It is Time to Plant Cool Season Annuals, Shrubs & Trees!

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It is Time to Plant Cool Season Annuals, Shrubs & Trees!

Categories: Blog, Garden Guru

Don’t listen to your weathermen who say to hold off on planting; NOW is the time to plant dormant shrubs and trees and to plant cool weather, frost tolerant types of annuals outside. DO heed the weatherman’s advice and do not plant outside any summer annuals or frost tender plants like tomatoes, peppers, marigolds and zinnias.

Production in the Powell Gardens’ greenhouses is on a springtime roll. Here Eric Perrette, Gardener-Grower, carefully gives each flat of plants the proper amount of water. It is more challenging than you might think! We are bursting at the seams and it is time for cool season plants to leave the greenhouses to make space to grow summertime’s flowers.

The first step for cool season annuals is to harden them off outside. Even a frost-tolerant, cool-loving annual cannot take the abrupt move from a cozy greenhouse to the unpredictable weather outside. Frost blankets can be seen on the right and they are pulled over the plants to protect them from deer and any hard frost at night. You see no flower colors because we disbud (remove any flowers). We want the plants to put on flowers when they are put in our display beds or containers.

Ornamental cabbages and kale are ideal for planting out at this season. Ruby Perfection cabbage (left), Redbor Kale (upper right) and Chidori White Kale (lower right) show a sample of the foliage plants we use outdoors for ornament in the cool season. All these plants are edible greens, too. Planting them early helps these cool-loving plants establish well and they often last well into summer. Redbor Kale often survives all the way until next spring and is a Plant of Merit.

Who can resist the whiskers of a Viola’s flower? This is one of the Sorbet Duet mix whose “faces” range from white to orange or purple and look splendid when planted together. Violas and their related pansies are great hardy flowers to plant now.

Sweet Alyssum is another good cool-loving annual. This is a new strain called ‘Mulberry Mix’ with a range of pink and purple flowers. We always like the soft perfume of these flowers in the spring air.

Dianthus or Pinks are another great, hardy annual to plant now. This one is called Floral Lace Picotee.
Here is a cool-loving container outside the Visitor Center. It uses Dutch Iris, a red Carnation Dianthus, lettuce, kale. and more.
Ranunculus with their crepe paper-like double flowers are some of our annual favorites at Powell Gardens. They only do well in the cool season of spring or fall.
Osteospermum or “African Daisies” also flourish in the cool weather of spring but we keep them near the building under the overhang to protect them from frost. Here is a pink flowering Osteo paired beautifully with redbor kale.
Here is a new shipment of unique plants from Fairweather Gardens. For unique and unusual mailorder plants we highly recommend the quality and size sent by Fairweather Gardens ( and they are supporters of the gardens. We also highly recommend Klehm Song Sparrow as a unique source for rare plants (
Yes it is time to plant dormant trees and shrubs (notice those in the pictures still have buds and no fresh new leaves)! It gives them time to root in before the heat of summer arrives. Dormant trees and shrubs are quite capable of taking any extreme cold that is likely lurking.
I challenge gardeners to head out to their favorite garden centers this Easter weekend and pick up their favorite cool-loving annuals, trees and shrubs. The weather is supposed to be on the cold side so why not spend it picking out the plants you will want to plant when the springtime weather returns next week. You can put together containers in a garage and place them out after this weekend’s expected cold snap. Just get out and get growing this season!

All photographs taken on March 21, 2008, at Powell Gardens.