Compiled by Stan Barrett, Colorado State University Cooperative Extension master gardener, Denver County.
My lilies have flowered beautifully for several years but for the last two years flowers have become sparse. Do they need special fertilizer?
No; the problem is probably overcrowding. Lilies continually produce new bulbs, from which grow new plants. As the clump of lilies grows bigger the plants at the center become less productive. The solution is to dig up and divide the crowded clumps every four years or so, in the fall. Take the opportunity to dig in some fresh low-nitrogen fertilizer, such as bone meal. Replant the bulbs growing at the edges of the clump, one to two feet apart, and discard the old bulbs from the center.
First, grow them properly during the summer! A healthy vigorous rose is much more likely to get through the winter unscathed than is a stressed or diseased plant. Sudden changes in temperature in the fall, before the plant has had a chance to harden off for the winter can be disastrous. Early freezes kill more canes than much colder winter freezes. Start your protection program by discouraging vulnerable new growth; avoid late summer applications of fertilizer and start to cut back on watering. Most hybrid teas that are reasonable hardy for the site can be adequately protected by mounding 8 to 10 inches of loose soil or compost over the root zone. Wait until after the first hard frost--the mound then helps to keep the soil temperature stable as the ambient conditions fluctuate. Prune the rose only enough to prevent wind or snow damage.
If the rose is known to be only marginally hardy additional protection can be provided by surrounding the plant with a cylinder of chicken wire, 14 to 16 inches diameter by 12 inches high, and filling it with leaves or chopped straw. If the winter weather is dry the rose will need to be watered every three weeks or so.
Be careful not to remove the protection too early in the spring. Any new growth under the blanket will be very tender--let it harden off gradually and be prepared to re-cover it in the event of a late frost.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010