How to Grow Capers USA

At a Glance

Quick Facts

Factor	Value
Drainage	Loam and sand, very sharp drainage (RHS/Wisconsin Horticulture); tolerates drought well once established.
Lifecycle	Tender, sprawling shrub. Wisconsin Horticulture gives a USDA zone 8 minimum, noting plants lose all their leaves in winter where only marginally hardy.
Edible parts	flower_buds, fruit

Growth Stages

Stage	BBCH	Notes
Propagation and potting	0	RHS: sow seed soaked in warm water for 2-3 days beforehand, at 64-70°F (18-21°C) -- germination is slow and erratic. Wisconsin Horticulture: fresh seed germinates best; stored seed needs scarification and/or cold stratification and can take up to three months, or propagate by softwood/hardwood cuttings.
Establishment	3	RHS: grow under glass in peat-free, loam-based compost with added grit; water moderately in the growing season with a monthly high-potash feed, sparingly in winter. Wisconsin Horticulture: needs very sharp drainage and limited water, similar to olive-growing conditions -- once established plants are notably drought-tolerant.
Flowering	6	RHS: in summer, plants produce white, four-petalled flowers with a tuft of white-to-pink stamens above round, grey-green leaves to 4cm across on a sprawling shrub to 1m tall.
Bud harvest	8	Wisconsin Horticulture: harvest unopened flower buds by hand while still dark olive-green and about the size of a corn kernel; the intense caper flavour only develops after picking, as mustard oil (glucocapparin) is released from the bud.

Harvest & Storage

When to pick: Wisconsin Horticulture: pick unopened flower buds by hand while dark olive-green and about the size of a corn kernel, mid-May to mid-August, ideally in early morning while buds are still tight.

Storage

Sun-dry the buds, then brine, salt, or pickle (Wisconsin Horticulture). Caperberries are also pickled.

Pests

Mealybugs

low

Pseudococcidae

RHS: may be susceptible to mealybugs under glass. Wisconsin Horticulture does not mention any significant pest problems, consistent with wider reporting that capers are largely pest-free.

What university and government growers’ guides add about caper bush

The caper bush is a plant of hot, dry Mediterranean rock, and both sources below say it is cold that limits it, not heat.

• It prefers dry heat and intense sun, and thrives in poor, dry, rocky or sandy soils. (Purdue, Missouri Botanical Garden)
• It is cold tender. Purdue compares its hardiness to the olive tree (about −8°C, 18°F), and Missouri Botanical Garden says plants will not survive winter when temperatures dip below 18°F. (Purdue, Missouri Botanical Garden)
• It grows well in nutrient-poor, sharply drained, gravelly soils, is salt tolerant, and easily survives summer temperatures above 40°C (105°F). (Purdue)
• Purdue says plants are productive where about 350 mm of rain a year falls, mostly in winter and spring; Missouri Botanical Garden says established plants need little watering. (Purdue, Missouri Botanical Garden)
• Capers are the flower buds, picked while still tight before they open, washed in salt water to remove grit, dried, and then salted or pickled in vinegar. (Missouri Botanical Garden, Purdue)

Caper bush in the USA: climate data

The sources give a survival limit of about 18°F (−8°C), which falls in the 15 to 20°F band of USDA zone 8b (Purdue, Missouri Botanical Garden). Of the 26 cities in the NOAA normals we use, 10 fall inside that range; Albany, NY (6a), Atlanta Hartsfield, GA (8a), Baltimore Wash, MD (8a), Bismarck, ND (4a), Charlotte Douglas, NC (8a), Denver, CO (6a), Des Moines, IA (5b), Duluth, MN (5a), Fargo Hector, ND (4a), Madison Dane Rgnl, WI (5b), Milwaukee Mitchell, WI (6a), Minneapolis, MN (5a), Nashville, TN (7b), Pittsburgh, PA (7a), Raleigh Durham, NC (8a), Sioux Falls, SD (5a) are colder than the lowest zone listed.

Dates are the median 32°F freeze dates and freeze-free days from NOAA NCEI U.S. Climate Normals 1991–2020; zones come from the USDA 2023 Plant Hardiness Zone Map (ZIP code of each city centre).

In practice an open-ground caper bush is a zone 8b-and-warmer, dry-climate plant. Further north the same limit points to a large, very well-drained pot that is moved under cover before the first hard freeze.

Sources for this section

• Purdue University Center for New Crops and Plant Products: Caper, Capparis spinosa (Crop Fact Sheet)
• Missouri Botanical Garden: Capparis spinosa (Plant Finder)

Section researched and checked on 24 October 2026 by the SoilCommander Editorial Team. How we check facts: editorial policy.

Sources

1. University of Wisconsin-Madison Division of Extension (Wisconsin Horticulture) - Capers, Capparis spinosa

   Light: high light intensity required. Soil: dry, sandy or gravelly, very sharp drainage, limited water, similar to olive-growing regions. Size: ~3ft tall, semi-prostrate branches spreading 6-10ft wide. Hardiness: zone 8 minimum; technically evergreen but loses leaves in winter where marginally hardy; Midwest plants must come indoors before frost. Native range: wild throughout the Mediterranean and other areas, native status unclear. Propagation: seed or softwood/hardwood cuttings; fresh seed germinates best, stored seed needs scarification/cold stratification with sporadic results, often taking up to 3 months. Harvest: unopened buds picked by hand when dark olive-green, about the size of a corn kernel; intense flavour develops after picking as mustard oil (glucocapparin) releases; buds sun-dried then brined/salted/pickled; larger fruits (caperberries) also pickled; dried leaves used as a rennet substitute in cheesemaking. Not commonly cultivated in the US; suited to container growing as a novelty plant in warm climates.

These source is specific to this region. The full list of 2 sources behind this guide (Royal Horticultural Society, University of Wisconsin-Madison Division of Extension (Wisconsin Horticulture)) is in the references of our UK guide to capers; they describe the plant itself, which is the same wherever it grows.