Dryland

Maintaining a xeriscape planting

A xeriscape bed is not a low-maintenance bed. It is a differently-maintained bed, and most of the ways it fails are maintenance failures rather than plant-selection failures. Plants chosen for very low water use will die from being watered on a lawn schedule. Shrubs that hold their shape for fifteen years will be ruined in one afternoon with hedge shears.

Maintenance splits cleanly into two jobs that are not the same job. The first three years are about getting roots down. Everything after that is about restraint. Treating year six like year one is the single most common way these plantings are lost.

Establishment: years one through three

Water deeply, not often

Water deeply every three to four days rather than lightly every day. The goal is to saturate the soil ten or more inches down, in the dripline area where the feeder roots run, so that roots grow down instead of sideways at the surface. Shallow frequent watering produces a shallow root system and a plant that cannot survive a missed week. (OSU Extension, EM 9136, Step 2.)

Check the soil instead of guessing

There is no correct number of minutes. Runtime depends on your soil, your emitters, and your pressure, and any figure published without knowing those is a guess. Use the soil itself as the gauge: before you irrigate, dig down eight to ten inches in the dripline with a hand trowel and read the soil you pull out. Dry and crumbly means increase output. Soggy means cut back. Soil that holds together in a ball in your palm means you are close to right. (OSU Extension, EM 9136, Step 2.)

Water in winter

This is the one nobody does, and it kills more new plantings in Central Oregon than summer drought. Plants desiccate over the winter. Water new plantings every six to eight weeks through the winter whenever the ground is warm enough to absorb water — most critical in a dry winter with little snow cover. (OSU Extension, EM 9136, Step 7.)

Leave new plants alone

New trees and shrubs need very little pruning. Remove what is dead, broken, or diseased and stop there. Structural shaping comes later, once the plant has told you what shape it wants. (OSU Extension, EM 9135.)

Mulch two to four inches, and no more

Two to four inches of mulch over the soil surface reduces evaporation, suppresses weeds, and moderates soil temperature. More than four inches starts to cut off oxygen to the root system and can kill roots outright. Keep it off the crowns and trunks. (OSU Extension, EM 9136, Step 6.)

Pull weeds before they seed

Weeds compete directly for the water you are trying to conserve. The work is front-loaded: pull them in the establishment years, before they set seed, and the bed gets quieter every season after. (OSU Extension, EM 9136, Step 7.)

Ongoing care: year three and after

Once established, most of a xeriscape bed wants supplemental water only in genuine drought, and one pass of pruning a year. What that pruning pass looks like depends entirely on how the plant grows, and getting this wrong is how good plants get ruined. The six groups below cover everything in the Dryland catalog.

Ornamental grasses

Cut the whole clump to the ground once a year — either in fall, which also stops the reseeders from reseeding, or in early spring, which leaves the seed heads standing for winter texture. Pick one and commit; do not do both. Never shear a grass part-way down: it will spend the season looking like a bad haircut, because the cut blade tips do not regrow. (OSU Extension, EM 9136, Ornamental grasses.)

Perennials

Cut back in early spring, before new growth breaks. Standing dead foliage over winter is not untidiness; it protects the crown and feeds birds. Deadhead through the season where you want a second flush or want to stop a heavy reseeder. (OSU Extension, EM 9136, Step 7.)

Deciduous shrubs that resprout

These renew themselves from the base and are close to indestructible. Prune in late winter or early spring. Take out dead wood first, then remove a portion of the oldest, thickest stems all the way to the ground each year, then take out anything crossing or heading back through the center. That is the whole job. Do not shear the outside into a ball; it produces a dense shell of twigs and a dead, bare interior. (OSU Extension, EM 9135; EM 9136, Step 7.)

Subshrubs and dieback shrubs

Russian sage, blue mist spirea, lavender, sagebrush, and their relatives are woody at the base and soft at the tips. They die back in winter and are cut back in late fall or early spring — Russian sage specifically tolerates either. (OSU Extension, EM 9136, Small shrubs.)

The rule that matters: cut into green, leafy growth, never down into bare gray wood. These plants do not reliably push new growth from old wood, and a hard cut into the woody base is a cut you may not get back. Leave a band of green above the wood on every stem. If a plant has become almost entirely bare wood with a thin fringe of green on top, it is at the end of its useful life and should be replaced rather than rescued.

Conifers and broadleaf evergreens

Prune conifers in late fall or winter. Fresh cuts made in the growing season attract sequoia pitch moth, which is not in flight in winter. (OSU Extension, EM 9136, Step 7.)

Prune sparingly. Junipers, pines, and their relatives do not regenerate from wood that has no foliage on it, so anything cut back past the green stays bare permanently. Never strip the side branches off a mature conifer, and never shear one into a shape it does not naturally hold.

Trees

Prune for structure, not size — a tree that needs to be smaller was the wrong tree. Remove branches at the collar, the slight bulge where the branch meets the trunk, not flush with the trunk itself; cutting the collar off causes serious damage whether the branch was living or dead. Any branch over about an inch and a half comes off in three cuts: an undercut about a foot out, a second cut a few inches beyond it to drop the limb, then a final cut to remove the stub. Never top a tree. (OSU Extension Master Gardener, Pruning Trees and Shrubs.)

How to kill this planting

Every one of these is common, and every one of them is avoidable.

  • Keep watering it on a lawn schedule. Very low and low water-use plants are adapted to drying out between soakings. Frequent shallow irrigation after establishment rots crowns and produces weak, shallow-rooted plants. This is the most common failure in a young xeriscape.
  • Pile mulch deeper than four inches, or heap it against the trunk. Deep mulch suffocates roots. Mulch against a trunk or crown holds moisture where the plant least wants it.
  • Shear the subshrubs. One pass with hedge shears into the bare wood of a Russian sage or a sagebrush and the plant does not come back.
  • Prune the conifers in June. Fresh growing-season cuts are an invitation to sequoia pitch moth.
  • Skip winter watering the first three years. Plants that came through a hot August fine will desiccate in a dry, snowless February.
  • Overfertilize. Overfertilization stimulates growth and increases a planting's water needs. OSU allows a single slow-release application in spring or early summer; more than that, or later than that, works against everything else on this page. (OSU Extension, EM 9135.)

Sources

Guidance here is general and class-level. Soil, exposure, and microclimate vary enough across the Intermountain West that no page can replace looking at the actual plant in front of you.

Your palette

No plants pinned yet.

Open my palette