These may bloom in summer of first season, but by second season your established desert rose can bloom from summer through to early winter or rain. Although Adenium is a popular houseplant in temperate regions it requires a sunny location outside in summer. When nights stay above 25 degrees place your plants outside and leave them there all summer long- the hotter and sunnier the better. The point is they like a change in day to night temperatures to grow and bloom properly. When temperatures drop below 20 degrees in the autumn, bring your plants inside. If you live where nights rarely drop below 15 to 20 degrees, you can leave your plants outside year round.