If you've dug into your backyard in Kamloops or the Nicola Valley and pulled up thick, sticky, greyish soil that clings to your shovel — you've got clay. And if you've struggled to grow a decent garden in it, you're not alone.
The good news is that clay soil isn't the problem most people think it is. With a bit of understanding and the right approach, it's actually one of the more forgiving soils you can garden in. This guide covers everything you need to know about gardening in clay soil in the BC Interior — from what it is and why it behaves the way it does, to how to improve it, water it, fertilize it, and choose plants that will actually thrive in it.
What Is Clay Soil?
Clay soil is made up of very fine, flat particles that pack tightly together. Unlike sandy soil — which drains quickly and dries out fast — clay holds onto water and nutrients for a long time. That's both its biggest strength and its biggest challenge.
You likely have clay soil if:
- Your soil is heavy, sticky, and hard to dig when wet
- It bakes hard and cracks in summer
- Water pools on the surface and drains slowly
- It's reddish, orange, or grey in colour
Clay soils are common throughout the BC Interior, particularly in the Kamloops area and the Nicola Valley. The region sits on glacial deposits and fine-grained sediments that produce heavy, clay-dominant soils in many neighbourhoods and rural properties.
The Good News About Clay Soil
Before you reach for the nearest bag of sand (more on why that's a bad idea later), consider what clay soil actually does well.
It holds nutrients. Clay particles have a high capacity to hold onto fertilizers and minerals. That means less feeding, less leaching, and more nutrients available to your plants over time.
It retains moisture. In a climate like Kamloops — where summer temperatures regularly push past 35°C and rain becomes scarce by July — a soil that holds moisture is genuinely valuable. Clay soils need less frequent watering than sandy soils once plants are established.
It anchors roots well. Clay gives plants a firm grip. Perennials and shrubs planted in clay are less likely to heave during BC Interior freeze-thaw cycles and more resilient during drought.
The goal isn't to replace your clay soil — it's to improve its structure so it works with you rather than against you.
The Challenges of Clay Soil
Poor drainage. Clay's biggest problem is that water moves through it slowly. In wet conditions, roots can suffocate. In summer, it bakes into something closer to concrete.
Compaction. Clay compacts easily under foot traffic, heavy rain, and machinery. Compacted clay is hard for roots to penetrate and almost impermeable to water.
Slow to warm in spring. Clay holds onto moisture and takes longer to warm up than sandy soil — which can delay planting in early spring.
Difficult to work when wet. Working clay soil when it's saturated makes compaction worse. If your soil is sticking to your shovel, stop — wait until it's moist but not soggy before digging.
How to Improve Clay Soil
Add Organic Matter — Every Year
Compost is the single most effective thing you can add to clay soil. It improves drainage, loosens soil structure, feeds soil microbes, and acts as a slow-release fertilizer. Steer manure and mushroom manure are both excellent options and are available at Purity Feed.
Add 5–10cm of compost to the surface of your beds each spring or fall. You don't have to dig it all in — earthworms and soil microbes will work it down over time. Do this consistently and you'll see a real difference in soil texture within two or three seasons.
Peat Moss
Peat moss adds organic matter and helps open up clay structure. It's slightly acidic, which can be helpful in the BC Interior where soils tend to be alkaline. Mix it into beds along with compost for best results.
Gypite (Calcium Sulphate)
Gypite is particularly useful for BC Interior clay soils. It helps break up compacted clay particles without changing your soil's pH — which matters here where alkaline soils are common. Work it into the soil rather than leaving it on the surface for best results.
Bark Mulch
A layer of bark mulch on the surface of clay beds does double duty — it protects soil from compaction caused by heavy rain and foot traffic, and it slowly breaks down to add organic matter. Keep it a few centimetres away from plant stems.
What NOT to Add: Sand
Adding sand to clay is one of the most common mistakes gardeners make. A small amount of sand mixed into clay can create a dense, cement-like mixture that's actually harder to work with than straight clay. If you want to use sand to improve drainage, you'd need to add enormous quantities — far more than is practical for most gardens. Stick with organic matter instead.
How to Water Clay Soil
Overwatering is the most common cause of plant failure in clay soils. Because clay holds moisture for so long, many gardeners water far more than their plants need.
Water deeply but infrequently. Rather than frequent light watering, give your garden a deep soak and then let it dry out a little before watering again. This encourages roots to grow deep rather than staying near the surface — which makes plants more drought-tolerant and resilient.
Check before you water. Stick a finger or a soil probe 5–10cm into the ground. If it's still moist, wait. Clay soil often looks dry on the surface while holding plenty of moisture below.
Watch for pooling. If water is sitting on the surface for more than an hour after watering, you're applying it faster than the soil can absorb it. Water more slowly or in shorter cycles with breaks in between.
In Kamloops specifically: The combination of clay soil and hot, dry summers means you may be able to water less than you think — especially for established plants. Deep-rooted perennials and shrubs in clay often need surprisingly little supplemental water once they've been in the ground for a season or two.
How to Fertilize Clay Soil
Clay soils are naturally nutrient-rich, so you generally need less fertilizer than gardeners working with sandy soil. Over-fertilizing in clay can cause lush, soft growth that's more susceptible to pests and disease — and wastes money.
- Start at a lower rate than the package recommends
- Wait longer between applications and monitor how your plants respond
- If leaves are yellowing, increase slightly — if plants are healthy and growing well, you're doing fine
- Organic fertilizers and compost work particularly well in clay because they release nutrients slowly
Best Plants for Clay Soil in the BC Interior
Plant selection makes a big difference when you're gardening in clay. The following plants are well-suited to clay soils and perform reliably in Kamloops and Nicola Valley conditions.
Perennials
- Coneflower (Echinacea) — tough, long-blooming, attracts pollinators
- Daylily — nearly indestructible in clay, blooms reliably every summer
- Salvia — handles both clay and BC Interior heat well
- Phlox — beautiful summer bloomer that anchors well in clay
- Ornamental grasses — excellent structure, very low maintenance in clay
Shrubs
- Spirea — reliable, easy to prune, handles clay well once established
- Potentilla — a BC Interior staple, blooms all summer in full sun
- Viburnum — excellent structure and fall colour, adapts well to clay
- Rose of Sharon — late-summer bloomer that thrives in heavier soils
What to avoid in heavy clay: Plants that need excellent drainage — like lavender, rosemary, and many Mediterranean herbs — will struggle in dense, wet clay unless you build raised beds or significantly amend the soil first.
Starting a New Garden Bed in Clay Soil
If you're breaking new ground, here's a practical approach:
- Mark out your bed and remove grass or weeds
- Spread 10–15cm of compost or aged manure over the surface
- Add peat moss if your soil is particularly heavy
- Work all amendments into the top 25–30cm with a fork or tiller
- Rake level and water well before planting
- Mulch the surface with bark mulch to protect soil structure
Avoid working the soil when it's saturated — wait until it's moist but not sticky.
Improving an Existing Bed
If you're working with an established planted bed, top-dress with compost each spring. You don't need to dig it in — it will work its way down naturally. Over several seasons this gradual approach makes a noticeable difference without disturbing existing plants.
For individual new plants going into an existing clay bed, dig the hole two to three times wider and deeper than needed, mix plenty of compost into the removed soil, and backfill around the plant with that improved mix. The surrounding soil won't be perfect, but your new plant will have a great start.
The Payoff
Clay amendment isn't a one-season fix — it's an ongoing process. But every year you add organic matter, your soil gets a little better. After two or three seasons of consistent improvement, most BC Interior gardeners notice a dramatic difference in how their gardens perform: better drainage, easier digging, healthier plants, and less watering.
The same compost and manure improving your drainage is also feeding your plants — so you're solving two problems at once.
Get the Right Products at Purity Feed
We carry steer manure, mushroom manure, premium growing mixes, peat moss, bark mulch, and garden amendments at our Kamloops and Merritt garden centres. Our team has seen every type of BC Interior soil and can help you figure out the right combination for what you're growing.
Stop in and ask — advice is part of the deal.
📍 Kamloops — 471 Okanagan Way 📍 Merritt — 1690 Voght St Open Monday–Saturday, 8am–5pm