How to Grow String and Pinto Beans: Harvest Green at 55 Days or Dry at 90

Most gardening guides treat string beans and pinto beans as variations of the same vegetable. Plant after last frost, water weekly, harvest when ready — that’s about as specific as most get.

But how you grow a bean depends entirely on what you’re harvesting. String beans — also called snap beans or green beans — are picked young and fresh, when the pods are still tender and the seeds haven’t yet filled out. Pinto beans are grown for the dried seed inside: you leave them on the plant until the pods rattle, then thresh the beans and store them for months.

That distinction shapes everything: how long each type takes (string beans are ready in around 55 days; pinto beans need 85–100), whether you succession-sow, when to stop watering, and how to know when you’re done for the season. This guide covers both from first sowing to final harvest.

Two Beans, Two Harvesting Strategies

String beans and pinto beans both belong to Phaseolus vulgaris, but their purpose in the kitchen divides their management in the garden. The table below shows where the differences matter most.

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For a broader look at how bush and pole varieties differ across bean types, see the complete bean growing guide.

Soil, Site, and When to Sow

Both bean types need the same starting conditions: full sun (at least eight hours), well-drained soil with a pH of 6.0–7.0, and soil that has genuinely warmed up. The minimum soil temperature for reliable germination is 60°F (15°C) — below that, seeds absorb moisture without sprouting and often rot before emerging.

This means sowing after your last frost date, not on it. Most US gardeners sow string beans from mid-May onward. Pinto beans need an extra one to two weeks of warmth, so aim for late May to early June, or when the top two inches of soil are consistently above 60°F.

For UK gardeners: Sow string beans from late May to late June when soil reaches 15°C. Pinto beans have a long maturity window (85–100 days), so in cooler northern areas choose an early cultivar and warm the soil under cloches for two weeks before sowing.

Before sowing either type, loosen the soil to about 12 inches and mix in a two-inch layer of compost. This improves drainage and water retention more than it adds fertility — beans make most of their own nitrogen from the air, so rich soil isn’t the goal here.

Sowing String Beans

Bush string beans: Sow seeds 1–1½ inches deep, 2–3 inches apart, in rows 18–24 inches wide. Once seedlings reach two inches tall, thin to 3–4 inches between plants. Bean seedlings don’t transplant well, so pull thinnings rather than moving them.

Pole string beans: Sow 4–6 inches apart in rows 24–36 inches apart, or plant four to six seeds in hills spaced three feet apart around a central support. Put your trellis or poles in before sowing — driving supports into the soil after seedlings emerge damages the roots.

Succession planting is the key to a steady string bean harvest: sow bush cultivars every two to three weeks from last frost until around August 1. Each sowing gives you roughly two to three weeks of productive picking. Reliable varieties include Provider (52 days), Bush Blue Lake (55 days), and Kentucky Wonder pole (65 days) — all well-documented through university extension programs.

For a side-by-side comparison of bush and pole growth habits, see bush beans vs pole beans.

Sowing Pinto Beans

Pinto beans are direct-sow only — they don’t transplant well. Sow seeds 1½–2½ inches deep with the hilum (the small scar, or “eye,” on the bean’s side) facing downward, spaced 3–4 inches apart in rows 28–30 inches apart.

One practical option worth knowing: untreated, non-irradiated grocery-store dried pinto beans germinate reliably and are a useful alternative when seed packets aren’t available or are too expensive for a large planting.

Because pinto beans take 85–100 days to fully dry down, the sowing date determines everything. In a Zone 6–7 garden, sow by late May for an October harvest. In Zone 8–9, you can sow as late as mid-June. No succession planting is needed — you’re working toward a single dry harvest rather than an extended picking season.

Supporting Climbing Varieties

Bush string beans and most pinto bean cultivars are self-supporting. Pole string beans need a trellis, fence, or sturdy poles at least 5–6 feet tall, installed before vines reach six inches high.

A practical alternative is the Three Sisters planting: pole beans sown around the base of corn stalks, with squash planted underneath. The beans climb the corn, fix nitrogen into the soil for the benefit of the whole planting, and the squash leaves suppress weeds. It’s a companion-planting system with centuries of documented use in Indigenous North American agriculture — and it works well in a home garden wherever you have the space.

Watering and Feeding — Why Nitrogen Backfires

This is the section where most bean-growing advice goes wrong.

Beans are legumes, which means they form partnerships with soil bacteria called Rhizobium. These bacteria colonize the roots, form small nodules, and convert atmospheric nitrogen (N₂) into ammonium (NH₄⁺) the plant can use. A healthy bean plant in adequate soil supplies most of its own nitrogen for free.

Add synthetic nitrogen fertilizer on top of that, and two things happen. The plant detects high soil nitrogen and redirects energy toward leafy, vegetative growth rather than flowers and pods. At the same time, excess nitrogen reduces the plant’s dependence on its Rhizobium partnership, slowing fixation. The result: lush, dark-green plants that produce very little fruit.

In my own zone 6 garden, the worst bean years were the ones where I added a general vegetable fertilizer at planting “just to give them a boost.” The plants looked spectacular for six weeks and produced almost nothing.

The practical rule: Don’t fertilize beans with nitrogen before or during the growing season. If you want to feed your soil, work compost in before planting. If a soil test shows a genuine deficiency, apply a balanced fertilizer (10-10-10) only after the first pods have set, at 3 tablespoons per 10-foot row.

Watering: Both bean types need about 1 inch of water per week. The critical window is flowering and early pod formation — drought during bloom causes flowers to abort and produces short, stringy pods. For pinto beans, reduce watering once the pods have swelled and the plants begin to yellow in late summer. Always water at soil level; wet foliage spreads bacterial blight.

Harvesting String Beans: The Fresh-Green Window

String beans have a narrow optimal harvest window. Pick too early and pods are thin and flavourless; wait too long and they become tough and fibrous.

The right moment: pods are 4–6 inches long, roughly the diameter of a pencil, and the seeds inside are still small — about one-quarter of their final size. The pod should break with a clean snap and feel firm, not spongy. If you can see individual seeds bulging through the pod wall, you’ve already passed the optimal window.

Pick every two to three days during peak production. Leaving mature pods on the plant signals it to stop producing new flowers — regular harvesting keeps bush types productive for two to three weeks and pole types for five to six weeks. Always harvest after the dew has dried off the foliage to reduce bacterial blight risk.

For guidance on harvesting different bean types including shell beans and dry varieties, see how to harvest beans.

Harvesting Pinto Beans: Wait for the Rattle

Pinto beans signal their readiness clearly. The pods turn from green to yellow-tan, the leaves brown and drop, and when you shake a pod you hear the dried seeds rattling inside. This typically happens 85–100 days after sowing, depending on variety and how warm the summer has been.

If the season cooperates, harvest by pulling pods by hand. If rain or an early frost is forecast before the pods are completely dry, cut the entire plant at the base and bring it indoors to finish drying on a tarp or screen for five to seven days — the pods complete their drying at room temperature.

Threshing: Once pods are fully dry and crisp, crack them open by hand over a bucket. For larger harvests, fill a pillowcase with dried plants and beat it against the ground. Winnow by pouring beans between two containers in a light breeze to blow away pod fragments.

Storage: Make sure seeds feel completely hard and dry before sealing — any residual moisture causes mold. Stored in an airtight container in a cool, dark place, properly dried pinto beans keep for one to two years.

Five Signs Something Has Gone Wrong

For a full diagnostic guide covering bean diseases, pests, and environmental problems, see common bean problems.

Key Takeaways

String beans and pinto beans reward different rhythms. String beans want your attention every few days — keep picking and they keep producing. Pinto beans want to be left alone until the plant signals it’s done: rattling pods, yellowed leaves, the whole plant winding down.

For both types, the two decisions that matter most are sowing into genuinely warm soil (above 60°F) and resisting the urge to fertilize with nitrogen. Get those right, and both crops will largely take care of themselves.

Sources

[1] Beans in the Garden — Utah State University Extension
[2] Growing Green Beans — Iowa State University Extension
[3] Growing Beans in a Home Garden — University of Maryland Extension
[4] Beans — Virginia Tech Cooperative Extension
[5] Green Beans: How to Grow It — South Dakota State University Extension
[6] How to Grow Beans — Part 2 — Michigan State University Extension
[7] How to Plant and Grow Pinto Beans — Gardener’s Path
[8] How to Grow Pinto Beans — Savvy Gardening