alpine gardening

Speaker - Ray Broughton

Alpine Gardening: Key Principles

• 68% of alpines die in the first year, mostly from overwatering or poor drainage

• Many alpines have 60% of their root growth underground: oxygen access is critical

• If using a water reservoir, empty it for 2 days per week to restore oxygen

• Alpines are not fully frost hardy despite mountain origins: many rely on snow cover or boulder microclimates

Soils, Rocks, and Containers

• Best rocks: sandstone (ages well), tufa (lightweight, neutral pH, chisel holes and fill with

compost)

• Avoid Portland stone (too hard, ages poorly) and standard limestone (algae-prone,

deteriorates)

• Compost: John Innes No 1 is reliable but buy quality, not supermarket own-brand

• Ratio matters more than brand; making your own from turned turf (takes 2 years) is best

• Pots: use clay with double drainage holes; avoid salt-glazed pots (white residue harms

alpines)

• Protect unglazed clay pots from frost: rub neat malt vinegar into the clay in October/

November

• Never tap pots to firm compost; use two fingers instead (tapping was for rough Victorian

clay, now obsolete)

• Watering cans: long spout for control; always use brass/alloy rose, never plastic

(electrostatic charge blocks it)

Pest and Disease Control

• Clean secateurs with Heinz tomato ketchup: leave on blades for 4 days, vinegar content

removes resin/burr

• Alternative: “Propeller” sterilising product

• Never use Coca-Cola on aluminium secateurs: highly acidic, causes damage

• Aphid control:

• Spray woody deciduous host plants with water around Christmas to destroy egg-laying

females before mid-January

• Results: up to 97% aphid reduction the following year

• Two-spotted ladybirds (semi-native UK): kill up to 250 aphids/day; sold as adults, too

fat to fly far so they colonise rather than disperse

• Milk-based spray (approved organic contact treatment): controls aphids, whitefly,

thrips, mealybug; use premixed

• Thermal/heat plate weeders (600W, mains electric): effective on ground elder and

horsetail

• Treat every 3 weeks for a full year to eradicate persistent weeds

• Do not use home remedies (e.g. Fairy liquid/bleach): illegal since 2015 and dangerous

Temperature and Frost Management

• Minimum/maximum thermometers using alcohol are unreliable: alcohol absorbs heat,

skews readings high

• DIY accurate thermometer: 1L container, silver foil exterior, polystyrene lid sealed with

beeswax, alcohol thermometer through the centre

• Above are used to calibrate systems at Kew Gardens

• Frost protection: fine mist spray on plants at dusk before a frost• Latent heat of evaporation prevents ice crystal formation; droplets must be fine (hose pipe spray too coarse)

• Works for grapes in flower, early potatoes, and alpines

Propagation and Feeding

• Seed dormancy: “baked bean method” (70% grit/sand, 30% seed, outside September to

April) breaks dormancy naturally

• Alternative: scarify with metal grinding paper (not sandpaper) in spring only or soak

seeds in malt vinegar for 30 minutes, then dry before sowing

• Bulb propagation (July only, when no roots or shoots):

• Dig up, clean, cut shoot tip, score or scoop stem base in a cross pattern, leave upside

down

• New bulbs form by Christmas; takes 2 years to reach flowering size

• Tulips: must be liquid-fed after flowering to produce a new bulb each year

• Remove the stigma (female organ) as soon as the flower opens: extends bloom 4x

longer

• Feeding with nettle tea (dry method, May onwards):

• Layer fleece, aquatic stone, broken nettles, vermiculite, fleece, stone in a 10-inch pot

• Water weekly; dilute output 1:20 for alpines; no smell, nearly zero waste

• Use aquatic stone only: local stone may contain copper/molybdenum

• CO₂ boost in spring: fill a 2L container with lumpy horse manure, seal with cling film,

make 6 holes

• Place in closed greenhouse in spring: oxidation releases CO₂, boosting early alpine

growth

Other Info

• Buff copper slug tape around pots with emery cloth weekly: copper oxidises and stops

working without regular buffing - emery cloth is supplied with the tape.

• Spray woody deciduous plants with water around Christmas - destroys egg-laying aphid

females before mid-January, reducing next year's aphid population by up to 97%.

• Start nettle tea feed setup in May

Collect nettles before they flower; layer in a 10-inch pot with aquatic stone and

vermiculite for a season-long, no-smell alpine feed.