Gadenin日本語Get the appStake at knee height, not when it leans
Every tall single-stem sunflower needs a stake, and the mistake almost everyone makes is waiting until the plant is already leaning. By then the root plate on the windward side has torn, and no amount of tying puts that back. Drive the stake when the plant is around knee high, roughly 18 to 24 inches (45 to 60 cm), while the root ball is still small enough that the stake goes in beside it without cutting roots.
Use a stake that reaches the height you expect the plant to finish at, less about a foot. For a type that will run to eight feet (2.4 m), that means a seven foot (2.1 m) stake driven at least 18 inches (45 cm) into firm ground. A short stake is worse than none, because the plant snaps at the top of it in the first gale.
| Finished height | Stake length | Depth to drive | Ties |
|---|---|---|---|
| Under 4 ft (1.2 m) | Usually none needed | Not applicable | None |
| 4 to 6 ft (1.2 to 1.8 m) | 6 ft (1.8 m) cane | 12 in (30 cm) | Two |
| 6 to 9 ft (1.8 to 2.7 m) | 8 ft (2.4 m) stake | 18 in (45 cm) | Three |
| Over 9 ft (2.7 m) | 10 ft (3 m) post | 24 in (60 cm) | Four, plus a guy line |
Drive the stake on the side the prevailing wind comes from. The plant is then pushed against the stake rather than pulled away from it, and the ties take far less strain.
How to tie without strangling the stem
A sunflower stem thickens fast, sometimes doubling in girth in a fortnight during peak growth. A tie that was comfortable in early summer can cut a groove into the stem by the time the head is filling, and that groove is exactly where it snaps.
Tie in a figure of eight, with the crossover between stem and stake, using soft twine or strips of old cloth. Leave a finger's width of slack. Then go back every two weeks and check the lower ties, loosening anything that has gone tight.
- First tie at 18 in (45 cm) Put the lowest tie on as soon as the stake goes in. This one does most of the work in early summer and is the one most likely to bite in later.
- Add a tie every 18 in (45 cm) of new growth Work up the stem as the plant grows. Long unsupported spans between ties bow in wind and the bow becomes permanent.
- Figure of eight, never a loop Cross the twine between stem and stake so the two are cushioned apart. A plain loop pulls the stem hard against the stake and rubs the skin off it.
- Final tie just under the head Once the bud is visible, tie four to six inches (10 to 15 cm) below it. That last tie carries the weight of a head that may reach two pounds (900 g) when the seed fills.
- Check ties fortnightly Run a finger under each tie. If it will not slide, cut it and retie. Five minutes here saves a plant that took four months to grow.
Water deep and infrequently
Sunflowers root deeply and a well grown plant will draw water from three feet (90 cm) down. Frequent light watering keeps the roots shallow and gives you a plant that wilts every hot afternoon and blows over in the first storm. Soak the ground thoroughly once or twice a week instead, applying enough to wet the soil eight inches (20 cm) down, and let the surface dry between waterings.
The one period when you must not let them go short is from the bud showing color through to the petals dropping. Water stress during that fortnight gives you a smaller head and hollow, unfilled seed at the center. After the petals drop the plant needs much less, and a drier finish actually helps the seed dry on the head.
| Stage | How often | How much | What goes wrong |
|---|---|---|---|
| Seedling to knee high | Twice a week | Enough to wet 6 in (15 cm) down | Wilting checks growth for good |
| Rapid growth | Once or twice a week | Deep soak | Shallow watering means shallow roots |
| Bud to petal drop | Twice a week without fail | Deep soak | Unfilled center in the head |
| After petal drop | Only in real drought | Light | Wet weather rots the back of the head |
A sunflower wilting at midday and recovering by evening in high summer is normal, not thirsty. Judge by pushing a finger four inches (10 cm) into the soil in the morning.
Feed lightly, and stop nitrogen once the bud shows
Sunflowers are not hungry plants and too much nitrogen is actively harmful. It gives you a soft, thick stem full of water that bends under the head, huge leaves, and a flower that arrives late. Work a moderate amount of compost in before sowing and that is most of the job done.
If you feed at all, switch to something lower in nitrogen and higher in potassium once the flower bud is visible. That builds a firmer stem and better filled seed. Stop feeding entirely once the petals open, because from then on the plant is only moving stored resources into the seed.
| Stage | Feed | Why |
|---|---|---|
| Before sowing | Compost dug in, modest amount | Slow, even supply and better moisture holding |
| Seedling to knee high | Nothing | Roots go deeper looking for their own |
| Knee high to bud | One balanced feed if growth is poor | Only if leaves are genuinely pale |
| Bud showing | Low nitrogen, higher potassium | Firmer stem, better filled seed |
| Petals open | Stop | Feeding now does nothing useful |
Side shoots, leaning heads and other things not to worry about
A single-stem type occasionally throws a side shoot low down. Rub it out while it is small if you want the biggest possible head, because the plant divides its resources otherwise. On a branching multi-headed type, leave every shoot alone: those side buds are the whole point of that kind of plant.
Young sunflowers track the sun through the day and swing back overnight, which is normal and stops once the flower opens. From then on an open head faces one direction, usually east, and stays there. A head that hangs steadily forward on a bent neck after the petals drop is not failing either; that is the seed weight doing exactly what it should, and it keeps rain off the seed.
- Remove low side shoots on single-stem types Pinch them out at an inch (2.5 cm) long. Left on, they take resources and produce two mediocre heads instead of one good one.
- Leave all shoots on branching types The side buds open in sequence over several weeks and give you a much longer flowering season. Cutting them off wastes the plant's main advantage.
- Strip yellowing lower leaves Once the bottom leaves yellow they contribute nothing and hold damp against the stem. Snap them off cleanly and get them off the bed.
- Do not straighten a bent neck The neck bends under seed weight by design. Trying to prop the head upright cracks the stem just below it and you lose the whole head.
Record the date you staked, the date the bud first showed color and the finished height of each plant. Those three numbers tell you next spring exactly how long a stake to buy and how early to drive it.