Knowing when to plant flowers in Utah is the key to a vibrant, successful garden. Our state’s unique climate, with its late spring frosts and early autumn chills, makes timing everything. Get it right, and you’ll be rewarded with a stunning display of color. Get it wrong, and you might be replanting. This guide will walk you through the best planting times for annuals, perennials, and bulbs across Utah’s varied zones.
When to Plant Flowers in Utah – Best Planting Times for
Utah’s planting schedule is primarily dictated by the average last frost date in spring and the first frost date in fall. These dates can vary by several weeks depending on your specific elevation and location. For most of the Wasatch Front, the last frost is around May 1-15. In warmer areas like St. George, it can be as early as April. In cooler mountain valleys, wait until late May or even early June.
Understanding Utah’s Planting Zones
Utah spans USDA Hardiness Zones 4 through 9. This is a huge range! Your zone determines which plants will survive your winter and informs your planting calendar.
- Zone 4-5 (High Elevations, Northern Utah): Short growing season. Last frost late May to early June. First frost early September.
- Zone 6-7 (Wasatch Front, Most Populated Areas): Moderate season. Last frost early to mid-May. First frost early October.
- Zone 8-9 (Southern Utah, Washington County): Long, warm season. Last frost early April. First frost late October or November.
Always check plant tags for zone hardiness. A plant rated for Zone 7 will likely not survive a Zone 5 winter without special care.
Spring Planting Schedule for Annual Flowers
Annuals, like petunias and marigolds, complete their life cycle in one season. They are typically planted after the danger of frost has passed. For tender annuals, planting too early is a common mistake.
- Hardy Annuals (Pansies, Snapdragons): These can tolerate light frosts. You can plant them 2-4 weeks before the last frost date, often in early to mid-April for Zone 7.
- Half-Hardy Annuals (Alyssum, Calendula): Plant them a week or so before the last frost date.
- Tender Annuals (Zinnias, Impatiens, Basil): Wait until 1-2 weeks after the last frost date. For Salt Lake City, this is usually around mid-May. In St. George, you can start in late April.
Step-by-Step: Preparing for Spring Planting
- Test Your Soil: Utah soils are often alkaline and clay-heavy. A simple test can tell you if you need to add sulfur or gypsum.
- Amend the Soil: Work in 2-3 inches of compost or well-rotted manure. This improves drainage and adds nutrients.
- Harden Off Seedlings: If you started plants indoors or bought them from a greenhouse, acclimate them to outdoor conditions over 7-10 days.
- Plant on a Cloudy Day: This reduces transplant shock. Water them in thoroughly with a starter fertilizer.
Fall Planting: A Secret for Perennials & Bulbs
Fall is actually an excellent time to plant many flowers in Utah. The soil is warm, the air is cool, and autumn rains help with establishment. This gives plants a head start for the following spring.
- Spring-Blooming Bulbs (Tulips, Daffodils): Plant these in fall, about 6-8 weeks before the ground freezes. For most areas, aim for late September through October. This allows them to develop roots before winter.
- Perennials (Coneflower, Russian Sage): Planting in early fall (September) gives perennials time to settle in. Avoid planting to late, as they need a few weeks to root before hard frosts.
- Wildflower Seeds: Sow native wildflower seeds in late fall. The freeze-thaw cycles of winter help break seed coats for better germination in spring.
Best Planting Times for Popular Utah Flowers
Here’s a quick-reference calendar for common garden favorites. Remember to adjust for your specific zone.
For Early Spring Color
- Pansies & Violas: Plant early spring (March-April) or in fall for early spring bloom.
- Spring Bulbs (Crocus, Hyacinth): Plant bulbs in fall. They will emerge and bloom as soon as the snow melts.
For Summer-Long Blooms
- Cosmos & Zinnias: Direct sow seeds or plant transplants after last frost (mid-May). They thrive in heat.
- Daylilies & Coreopsis (Perennials): Plant in spring or early fall. They are drought-tolerant once established.
For Fall Interest
- Mums (Chrysanthemums): For best winter survival, plant hardy garden mums in spring so they establish roots. Potted mums sold in fall are often treat as annuals.
- Ornamental Grasses: Plant in spring or early fall. They provide texture and movement in the autumn garden.
Special Considerations for Utah’s Climate
Our dry air and intense sun present unique challanges. Smart planting goes beyond just dates.
- Water Wisely: Water new plantings deeply and regularly. The goal is to encourage deep roots. Morning watering is best to reduce evaporation.
- Mulch is Essential: Apply a 2-3 inch layer of mulch (wood chips, bark) around plants. This conserves moisture, suppresses weeds, and moderates soil temperature.
- Sun Exposure: Pay close attention to sun requirements. A “full sun” plant in humid climate might appreciate afternoon shade in Utah’s intense high-desert sun.
- Soil pH: Many Utah soils have a high pH. If you’re growing acid-loving plants like blueberries or some hydrangeas, you’ll need to amend the soil significantly.
FAQs: Planting Flowers in Utah
What month is best to start planting flowers in Utah?
It depends on the flower. For hardy annuals and perennials, April is often a good start. For tender summer annuals, wait until mid to late May to avoid frost damage. Fall planting in September is ideal for many perennials and spring bulbs.
Can you plant flowers before the last frost?
Yes, but only certain hardy varieties like pansies, snapdragons, and sweet peas. Always check the plant’s tolerance. Most common bedding plants cannot handle frost.
When should I plant perennials in Utah?
The best times are early spring (after the ground thaws) and early fall (September). Fall planting allows them to focus on root growth without the stress of summer heat.
Is it to late to plant flowers in July?
For most perennials, July is too hot and stressful for planting. However, you can still plant fast-growing annuals from containers, like marigolds or zinnias, if you keep them well-watered. It’s also a good time to start planning your fall bulb order.
How do I protect my flowers from a late Utah frost?
Keep old sheets, frost cloth, or even cardboard boxes handy. Cover tender plants before nightfall when a frost is forcasted. Uncover them in the morning once the temperature rises.
Successful gardening in Utah is all about working with our distinct seasons. By following these planting windows and preparing your soil properly, you can create a resilient and beautiful flower garden. Remember to keep a simple garden journal each year, noting what you planted and when. This personal record will become your most valuable tool for perfecting your timing season after season.