How to Stop Basil Bolting and When to Let It Flower for Seed

Once it flowers, the leaves go tough

As soon as basil flowers it starts diverting everything into seed, and the leaves come small, thick and stringy. The essential oils that carry the scent drop too, so leaves from the same plant taste noticeably different before and after flowering. On a plant grown for leaves, do not let it flower.

A shoot that flowers also stops extending: the stem goes woody and produces no more leaves. Left alone the whole plant switches over and the harvest is finished by midsummer. Keep taking the flower spikes off and it keeps making leaves into autumn.

1. Flower buds start in early summer The first spikes rise around the start of summer. The later you were with the first pinch, the earlier they appear.
2. It comes back every time As long as you keep removing the spikes the plant keeps making leaves. Kept up, it picks into mid autumn and yields more than double a plant left to flower.

Spot the flower bud by the shape of the tip leaves

The spike forms at the tip of a shoot. Smaller leaves crowd together, and between them a spike of green beads pushes up. Caught at that stage the leaves have not toughened yet, so cutting it the day you notice costs you nothing.

1. The tip leaves suddenly get smaller When the leaves at the end of a shoot drop in size and the gaps between them close up, the plant is heading for flower. The spike shows within days.
2. Green beads in rows The spike carries beads in tiers. Cutting at that point, before the white flowers open, is ideal. Once they open the leaves have already begun to toughen.
3. Look over the plant weekly Once one shoot flowers the others follow. Look down over the whole plant once a week and check every tip.

Flower buds come fastest in the hottest part of summer. Shortening the interval between checks in those weeks extends the picking season.

Cut two joints below the spike

Pinch off just the spike and another one comes from the joint immediately below. Cut two joints down, just above a pair of leaves, and the buds at that joint grow away as leafy shoots instead. It doubles as a harvest.

1. Taking the spike alone is a stopgap If you are short of time, taking just the spike is better than nothing, but another one is up within a week. Go back and cut below a joint properly.
2. Cut two joints down Cut back to a point with two pairs of leaves below. The leaves on what you cut are usable, so the job is your harvest as well.
3. Level the whole plant When several spikes appear, cut the whole plant to one height. The shape stays good and the new shoots come away evenly.

Rescuing a plant that has flowered

Even after the white flowers open, a plant that is still green can be brought back. Cut the flowering shoots down to where there is still green, roughly halving the height of the plant. Within a fortnight side shoots grow away and you are picking soft leaves again.

Give it a pinch of fertilizer when you cut back. Cutting a weakened plant without feeding it leaves the new shoots stunted.

If you want seed, set plants aside for it

You cannot take seed and leaves from the same plant. Trying to do both means a long stretch of tough leaves and a poor set of seed. Pick one or two plants for seed and stop removing their flower spikes from mid summer.

1. Choose the seed plants in mid summer Plants that start flowering in autumn will not ripen seed before the cold. Choose your seed plants while there is still plenty of summer left.
2. Water less once it flowers Cut back the water after flowering. Kept wet, the spikes go moldy and the seed spoils before it ripens.
3. Cut when the spike is brown and dry Once flowering is over and the whole spike has dried brown, cut the shoot and dry it indoors. Taken green, a lot of the seed will not germinate.

Ripe seed is black and rubs out of the spike between your fingers. Dry it in a paper bag and store it somewhere cool and dark with a desiccant and it will keep until spring.

Do not save seed from mixed varieties

Basil is insect pollinated, so a different variety flowering nearby will cross with it. Save seed from sweet basil growing next to lemon basil and next year you get plants with a muddled scent. If you want to keep a variety true, flower only one.

If the packet says the variety is a hybrid, saved seed will not come true whatever you do. Buy fresh seed to repeat the same variety.