Some seeds don’t want to sprout, no matter how well you prepare them. Perhaps you’ve purchased high-quality seed, made soil ready, watered carefully, and still: nothing but bare ground.
Most often it’s a question of depth. Whether your crop emerges depends not only on the laws of agriculture, but also on those of physics. A seed needs to be buried deeply enough to force its way out of soil above, but not so much that it stays parched, unable to rouse. Where does each crop fit in the spectrum? From celery (which likes light covering) to sweet corn (requiring a deep trench), here’s an illustrated guide to the range. This will kick the guesswork to the curb.
How Deep to Plant Seeds
Here’s how it works: Basic botany says tiny seeds (such as carrots or lettuce) contains little reserves of stored fuel. Best to get most of them near-surface for their shoots to grab some sun before running out of gas. Plant those too deeply and they dies in the dark.
Biggies such as corn and beans is self-sufficient; they come equipped with nutrient-rich starch to muscle up a couple inches of soil. So plant those deeper, where moisture levels will be more constant. It’s all about seed size and stored energy; it makes sense. The chart classifies each crop accordingly, so there’s no need to remember each variety.
The trick: It depends on your soil type. Too shallow in heavy clay? Not enough in sandy loam. Sandy loam drains rapidly; get it wet and it will dry out again on top soon. So maybe a little deeper than the pack says (to ensure good contact with moist soil).
Heavy clay retains water, but can become compacted. Perhaps the shoot simply could of not push its way up through a tough crust of clay. You want to go shallow in heavy soils; because it is easier for the sprout to break through. The infographic recommends going 20 percent deeper or shallower based off clay beds if you like. This will help you avoid frustration.
The trick is not to think too much: There are common pitfalls here. Some gardeners make mistake of tilling under fine seed when they broadcast it, smothering it deeper than it can ever emerge. Or else they pile on thick mulch immediately, which smothers delicate things that grow close to the surface, such as lettuce or radishes.
The key is to keep it simple. Cover the seed; firm gently so there’s good seed-soil contact, and water gently. A heavy downpour may do some washing away, or even bury them deeper. Then be patient. Don’t dig around in the bed to see how far along things are once you’ve set your depth, just let them do their thing. They’ll show themselves if time is right, and the depth is right.
Timing is a big part of success. Preparing to plant; for instance, irrigating within two hours of sowing settles the soil around the seed, eliminating air pockets that cause drying. With slow starters such as parsnips (they can emerge in up to three weeks), maintaining steady moisture is the difference between a row of greens and a field of weeds. Too easily we give up hope prematurely. And all too often there is quiet work of the root belowground.
You must read the seed and read the dirt. Respecting the seed and understanding the soil make all the difference in successful plantings. Lighter seeds hover closer to the surface; heavier seeds go down deeper. Clay requires less cover; sand requires a bit more.
Matching what’s naturaly required of each seed saves you from struggling against the dirt, and starts to work with it instead. It’s less about forcing things to grow then providing conditions under which they’ll do so on their own. Know the trench for the big seeds, the dust cover for the small, and the rest will follow. Doubt will turn to a full harvest, and your garden will thank you for that extra attention.