The weatherman has been predicting that temperatures will be below normal well into June. Gardeners should consider this when selecting annuals to plant this season. Bulbs and perennials appear as usual and they are wonderful. However, in order to have continuous bloom throughout the summer and fall and to fill in blank spots in the landscape and containers we need annuals.
With the prospect of a cool summer we would do well to plant 'cool season' annuals. Pansies and violas are prime examples. They do not like heat at all. Deadhead pansies frequently to keep them blooming for weeks. If they survive the summer heat, they may bloom again in the fall and some will live over the winter or re-seed themselves. Violas are more apt to do so, especially the little 'Johnny Jump Ups.' They tend to re-seed prolifically, so you really need to love them.
Plant some Bachelor's Buttons for a short season of blue flowers. Spiky Larkspur is a good substitute for the perennial delphinium. You can get a second bloom in the fall if you deadhead them or use them for cut flowers.
The blue to lavender shades of Lobelia look great in containers or as an edging plant. It gives out in heat, but you can give it a haircut and it may bloom again when cool weather returns. The newer cutting grown varieties, such as 'Laguna' have more heat tolerance and form larger plants. Diascia is another trailing container plant that comes in red, pink and coral shades. Some of its newer varieties can handle a little heat. Keep in mind that the soil in containers gets warmer than ground soil.
For color and height, you cannot beat snapdragons and there are even some trailing varieties. They can handle a light frost or two. Pinch them back when there are six true leaves so that they will branch out. Deadhead regularly and cut them back by half in August for fall blooms. Plant them closely as they have a narrow growth pattern.
Brightly colored Nasturtiums like it cool and can be direct seeded. Soak the seed overnight or scarify them with an emery board before you plant them. They do not transplant well, so if you buy seedlings try not to disturb the roots. Calendula or Pot Marigold is an annual in the yellow to orange range. It is a re-seeder and once you plant it you usually will not have to replant it for several years.
Nierembergia makes mounds of tidy violet blue or white ('Mont Blanc') cup-like flowers and is a good edging or window box plant. These are half-hardy perennials that we treat as annuals and bloom from spring to frost. Fragrant Stocks like it cool and make an excellent cut flower. Plant some each week for a month to get the longest bloom time. Primroses grow in shady areas, but slugs love them and they are expensive considering their short bloom period. Annual Dianthus or Pinks and Alyssum are two more plants that do well in cool temperatures. Pinks will often live two or three years. Alyssum freely re-seeds, but the subsequent plants are gangly and not as pretty as the originals.
Swan River Daisies have one-inch blossoms on 12-inch mounds in lavender, blue and white. The Cobbity Daisy (Argyranthemum) tends to go out of bloom when it gets hot. Gerbera Daisies are best with less heat so they do better when kept in partial shade in summer.
The Sweet Pea is an old-fashioned plant that is not easy to grow. It needs both cool days and nights and goes out of bloom when the temperature gets over 65 degrees. It also cannot tolerate any frost. Never the less it is a great cut flower and if you get a variety that says 'old-fashioned' it has a wonderful fragrance. Soak the seeds over night before sowing them next to a fence, bamboo tripod or shrubby plant.
Some annuals should not be planted before the weather warms up. Impatiens are tropical plants that refuse to grow if planted too early in cold soil. The night temperature should be 50 degrees consistently before setting out the transplants and the soil should not feel cold. Impatien seedlings and coleus plants are extremely sensitive to frost. Wait until the soil is warm to plant zinnias.
Some plants like it hot and since we live in North Dakota, we know that it will eventually get hot. I will discuss heat lovers in the next article.