Repotting guide

When & how to repot Boissier's Silverbush (Convolvulus boissieri)

Also called Boissier's silverbush, Spanish silverbush.

More about boissier's silverbush

About Boissier's Silverbush

Convolvulus boissieri · also called Boissier's silverbush, Spanish silverbush · flowering

Convolvulus boissieri (synonym C. nitidus) is a dwarf, cushion-forming evergreen sub-shrub native to rocky, sun-baked mountain slopes of southern Spain. It produces large, gleaming white to pale pink funnel-shaped flowers against dense, silver-silky foliage, making it a sought-after plant for alpine gardens, troughs, and rock gardens. It requires near-perfect drainage and full sun; it is particularly intolerant of winter wet at the root crown. It is not documented as toxic to pets.

Mature size: 5–15 cm tall and 20–40 cm wide.

Watch for — Vine weevil grubs: The compact root system makes this plant particularly vulnerable to vine weevil larval feeding; inspect roots at repotting and treat with biological nematodes or imidacloprid-based drenches as permitted.

How to tell boissier's silverbush needs repotting

Repotting on a calendar is less reliable than reading the plant. For boissier's silverbush, watch for these signs:

Roots growing out of the drainage holes, or the rootball lifting the plant proud of the rim.
Soil that has shrunk away from the pot sides and no longer holds water.
The pot is unstable because the plant has grown top-heavy.
Old, compacted, broken-down mix that stays wet too long — for a succulent that is a rot risk, so refresh it even if the pot size is fine.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot boissier's silverbush

Every 2–3 years, into bone-dry mix. Boissier's Silverbush's growth habit — compact, cushion- or mat-forming evergreen sub-shrub. — sets the pace. Convolvulus boissieri (synonym C. nitidus) is a dwarf, cushion-forming evergreen sub-shrub native to rocky, sun-baked mountain slopes of southern Spain. It produces large, gleaming white to pale pink funnel-shaped flowers against dense, silver-silky foliage, making it a sought-after plant for alpine gardens, troughs, and rock gardens. It requires near-perfect drainage and full sun; it is particularly intolerant of winter wet at the root crown. It is not documented as toxic to pets.

What size pot to step boissier's silverbush up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Boissier's Silverbush stores water and rots in a large pot of slow-drying soil. A tight terracotta pot that dries fast is far safer than a generous plastic one. Never up-pot a succulent by several sizes.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot boissier's silverbush

Spring or summer, while boissier's silverbush is in active growth and warm, is best — roots recover fastest then, and the plant is not sitting in cool damp soil. Avoid repotting a succulent in winter dormancy.

Step-by-step: repotting boissier's silverbush

Repot dry. Do not water boissier's silverbush for several days first. Working with dry roots and dry mix dramatically lowers the rot risk for a succulent.
Pick a snug, fast-draining pot. Choose terracotta one size up at most, with a drainage hole. Have gritty sharply drained, gritty or stony, low-fertility soil ready.
Tip it out and clean the roots. Slide the plant out, crumble off the old soil, and trim any black, mushy or dead roots with clean snips.
Pot into dry mix. Set boissier's silverbush at its original depth in dry gritty mix, firming gently. Do not bury the stem deeper than it was.
Wait a week before watering. Leave it completely dry and out of harsh sun for about 7 days so any damaged roots callus. Only then water lightly.

Aftercare

Keep boissier's silverbush completely dry and out of fierce sun for about a week so any nicked roots callus before they meet moisture; watering a freshly repotted succulent is the classic way to rot it. Then resume the normal lean, dry rhythm. Do not fertilise for about 3 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for boissier's silverbush

Boissier's Silverbush wants sharply drained, gritty or stony, low-fertility soil. Grow in alpine house conditions or in a raised scree bed with at least 50% horticultural grit; any moisture-retentive medium will cause rapid crown rot in winter. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting boissier's silverbush — frequently asked questions

How often should you repot boissier's silverbush?

Every 2–3 years, into bone-dry mix for boissier's silverbush. Repot boissier's silverbush every 2–3 years into a snug pot of sharply drained, gritty or stony, low-fertility soil, ideally in spring or summer. Let it sit in dry soil and do not water for about a week afterwards so any nicked roots can callus. Over-potting and watering straight away is what rots succulents.

What size pot does boissier's silverbush need?

When is the best time of year to repot boissier's silverbush?

Should you water boissier's silverbush after repotting?

No — not straight away. Repot boissier's silverbush into dry mix and wait about a week before the first watering so any damaged roots callus over. Watering a freshly repotted succulent is the single most common way to rot one.

Should you fertilise boissier's silverbush after repotting?

Not immediately. Wait about 3 weeks after repotting boissier's silverbush. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.