Late January
Start germinating violas and pansies indoors for early spring planting.
Germinate perennial and wildflower seeds indoors for transplanting
outdoors in May.
Fertilize houseplants once a month or as directed on the fertilizer label.
Deep water all outdoor plants every 3 – 4 weeks when the ground is not frozen to help the plants survive our dry warm winters. This can be done on a nice sunny day using a soil needle or soaker hose.
Feed the birds
Plant tuberous begonias indoors now.
Mid-February
Start kohlrabi, kale & cabbage from seed indoors.
Late-February
Start broccoli, brussel sprouts, cauliflower, parsley, collards, onion seeds, lobelia, ageratum, verbena & double petunias from seed indoors.
Plant pansy plants as early as late February if the weather is nice. Be sure to harden them off by slowly introducing them to the outdoors by putting them out during the day to get used to the sun and cooler temperatures.
Fertilize houseplants once a month or as directed on the fertilizer label.
When seeds have germinated, place in bright light or under a grow light to prevent them from getting too leggy.
When seedlings have developed their first two true leaves, thin to one plant per container. Use tweezers to pinch off unwanted seedlings to avoid disturbing the desired seedlings.
Deep water all outdoor plants every 3 – 4 weeks when the ground is not frozen to help the plants survive our dry warm winters. This can be done on a nice sunny day using a soil needle or soaker hose.
Feed the birds
Late-March
INDOORS
lettuce, Swiss chard, turnips, and sage. Also start annuals such as zinnias, dahlias (from seed), and marigolds.
Start tuberous begonias, dahlias, callas and caladiums in 8” pots INDOORS.
OUTDOORS
Plant bare-root strawberries, pea seeds, potatoes and onion sets. Plant tomato plants only if using a ‘wall o’water’ for protection from the freezes.
Fertilize houseplants once a month or as directed on the fertilizer label.
Spray with dormant oil spray before mid-March to control scale.
Also apply borer control if there is evidence of borers.
Prune plants at this time. Prune out dead wood and to shape and renew the plant. DO NOT PRUNE plants that flower in the spring since you will be cutting off the blooms.
Cut back late summer flowering plants such as Russian Sage, Blue Mist Spirea and Butterfly Bush to encourage new lush growth. These plants bloom on this year’s growth so you are doing them a favor by encouraging new growth.
Remove all tree wrap mid to end of March. This prevents the harboring of insects and disease.
Remove mulch from strawberries as soon as new shoots appear. Thin to 9” apart. Do not use high nitrogen fertilizer on strawberries as this will result in soft berries.
Deep water all outdoor plants every 3 – 4 weeks when the ground is not frozen to help the plants survive our dry warm winters. This can be done on a nice sunny day using a soil needle or soaker hose.
Feed the birds – March is Denver’s snowiest month, covering up their food source.
Early April
INDOORS
From seed: peppers, New Zealand spinach, collards, beets and eggplant.
OUTDOORS
From seed: carrots, kohlrabi, peas, radishes, sage, spinach (not New Zealand) and turnips. Also from plants and roots: Chinese cabbage, parsley, spinach, broccoli, kale, and cauliflower, potatoes, onion sets, garlic and asparagus roots.
Mid-April
INDOORS
From seed: celery, garlic, leeks, onions, lima beans, endive and escarole.
OUTDOORS
From seed: parsnip, beet, carrot, endive, escarole, lettuce, pea, parsnip and turnips. From plants: Broccoli, brussels sprouts, cauliflower, collards and kale.
Late April
OUTDOORS
Plant spring bulbs and roots – Ixia, lily of the valley, anemone, lilies, freesia, gladiolus, dahlia, canna and peonies. Plant hardened-off perennials.
When active growth appears on roses, fertilize with a “rose food” formulation according to the label.
Prune roses now (prune back to approximately 1-2 feet above the ground or to live wood). Don’t prune climbers except to shape or remove dead canes.
Feed your turf areas according to the directions on the fertilizer.
Fertilize all established plants starting to grow with 5-10-5 (or similar) fertilizer.
Fertilize trees and shrubs with the appropriate fertilizer (Ornamental, fruit, evergreen, etc.)
As weeds begin to actively grow, spray with weed control according to the directions on the container.
Remove mulches from perennials and roses.
Remove tree wrap if not done already since this is an excellent incubation area for insects and diseases if not taken off.
Feed our feathered friends – there are not enough natural foods available yet.
Early May
OUTDOORS
Broccoli, peas, beets, Brussels sprouts, carrots, collards, kale, radishes, spinach, tomatoes with “Wall O’Water” only, sage, pansies, all potted perennials, summer flowering bulbs. Make sure to ‘harden’ (slowly acclimate) the plants before putting them in the ground.
From seed: corn, snap beans, mustard, pumpkin, summer & winter squash.
Mid-May
OUTDOORS
Anything listed in early May, plus lemon balm, New Zealand and Malabar spinach, all herbs, all annual flowers, dahlia tubers, gladiola corms, all potted perennials (hardened off).
Late May
OUTDOORS
Anything listed in early and mid-May, plus cucumbers, pumpkins, summer & winter squash, basil, lima beans, peppers, corn and tomatoes.
Throughout May
Plant trees, shrubs, evergreens, annuals and perennials (Make sure your annuals and perennials are ‘hardened off’.
Use a root-stimulating fertilizer (high in the middle number) when planting new plants or transplanting “old” ones.
Container grown plants can be planted anytime this month (be sure to ‘harden’ (slowly acclimate) before planting if they were greenhouse grown. Otherwise they will struggle.
Early June
OUTDOORS
From seed: snap beans, beets, corn (early types), lima beans, and mustard seeds. From plants: cantaloupe, pumpkin, tomato, summer & winter squash, cucumber, oregano, pepper, endive, kale, kohlrabi, leek and eggplant.
Give your lawn a light feeding if necessary (it will tell you by its look).
Give roses their monthly feeding.
Give all flowering and fruiting plants with a food high in phosphorous (the middle number in the “3-number” formulation.
Check your outdoor hanging baskets twice a day (morning and afternoon).
Fertilize outdoor hanging baskets and container gardens frequently. Since these plants are watered daily, nutrients are quickly leached out of the soil. Fish emulsion works well for an organic alternative. Water thoroughly so water runs through drainage holes in the pot.
Continue to closely watch for pests and treat immediately (follow label directions carefully when applying these or any herbicides).
Prune to shape plants and cut back shrubs as needed after they complete their blooming period.
Don’t remove green leaves from spring flowering bulbs. They are energizing the bulb for next years bloom and the dry leaves will decay providing more nutrients.
Remove all spent blooms on annuals and perennials to prolong the blooming period.
Apply mulch to plants to conserve moisture and cut down on weeds.
Plant container grown trees and shrubs.
Plant annuals and perennials now. Plant in the cooler temperatures in the evening or early morning rather than during the heat of the day. A cool, cloudy day is best.
Plants in containers dry out quickly so check hangings baskets and containers for water needs twice a day, especially if they are in direct sun.
Apply fertilizer to annuals, hanging baskets, and container gardens weekly to compensate for the leaching of nutrients with frequent watering.
Give roses their monthly feeding. After each bloom fades, cut back the stem to 1/4” above the first leaf set with 5 leaves.
Check your lawn for fungus and treat immediately if necessary. High temperatures and too much water can cause disease outbreaks.
Inspect your trees and shrubs for insects and treat accordingly. Don’t forget to check the underside of the leaves since this is where they hide to stay cool.
Prune to shape plants. Thin and cut back spring flowering shrubs after they complete their bloom period if needed. Pruning later in the season will remove the flower buds for next year.
Divide and transplant Bearded Iris after the leaves dry up.
Plant container grown trees and shrub - see these CSU planting instructions
Plant perennials and transplant Oriental Poppies after their foliage has dried.
Early August
Plant cool season vegetables – lettuce, radishes. etc., for your fall garden. It is a good practice to plant them near taller, established vegetables to give some shade to the new seedlings.
Mid to late August
This is a good time to seed fall lawns. It is also a good time to divide or transplant spring-flowering bulbs.
Prune to shape plants. Thin and cut back the flower heads as they complete their bloom.
Check daily for ripe vegetables and enjoy them before the birds and other animals get them.
Make sure to keep plants well watered since August is hot and dry. Don’t overwater – use a moisture meter to check the water condition of the plants before watering.
Apply mulch to plants to conserve water, keep the soil temperature constant, and to cut down on the weeds.
Fall lawns can be seeded until late September.
Apply lawn food to you lawn to revitalize soil after a hot summer.
Plant container grown trees, shrubs and perennials. Be sure to follow the CSU planting instructions
Plant mums, fall asters, and pansies for fall color.
Take cuttings from geraniums now (before frost) and root them in a moist vermiculite or potting soil for next summers crop of geraniums.
Dig and pot herbs from your garden. Put in a sunny window to enjoy all year.
Make sure that you treat insect problems before bringing them inside.
Divide and transplant perennials now – this will give them a chance to recover before the winter.
Dig dahlias, cannas, tuberous begonias, callas, gladiolus, and other winter-tender bulbs and corms after a frost kills the tops. Dry the bulbs and corms for a few days and store in sawdust, vermiculite or perlite in a cool, dry place until next year.
When planting fall bulbs, wait until the soil is cool and apply a fertilizer high in phosphorous (bone meal, super phosphate or triple super phosphate)
Prune single-crop raspberries to 8-9” apart. Cut weak canes and those that have borne fruit.
Plant container grown trees and shrubs. Be sure to follow the CSU planting instructions
Plant Spring flowering bulbs for next spring’s color – tulips, daffodils, crocus, hyacinths, etc. Plant when the soil is cool. Apply a fertilizer that is high in phosphorous (bone meal, super phosphate or triple super phosphate) to give your bulbs the extra nutrients to produce a dazzling display of color.
Early October
Plant amaryllis in pots for Thanksgiving bloom.
Mid to Late October
Plant amaryllis in pots for Christmas bloom.
Now is the time to put in garlic.
Late October
Apply Richlawn Winterizer to your lawn to give it a great start for next spring.
Watch for insect and fungus problems on your trees, shrubs and perennials and treat immediately. If you don’t treat the problems now, they will winter over and pose a greater problem next spring.
If you have had ‘Black Spot’ on your Aspens or any other leaf diseases on your plants, clean up all the leaves and dispose of them in the trash. Do not compost, as you will just be spreading the problem.
Prune trees and shrubs to remove dead wood.
Deep-root water your trees and shrubs to make sure they receive adequate moisture before going into dormancy and before the ground freezes.
When preparing your perennial gardens for the winter, remove dead plant debris that could harbor bacteria and fungus. Leave the ‘winter interest’ plants that are still standing such as ornamental grasses, tall stalks such as Autumn Joy Sedum, Rudbeckia and Coneflowers.
Late October
Mulch perennials and roses (after the first hard frost) using straw, compost, or shredded bark to help protect them through the winter.
Plant container grown trees and shrubs as long as the ground can be worked. Be sure to follow the CSU planting instructions Plant Spring flowering bulbs for next spring’s color – tulips, daffodils, crocus, hyacinths, etc. as long as the ground can be worked. Apply a fertilizer that is high in phosphorous (bone meal, super phosphate or triple super phosphate) to give your bulbs the extra nutrients to produce a dazzling display of color.
Prune summer annuals if you are wintering them inside by cutting up to ½ of the plant to promote new, bushy growth.
Prune dead wood from trees and shrubs. This is also a good time to thin and shape them if necessary.
Keep an eye out for scale (hard, small shell-encased insects that cling tightly to the park of trees and shrubs (especially Aspen and Poplar). If they are present, scrub lightly with a plastic ‘scrubby’ and apply dormant oil spray when the tree loses its leaves to effectively smother these insects.
Deep-root water your trees and shrubs on a warm day if the soil is not frozen or covered with snow.
Early November
After snow compacts your garden soil, hand spade and leave soil rough and chunky. The freeze-thaw cycles will break up the clods of soil and hold the snow to provide moisture.
Feed the Birds: Their source of food is disappearing so give them a helping hand.
Late November
Use tree wrap on young fruit and other light colored barked trees. This will prevent sunscald which is a result of our intense winter sun. Wrap from the bottom up and remember to remove the wrap in early Spring.
Move houseplants away from heat vents. The forced-air heat dries out the foliage and soil.
Cooler temperatures and shorter days mean slower growth for houseplants. Water and fertilize only according to the plant’s needs. Use a moisture meter to determine if your houseplant needs water.
Plant Paperwhite Narcissus and Amaryllis bulbs inside for bloom in six to eight weeks.
Move houseplants away from heat vents. The forced-air heat dries out the foliage and soil.
Cooler temperatures and shorter days mean slower growth for houseplants. Water and fertilize only according to the plant’s needs. Use a moisture meter to determine if your houseplant needs water.
Always be on the lookout for houseplant insects (scale, aphids, woolly aphids, mites, etc.) and treat accordingly. Don’t let a small problem get out of hand and spread to other plants.
Poinsettias will benefit from a light feeding of a general purpose fertilizer throughout the bloom period.
Deep-root water your trees and shrubs on a warm day if the soil is not frozen or covered with snow. This should be done every month in the winter to keep the roots moist.