SEPTEMBER in the garden
Springtime is now the time that all things dahlias can be activated.
I know some of you may have started already in the warmer climates, but September is usually the time to get your seeds out of their packets and into the growing medium.
I use simple seed raising mix and put it in the 6 pack seedling punnets. These small packs are easier to manage for me then the large trays.
Seeds should be "fat" and have substance. If you can bend them easily and they dont bounce when dropped then chances are they are not viable. By using seedling punnets you can avoid handling seedlings unnecessarily. You may need to pot to a bigger pot prior to planting, but I try not to if I can.
Moisten your seed mix prior to sowing the seed. A cover to provide a moist even temperature is helpful. I use Gladwrap over seedling punnets or plastic bottles with their bases cut off over individual pots. Keep seedlings moist but not wet (soggy) as they will rot. The plastic is usually enough to keep moist enough without adding more water. Bottom heat will help speed things up. If you cant afford a heatpad or you have too many seeds then I find it easier to use a single electric blanket. Much cheaper and easier than a heatpad. I put it on a table with my polystyrene lids underneath for insulation. You will also need plastic sheeting between the blanket and the punnets to protect from moisture contacting with an electrical appliance!! Bottom heat is not essential but I find in our cold springs it helps to get things going.
As seedlings emerge it is important to make sure they are in a well lit position so as to prevent long, leggy shoots. ( which are very difficult to fix and make for weak stems later on.) Do not put them in direct sun as they can burn.
New seedlings will attract slugs and snails, so keep the slug bait spread around.
If you are not using bottom heat then I find the polystyrene bins are ideal for multiple seed punnets. Once seeds have sprouted it is so much easier to take them outside to start hardening off and bring them in overnight.
You can make a mini glasshouse using recycle plastic containers put on the windowsill. Ideal for sprouting seeds.
Tubers can now be dampened down in their sawdust beds. Enough water to dampen the sawdust, but let excess water run out. This is where I find that tubers lined up in trays, plastic crates or bins with holes in the bottom is ideal. If you have faced all your tubers with the crowns facing outwards then you only have to put water down the centre of your bin. Sprouting shoots will be easily seeen around the edges of the bin without having to handle the tuber too much and potentially damage shoots.
Bottom heat can also be used to start shoots off early ready for taking cuttings. Start bottom heat around August on your tubers for cuttings ready to be taken in September/October.
You can either cut or snap off cuttings. I prefer to cut with a sharp blade.
The easiest medium to use is bought cutting mix. You can make your own with any free draining mix that holds some moisture but wont go soggy. eg sand/seed raising mix 50/50. As long as the mix doesn't have fertilizer in it, as this may burn the new roots. You can use rooting hormone if you wish, but I find dahlia cuttings strike very readily and I don't use it.
If your planted tuber puts up more than one shoot you can break that off close to the tuber and pot it up or simply plant next to the parent plant directly into the ground if weather is warm enough.
The base of the cutting should have a node. This is where roots will develop.
Bottom heat will speed up root formation.
Do not cut a piece of the tuber with the cutting. By cutting between the bottom node and the crown, it will stimulate more shoots to grow. You can get many cuttings from one tuber.
You can grow cuttings for planting out or for pot tubers for the next season. A pot of 100mm or so should be big enough.
Cuttings ideally have 1-2 sets of early leaves, but can be taken much shorter if needed.
Remember to harden cuttings off before planting out into the main garden in November.
I like the punnets for cuttings as cuttings can be planted directly into the garden from them. You can also pot up up into small pots if needed.
Cuttings can be taken at any time there is green growth. However, cuttings taken late in the season, April/May will be more difficult to start and maintain through the winter. A lot of work for doubtful results, considering they do so well taken in the spring.
Leaf cuttings come in handy if you have a hollow stem you want to try a cutting from. Very good if you have a sport growing from your main plant.( A sport is a radically different flower growing on a recognized variety.) Hollow stems will not grow if you just cut it like a new shoot. So take all the leaf stem and a piece of the main stem. Roots will come from the node at the junction of the stems.
Leaf cuttings, tuber cuttings, tubers and seedlings all started in oct/nov will give you flowering plants in the summer.
Garden preparation should be well underway by now. Compost added to the beds,staking and watering system worked out, garden plan and map started.
Check out where all tuber sales days are happening. Ideally these should not be until October when tubers are showing viable eyes or shoots. That way you are guaranteed of tubers that will grow. It is very tempting to buy tubers too early and then be disappointed when they don't grow and too many problems trying to get your money back!
Identify the parent tuber is in most cases fairly easy, particularly if you planted only one tuber the season prior.
The parent is blunt at the roots end with many feeder roots. The outer skin is darker and rougher. It has a shorter, or no neck at all. It will be at 90 degrees to the main stem.
Is it worth keeping and planting the parent tuber?
Parent tubers have spent the whole of the last season feeding and supporting the plant. By the time they are dug up in winter they have spent most of their energy and will usually rot out in the coming season if they haven't done so already. So even if you have a parent tuber that looks like it is trying to put up a shoot (doesn't happen very often) I find it is not worth worrying about. You could take any shoots from it as a cutting.
These two tubers show the old with the new. Feeder roots trimmed off.
Any new eyes will come from the new tuber and ideally the old tuber should be trimmed off as close to the new crown as possible.
If you leave a parent tuber attached there is the possibility that as the parent rots out it may take the new tuber with it.