Gadenin日本語Get the appThe first month is slow, and the weeds know it
For three to four weeks after emergence sesame does almost nothing above ground. It is putting a taproot down, and the visible plant stays a small rosette of paired leaves that a summer weed will bury in a fortnight. This is the only period in the whole season when the crop is genuinely vulnerable to competition, and it is the period people ignore because there is so little to look at.
Keep the rows clean by hand or with a hoe run shallow, an inch (2.5 cm) at most, since the surface roots spread wider than the plant does. Once the canopy closes and the stems start extending, the crop shades its own ground and you can stop weeding entirely. From that point on the plant is competitive with almost anything.
Growth from then on is driven by heat. Sesame extends fastest with daytime temperatures between 80F and 95F (27C and 35C), and simply stalls when nights drop below 60F (15C). A cool spell in the middle of summer will pause the crop for its duration. Do not respond by watering or feeding it, which only makes matters worse in cool weather. Wait for the heat to return and it resumes as if nothing happened.
Hoe shallow and hoe often while the plants are small, and stop once the rows meet. Deep cultivation near an established sesame plant cuts the shallow feeder roots that support it through the hottest weeks and shows up as midday wilting that no amount of watering fixes.
It hates wet feet more than it minds drought
Sesame roots two to four feet (60 to 120 cm) down and is genuinely drought tolerant once established. What it will not survive is standing water. Twenty-four to forty-eight hours of saturated soil around the roots is enough to cause collapse, and in a warm summer the plant that goes yellow from the bottom up and then wilts in full leaf has almost always drowned rather than dried. This is why the crop is grown on ridges or raised beds anywhere the soil is heavy, and why a low corner of the garden is the wrong place for it.
There are two periods when water genuinely pays. The first is establishment, the three to four weeks while the taproot is still short, when the top few inches must not dry out completely. The second is from the start of flowering through the first two or three weeks of capsule filling, when a serious drought reduces both the number of capsules set and the size of the seed inside them. Between and after those two windows, water only when the plants are still wilted in the early evening rather than merely at midday.
Water deeply and infrequently rather than a little every day. A thorough soak every seven to ten days in hot dry weather draws the roots down, whereas daily sprinkling keeps them shallow and makes the plant less able to cope with the next hot spell. Water at the base, not over the top, since wet foliage overnight is what starts the leaf spots this crop is prone to.
| Stage | Water | Sign you have it wrong |
|---|---|---|
| Sowing to emergence | Keep the top inch (2.5 cm) evenly moist | A hard crust over the row, or seed that never appears |
| Seedling to 8 inches (20 cm) | Light watering when the surface dries | Yellowing from the lowest leaves upward means too much |
| Vegetative growth | Deep soak every 7 to 10 days in dry heat | Wilting still present in the evening means too little |
| Flowering and early capsule fill | Do not let it run dry, soak weekly | Flowers dropping without setting capsules |
| Capsules filling out | Reduce, water only in extreme drought | Soft green growth at the top instead of ripening |
| Lower capsules turning color | Stop entirely | Late watering delays ripening and splits capsules unevenly |
Feed lightly, or you will grow a hedge
Sesame responds to nitrogen by growing leaves and stems, and it responds enthusiastically. On a rich bed or after a heavy manuring you get a five-foot (150 cm) plant that is dark green, soft, very handsome, flowers two weeks late, sets fewer capsules than a leaner plant beside it and falls over in the first storm. It is one of the few garden crops that is reliably better on moderate ground than on rich ground.
Work in a modest dressing of compost before sowing and leave it at that on any reasonable soil. If the crop is on genuinely poor sandy ground, a single light feed at the start of flowering is useful, and it should be balanced or slightly potassium-leaning rather than nitrogen-heavy. Once the first capsules are set, stop feeding altogether. Anything applied after that point pushes new soft growth at the top of a plant that needs to be shutting down.
Phosphorus and potassium matter more than the volume of nitrogen for a seed crop, because they go into filling the seed rather than extending the stem. Tall sesame with plenty of capsules but small, light seed calls for less nitrogen and more potassium, not more of everything.
Keeping a top-heavy plant upright, and when to stop it
By late season a sesame plant is a tall, narrow, shallow-buttressed stem carrying a column of filling capsules, and it goes over in wind or heavy rain. A plant that lodges rarely straightens, its lower capsules end up on wet soil, and those are the best-filled capsules on the plant. Prevention is worth more than any rescue.
Earth soil up around the base of the stems when the plants are about knee height, which stiffens them considerably. On an exposed site, run a line of stakes down each side of the row with twine at eighteen inches (45 cm) and again at three feet (90 cm), the same way tall beans or peonies are corralled. Individual staking is unnecessary and, on a row of plants, not worth the labor.
Four to six weeks before your average first frost, pinch out the growing tip of each plant. Sesame flowers indeterminately and will keep making new flowers at the top until frost kills it, and every one of those late flowers is a capsule that will never ripen while pulling resources from capsules that could. Topping stops the plant extending and pushes everything into filling and ripening what it already carries. It is the single most useful intervention of the whole season and it takes about a minute a row.
- Earth up at knee height Draw two to three inches (5 to 8 cm) of soil against the base of each stem. It anchors a plant that has a narrow footprint relative to its final height and does more for lodging than anything you can add later.
- Corral exposed rows with stakes and twine Stakes every six feet (180 cm) down both sides, twine at knee height and again at chest height. Add the upper line before the plants need it rather than trying to lift a leaning row afterwards.
- Top the plants four to six weeks before first frost Pinch or snip out the top two inches (5 cm) including the growing point and any unopened flower buds above the highest capsules. Do it in one pass across the whole row on the same day.
- Strip the lowest leaves once the bottom capsules are full size Removing the bottom six inches (15 cm) of leaves opens the base of the row to air, dries the crop faster and lets you see the lowest capsules, which are the ones that will tell you when to harvest.
What to record through the season
Keep three dates: the day the first flower opened, the day you topped the plants, and the day the lowest capsules first showed color. The interval from first flower to first color is the number you will use every year afterwards to decide when topping should happen, and it varies far more with your own summer than with anything you can read.
Record when the plants wilted and where each row stood. If a stretch of row collapsed or yellowed from the bottom, mark that spot on a sketch of the bed. Nine times out of ten it is the low end that drains slowest, and knowing that is what stops you repeating it next season.