As winter fades and spring arrives, several things can be done to prepare the garden for the upcoming growing season.
Clean-up Perennial Beds
If you left the plant debris and leaves in the perennial garden all winter (a good idea), then spring is the time to do some clean-up.
Typically, perennial garden clean-up in Iowa can start in late March through April. Some beneficial and native insects overwinter in the plant debris (others overwinter in the soil). Wait until temperatures are consistently at 50°F before removing spent plant material to protect these insects. The magnitude of waiting to clean up on population size is not yet well-known. Early research shows that it has a relatively small effect on insect populations, so if you can’t wait, don’t fret. But if you can wait, every little bit helps!
Removing dead foliage and any accumulated leaves from plant crowns can help prevent smothering. This material can be removed from the garden bed and placed in the compost pile or simply pulled aside to the spaces in between the plants allowing it to become an informal mulch. Remove also the mulch "blankets" added last fall to newly planted perennials or those that easily frost-heave. Sometimes this has to be done in stages as the upper layer will thaw but the lower layer may still be frozen.
As you work in the garden, be careful not to damage any newly emerging foliage, especially from spring bulbs and other early emerging perennials like catmint, daylily, columbine, and poppy. Never work in the garden when the soil is wet as it can cause a lot of soil compaction.
This is a great time to add any stakes, trellis, rings, or other support structures needed for certain perennials like peonies so plants can grow through them. Don't forget to weed while you clean up. It's best to get those newly emerging weeds early while they are still small and easy to pull.
Refresh Garden Borders
Winter can heave edging and turf and weeds can encroach on the garden border over time. It is easier to clean up bed borders before perennials are big. Reset edging materials and re-cut sod to create a nice clean edge. This is also a great time to enlarge the bed to make room for the growing garden if needed.
Divide & Transplant Perennials
As the perennials are just emerging from the ground is a great time to divide or move them. At this stage, it is easy to see where the plants are located, and there is no foliage in the way. It also allows for plants to grow out symmetrically, avoiding that "one-sided" perennial look for the rest of the growing season that happens when you dig and divide later in the growing season.
Lay Down a Fresh Layer of Mulch
Early in the spring, just before or just as perennials emerge (or after you've transplanted and divided the plants), is a perfect time to refresh the mulch layer. It is easier to spread mulch without the foliage getting in the way. Just don’t bury plant crowns.
It is typically best to wait until the ground starts to warm and the perennials are just emerging, as putting down a layer of mulch too early can further insulate the ground and slow plant emergence. Plus, the mulch pile may still be frozen anyway!
Fertilize Where Needed
Most perennial gardens in Iowa do not need a lot of fertilizer. A soil test will tell you where and how much may be needed. In spring as the new growth emerges is the best time to apply fertilizers around the base of perennials. Use an all-purpose fertilizer and lightly work it in the top layer of soil.
Go Plant Shopping
One of a gardener's favorite things about spring is shopping for new plants! Start shopping, online or in-person, at the greenhouse or garden center early for the best selection.
Be sure while shopping that you don’t only buy the plants that look good right now (in spring). Make a special effort to purchase perennials that bloom in summer and fall so your garden has color and interest all growing season.
Learn more about selecting high-quality perennials in this article: Tips for Shopping and Selecting Quality Plants.
Plant New Perennials
Spring is a great time to add new plants to your perennial border. Plants may need to be hardened off before planting earlier in spring, especially if grown in a greenhouse.
Bare root perennials are an economical way to add new perennials to your garden. Learn more about planting bare root perennials in this article: Planting Bare Root Plants.
All newly planted perennials should be regularly watered during the first growing season. Check frequently (several times a week) at first. Water only when the root zone is dry. As the season goes along you can reduce the frequency you check the soil moisture.
Conduct a Soil Test
As soon as the soil can be worked (and isn’t too wet), collect samples and submit them to a soil testing lab. Soil samples should represent areas managed similarly or where the same crops/plants are grown. Be sure to conduct separate tests for your vegetable garden, perennial border, or lawn (and not mix them together).
The soil testing lab will provide instructions on how to collect the sample. When you receive results from the lab, it will give fertilizer recommendations if needed.
More information on collecting and submitting a soil sample for testing can be found in this article: Soil Testing Resources for Home Gardeners.
Start Seedlings Indoors
Mid-March is the best time to start many vegetables indoors for transplanting outside once the threat of frost has passed. Regardless of what type of seed you're growing, to have the best success, follow these basic tips:
- Start with fresh seeds and clean materials.
- Consult the package to determine how early to start the seed indoors - do not start the seed too early.
- Use clean containers and germination mix
- Provide warm, humid conditions for germination
- Provide ample light – If needed, add supplemental light from a fluorescent or LED fixture
- Do not over-water!
- Harden off all transplants before putting them outside
Learn more about starting seed from this article: Guide to Starting Seed Indoors.
To Till or Not To Till?
In general, fall tilling is preferred to tilling in the spring. For most home gardeners with average-sized gardens, a light tilling is all that is needed in spring – simply turn soil with a fork, shovel, hoe, or rake. This will only minimally disturb soils allowing you many of the advantages of tilling, without many of the disadvantages.
Never till soil when it's wet, as it will lead to compaction. Soil that is too wet will stick to tools, tines, or shoes and will maintain a ball instead of crumbling when squeezed.
While preparing the soil is the perfect time to add organic matter. Empty the compost bin and incorporate it into the vegetable garden soil.
Plant Cool-Season Vegetables
April is the time to plant cool-season vegetable crops. Cool-season crops can tolerate light to moderate frosts but are often intolerant of high summer temperatures. Listed below are common cool-season crops. Direct seeding of most cool-season crops can be done with the exceptions of broccoli, cabbage, cauliflower, and Chinese cabbage which would be better started by transplants.
- Chinese cabbage
- mustard greens
- Swiss chard
While not a cool season crop, potatoes should also be planted in mid-April. More information about growing potatoes can be found here: Potatoes.
Set-up Irrigation Systems
Vegetables will need irrigation at some point during the growing season to produce well. In some years, irrigation is needed more than others. Before plants are large is a great time to set up soaker hoses or trickle irrigation systems in the vegetable garden for use later in the summer.
Start Seedlings Indoors
Mid-March is the best time to start many annual flowers indoors for transplanting outside once the threat of frost has passed. Regardless of what type of seed you're growing, to have the best success, be sure to start with fresh seed, plant in clean containers, provide warm and humid conditions for germination, and provide ample light after germination.
Learn more about starting seed from this article: Guide to Starting Seed Indoors.
Plant Cool-Season Annuals
Consider planting cool-season annuals to introduce color and interest early in the spring season.
Plant cool-season annuals mid-March through early April, depending on the weather conditions.
Popular cool season annuals include pansy, ornamental cabbage and kale, snapdragons, stock, sweet alyssum, and pinks, among others.
Prune Most Trees and Shrubs While Dormant
Late Winter/early spring is the ideal time to prune nearly all woody plants. The focus of pruning should be on removing damaged, diseased, or dead material first. Then, remove rubbing, crossing, and structurally deficient branches (like double leaders). Finally, remove those branches that improve appearance.
Learn more about all things pruning, including tips, timing, tools, and techniques, in this article: Your Complete Guide to Pruning Trees and Shrubs.
Remove Winter Protection
Young trees and shrubs benefit from protection from harsh winter conditions. Sunscald and animal damage can be prevented when woody plants are wrapped or "caged" with fencing or other materials. These protective measures need to be removed in spring to prevent damage like girdling.
More information about protecting trees and shrubs in winter can be found in this article: Winter Damage on Trees.
Remove Staking on Young Trees
Many newly planted trees are staked to provide some support while new roots are establishing. These materials easily cause abrasion to the stem and can potentially girdle the trunk when left on too long. The first spring after planting is a great time to evaluate the continued need for support staking. Remove the stakes as soon as possible. In most cases, stakes can be safely removed after one growing season.
More information on staking young trees can be found in this article: Care of Newly Planted Trees.
Propagate Woody Plants by Hardwood Cuttings
Propagation by hardwood cuttings is the best form of propagation for several trees and shrubs like willow, poplar, dogwood, forsythia, grape, and gooseberry. Hardwood stem cuttings are collected in late winter (when the plant material is dormant) from the wood of the previous season's growth. In Iowa, hardwood stem cuttings should be collected in late February or early March.
Learn more about propagating by hardwood cuttings in this article: Propagating Woody Deciduous Plants by Hardwood Stem Cuttings.
While not common, sometimes shrubs need to be moved in the landscape. Early spring, before the growth begins but after the ground has thawed, is the best time to transplant deciduous shrubs.
Learn more about transplanting woody shrubs in this article: Transplanting Deciduous Shrubs.
Forces Branches into Bloom Indoors
A wonderful way to brighten up the last few weeks of winter is by forcing branches of flowering trees and shrubs indoors. Forsythias, pussywillows, serviceberries, crabapples, magnolias, redbuds, and many fruit trees can be coaxed into early bloom indoors.
Learn more about forcing branches in this article: How to Force Branches of Spring-Flowering Trees and Shrubs.
Fertilize and Apply Amendments Where Needed
Most woody plants in the Iowa landscape do not need much fertilizer. A soil test will tell you where and how much may be needed. In spring as new growth emerges is the best time to apply fertilizers around the base of shrubs and roses. Use an all-purpose fertilizer and lightly work it in the top layer of soil.
Spring is also a good time to apply sulfur to the soils around acid-loving plants such as azaleas and rhododendrons to help lower the pH of the soil. A soil test will tell you if the pH is too high. Acid-loving shrubs typically want a soil pH between 5.5 and 6.0.
More information about soil pH can be found in this article: How to Change Your Soil's pH.
Plant New Trees & Shrubs
Spring is a great time to add new plants to your landscape. Containerized and balled and burlapped (B&B) woody plants can be planted at any point in spring.
Bareroot trees and shrubs are an economical way to add new plants to your landscape. Learn more about planting bare root trees and shrubs in this article: Planting Bare Root Plants.
All newly planted plants should be regularly watered during the first growing season. Check frequently (several times a week) at first. Water only when the root zone is dry. As the season goes along you can reduce the frequency you check the soil moisture.
Learn more about planting and caring for newly planted trees in this article: Planting Trees in the Landscape.
Clean-up Winter Debris
In late March or early April, once the snow has melted, rake and remove leaves, twigs, and other debris from the lawn that accumulated over winter. This is also a great time to clean up lawn edges around perennial borders, sidewalks, and driveways.
Prepare the Mower and Sharpen the Blades
Spring is the best time to service the engine to ensure the mower runs smoothly and a great time to clean the mower deck.
Spring is also the best time to sharpen the blades to ensure it cleanly cuts the lawn. Dull mower blades make the engine work harder and tear or rip grass blades rather than cleanly slicing them. The ragged edge of a grass leaf cut with a dull mower blade will turn brown and allow some disease pathogens to infect the leaf more easily.
There is no set date to start mowing. It will depend on the growing conditions and the type of grass growing in the area. Most lawns will be ready to mow by mid to late April in much of Iowa. Set mowers to cut at 2 to 3” in height and mow once the grass reaches 3 to 4” tall, so you never remove more than one-third of the leaf blade in a single mowing. Mowing will need to be done frequently as the cool-season lawns in Iowa love the cool spring temperatures and abundant spring rains.
Learn more about mowing lawns in this article: Mowing Your Lawn.
Seeding the Lawn
Late summer/fall is the best time to start new lawns from seed, so don’t renovate any lawn areas in spring. However, any bare spots in the lawn in spring will be full of weeds by summer if left unmanaged. Seed any bare spots in early April.
More information about seeding lawns can be found in this article: Seeding a New Lawn.
Apply Preemergent Herbicides
Spring is the best time to apply preemergent herbicides for crabgrass and other summer annual weeds. The timing of the application is essential. If applied too early, the product washes away before it can be useful. Since preemergent herbicides disrupt the germination process, they will not work effectively if applied too late. Apply herbicide for crabgrass control just before soil temperatures reach 55°F. This is usually about when the forsythia finishes blooming (although not always), which is mid to late April in most of Iowa.
Don’t apply other broadleaf herbicides in spring, as they will not be very effective (and a waste of money). Fall is the best time for broadleaf weed control using herbicides. Hand-pull weeds as needed and make plans to treat for weeds appropriately in the fall.
Learn more about weed control in home lawns in this article: Weed Control in Home Lawns
Aerate the Lawn
Aerification helps reduce compaction and thatch, and it promotes better growth of the turfgrass. September or April are the best times to core aerate lawns in Iowa. Most lawns will only need aerification once a year. If done in the spring, aerify while the grass is actively growing and before preemergence herbicides are applied.
Learn more about aeration in this article: Core Aeration for Lawns
Many Lawn Tasks are Best Done in the Fall
Seeing the lawn green up in spring can make you excited to get out and work on the lawn, but many common lawn tasks (apart from mowing) are best done in late summer and early fall.
Learn more about what you can do in the fall to promote healthy lawns in this article: Fall Tips to Ensure a Healthy Green Yard in the Spring.
Repot Potbound Houseplants
Potting or repotting can be done any time of the year, although most gardeners have the best success doing it in late winter or early spring, as houseplants start growing more vigorously with the warmer temperatures and longer days of spring.
Evaluate your houseplants and repot those plants that need it. Most houseplants prefer a root ball in slightly cramped quarters, so frequent repotting is not always needed. You will know it's time to repot when plants become top-heavy, growth slows, and/or potting soil quickly dries out.
When repotting, only move up a size, maybe two. Houseplants do not benefit from moving from super cramped quarters to enormous pots. Pick broad, wide-based pots for taller plants so they will be stable and less likely to tip. Get step-by-step instructions on repotting in this article: How to Care for Houseplants.
Propagate Leggy and Large Houseplants
When houseplants get large or more plants are desired, many can be easily propagated. Most houseplants can be propagated any time of the year, but early spring through summer tends to be the best time for the health of the propagules and the parent plant.
Many species easily propagate at home utilizing techniques like cuttings, division, and layering. Learn more in this article: Propagating Houseplants.
Move Houseplants and Tropical Plants Outside for the Summer
Many houseplants enjoy spending the warm summer months outside in a full or part-shade location. Wait until nighttime temperatures are consistently and reliably above 50°F before moving houseplants outdoors. In much of Iowa, this is mid to late May. It is important to acclimate houseplants to outdoor conditions to prevent leaf burn, discoloration, or drop.
Learn more about moving houseplants outside for the summer in this article: Moving Indoor Plants Outside for the Summer.
More information about other common tasks in the spring can be found at these links.