How to Start Summer Flowering Bulbs

Dahlias, Anemones, Ranunculus & More!

Anemone and ranunculus packages

The blooms from summer flowering bulbs like dahlias, ranunculus and anemones are perfect for bringing colour to the garden and creating cut flower arrangements. In our cooler climate where hard frost hits every fall, these beauties aren't perennial and must be planted every spring. Luckily the bulbs store well if properly cared for and can be replanted many years in a row. For early blooms, you can start summer flowering bulbs indoors 6-8 weeks before the last frost. This gives the bulbs time to wake up from dormancy and establish roots before transplanting out into the garden, and means you'll get a chance to enjoy their blooms for longer before the frost hits in the fall!

Dahlias, anemones and ranunculus produce stunning, colourful blooms and only require a small space and a bit of work to pre-sprout indoors Here are our step-by-step instructions to help get you on your way to growing your own bouquets! 

Starting Summer Bulbs - Equipment


Dahlia tuber and eye

Bulbs contain the energy stores and genetic material needed for a plant to sprout. The term bulb is often used as a catch-all to refer to any underground plant storage structure, but many are not technically true bulbs. Dahlias grow from tubers that also require a crown to be viable. Anemones and ranunculus grow from corms, which are another nutrient-storing body that are often flat and round in appearance. Many other bulbs, tubers, and corms can be pre-sprouted to get a head start on the growing season, including begonias and gladiolus.

When choosing a bulb, look for ones that are firm and show no signs of rot. A small amount of superficial surface mold is okay and will not impact the viability of the plant. With dahlia tubers, be sure your tubers have a neck and a crown. Eyes will develop on the crown, but tubers without a crown will not produce growth. 

Growing Materials 

- Cell sheets or small pots with drainage holes to hold your soil and bulbs. Anemones and ranunculus will fit easily in medium cell sheets, while some larger dahlias may require pots

- Tray without holes to hold your cell sheets or pots. Trays will catch excess water and provide a solid base for your cells or pots

- Sterile potting mix for planting

- Plastic dome, 4"-7" high, to retain humidity

- Container for soaking corms

Starting Summer Bulbs - Planting Instructions

Anemone and ranunculus corms soaking in water

Both anemone and ranunculus corms should be soaked prior to planting. Soak in room temperature water for 3-4 hours, until corms have nearly doubled in size. We recommend setting a timer as soaking too long can lead to rotten bulbs. 

Pre-moisten your potting soil before planting to ensure it is evenly hydrated and not too wet. Soil is perfectly saturated if a handful of soil retains its shape after being squeezed, with no excess water running out.

If reusing materials from a previous year, ensure they've been thoroughly cleaned to prevent the transmission of soil-borne fungi or disease.

Fill your cell sheets or pots about halfway full with a sterile potting mix. Your soil should be pre-moistened before planting and is the perfect consistency when it holds together when squeezed but does not contain excess water.

Plant anemone corms with the pointed end facing down, around 2" (5cm) deep. 

Ranunculus corm held above cell sheet filled with soil

Plant ranunculus corms so that their "tentacles" are pointing down, around around 2" (5cm) deep. 

Plant dahlias horizontally with the eye facing up and cover with soil, leaving the eye exposed.

Cover your tray with a high dome to keep the soil moist. Place your tray in a cool spot (5-10°C) for 2-4 weeks, checking every few days to ensure the soil has not dried out. Use a spray bottle to rehydrate the surface of your soil if it does become dry, and remove the dome for a few hours or days if your soil becomes too moist. Remove any corms that show signs of rotting or mold.

Once sprouted, your corms can be gradually hardened off to acclimatize to outdoor conditions. Hardening off is the gradual process of slowly exposing plants grown indoors to outside conditions. As a general guideline, plants will be okay outside when the temperature is warm enough that you're comfortable in a t-shirt. Start on a mild day and place your trays outside for about an hour, then bring them back in for the rest of the day. Increase the amount of time they spend outside each day until they're ready to move outside permanently. For the first week, keep your sprouted bulbs out of direct sunlight and strong wind and don't move them outside if the weather is harsh. 

Starting Summer Bulbs - Transplanting and Care

Planted dahlia tuber with green sprouting leaves

Finally, when the risk of frost has passed your sprouted corms can be planted out into a prepared garden bed! We recommend amending your beds with a mix of composted organic material, fresh topsoil, and bone meal

Dahlias grow on hollow stems that are susceptible to collapse in strong winds or even when overburdened by the weight of their own blooms, so they benefit from trellising. Stakes, cages, or trellises can be placed when you plant your tubers. Be sure to leave an appropriate amount of space between each planted tuber, as dahlias can grow quite large and will be at less risk of problems with fungi and mold if there is proper airflow between plants. 

Bouquet of pink and white dahlia blooms

Anemones, ranunculus, and dahlias are sensitive to cold and should be covered if the temperature dips around or below freezing. You should see a garden full of blooms in just a few more weeks! Aphids, slugs, and other damaging insects can be common in cut flower gardens, so keep an eye on your plants as they grow and be prepared to deal with pests whether using pesticides or organic methods like diatomaceous earth. Fertilize regularly throughout the growing season to promote large, healthy blooms. Different varieties can take more or less time to bloom, and the climate and weather can also have an impact on how quickly your plants mature, but pre-sprouting at least two weeks before transplanting will help you get the most from your summer flowering bulbs before the first frost.

Ready to get started? Shop our full selection of summer flowering bulbs here!