Now is the time to make sure you’ll be enjoying blooms and greens throughout the summer.
It’s time to plant up patio pots, but keep an eye on wild temperature fluctuations. Plants may need to be covered.
Pinch back vigorous annuals to encourage fullness and to prolong blooming.
After planting, monitor the moisture in the flower and vegetable beds, keeping it slightly moist as plants take root. Slowly apply 1 to 1.5 inches of water.
Mulch beds after planting, topping with 1 to 2 inches of organic mulch.
Practice aggressive weed removal. This month, weeds can really take over the garden.
Attend garden tours for new ideas including plant combinations, designs and new cultivars.
In the perennial garden
This is the perfect month to plant. At the nursery or plant sales, choose your favorite and the healthiest specimens.
No garden? No problem. Plant perennials in containers in soil-less growing mixture amended with an organic slow-release fertilizer.
Now is the time to divide perennials that are too large or are crowding other plants. It’s best to divide them when new growth is only a few inches tall.
Seedlings started indoors may be planted now, and all new plantings should be mulched with a 2 to 3 inch layer of rich organic compost.
Early blooming perennials may be deadheaded.
Start tying the tall perennials to their supports. Leave enough space for the stems to thicken, but don’t let them flop about.
Bulbs and corms
When the danger of frost is passed, set out those tender bulbs such as lilies and dahlias. Stake the tall ones as you plant them, being careful not to poke the stake through the tuber.
Were there bare spots in the spring bulb display? Make a note of it now, and keep it in the garden journal or calendar so you know what to buy and plant next fall. If you have a smart phone, then snap pictures of the trouble spots as reminders.
After your last frost date, plant out the tender vegetables: tomatoes, peppers and eggplants. Be prepared to cover plants if a late frost is anticipated.
Direct sow seeds of melons and squash, beans and lettuces. Hill up your potatoes and leeks as they grow.
Water new plants on a regular basis, and if possible, install drip irrigation hoses and emitters.
Keep the root crops thinned, making salads of the edible greens with your thinnings (the ones you have to pull out). Add trimmings from the herb garden to your salads, too.
Pick off or wash pests off plants. If you must, use an insecticidal soap according to the label instructions. Remember: If you are feeding it to your family, then grow it organically.
Now is an excellent time to divide your established, older ground covers and move them to parts of the garden where they can be of good use.
If you discover dead patches in the ground cover areas, then clean them out and wait awhile. New growth will likely fill in and repair any holes.
Lawns and ornamental grasses
This is a good time to aerate your lawn. Leave the soil plugs where they fall. They decompose and add organic matter to the turf area.
Top dress lawns with a thin layer — less than 1 inch — of organic compost.
Warm-season grasses such as buffalo grass and blue grama should be sown in May or June because they need warm soil to germinate successfully.
Ornamental grasses will be arriving in the nursery centers. They don’t look like much — most of them are still dormant — but they can be planted now.
Plant container-grown shrubs this month. Garden centers have the latest cultivars, and new plants are arriving daily.
Finish pruning spring flowering shrubs (lilacs, forsythia) after they bloom and before they set next year’s buds.
Conifers and deciduous trees
This month, you can transplant evergreens in your garden. Be sure to water them in well.
Plant container-grown trees, both deciduous and evergreens. Make sure your irrigation system is set up to give them adequate water in their first year.
Fertilize trees that are showing signs of nutrient deficiency. The alkaline soils of the Rockies may cause trees to look chlorotic (yellowish). Talk to your local extension office for recommendations on treating this condition.
Check trellises and other supports to make sure they are securely fastened to a wall or post. Vigorous vines are heavy. Ensure adequate air circulation behind trellises and screens so vines won’t bake in the sun. They should be positioned 12 to 18 inches from a wall.
Plant new clematis and protect the transplants the first couple years with a tomato cage or similar structure since the new plants are quite brittle. Keep the tags so you know how to prune them in the future.
Honeysuckles, ivies, Virginia creeper and trumpet vine are taking off right now. Aggressively prune unruly shoots and branches and redirect the growth where you want it.
As all gardeners know, this is going to be the best gardening year ever!
Mary Ann Newcomer is the author of “Rocky Mountain Gardener’s Handbook.”