Sowing Lentils: Cool Soil, Shallow Seed and How Thick to Sow

A cool-season crop that wants a dry finish

Lentils germinate in genuinely cold soil, from about 40F (4C), and they do their growing while the days are still short and the weather is damp. What they will not tolerate is heat and wet at the end of their life, when the pods are drying. The entire timing of the crop follows from that: sow as early as the ground can be worked so the plant flowers, sets and dries before the hottest, most humid part of your summer arrives.

In practice that means sowing three to five weeks before your last expected frost. Young lentil plants take a light frost without harm, and a check from cold costs far less than a wet, moldy ripening period at the other end. Sowing late is the single most common reason a home lentil patch produces nothing worth threshing: the pods reach full size just as the weather turns muggy, and they mold on the plant instead of drying.

Sowing in autumn to overwinter is possible in mild-winter climates but it is not the general case, and the reward is modest. In a home bed the advantage of an autumn start is mostly a slightly bigger plant, not a meaningfully bigger yield, and the risk of losing the whole patch to a wet winter is real. Start with a very early spring sowing and only experiment with autumn once you have seen how your ground drains.

Judge the sowing moment by soil, not by the calendar. If a handful of soil crumbles rather than smearing, and the top few inches are above about 40F (4C), sow. Waiting for warmth pushes the harvest into the wrong weather.

Depth, spacing and why you sow thick

Sow the seed one inch (2.5 cm) deep, or an inch and a half (4 cm) in light sandy ground. The seed is small and its reserves are limited, so deeper sowing costs you emergence. Firm the soil over it. Lentil seed makes contact and germinates within seven to twelve days in cool ground, faster as the soil warms.

Space the seed one to two inches (2.5 to 5 cm) apart in rows six to eight inches (15 to 20 cm) apart, which is far denser than most garden legumes. That density is deliberate. A lentil plant is knee high at best, around 14 to 20 inches (35 to 50 cm), with thin wiry stems and small tendrils, and a plant standing on its own simply lies down in the first heavy rain. Sown thick, the plants tangle their tendrils into each other and the whole stand holds itself up as a mat, which keeps the pods off the soil where they would rot.

Do not enrich the ground first. Lentils fix their own nitrogen and thrive on poor, thin, well-drained soil. Manure or a nitrogen feed produces tall soft leafy growth that flops, shades its own pods, delays ripening and gives you fewer seeds, not more. If your soil is heavy or has just had compost worked in, this is a crop to put somewhere else. A neglected, stony, free-draining corner is genuinely the right place for it.

1. Pick the poorest, best-drained bed you have Full sun, thin soil, no recent manure. Ground that puddles after rain will rot the seed at sowing and mold the pods at ripening, which are the two failures that lose the whole crop.
2. Rake to a fine surface and mark shallow drills Draw drills one inch (2.5 cm) deep and six to eight inches (15 to 20 cm) apart. A short block of several close rows works far better than one long single row, because the plants support each other across the block.
3. Sow thickly along the drill Aim for a seed every one to two inches (2.5 to 5 cm). Do not thin afterwards. Crowding is what keeps this crop standing, and thinning a lentil patch actively makes it worse.
4. Cover, firm and water once Draw the soil back, press it down with the back of the rake, and water once if the ground is dry. Leave it alone until the shoots appear. Repeated watering of bare soil packs the surface and rots slow seed.
5. Net or cover against birds for two weeks Emerging lentil seedlings are small, soft and attractive to birds, and a stripped row does not recover. Row cover or netting until the plants are three inches (8 cm) tall is enough.

How much to sow, honestly

It is worth being clear about scale before you commit a bed. Each lentil pod holds one or two seeds, the plant is knee high, and a square yard (about a square meter) sown at this density gives you something in the region of a small handful to a cup of dried lentils depending on the season. That is not a store cupboard. Nobody grows lentils at home to become self-sufficient in lentils, and a claim otherwise does not survive contact with a threshing tray.

What a home patch does give you is a crop that is genuinely interesting to grow and unfamiliar to most gardeners, seed to save and sow again at no cost, and a legume that leaves the ground better than it found it. Grown as a soil improver on a poor bed, with the roots left in and the straw returned, it earns its space even if you never eat a single seed.

So sow the area you actually have to spare rather than the area you would need for a year of soup. A block of four square feet (about 0.4 square meters) is enough to learn the whole crop and to produce plenty of seed for next year's sowing. If it goes well and you want more, scale up next season with numbers you measured yourself.

What to write down at sowing

Record the sowing date and the area sown, in whatever unit you use. At harvest you will weigh what you actually got, and the ratio between the two is the only honest way to decide whether to give this crop more space next year. Memory always flatters a novelty crop.

Note the bed position as well. Lentils leave nitrogen-fixing nodules on their roots, so the following crop in that spot benefits, and like all legumes they should not come back to the same ground for three years because root rots build up. If you sowed seed you saved yourself, note which year's saving it came from, so you can tell whether your own seed is still germinating as well as it did.