Gadenin日本語Get the appWhy seed set costs you next year's flowers
A truss of mountain laurel that is allowed to run on after the petals brown does not simply sit there looking untidy. Each faded flower swells into a small round capsule, and filling those capsules with seed is one of the most expensive things the shrub does all season. The energy comes out of the same pool that would otherwise go into extending shoots and, at the tip of each of those shoots, initiating the flower buds for the following spring.
The result is the alternating pattern that so many neglected plants fall into: one heavy year, then a thin one, then a heavy one again. A plant that is deadheaded promptly every season does not swing like that. It puts the same effort into growth and bud set each year and flowers evenly, and the difference between a deadheaded and an undeadheaded shrub of the same age standing side by side is obvious enough that it is worth the half hour it takes.
This matters more here than on most flowering shrubs because mountain laurel is so slow. Annual extension on an established plant is often only two to six inches (5 to 15 cm), so there is very little spare capacity. Whatever the seed capsules take is genuinely taken, and the plant has no reserve of vigor to make it up with.
Deadheading is not tidying and it is not pruning. You are removing spent flowers before they become fruit, and you are doing it in a window that closes as soon as the capsules begin to firm up. Left a month, the job is largely pointless for that year.
Use your fingers, not pruners
Directly beneath every flower truss sit the buds that will make this season's new shoots, and they are close, small and easy to cut off by accident. A pair of pruners held at arm's length in a dense shrub will take those buds along with the truss more often than not, and the shoot that would have carried next spring's flower is gone. Fingers are more accurate and considerably faster.
The stalk of a spent truss snaps cleanly at its base with a sideways push of finger and thumb while the tissue is still soft, which is roughly the fortnight after the last petals brown. Work upward and outward with a slight twist rather than pulling straight out, because pulling can tear a strip of bark down the shoot behind it. If a truss resists, you have left it too late and it needs a snip with fine scissors just above the topmost pair of new buds instead.
The trusses are sticky, and after twenty minutes your hands will be coated with a gum that also holds pollen and plant sap. Wear gloves. Every part of this plant is seriously poisonous, and while handling it is not the same as eating it, there is no reason to be casual about sap on your hands and then eating lunch.
Do not go on to shorten shoots while you are there. Mountain laurel dislikes hard pruning and recovers from it very slowly, and the new growth you are looking at is the flowering wood for next spring.
- Start as the last petals brown Do not wait for the whole shrub to finish. Work over it in two or three passes as different trusses go over, beginning with the earliest, so nothing sits long enough to set fruit.
- Find the join at the base of the truss Follow the flower stalk down to the point where it meets the shoot. Two or more small new buds or short soft shoots sit just below that join. Those are what you are protecting.
- Snap sideways with finger and thumb Push the truss to one side with a slight twist. Soft tissue breaks at the natural joint. Never pull straight up and away, which tears bark down the stem.
- Leave every new shoot intact Anything green, soft and growing stays. If you find yourself removing green growth, you are working too far down the stem.
- Take off any capsules you missed last year Old brown capsules from previous seasons cost nothing now but remove them anyway, so that next spring you can see at a glance whether you kept up.
- Wash your hands and the gloves The residue is sticky and the plant is toxic in every part. Clean up before handling food, and keep the prunings away from anywhere livestock or pets can reach them.
What the plant does over the rest of the summer
Once the trusses are off, the shrub pushes its new shoots from the buds you protected. Those shoots extend for a few weeks, harden through midsummer, and then set the flower buds for the following spring at their tips. From that point the display for next year is fixed, and nothing you do afterwards will add to it, though plenty can subtract.
The practical consequence is that summer water is not optional. The buds are being filled at the hottest, driest time of the year, on a root system that is fine, fibrous and shallow, and a fortnight of drought during bud set shows up as a thin spring rather than as any immediate symptom. Keep the mulch at three inches (8 cm) and soak deeply whenever the top two inches (5 cm) of soil are dry.
Stop feeding after the deadheading is done. A late dose of nitrogen produces soft growth that is still extending when it should be hardening, and soft shoot tips both fail to set good buds and take frost damage in autumn.
Resist any urge to shape the shrub through the summer. From midsummer onward every cut takes flowers with it, and on a plant that grows this slowly the shape you cut into it in midsummer is still visible three years later.
| Stage after flowering | What the shrub is doing | Your job | Do not do |
|---|---|---|---|
| Petals just browning | Capsules starting to swell | Deadhead by hand, truss by truss | Cut with pruners into the buds below |
| Two to four weeks after | New shoots pushing from below the old trusses | Water, keep mulch topped up | Shorten or shape the new growth |
| Midsummer | Shoots hardening, buds being initiated | Deep soaks in dry spells | Feed, prune, or cultivate the root zone |
| Late summer | Buds filling at the shoot tips | Keep watering, watch leaf undersides | Anything that removes shoot tips |
| Autumn | Buds dormant and fully formed | Tidy fallen leaves, note the year's notes | A tidy-up trim, which removes the flowers |
When deadheading is not worth it, and what to record
On a large old shrub where most of the flowers are well above head height, deadhead what you can comfortably reach and leave the rest. Ladder work in a brittle-branched plant is not a sensible trade for a marginal gain, and the lower two thirds is where you look at the flowers anyway. On very young plants the reverse is true: the first few trusses a small plant produces are the most expensive it will ever set, so take every one of them off promptly.
If you actively want seed, choose one truss on one branch, mark it with a loop of string, and deadhead everything else. That gives you capsules to collect in autumn without letting the whole shrub pay for them.
Write down the date the last flowers browned and the date you finished deadheading, because the gap between those two numbers is the honest measure of whether you got to the job in time. Add a line each spring on how heavy the flowering was, scored simply as light, moderate or heavy. Three years of those two entries will show you the alternating pattern breaking down as the deadheading becomes routine, and that is the clearest evidence you will get that the work is doing something.
Note the position of any branch that flowers noticeably less than the rest of the plant. On mountain laurel that is usually shade from something that has grown up beside it over several years, and it is easy to miss when you only ever look at the shrub from the front.