Yes, it will aggressively take over once established—that is one of its defining traits—but full, reliable coverage across 19 acres still benefits from solid initial planting rather than minimal seeding.

How aggressively it spreads

Crownvetch spreads both by seed and (more importantly) by underground rhizomes that can extend up to ~10 feet. A single plant can expand to cover 70–100 square feet within about four years. It readily moves outward from planted areas into open, sunny ground and can form dense monocultures that suppress other vegetation.

You do not necessarily need to seed every square foot at the full rate if your goal is eventual takeover. Strip or patch planting (for example, drilling or broadcasting in bands or blocks across the site) can allow natural vegetative expansion to fill gaps over several years. However:

• Establishment is slow the first 1–2 years (often little top growth while roots develop).
• Full dense cover commonly takes 2–4 years even with good seeding.
• Partial seeding delays full coverage and leaves more opportunity for weeds or erosion in the meantime.
• For 19 acres where you specifically want it to dominate, a moderate-to-full rate across most of the area is the more reliable path.

Seeding rates and methods

Typical pure-stand rates are 10–20 lbs per acre (some guides list 5–15 lbs or up to 15–20 lbs PLS). Lower rates work when combined with good seedbed preparation and a nurse crop; higher rates speed canopy closure.

• Nurse crop: Annual ryegrass (often 20–30 lbs/acre) is commonly mixed in. It provides quick cover and erosion protection while the slower crownvetch establishes, then declines.
• Inoculation: Use the correct Rhizobium inoculant for crownvetch (or a general legume inoculant specified for it). This is important for nitrogen fixation and establishment.
• Timing: Spring (roughly March–May in Kansas) is often preferred; late summer/early fall also works if there is enough moisture and time before hard freezes.
• Depth and method: Shallow—¼ to ½ inch. Drill or broadcast onto a firm, prepared seedbed and lightly cover/pack. It tolerates a range of soils but prefers well-drained sites and open sun; it does poorly in heavy shade or prolonged wet conditions.
• Expect slow start: Visible cover is often limited the first season; the plant invests heavily in roots and rhizomes first.

For 19 acres at 12–15 lbs/acre you would need roughly 230–285 lbs of seed (plus nurse crop). Get current bulk pricing—seed is not cheap.

Best places to buy bulk seed

Commercial suppliers that regularly handle crownvetch (often the Penngift, Emerald, or Chemung varieties) include:

• Ernst Conservation Seeds (Meadville, PA) — well-known for larger quantities and mixes; Penngift is a common offering.
• Stock Seed Farms, Great Basin Seeds, Seed Barn, American Seed Co., and similar farm-seed houses.
• Regional options: Check Hancock Seed, DeLange Seed (Girard, KS area—has listed crownvetch), Feyh Farm Co., or other Kansas/Midwest farm-seed dealers and co-ops. Local agricultural suppliers or NRCS-affiliated sources can sometimes arrange bulk or help with inoculant.

Call for current bulk quotes, availability, shipping restrictions, and pure-live-seed (PLS) percentages. Some sellers restrict shipment into certain states (e.g., Minnesota, Wisconsin, Indiana, Missouri in some cases) because of invasive-species rules; Kansas does not appear on the common restriction lists for the sellers checked, but confirm when ordering. Ask specifically about inoculated seed or separate inoculant.

Practical recommendations for your 19-acre site

1. Soil test and correct major deficiencies (lime/P/K as needed; avoid high nitrogen that favors weeds).
2. Prepare a reasonably clean, firm seedbed if possible.
3. Use a nurse crop + inoculant.
4. Plant enough seed for good initial density if you want relatively quick dominance; otherwise accept a multi-year fill-in process.
5. Monitor and control competing weeds the first couple of seasons if needed.

Because crownvetch is non-native and can become invasive in prairies, pastures, and natural areas across the Midwest (including neighboring states), confirm any local or county rules and consider whether the long-term “takeover” outcome is acceptable for the site and surrounding land. Once well established it is difficult and expensive to remove.

For the most current bulk pricing, shipping to the Topeka area, and site-specific advice, contact one or two of the larger suppliers plus your local K-State Research and Extension office or NRCS. They can also advise on any regional restrictions or better alternatives if the invasiveness becomes a concern later.