Midwinter to Early Spring

Check trees and shrubs for animal damage from deer, rabbits, and rodents.
Use fencing or protective collars to prevent injury.

Keep road and sidewalk ice melters away from plants.
Shovel snow away from plants, and don’t pile snow with ice melter in it onto your garden.

Uncover plants weighed down with heavy snow.
Gently brush snow off branches to prevent breakage. If the snow is frozen, let it melt naturally.

Continue to feed birds.
Many plants offer winter berries, seeds, and pods for birds and other wildlife. Consider adding four-season plants to your landscape to attract and provide food for birds during this time of year, as well as add beauty to the winter landscape.

Monitor tree health.
It is easier to notice dead branches, trunk damage, and cankers on trees when there are no leaves. Cankers are signs that the tree has a disease.

Prune dead, diseased, crossing, or rubbing branches anytime.
Remove water sprouts and suckers now, too.

Prune some trees and shrubs.
The dormant season is a good time to prune many species (see exceptions below). Don’t prune spring-flowering plants until after they flower, or you will remove this year’s flower buds.

Prune birch, maple, and walnut trees during the coldest part of winter.
These trees “bleed” sap on sunny days if they are pruned when temperatures are warming. If you don’t get these trees pruned in the cold of winter, wait until very early summer when all the leaves on the tree have expanded.

Prune elm and oak trees from about mid-October through mid-April.
The insects that can spread Dutch elm disease and oak wilt are dormant during this time. Be aware that this time frame may change a little from year to year, depending on weather. The spring end of that time frame could hold danger if a very warm spring brings insects out of dormancy early.

Prepare for spring planting.
Reflect and evaluate last year’s garden. Decide what changes need to be made. Draw garden plans on paper, including a wish list of plants you would like to add. Use the Arboretum’s Search Trees and Plants database to find suitable plants for your site.

On warm days, check perennials for heaving.
Abrupt temperature changes can cause shallow-rooted plants to push out of the ground, exposing roots. If the ground is thawed, gently push roots back into the soil. Cover the root system with a three to four inch layer of mulch.

Don’t be fooled by warm, sunny days in winter.
It is still too early to remove mulches, screening, and other winter plant protections. Make sure they are still in place until the weather is more consistently warm.

Clean, sterilize, and sharpen garden tools.
Get ready for the upcoming growing season.

Check the summer bulbs that are stored in a cool, dry place.
Make sure they have not sprouted or dried out.

Order seeds to start indoors or to direct-plant outside.
Cool season vegetables can be planted outside even when frosts or freezes are still expected. Warm season vegetables must wait until after the risk of frost is over. Vegetable and annual seeds can be started indoors. Check seed packets for the number of weeks to start prior to moving seedlings outdoors.

Start cutting ornamental grasses back just before new growth begins.
Cool season grasses will be among the earliest to actively grow. They may need only minor trimming if the winter was mild or snow cover was good. Warm season grasses are slower to become active. Cut them down near the ground, but don’t cut into the base of the plant.

Create a sense of spring.
Force branches of early spring flowering plants, such as forsythia, crabapple, and lilac. Place in a container of water in a cool room, away from direct sunlight. Cuttings can take from two to three weeks to force indoors.

Crabgrass preventers are often available in stores in very early spring, but it may not be time to apply them.
Crabgrass will not start to germinate until soil temperatures have been above 55℉ for five to seven consecutive days. Many crabgrass preventers only last about 60 days, so apply them as soil temperatures start to get into the 50s. Redbud is a good indicator tree. Crabgrass germination begins around the time redbuds are in full flower, so put the preventer down while redbud flowers are still closed.

Mid- to Late Spring

Finish cutting ornamental grasses back before new growth begins.
Cool season grasses will actively grow early in the season. They may need only minor trimming if the winter was mild or snow cover was good. Warm season grasses are slower to become active. Cut them down near the ground, but don’t cut into the base of the plant.

Check for winter snow and salt damage.
Prune dead tips and broken branches.

Don’t remove winter protection until temperatures stabilize.
Leaves raked into flower beds last fall protect plants from fluctuating temperatures and late spring freezes. Don’t rake them away just because we get a couple of warm days.

Begin general cleanup when temperatures moderate and soils are not wet.
Avoid walking across saturated lawns and garden beds as this can be damaging to soils and root systems. Rake the lawn to remove leaves, twigs, and debris. If tree wraps were applied to trees last fall, remove them to allow for trunk expansion.

Begin inspecting plants regularly for disease and pest problems.
Contact the Plant Clinic for advice on identification and management of these problems. The sooner a problem is detected, the easier it is to manage. Dormant oil can be used when temperatures remain above 40°F, but this product is not for use on all pests. Check the label. For trees and shrubs that need treatment with a fungicide, the time to treat most problems is at bud break, when buds begin to swell and open. When buying new plants, consider disease-resistant varieties that don’t need treatment.

Crabgrass preventers are available in stores, but it may not be time to apply them.
Crabgrass will not start to germinate until soil temperatures have been above 55℉ for five to seven consecutive days. Many crabgrass preventers only last about 60 days, so apply them as soil temperatures start to get into the 50s. Redbud is a good indicator tree. Crabgrass germination begins around the time redbuds are in full flower, so put the preventer down while redbud flowers are still closed.

Some shrubs can be pruned in mid- to late spring.
Prune summer-flowering shrubs, such as panicled hydrangea, snowberry, winterberry, and rose of Sharon, before new growth begins in spring. Prune spring-flowering shrubs, such as forsythia, viburnum, and lilac, immediately after flowering ends. Evergreen shrubs can be pruned just before new growth begins (look for buds to start swelling). Evergreens often start their new growth later than many deciduous shrubs.

Avoid pruning oaks and elms between mid-April and mid-October.
Oak wilt and Dutch elm disease are spread by insects carrying these diseases from tree to tree. Fresh pruning cuts can attract these insects. Be aware that this time frame may change a little from year to year, depending on weather. The spring end of that time frame could hold danger if a very warm spring brings insects out of dormancy early.

When soil temperatures warm and the soil has thawed and is not too wet, you can:

• Prepare new planting beds by working organic matter, such as compost, into the soil.
• Replenish mulch around trees and shrubs to a depth of 3 to 4 inches, keeping it away from trunks. Apply 1 to 2 inches of mulch around perennials. This reduces weeds, conserves moisture, and controls temperature fluctuations in soil. Don’t mulch soils that are cold or wet.

Planting can begin when soils warm and dry out a bit.

• Dig and move trees and shrubs prior to bud break.
• Begin planting trees, shrubs, and perennials.
• Divide and transplant perennials.
• Plant a tree in celebration of Arbor Day!

Fertilize trees and shrubs, if needed.
Apply fertilizer to trees and shrubs no more than once a year, either in spring, as new growth begins, or in autumn when plants go dormant. Fertilizer only addresses the tree’s need for nutrients. It will not compensate for other problems. A soil test will indicate a nutrient deficiency.

Pull weeds early, before they flower and go to seed.
Avoid deep cultivation around shallow-rooted plants. Pull weeds by hand when they are small, or cut them off at the surface with a sharp hoe.

Deadhead spring bulbs when they are finished flowering to direct energy back into bulbs.
Do not remove foliage until it dies back naturally. The leaves produce food for the bulb.

Stake tall and floppy perennials early, as they begin to grow.
Grow-through support rings and cages allow the plant to grow up through the support and then hide it for a tidier garden.

Plant annual flowers and summer bulbs after all danger of frost has passed.
Keep an eye on the weather, rather than relying on traditional calendar dates such as Mother’s Day. While mid-May is often thought of as the average last frost date, our changing weather often gives us frosts or freezes as late as the end of May.

Early to Midsummer

Water trees, shrubs, and flower beds thoroughly if rainfall is less than one inch per week.
Water the soil and not the foliage to reduce leaf spot diseases.

Monitor container plants daily for watering needs.
Many containers may need to be watered daily, due to their small volume.

Limit pruning in summer for most plants.
Maple, birch, and black walnut are bleeders (lose excess sap) when pruned in spring. While the very cold days of winter are the best for pruning these species, early summer, when the trees have leafed out fully, is another good time to prune them. Water sprouts and suckers can also be removed from fruit trees and ornamental flowering trees now.

Avoid pruning oaks and elms between mid-April and mid-October.
Oak wilt and Dutch elm disease are spread by insects carrying these diseases from tree to tree. Fresh pruning cuts can attract these insects.

Pull weeds early, before they flower and go to seed.
Avoid deep cultivation around shallow-rooted plants. Pull weeds by hand when they are small, or cut them off at the surface with a sharp hoe.

Plant summer flowering bulbs and annuals in early summer when danger of frost is completely over.

Start pinching garden mums when they are about six inches tall. This produces shorter, fuller plants.
Stop pinching after mid-July so plants can set flower buds.

Remove faded flowers (deadhead) from annuals and perennials to encourage more flowers.

In midsummer, pinch back leggy annuals and perennials.
Annuals will produce more flowers. Perennials will respond with new growth for a fresh look, and some may produce new flowers.

Divide and replant irises after flowering ends. Discard any plants that show signs of insects or disease.

Monitor all plants regularly for insect and disease problems.
Early detection can make a difference for pest and disease problems. Contact the Arboretum’s Plant Clinic for proper identification, diagnosis, and management of plant problems.

Late Summer

Monitor rainfall with a rain gauge.
Keep plants well-watered during times of heat or drought, especially newly planted trees and shrubs.

Continue to remove faded flowers and pinch back leggy growth on flowering plants.

Don’t fertilize or prune trees and shrubs now.
Fertilizing or pruning may stimulate new growth that will not have time to harden off before winter. Fertilizer may further stress roots dealing with the dry soils of late summer.

When temperatures moderate in late summer, it is a good time to establish a new lawn or to overseed bare spots.

Late summer into early autumn is a good time to divide perennials that bloom in the spring and summer.
Be sure to water newly divided perennials to help them establish new roots.

Plant perennials in the late summer through mid-autumn.

Continue regular weeding and monitoring for insect and disease problems.

Order spring-flowering bulbs to plant this fall.

Harvest flowers, such as strawflower, statice, and celosia for drying.
Hang upside down in a dry, well-ventilated area out of direct sunlight.

Continue to maintain perennials.
Remove and discard dead and diseased foliage to reduce infection next year.

Birds are beginning to migrate south.
Restock bird feeders and put out fresh water to help them on their long journey.

Early Autumn

If the autumn weather is dry, continue to water plants thoroughly.
Continue to water through autumn, until the soil freezes. Evergreens, in particular, will benefit from watering in autumn.

Plant spring flowering bulbs in the early part of autumn.
The soil is still warm so the bulbs can form roots. Be sure to water the bulbs to encourage rooting.

Bring houseplants indoors before night temperatures drop below 55°F.
If plants look overgrown, repot them into a container one size bigger than the current one. Watering needs may change as plants transition from the outside environment into the home environment.

Protect tender plants and annuals from light frosts by covering them with sheets or light tarps on nights when frost is predicted.
Be sure to uncover plants the next morning when temperatures rise.

Continue to mow the lawn as needed.

Dig summer bulbs such as dahlias, gladiolus, and cannas, after the first frost or as their foliage dies back, whichever comes first.
Discard tops and store bulbs, corms, and rhizomes in dry peat moss or vermiculite.

Tidy flower beds by removing faded flower heads and cutting back dead stems from perennials.
Refresh annual flower beds by replacing summer annuals with cold-tolerant annuals, such as pansies and ornamental cabbages.

Start a compost pile.
Add plant debris such as leaves, lawn clippings, and garden plants. Discard heavily diseased and infested foliage.

Autumn is a good time to prepare for a new flower bed.
Turn soil and amend if necessary. Freezing and thawing over winter makes soil more friable.

Mid-Autumn to Midwinter

Force spring bulbs in containers inside to enjoy a little bit of spring in February.

Fertilize trees and shrubs, if needed.
Apply fertilizer to trees and shrubs no more than once a year, either in spring, as new growth begins, or in autumn when plants go dormant, but the soil is still warm. Fertilizer only addresses the tree’s need for nutrients. It will not compensate for other problems. A soil test will indicate a nutrient deficiency. Plants fertilized in autumn will store fertilizer in roots and strengthen the tree overall. Wait until spring to fertilize evergreens.

Empty plants from containers.
Bring delicate containers indoors to prevent breakage from alternating freeze and thaw cycles.

Rake fallen leaves, add them to a compost pile, or shred with a lawnmower.
Place leaves around landscape plants as protective mulch for winter.

Cut back foliage of perennials to the ground after a few hard freezes, if you choose.
You can also choose to leave the plant material in place until spring to provide food and shelter for birds or insects and create winter interest.

Apply winter mulch, if needed, to perennials as the ground begins to freeze.

Drain and store garden hoses.

Store garden chemicals in an area above 40°F.
Keep out of reach of children and animals. Do not store near food.

Construct a cylinder of hardware cloth, chicken wire, or fencing around plants to protect against rabbits, mice, and other small animals that damage the bark and twigs of plants.

Prune dead, diseased, crossing or rubbing branches anytime.
Remove water sprouts and suckers now, too.

Prune some trees and shrubs.
The dormant season is a good time to prune many species (see exceptions below).
Don’t prune spring-flowering plants until after they flower, or you will remove flower buds for the coming spring.

Prune birch, maple, and walnut trees during the coldest part of winter.
These trees “bleed” sap if they are pruned when temperatures are warming.

Prune elm and oak trees from about mid-October through mid-April.
The insects that can spread Dutch elm disease and oak wilt are dormant during this time. Be aware that this time frame may change a little from year to year, depending on weather. The spring end of that time frame could hold danger if a very warm spring brings insects out of dormancy early.

Clean, sterilize, sharpen, and repair all garden tools before storing.

Protect multistemmed evergreens, such as upright arborvitae, junipers, and yews, from heavy snow or ice damage during a winter storm by tying trunks or branches together loosely with strips of cloth or coated twine.
Be sure to remove the cloth or twine in spring.

Keep road and sidewalk ice melters away from plants.
Shovel snow away from plants and don’t pile snow with ice melter in it onto your garden.

Uncover plants weighed down with heavy snow.
Gently brush snow off branches to prevent breakage. If the snow is frozen, let it melt naturally.