Background
Originating from Mexico and dating back to the 1800’s, the Dahlia symbolises love, dignity and elegance. Dahlias are part of the daisy family and are said to have made their way to Europe around 300 years ago.
There are over 40 known species of Dahlia. The World Dahlia Directory holds records of more than 60,000 different Dahlia varieties/cultivators!
Types/Categories of Dahlia
My Dahlia addiction started many years ago knowing nothing about them, with a single dwarf pot Dahlia which was purchased from a local big-box retailer. Mesmerised by the colour and form of the blooms, I knew immediately that I was hooked. Through endless hours of research and conversation, I was gradually introduced to the different types of Dahlias available and the enticing world of growing them. My personal favourite is a ball Dahlia with it’s full, almost perfect round structure. Perfect cut fresh from the bush with long straight stems, these beauties last well in a vase arrangement for indoor enjoyment and are very popular as part of a gorgeous bridal bouquet.
Dahlia plants grow as a bush, ranging greatly in size between different varieties and growing methods. Dwarf plants can remain as compact as 20cm in height, with other varieties reaching 1.8metres, often needing additional support from stakes to prevent damage.
Dahlias are catergorised slightly different in various countries according to structure and size of blooms. For home growers, a simplified group of categories is all we need to worry about, but if getting into breeding exhibition grade blooms then a little extra research will be needed. The following are categories of Dahlia grown here each year at The Potted Patch. Dahlias are classified according to both the shape and size of their blooms, which vary significantly. Each variety can be grown in an almost endless option of colours.
Ball Dahlias
Fully double flowers with densely packed blunt or round ended petals arranged in precision that extend all the way back to the stem….forming the shape of a ball. The blooms have a firm structure, perfect and long lasting as cut flowers in a vase or bouquet arrangement.
Decorative Dahlias
With fully-double, closed centre blooms, available in almost every colour imaginable, you can’t go wrong with a decorative Dahlia. Decorative Dahlias can be classified as formal or informal, based on the precision of their petal formation. The petals on decorative Dahlias are softer and more gently structured than ball Dahlias. Both plants and blooms range dramatically in size between different varieties.
Pompon Dahlias
While plant heights can still reach approximately 90cm, Pompon dahlia blooms are miniature ball varieties, resembling an adorable round lollipop on a stick. To be classified as a pompon variety, the bloom size is generally expected to be under 5cm in diameter.
Dinner Plate (Giant) Dahlias
The name says it all! These beauties are show-stoppers with blooms that can be bigger than your head (!!) reaching between 20-30cm in diameter. In addition to oversized blooms, the plants can also reach heights of around 2metres tall. The oversized blooms can be heavy, so these giant beauties will require staking for extra support. Petals are generally appear softer and more flowing than their decorative cousins.
Dwarf (Bedding) Dahlias
These Dahlia varieties offer smaller plant sizes of between 20cm – 40cm in height and width. Bloom sizes vary as much as other varieties from small 4-5cm blooms to large palm-sized beauties. Whilst still beautiful in a vase, stems are often very short. Bedding Dahlias are ideal for planting in pots along patios, great for those with limited space, and perfect as border edging along paths and driveways.
Cactus and Semi-Cactus Dahlias
Another variety of a fully double bloom, the petals on Cactus dahlias curl tightly to resemble a spike (hence the name Cactus dahlia). Semi-Cactus varieties fall somewhere in between a full cactus dahlia and a decorative dahlia, with the petals curled half as tightly as a full-cactus variety.
Anemone Dahlias
Anemone dahlias have a unique form comprised of one or two outer ring of flat, disc-like petals surrounding a full, central dome of tubular florets with a fluffy appearance. Blooms often tend backwards in the direction of the stem.
Collarette Dahlias
Around a central open disc, Collarette blooms have an single outer layer of large flat petals surrounding an inner “collar” of smaller florets, often in wonderful contrasting colours. Collarette Dahlia are perfect for attracting pollinators due to the open centres, and their striking colours look great in a vase.
Waterlily Dahlias
Waterlily Dahlias are a form of decorative full-double Dahlia, but the petals are usually more delicate and the bloom is more shallow than other decoratives, resembling the shape of a waterlily. The softer petals are lovely to look at, but it also means they don’t last as long as a cut flower in a vase than ball or decorative varieties.
Single Dahlias
As the name might imply, single Dahlias exhibit a simple, single row of petals around a central disc. Whilst they might be simple in structure, their colour can still pack a punch, and they are the best version of Dahlia for attracting pollinators due to their open pollen centres. Petal shape differs between varieties, from rounded to pointed, flat to rolled. Single Dahlias are available in dwarf (bedding) varieties through to full sized plants.
Variegated Dahlias
Variegation is not a separate category or type of Dahlia, but simply refers to petal of two or more colours in a pattern that can range from splashes or stripes, to dots and speckles. Variegation has quickly become a much sought after trait for many modern Dahlia lovers. Love it or hate it, which are you?
Fimbriated Dahlias
Fimbriation (also known as lacination) places blooms in a sub-category of their parent form, most frequently seen in cactus and semi-cactus varieties. These words mean ‘bordered with a fringe’. Petals are split at the end, with fimbriation ranging from subtle to extreme in different varieties.
Planting: Tubers, Seeds and Cuttings
Dahlias are best planted in full sun, however, some protection from harsh summer afternoon sun can be helpful if you experience very hot days. In our region, we can have scorching summer days up to 45degrees celcius, so our plants are protected with some white, 50% shadecloth during the harshest months.
Plant outdoors after the last frost, or start early in a greenhouse or on a warm windowsill in later winter. Whether growing in the ground, raised garden beds or pots, plant your tubers into well prepared soil (Dahlias love organic composted material in their soil) that is well draining and not too heavy. Remember – the greatest risk to tubers at this stage is rot, from being too wet. Plant into moist (but not wet or soggy) soil. There are an endless number of resources available online to assist with soil preparation for Dahlias.
Plants tubers approximately 10cm deep…….horizontally, ideally with the ‘eye’ facing upwards (the eye is the point from which the spout will shoot). Most growers will wait to see a visible ‘eye’ on the tuber before planting, but this isn’t mandatory. A tuber without an ‘eye’ is called a blind tuber, and will not produce a plant. Some tubers will have multiple eyes. If you plant your tuber and the eye is facing down, don’t worry, the shoot will find it’s way to the light.
Spacing is another important factor to consider, and like anything else, each grower has their preferred method for spacing. It is worth noting that just like varying in height, Dahlia plants also vary considerably in the amount and thickness of leafy growth they produce. A lack of airflow is a major risk to the health of Dahlia plants, so ensuring adequate space between plants for airflow is important, while also trying to squeeze in as many of these beauties as we can. Due to having flood prone, heavy clay ground soil, I grow all of my dahlias in a combination of long raised beds (2 rows per bed which is 100cm wide) and large 40cm+ pots. If your beds or growing area is wider, you can do multiple rows, but remember that you need to be able to easily access each plant to remove damaged growth, deadhead flowers and access for pest control. I generally allow 40-50cm spacing between each plant, however, as I become familiar with the growth habit of each individual plant, the following year I will adjust and individualise spacing accordingly. For example, I have some plants happily spaced at 30cm, and others that would easily take up 80-90cm if left to their own devices.
Importantly…remember to label your plants. Most growers will have tales of early years of growing where poor quality labels or markers have resulted in a garden full of un-labelled plants, which can be incredibly frustrating. Everyone has their preferred methods of labelling which might include using marker on tubers, tying metal or plastic tags to stakes or plants, maintaining a planting map recording the names of each tuber and the location in which it was planted etc. My preferred methods are (a) maintaining a detailed planting map (which I also use to record note about the growth habits and blooms produced by each plant), as well as labels written on UV stabilised flagging tape using an Artline Garden Marker (this is the only combination of label and marker I have found that doesn’t fade or disintegrate in our super harsh summer conditions). I tie the flagging tape to a weedmat pin, pressed into the soil (at the edge of the bed away from the tuber) which is easily changed out if I lose a tuber and need to replace it. In the early years of growing I had too many instances of un-labelled plants due to faded marker, rotted wooden stakes, cracked and brittle plastic tags etc.
As long as your soil is moist (not wet) in most climates you should not need to water your Dahlia until the shoots are approximately 10-15cm tall. Avoid disturbing the tuber in this growing phase, as disturbance of the roots can slow the growth process. If you are concerned that a tuber might be waterlogged or rotting, carefully brush some soil away until you can feel the tuber with your fingers…if it is still firm then it might just need a little longer to get started, but if it feels soft or squishy it might need replacing.
Dahlia plants vary a lot in height, with many varieties reaching 180cm tall…or more! Staking is critical to ensure tall plants are not damaged in windy conditions or under the weight of heavy blooms. There are many ways plants can be supported, for example, each plant can have it’s own stake….just make sure you put the stake in the ground before planting the tuber, you don’t want to add one mid growth only to puncture and damage the growing tuber (which I have learnt the hard way from personal experience!).
This one is just my personal preference, but is something I also do with my vegetables. Through the growing season, I remove all of the lower leaves and branches from my each of my plants so that I have a 15-20cm ‘gap’ from the ground to the first set of leaves. I do this for three reasons……(a) it allows for clear airflow around the stem and base of the plants, (b) it ensure leaves and branches are not sitting on the mulch/ground where they will be wet, and (c) we live in an area with Australian Eastern Brown snakes, so I definitely don’t want any of those guys hiding under low lying Dahlia leaves ready to strike as I reach for a bloom or to check for pests!
Once your new plant have grown approximately four ‘true pairs’ of leaves, most growers (including myself) like to ‘pinch out’ their Dahlias. This involves pinching or cutting off the main growing tip of the plant. For new grower this might sound counter-intuitive, but the reason we do it is that pinching out the main growing stem encourages more growth of the lower laterals of the plant, resulting in a thicker/fuller plant that produces more blooms. Pinching out however, is likely to reduce the overall size of the blooms produced, but will produce them in a greater quantity so perfect for those growing for cut flowers. Growers aiming to exhibit their blooms with often not pinch out, as they are aiming for the largest and best quality bloom possible. In addition to not pinching out the growing stem, these growers will also often disbud all apart from a single bud, to allow the plant to put as much energy as possible into that single bloom.
Care & Maintenance
Dahlias definitely benefit from some TLC and can sometimes be a bit of a challenge in adverse weather conditions, however, with a little understanding and being prepared for trial & error in your local area, almost anyone can grow a beautiful Dahlia. The key is to become familiar with the growing conditions and requirements in your local area. Weather and other conditions can make a considerable difference to if/how you should store your tubers over winter, when to plant, watering, feeding and pest management. It is a good idea to consider joining an online Dahlia growers group or your closest Dahlia Society. Growers are keen to share information and advice, particularly in relation to your local area and conditions.
Dahlias require regular watering. The frequency and amount required will vary significantly depending on your climate and growing conditions. As a general rule watering approximately 3 times per week in average conditions should suffice. Water deep, at the base of the plant to get down to the roots, but not so the soil is soggy. Avoid overhead watering on the leaves to reduce the chance of powdery mildew. Dahlias respond best to early morning watering, especially on hot summer days.
Dahlias are fast growers and hungry plants. They will appreciate a planned feeding regime. Different growers have different feeding regimes and everyone swears by their own program. The trick is to find out what works well for you. Basically, Dahlias initially require higher levels of nitrogen to help them produce healthy, leafy growth. Once the plant starts budding, reduce the nitrogen and switch to a higher potassium feed to promote flower production. Continue this potassium feeding through to mid autumn. Dahlias grown in pots often require more frequent feeding than Dahlias gornw in beds as pots lose their nutrients at a faster rate. When it comes to feeding, a common saying in the Dahlia growers community is ‘weakly weekly’. Yours plants will love you for it!
Overall, once established, Dahlias a relatively low-maintenance. One ongoing-maintenance tasks that is most worthwhile is ‘dead heading’ – removing any dead flower heads when each bloom is finished. Either picking your blooms, or dead heading once the bloom is finished, promotes more bud growth and more blooms. In most regions, you should be abl eto keep picking and producing blooms through until late autumn when the first frosts arrive.
Pesky Pests
Pests can overwhelm a healthy dahlia patch in a short period of time, so being prepared and maintaining a watchful eye is important. As tubers are sprouting, watch out for snails and slugs who love to munch on new shoots. During the growing there are a number of common pests and diseases that as growers, we are all too familiar with. The below is by no means a thorough list of all possible pests that you might encounter when growing Dahlias, a few of the ones that tend to be the most challenging for me in our environment;
Pests and disease vary not only from region to region, but also vary significantly in each area depending on temperate and weather conditions. Each year you will deal with a different degree of these. The key is being well prepared and vigilant. I check all of my plants at least every second day, looking for signs of grey powdery mildew forming after wet or humid weather, checking under leaves and around blooms for aphids and whitefly, or for me, the most dreaded each season is the tiny spider mite. Be aware of treatment options, different options for different weather situations, and be ready to treat as quickly as possible as soon as pests are discovered. There is increasingly a range of environmentally friendly prevention and treatment options that reduce risk to bees and other ‘good’ predatory bugs. In the cases of severe pest outbreaks, chemical options may be necessary to reduce further spread.
A fabulous natural preventative is companion planting and growing ‘trap’ crops, which is something I have increased doing over recent years. In between my dahlias, at the ends and scattered around the edges of each bed, I plant things including Marigolds, Alyssum and Basil. Each plant serves a different purpose including excreting scents that deter many pests (Marigolds and Basil) and other than attract the ‘good’ predatory bugs (Alyssum). I also swear by planting multiple small pots of Nasturtium trap crops. These pots are strategically placed nearby the ends of each Dahlia bed. The trap crop attracts the mites, aphids and many other pests as a preference to the Dahlia plants. When the trap plant is infested, it is simply destroyed. There are many varieties of plants that work as great trap crops for Dahlias. I choose Nasturtium as they are super quick and easy to grow from seed, only need small pots, and are essentially maintenance free.
Tuber and Seed Sales
Tubers are generally available for sale in early spring when eyes on the tubers become visible as they start to wake from their winter slumber. Our stocks are very limited as we usually only grow between 1-3 plants of each variety. Tubers available for sale will be listed for sale in September/October via our Facebook Page: ‘The Potted Patch’. Seeds are available for purchase throughout winter, however, tend to sell out very quickly. In addition to our Dahlia seeds, there is also a limited range of other flower seeds harvested from the most recent growing season, including zinnias, marigolds, celosia, scabiosa (pincushion flower) and foxgloves, all in a range of colours.
For now, here is a list of our current Dahlia cultivators;
- Potted Patch Pumpkin Puree
- Cafe au Lait
- Show n Tell
- Formby Quest
- CK Faye
- Winkie Rhubarb
- Pink Ball
- Breannon
- Freckles
- Winkie Raven
- Shirley Yeoman
- Pink Show
- Tropical Dream
- Anne’s Delight
- Florelie Christie Merlot
- Sugartown Sunrise
- Devon Splendour
- Winkie Kestrel
- Eureka
- Shirley Yeoman
- Bracken Palomino
- Mr Frank
- Kim’s Christie
- Tiger Cub
- Bloodshot
- Melancholy
- Warraview Leanne
- Florelie Ponyo
- Glenmarc Francis
- Pam
- Moorplace
- Hansford Honeypom
- Taffy Pom
- Hotshot
- Little Peaches
- Formby Crest
- Peachy
- Florelie Morello
- Beverly
- Otway Gem
- Devon Odyssey
- Urica
- Granite Embers
- Wonderland
- Sand Dune
- Florelie Royal
- Draya
- Purex
- Tango
- Homicide
- Devon’s Choice
- Cherry Valentine
- Glenmarc Rufus
- Boundary Snowflake
- Formby Alpine
- Florelie Magpie
- Winkie Cavalier
- Combo
- Fairy Floss
- Winkie Whopper
- Dahlinova Bronze
- Glenmarc Galaxy
- Dalitza Big Candy