Spring in Northern Colorado is an exercise in patience. One day it is 70 degrees and sunny; the next, we wake up to six inches of snow. For native garden owners, this erratic weather creates a real dilemma: when do you start cleaning up? Cut back too early and you expose tender new growth to a late frost. Wait too long and you are fighting through a tangled mess while your plants are already pushing up.
After a decade of managing native gardens in Fort Collins, Loveland, and Windsor, I have landed on a simple rule: wait until you see three consecutive nights above 35 degrees and at least two inches of new green growth at the base of your perennials. In our area, that usually happens between mid-March and early April, depending on the year. Do not go by the calendar. Go by what you see.
What to Cut Back First
Ornamental grasses are your first priority. Grasses like Blue Grama (Bouteloua gracilis), Little Bluestem (Schizachyrium scoparium), and Prairie Dropseed (Sporobolus heterolepis) should be cut to about four to six inches above the ground. Use hedge shears or a power trimmer for large clumps. The key is to cut before new growth reaches more than a few inches tall, because once those bright green blades appear, cutting through them damages the plant and looks rough for weeks.
Perennials come next. Most native perennials like Purple Coneflower (Echinacea purpurea), Black-eyed Susan (Rudbigckia hirta), and Blanketflower (Gaillardia aristata) can be cut to about two to three inches above the soil line. Do not pull on old stems — always cut cleanly. Pulling can uproot shallow root systems, especially in our heavy clay soils.
What to Leave Alone
This is where people make mistakes. Do not cut back anything that is still green from last fall. Evergreen-ish perennials like Lavender Hyssop (Agastache foeniculum) and some Penstemons may still have live foliage at the base. Leave that alone and just remove the brown flower stalks above it.
Also leave your leaf litter and mulch layer intact. In native gardens, the duff layer — that spongy mix of decomposed leaves and organic matter — is doing critical work. It insulates roots, retains moisture, feeds soil biology, and provides overwintering habitat for native bees and beneficial insects. I know it looks untidy, but resist the urge to rake it all out. Just remove any thick, matted layers that are smothering new growth.
Dividing and Transplanting
Spring is the ideal time to divide many native perennials. If your Black-eyed Susans have formed a dense, dying-out center with all the growth around the edges, that is a classic sign they need dividing. Dig the entire clump, split it into sections with a sharp spade, discard the dead center, and replant the healthy outer divisions. Water well and they will establish quickly in the cool spring weather.
Grasses can also be divided now, but be aggressive — large clumps of Little Bluestem may need a reciprocating saw or an axe to split apart. It sounds violent, but these plants are tough. I have divided grasses with a chainsaw and had them thrive.
Soil Amendments and Mulching
Fort Collins soils are notoriously alkaline clay, with pH levels often between 7.5 and 8.2. Most Colorado natives are adapted to this and do not need soil amendments. In fact, adding compost or fertilizer to native plant beds can actually cause problems — it encourages the plants to grow tall and floppy, reduces flowering, and gives weeds a competitive advantage.
The exception is newly planted areas where the soil was severely compacted during construction. In those cases, working in two to three inches of composted wood chips (not bagged compost) can help break up the clay and improve drainage. But for established native gardens, skip the amendments and let the soil biology do its job.
For mulch, I recommend a two-inch layer of small wood chips or shredded bark around perennials, keeping it a few inches away from the crown of each plant. For grasses, I prefer leaving the soil surface exposed or using a very thin layer of pea gravel — grasses grow best with warm soil and good air circulation at the base.
Weed Prevention
The best weed prevention in a native garden is a dense, healthy plant community. But spring is when annual weeds germinate, and a few hours of hand-pulling in March and April can save you dozens of hours later in the season. Focus on pulling weeds before they set seed. The common culprits in our area are field bindweed, cheatgrass, kochia, and puncturevine.
Do not use pre-emergent herbicides in native plant beds. Most pre-emergents do not distinguish between weed seeds and the seeds of desirable native plants. If you have self-sowing natives like Coneflower or Prairie Sage, a pre-emergent will kill those seedlings too.
A Simple Spring Checklist
Here is my quick-reference list. Print it out and tape it to your garden shed: cut back ornamental grasses to four to six inches, cut back dead perennial stems to two to three inches, leave green basal foliage intact, do not remove the leaf litter layer, divide overcrowded perennials, hand-pull early weeds while they are small, check irrigation systems for winter damage, and skip the fertilizer. Your native garden does not need it.
Spring cleanup does not have to be complicated. The biggest mistake I see is people treating their native garden like a conventional landscape — raking everything bare, piling on amendments, and going heavy on the mulch. Native plants evolved in lean, undisturbed soils. The less you fuss, the better they perform. Give them a clean start, step back, and watch them do their thing.