Alpines and rock gardens

Question 1

Where should a rock garden be sited?

Answer 1

• open position, away from overhanging trees, where plants will receive sun for greater part of the day.
• area with good drainage unless using raised beds in which case drainage can be added
• avoid frost pockets
• slight slope will show off plants to best effect
• Use stones that complement the other hard landscaping in the garden and house materials.

Question 2

What are the soil requirements for a rock garden?

Answer 2

• free draining
• Good aeration
• ability to hold moisture
• appropriate pH for plants
• low nutrient content
• basic soil composition
  
  • 1 part loam
  • 1 part horticultural grit
  • 1 part leaf mould or coir

Question 3

Describe the planting of a rock garden

Answer 3

• position plants while still in pots. Allow for height and spread when fully grown.
• remove plant from pot, tease out roots, plant firmly in compost mix and top-dress with gravel or grit

Question 4

Describe the routine maintenance of a rock garden

Answer 4

• Weeding (ensure free of perennial weeds before planting
• watering
• deadheading
• trimming and pruning including reduction in size of encroaching plants
• top-dressing with grit
• control of pest and diseases e.g. slugs and snails, grey mould (botrytis)
• winter protection e.g. covering with glass cloche to reduce moisture in soil

Question 5

Describe the choice of container for alpine display

Answer 5

The following may be used as containers for alpine displays:

• Stone troughs with drainage hole(s). NB type of stone may affect soil pH e.g. limestone container will be alkaline, granite or sandstone will be acidic so choose appropriate plants
• sinks
• frost-proof terracotta
• hypertufa trough

Site on flat surface where will have sun for most of day.

Raise off the ground for protect from frost and allow free drainage

Question 6

What are the growing media characteristics for an alpine container display?

Answer 6

• free draining
• Good aeration
• ability to hold moisture
• appropriate pH for plants
• low nutrient content
• basic growing medium composition
  
  • 1 part loam/John Innes No. 2 (ericaceous if lime-hating plants)
  • 1 part horticultural grit (lime free if need ericaceous medium)

Question 7

Describe the planting of an alpine container

Answer 7

1. put crock over drainage hole to prevent growing medium washing out
2. fill container with growing medium, leaving gap of 2cm to accommodate grit dressing after planting
3. add plants, planting them a little high to accommodate 2cm deep collar of sharp grit or decorative aggregate. Will help conserve moisture, prevent heavy rain splashing soil on flowers, and reduces risk of stem rot. Grit will also reduce weed growth.
4. Add girt.
5. Water with watering can with sprinkler rose, soaking well until water seen from drainage hole.

Question 8

Describe the maintenance of an alpine container

Answer 8

• Do not allow to dry out, especially during first growing season. Won’t need water in normal winter conditions.
• winter protection e.g. covering with glass cloche to reduce moisture in soil and protect from frost
• Deadhead as necessary
• Cut back herbaceous-type plants in autumn
• Feed with slow release fertiliser in spring
• check for pests and diseases e.g. slugs and vine weevils