Lupines After Flowering: Deadheading for a Second Spike and Cutting Back

Cut the spike as soon as it fades, not later

A lupine spike opens from the bottom up, and by the time the top flowers are out the bottom ones have already dropped their petals and set small green pods. The moment the last flowers at the tip go over, the entire spike is a seed factory, and every day it stays on the plant is a day of reserves going into pods.

Cut it off then. Follow the flower stem down to where a leaf joins it, or to the base of the plant if there is nothing to cut back to, and take the whole stem cleanly. Do not just snap off the faded tip: leaving eight inches (20 cm) of developing pods below the cut defeats the point entirely, which is the mistake most people make the first time.

Two things follow from a prompt cut. The plant does not exhaust itself on seed, which matters enormously for a perennial that only has three or four good years in it. And it very often responds by pushing a second set of flower stems from the crown, opening four to six weeks later.

Go round the plants twice a week while they are going over. Spikes fade at different rates and one missed for ten days will already have firm pods on the lower half.

1. Wait for the tip to finish Cut when the topmost flowers have dropped their petals. Cutting earlier throws away flower you have not yet had; cutting a week later starts the seed drain.
2. Take the whole stem Follow the flower stem down to the first leaf joint or to the crown and cut there. Removing only the faded head leaves the developing pods behind and gives you neither the second flush nor the saved energy.
3. Bin the pods, do not compost them Pods left on a compost pile ripen and shed, and lupine seed survives to germinate wherever that compost is spread. Bag them if you do not want seedlings coming up across the garden.
4. Water once after cutting A deep soak after deadheading, if the ground is dry, is what turns the possibility of a second flush into an actual one. Do not feed at the same time.
5. Check the fresh growth for aphids The soft new shoots that follow a cut are exactly what lupin aphid colonises. Look over the crown twice a week for the fortnight after deadheading.

The second flush, and how to help it happen

The second flush is shorter than the first in every way: fewer stems, spikes about two thirds the length, and a display that lasts a fortnight rather than a month. It is still worth having, and in a mixed border it arrives when the early perennials are over and before the late ones get going.

It depends on the plant having something left to spend. A young, well-established plant on decent ground and deadheaded within days of fading will usually flower again. A four-year-old crown that is already declining, a plant that ran dry through the first flowering, or one carrying a heavy aphid population very often will not, and there is no point forcing it.

Heat suppresses it too. Where midsummer is hot and dry, lupines shut down after the first flowering regardless of what you do, and the growth you get after cutting is leaf rather than flower. In cool summers the second flush is close to reliable.

Do not feed to encourage it. Nitrogen after deadheading gives soft leafy regrowth and no extra flowers, and hands the aphids a target. Water and prompt cutting are the whole of the technique.

If you want seed from a particular plant, leave two or three spikes on it and cut all the rest. Do not let a whole plant set seed: it costs the plant a year of its short life and gives you far more seed than you can use.

Cutting the foliage back and renewing the plant

Lupine foliage frequently looks tired by high summer, whether from mildew, aphid damage or simple age, and a bed of yellowing fingered leaves is not worth looking at for the rest of the season. Cut the whole plant back to two or three inches (5-8 cm) above the crown once flowering is genuinely finished.

It regrows. Within three or four weeks the crown pushes a fresh rosette of clean leaves, which stays neat into autumn and gives the plant healthy foliage rather than infected leaves for its last weeks of growth. This is the standard treatment for a mildewed plant and works far better than trying to spray one.

Do the hard cut only after the last flowers. Cutting foliage away while the plant is still flowering or immediately after the first flush ends the second flush before it starts. And do not cut back so late in the season that the regrowth is caught soft by the first hard frost; if the season is nearly over, leave the tired leaves and clear them in autumn instead.

In autumn, cut everything down and take the debris away from the crown rather than leaving it as cover. Old lupine leaves harbor mildew spores over winter and re-infect the new shoots from below, and a mat of wet leaves against the crown is an invitation to rot on a plant that already dislikes a wet neck.

What to record while the plants are going over

The weeks after flowering are the best time to make notes, because everything you need to judge each plant has just happened and is still visible. Write down, for each plant, when its first spike opened and when the last one faded, how many spikes it carried and roughly how long they were, and what color it actually flowered rather than what the label claimed.

Add whether it produced a second flush and how long after cutting. Over three or four years those entries show you plainly which plants respond to deadheading, which position in the garden is dry enough to abort bud tips, and which crown is on its way out and needs replacing before it fails.

Mark the position of each crown before the foliage goes. Lupines disappear entirely over winter, and a fork through a dormant crown is a common accidental loss. It also tells you next spring which shoots belong to plants you set out and which are seedlings that need pulling.

Finally, note the date you deadheaded. If the second flush failed, the record usually shows you cut ten days too late, which is a fixable mistake and one worth not repeating.