When to Plant

• Daylilies are hardy flowers that can be planted any time of year the ground isn't frozen, from early spring to late fall. They have thick, tuberous roots, and like all plants with such roots, such as sedums and irises, they store plenty of water and energy. These stored nutrients enable them to survive while their root system develops, making them an easy flower to transplant and later divide, if you'd like to do that. They almost never fail to survive and develop.
  
  That said, try not to plant daylilies in extreme temperatures, especially if you are a novice gardener or not used to working with the plants. Depending on where you live, summer temperatures may be too humid or late fall temperatures may be too cool for effective planting.
  
  

Considerations

• The native daylily varieties are fairly aggressive and may have to be divided fairly frequently to keep them from taking over your garden. The hybrid varieties are better behaved, but even they need to be thinned from time to time. Better behavior isn't the only advantage of the hybrid plants. They also have a larger variety of colors, and many bloom for the entire summer, in excess of 110 days.
  
  One way to control daylilies is to plant them in full or partial shade. These plants will grow literally anywhere, but they'll grow best (and fastest) in full sun. That makes them a good candidate for growing under your trees, where not much else besides liriopies and impatiens will thrive. Even better, they won't grow so aggressively without the encouragement of the sun, so that you won't have to work so hard to keep them in check.