Gadenin日本語Get the appPinch at four pairs of leaves and multiply the stems
Left alone, a dahlia grows as a single dominant stem that flowers at the top and branches reluctantly below. The tip produces a hormone that suppresses the side shoots waiting in every leaf joint. Take the tip out and that suppression ends, and the pairs of shoots below all move at once.
The moment to do it is when the plant has made three or four pairs of leaves, usually at 12 to 16 in (30 to 40 cm) tall. Snap or cut the soft growing tip out just above the fourth pair, taking about 3 in (8 cm) of stem. Within a fortnight the top two or three pairs of leaf joints each push a shoot, and instead of one stem you have six or eight, each of which will flower.
The cost is two to three weeks of delay to the first flower. The gain is several times as many flowers, on a plant that is bushier, lower centered and far less likely to be flattened by wind. Over a season it is not close. Pinch every plant except the ones you deliberately want tall and early, and pinch bedding types as well, which respond just as strongly at a smaller size.
- Wait for four pairs of leaves Count pairs, not single leaves. Dahlia leaves come opposite each other on the stem. Pinching earlier than three pairs gives a weak plant with too little leaf to drive the new shoots.
- Take the tip out just above the fourth pair Pinch with finger and thumb while the tip is soft, or use snips if it has hardened. Remove roughly 3 in (8 cm), leaving the fourth pair of leaves on the plant.
- Leave the plant alone for two weeks Do not feed heavily or cut anything else while the side shoots break. You should see shoots at the top two or three leaf joints within ten to fourteen days.
- Thin to the strongest shoots if it is crowded On a vigorous plant, remove the weakest of the new shoots at the base so five or six strong stems remain. Crowded stems give small flowers and hold damp air.
- Stake the new framework Six stems catch far more wind than one. Run string around the plant or tie the outer stems in as soon as they reach 18 in (45 cm).
If you have never pinched a dahlia, pinch half your plants and leave the other half. The difference in stem count by midsummer is obvious enough that you will not need to run the trial twice.
Disbud for one large bloom instead of three small ones
Every flowering stem on a dahlia ends in a group of three buds: one central bud with a smaller bud on a short stalk either side of it. If all three are left, they open in sequence, each of moderate size, and the two side buds crowd the central flower and shorten its stem. Remove the two side buds while they are still the size of a pea and everything the stem has goes into the one remaining flower.
The result is a noticeably larger bloom on a long, clean, straight stem with no side growth in the way. This is how exhibition sized flowers and long cutting stems are produced, and it takes about five seconds per stem. Do it as early as you can see the side buds clearly, using finger and thumb or the tip of a pair of snips, taking care not to knock the central bud.
Whether you should do it depends on what you want. For a border that reads as a mass of color, leave all three buds and get more flowers over a longer period. For cutting, or for large single blooms, disbud every stem. There is no wrong answer, but doing it inconsistently across a plant just gives you an uneven display.
| Goal | Pinch the tip | Disbud the side buds | Result |
|---|---|---|---|
| Maximum number of flowers | Yes, at four pairs | No, leave all three buds | Many medium flowers, short stems |
| Cut flowers for the house | Yes, at four pairs | Yes, on every stem | Fewer, larger blooms on long stems |
| Largest possible single blooms | Yes, then thin to 4 stems | Yes, on every stem | Show sized flowers, low total count |
| Bedding and container display | Yes, at three or four pairs | No | Dense low plant covered in flowers |
| Earliest possible flower | No | Optional | One early flower, then a lull |
Deadhead correctly or the plant stops
A dahlia flowers to set seed. Once seed is developing it slows down, and a plant carrying half a dozen fading heads will visibly reduce its output within a fortnight. Removing spent flowers is not tidying, it is what keeps the plant producing from midsummer until the frost.
The trap is that a spent dahlia head and an unopened bud look alarmingly similar, and people cut off buds all season without realizing. The difference is the shape: an unopened bud is round and domed, while a finished flower closes into a cone with a pointed tip and its stalk goes limp and bends. Squeeze it gently. A bud is firm and springy, a dead head is soft.
Do not just snip the head off. Follow the stem down to the first pair of leaves or the next set of buds and cut there, so no bare stub is left. A stub is hollow, holds rain and rots back into the plant. Cutting flowers for the house does exactly the same job as deadheading, so a dahlia that is picked hard every few days is the one that flowers longest.
Keep a note of the date each plant produced its first open flower and how long it kept going after the pinch. This tells you next spring whether to pinch earlier, later, or not at all in a short season.