Why is my plant dropping its buds before they open?

A plant sheds buds for the same reason it sheds leaves: it cannot support them. Buds are expensive, they are formed months before they open, and they are the first thing to be abandoned when supply falters. That means the cause of this spring's bud drop is frequently last July.

Step by step

1. Establish when the buds were formed.Camellias, rhododendrons, wisteria and many spring shrubs set the buds for next spring in mid to late summer. A dry summer, or a summer where you stopped watering a container, produces buds that form but are never properly supported and drop the following spring.
2. Water thoroughly in summer, not just in flower.This is the single most effective action for camellias and rhododendrons. Water deeply through July and August, especially plants in pots, against walls or under trees, and mulch to hold it. Use rainwater on acid-lovers in hard water areas.
3. Check the current watering rhythm.Cycles of bone dry then soaked cause bud drop directly. A plant in a pot that dries out once while in bud will often shed the lot. Consistency matters more than volume.
4. Stop moving it.Many plants abort buds when the direction they face changes — camellias, azaleas, gardenias, hibiscus, citrus and Christmas cactus are notorious. Choose the position before the buds form, and mark the pot so it goes back the same way round after any move.
5. Look for frost damage on early-flowering plants.Camellia and magnolia buds and flowers are damaged by frost and, in camellias, by early morning sun thawing frozen buds too quickly. That is why camellias are traditionally planted where the morning sun does not reach them. Damaged buds turn brown and drop.
6. Check for a sudden change in temperature or draught indoors.Gardenia, hibiscus, citrus and orchid bud drop indoors is usually a draught, a cold windowsill at night, or a move from a humid nursery into a dry room. Stabilise the position and the humidity.
7. Look for pests inside the buds.Split a fallen bud open. Thrips, capsid bug and, on some plants, midges feed inside developing buds and cause them to abort. Rhododendron bud blast, which turns buds dry, brown and bristly with tiny black spikes, is a fungal disease spread by leafhopper.
8. Rule out over-feeding with nitrogen.A plant pushed with a high-nitrogen feed makes leaf at the expense of flower, and can shed buds in favour of growth. Switch to a high-potash feed from midsummer on flowering plants.
9. Accept a proportion as normal.Many plants set more buds than they can carry and shed the surplus. A camellia dropping a few buds and opening the rest is behaving normally; one dropping all of them is not.

Tips

• Mulch a camellia or rhododendron with leafmould or composted bark in spring. They are shallow-rooted and a mulch does more for bud set than any feed.
• A camellia in a pot needs watering right through summer, including on days it rains, because the canopy sheds rain away from the compost.
• If you must move a budded plant indoors, mark the side facing the light with a piece of tape and put it back exactly.
• Rhododendron bud blast is controlled by picking off and binning the affected buds and by reducing leafhopper, not by spraying.

Common mistakes

• Only watering when the plant is in flower — The buds were made the previous summer. Watering in March cannot repair a dry July.
• Feeding a plant that is dropping buds — It is a water and consistency problem in most cases, and a nitrogen-rich feed makes it worse by favouring leaf.
• Turning a budded houseplant to even up its shape — Gardenias, hibiscus and Christmas cactus reliably drop their buds when reoriented. Turn them before buds form.
• Assuming brown dropped buds are disease — Frost and drought both brown buds. Bud blast is distinctive — dry, grey-brown and covered in small black bristles — and the buds stay on the plant.

Questions people ask