The Foxgloves may suffer in very dry conditions. But, Lavender and Pelagoniums are both quite draught resistant.
The dry garden is a garden designed to flourish in hot and dry conditions without additional water. Sometimes, we try hard to fight nature, but, sometimes it is good to grow the plants which will thrive in the conditions we have. A dry garden doesn’t have to be an arid and boring place with nothing more than a few cactus, there are many plants which will thrive in dry conditions.

Californian poppy thrive in hot dry conditions. A good example of a vibrant colourful annual you can grow in a dry garden.

Good Plants for Dry Conditions

Trees

• Acers
• Betula Pendula

Shrubs

• Buddleia davidi
• Hamamels mollis
• Helianthemum nummularium (common Rockrose)

Draught Tolerant Annuals

• Chrysanthemum
  Cleome spinosa (Spide Plant)
• Corydalis lutea
• Cosmos
• Dianthus chinensis
• Eschscholzia californica
• Euphorbias
• Gazania
• Ornamental Grasses
  -Agrostis nebulosa
  -Avena sterilis
  -Briza maxima
• Gypsophila, elegans
• Helichrysum bracteatum
• Helipterum manglesi
• Layia elegans
• Mesembryanthemums (the Livingstone daisy)
• Nasturtiums
• Pelargoniums
• Petunia Hybrids
• Phlox drummondi (though Phlox can start to wilt a little)
• Rudbeckia bicolor
• Rudbeckia hirta
• Tagetes
• Verbascum
• Verbena

The Dry Garden by Beth Chatto
Related

• Dry Shade
• Tips for saving water in the garden
• Plants for hot sandy soil
• The Dry Garden at Cambridge Botanic Gardens