna Beville*, Derek Hilfiker*, Forrest Brown*, and Jonathan O. C. Kubesch*, ***

*Virginia Tech School of Plant and Environmental Sciences

**Hoot Owl Hollow Farm, Woodlawn, VA

***Country Home Farms, Pembroke, VA

Introduction

Buffalo clover (Trifolium reflexum), is a rare native clover present in the eastern United States. In Kentucky, this species occurs in the vicinity of Mammoth Cave, as well as further west. Conservation efforts in the eastern United States have maintained many of these native populations, though there is interest in using horticulture and agriculture to increase buffalo clover populations (Quesenberry et al., 2003; Kubesch, 2020; Kubesch et al., 2022). 

A limitation of these alternative approaches is the lack of data regarding the establishment of native clovers. For many rare plants, plugs are grown in nurseries and then planted to field sites (Littlefield, 2022). Even in the only published horticultural research, seed was grown into plugs for field plantings (Quesenberry et al., 2003). Buffalo clover has a fair degree of phenotypic variability in growth form, life history, and flower color across the geographic range. These differences in plant material might also suggest diversity in seed characteristics. 

Seed weight is an important seed characteristic for increasing buffalo clover populations. Seed weights are associated with increased establishment success (Catano et al., 2022; Westoby, 1998). Published seed weights of red (Trifolium pratense), white (Trifolium repens), and buffalo clover come from a publication using buffalo clover accessions from the Coastal Plain (Quesenberry et al., 2003). Coastal Plain accessions appear to have annual life histories whereas Ohio River Valley accessions appear to be short-lived biennials or perennials (Kubesch, unpublished observations). The present study sought to map and determine seed weights for buffalo clover. The authors hypothesized that Coastal Plain accessions would have different seed weights than the Ohio River Valley accessions.  

Materials and Methods

This study consisted of a mapping exercise, seed weight data collection, and then analysis. The mapping exercise discerned the positions of Coastal Plain and Ohio River Valley accessions using the geographic Fall Line as the demarcation between Coastal Plain and Ohio River Valley accessions. Accessions found on the corresponding side of the Fall Line were assigned to a Coastal Plain or Ohio River Valley. This mapping was conducted in ARCGIS software.

Seed weight data for a handful of accessions was accessible from the USDA GRIN system. Notably, these seed weight data overrepresented Coastal accessions rather than Ohio River Valley accessions. Additional data came from Quesenberry et al (2003) as well as manual measurements. Quesenberry et al (2003) selected accessions from TX, GA, MS, and FL. One accession in this study came from the Ohio River Valley. Seed from single plant selections of Cincinnati and Clarks River accessions were measured on a lab balance (Bonvoisin scale). 

Data Analysis

Seed weight was treated as a completely randomized design. Initial analysis at the state-level was considered to address potential accession grouping at local scales. Differences in seed weight between accessions from the Coastal Plain and Ohio River Valley were also considered to test other known differences in accessions (e.g. annual or biennial life history). All analyses were conducted in SAS v9.4 (SAS Institute, Cary, NC). PROC GLIMMIX coded for a simple  one-way ANOVA.