How to Grow Divine Dahlias - The Gloss Magazine
2 months ago

How to Grow Divine Dahlias

Erin Benzakein, founder of Floret Flower Farm, is known for her lush, romantic floral designs and the enormous selection of unique floral varieties she grows on her small-scale farm in Skagit Valley, Washington. Here she discusses her love of dahlias …

Of all the flowers I’ve ever grown, dahlias are my favourite. These treasures are one of the most most-loved and widely grown flowers for cutting because they come in a dazzling rainbow of colours. They produce an abundance of flowers from midsummer into autumn, and the range of shapes and sizes available is staggering. In addition to being such a well-loved cut flower, their incredible ability to multiply over the course of a growing season is unmatched. You can start with a single tuber or rooted cutting, and by season’s end be digging a full clump that contains three to ten babies from the original plant. Similar to a sourdough starter, once you have it and as long as you take care of it, you’ll have a steady supply to share with others and plant for yourself, every season.

Many years ago, when I was just starting to grow cut flowers, I got a phone call from a local flower grower telling me to load up the kids and my shovel and head over to her house. It was a crisp morning in October, just after our first autumn frost, and I found her digging up dahlias. At the time I knew very little about these bloomers, only that I admired them every time I visited her garden. We worked through the morning lifting her massive clumps of tubers, splitting off a chunk of each variety for me to take home to my garden. Her generosity was my first real taste of just how giving and passionate flower people are. When I offered to pay her or pull weeds in exchange for the station wagon full of tubers that she had so generously shared, she said she didn’t want anything in return. Her one request was that I pass along some of the abundance to another gardener in need once my garden was established.

Since that fateful October day many years ago, my dahlia garden has grown beyond anything I ever imagined. This past season we grew nearly 800 unique varieties and over 18,000 plants in total, a far cry from a station wagon full of muddy tubers. One thing I’ve learned when it comes to dahlias is that once you’ve been bitten by the bug there’s no going back. They have a strangely magical quality that somehow ends up taking over your life in the most fun and beautiful way. But the best part of all is having the opportunity at the end of each season to pass their magic on to others.

While dahlias have a large and passionate fan club, with growers spanning the globe, there has been a notable shortage of current information about how to cultivate these beloved plants. In my new book Discovering Dahlias: A Guide to Growing and Arranging Magnificent Blooms, I share how to get started with dahlias; demystify their many sizes and forms; teach you step by step how to grow, harvest, and arrange these spectacular flowers; and feature hundreds of my favourite varieties, sorted by colour. Here is my advice for THE GLOSS on how to take cuttings.

When taking cuttings, keep in mind that they are very tender and require a warm, bright space to thrive, so unless you have a heated greenhouse, you’ll need to construct a growing station. A table or shelf with a heat mat on top and some inexpensive shop lights (LED or fluo­rescent) hanging from above will do the trick. I converted a corner of my heated garage into a cutting station and produce thousands of cuttings every winter. Once you get the hang of it, you’ll be hooked and have more dahlias than you know what to do with.

For supplies you’ll need: a coarse potting soil; Pots that are at least 9 cm wide and 13 cm tall; Bottom trays with drainage holes; Plant labels; X-Acto knife; 72-cell seed tray filled with coarse potting soil; Pencil, chopstick, or bamboo skewer; Rooting hormone (I prefer gel types); Flat-bottomed tray with no holes; Clear dome lid; Heat mat; Shop lights (LED or fluorescent); Small pots

1. In late winter, pull out the tubers you want to multiply and plant them vertically in soil-filled pots that are at least 13 cm tall, leaving at least 2.5 cm of the neck poking out of the soil so that the eyes are easily accessible. Label each pot with the variety name and date potted up, and set them on a plant tray with drainage holes.

2. Place the potted tubers in an 18°C to 21°C spot to wake up; I keep ours in a heated hoop house. Note that your tubers should not be placed on a heat mat at this point, since that would encourage rotting from below. The first year I took cuttings, I lost almost half of my stock to this mistake. The process of waking up the tubers usually takes two to three weeks. Once the eyes swell and sprouts begin to emerge, they should be moved to an area that stays warm and has plenty of light, such as a heated greenhouse, or indoors under shop lights.

4. Once the sprouts are 8 to 10 cm tall, you can start taking cuttings. (If sprouts are shorter or much taller than this, their chances of rooting will be greatly diminished. I regularly monitor the tubers to catch the sprouts at their optimal size.) As cleanly as you possibly can, use an X-Acto knife to gently slice off the sprout where it connects with the tuber.

5. It’s important that you make your cut flush with the tuber so that you don’t cut out the growing eye or cut too high into the stem of the sprout where it is hollow. If the cut was made at the proper location, you’ll see a white ring in the centre of both the sprout and where it was removed.

6. Once you have collected a small pile of cuttings, carefully remove the lower two to three sets of leaves from each so that you have at least 2.5 to 5 cm of cleaned stem to work with. If the leaves that sit below the soil line are not removed, they will rot. Do not let your cuttings sit out for more than 15 to 20 minutes, or in direct sunlight, because they will wilt and likely won’t recover.

6. Fill a seed tray with coarse potting soil, water it deeply, and poke holes in the centre of each cell, using a pencil, chopstick, or bamboo skewer. Make sure your holes go all the way to the bottom of the tray. You will insert your cuttings into these holes, and poking them ahead of time will help ensure that the tender cuttings aren’t damaged when you place them.

7. Dip the bottom 2.5 cm of the cleaned cuttings into some type of rooting hormone. There are many products available, but I find that gel is easiest to use and the least messy to work with, though it smells terrible!

8. Insert dipped cuttings into the pre-poked holes until they touch the bottom of the tray. This will ensure that they have contact with the heat mat and root more quickly. Using your fingers, press the soil firmly around the cuttings so that there are no gaps between the soil and the stems. Continue until the tray is full, taking care to label individual varieties as you go.

9. Add about 2.5 cm of water to your no-hole tray and place the tray of cuttings inside. Set the dome lid over the top of the tray; if you prefer not to use a dome lid, you’ll need to mist the cuttings with water (a small spray bottle works great) three to four times a day so they stay consistently moist. Put the tray on a heat mat set at 21°C, under lights. Suspend the lights 2.5 to 5 cm above the top of the dome lid, and leave them on for 14 to 16 hours per day (you can use a timer if you like). Check cuttings daily and remove any that turn yellow or mouldy. Make sure to keep the water level in the tray at 2.5 cm deep. If you have too much water, the cuttings will rot; if you have too little, the cuttings will wilt.

10. I find that, given the ideal environment, it takes 12 to 14 days for cuttings to develop white roots, which indicate that they’re growing. After years of propagating tens of thousands of plants, I have found that the sprouts will take on a greyish cast, and a whole tray will look as if it’s starting to go downhill, about two days before they send out their first white roots. It’s like clockwork: every time I think a tray of cuttings is starting to die, they inevitably send out roots one to two days later. You can gently pull up the cuttings to check on root development.

11. Once the cuttings have developed enough roots to keep their soil intact (one to two weeks after they’ve developed white roots), move them into larger pots. Fill a small pot with coarse potting soil and make a hole in the centre (I find that a butter knife works well for this.) Slip the rooted cutting into the hole and press the soil firmly around the baby plant. After potting up the cuttings, water well, and place them either back under the lights or in a heated greenhouse. It’s important that cuttings are held in a warm, bright environment (over 15.5°C) so that they can continue to actively grow.

12. After three to four weeks, the rooted cuttings should have filled out their pots and are ready to plant into the garden. Be sure to wait until all threat of frost has passed before planting outside because cuttings are very tender – in Washing¬ton, this is around Mother’s Day. If it is still too cold to plant outdoors but your cuttings are becoming rootbound, you can transplant them into larger pots while you wait for the weather to warm.

From: Floret Farm’s Discovering Dahlias: A Guide to Growing and Arranging Magnificent Blooms by Erin Benzakein (Chronicle Books, £18.99) photography Chris Benzakein;


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