By Sally Ferguson – For a jump in the season, start your summer bulbs indoors. Bulbs and tubers such as canna, calla lilies, begonias, dahlias and gloriosa provide some of the most dramatic flowers in the summer garden. They’re very easy to grow, but they’re also very sensitive to frost. In fact, in the trade, they’re called tender bulbs.
But tender bulbs respond incredibly well to a little tough love. Wake them up early and get a jumpstart on summer by potting them up indoors. It’s easy to do. This simple head start will afford you weeks more color from you bulb flowers in the summer garden.
Summer bulbs are available as bare bulbs for planting from late winter through late spring and as pre-grown bedding plants in pots in late spring through summer. In most parts of North America, tender summer bulbs can be started indoors four to six weeks prior to the usual last local frost date and then planted outdoors to begin their regular summer growing season.
The Netherlands Flower Bulb Information Center provides a list of summer bulbs that are easy to start up indoors. These plus other bulb planting details are available on www.bulb.com (see summer-blooming bulbs).
Tips for Starting Summer Bulbs Indoors
1. Select bulbs (true bulbs, tubers, rhizomes, roots) that are firm to the touch.
2. To get earlier blooms, pot them up indoors to start growing about six weeks before your planting-out date, the date in your area when the threat of night frosts is past. Choose clean containers with drainage holes. Good drainage is essential. Use a commercial potting soil mixed with equal parts peat moss and a drainage material such as sand or Perlite.
3. Place bulbs in the soil mix, following the planting directions suited to that type of plant. Different types of summer bulbs require very different planting methods. Some are planted barely covered with soil, others deep, others laid in horizontally, some concave side up. For specific details related to planting depth and positioning, look for instructions on www.bulb.com (Summer Flowering Bulbs) or on bulb packaging.
4. Warm humid settings are optimal for growth. Keep soil moist, but not wet.
5. Once the threat of frost is past, transplant tender bulb plants to the garden or outdoor containers. Summer bulbs prefer warm soil, close to 60° F (15°C). This soil temperature is generally reached once nighttime temperatures have stayed at/or above 60°F (15°C) for about two weeks.
(Images of pink canna, pink calla and gloriosa lily © Hilda M. Morrill.)