Why we plant our cuttings in DEEP pots.

For those new to dahlias, rooted cuttings are clones of plants that we propagate to create more of a particular variety. Some varieties (notably Bloomquist Tory P) are very stingy at producing tubers, other dahlias produce long skinny tubers that are difficult to store over winter. For these and other reasons, in late winter we propagate some varieties by making clones through rooted cuttings.

We sprout the dahlias we wish to take cuttings from, basically waking them up earlier than we normally would. They are taken out of the 40-50 degree storage, and brought into the house to warm up. They don't need light, and they don't need water. The tuber will feed the plant and the indoor temperatures will spur the tuber to push new growth.

Pot tubers sending up their sprouts

We look for the early shoots from the tuber, and then take cuttings from the plant to make more of that particular variety. It is best to have at least 3 sets of leaves on the shoot before taking the cutting. We gently remove the two lower sets, leaving the upper leaves to photosynthesize the artificial light. We use a rooting hormone before inserting the cutting into the rooting cube. Some feel that it isn't necessary to use rooting hormone, but we have found that it increases our success.

Taking a cutting just above the eye with sanitized scalpel

Like many growers, we use "Root Riot" plugs when we make our dahlia cuttings. We have found that the Root Riot plugs maintain an adequate level of moisture for the cuttings to survive and to put out roots.

One downside to using Root Riot plugs is that sometimes the mature dahlia produces misshapen or few tubers. The rooting medium can constrict the root ball, inhibiting good tuber production. As mentioned earlier, many varieties are good tuber producers, so using the rooting medium isn't much of a concern. Other varieties do not produce useful tubers reliably, so some growers try to remove some of the root riot cube prior to planting their dahlia cuttings in an effort to promote tuber production.

We know that dahlias will produce roots from the meristem tissue where the leaf nodes attach to the stem.

By removing the lower sets of leaves from the stem, and planting the cutting deep, new roots will form from where the leaves were attached. These roots are not encumbered by the root riot cube. As such, we increase the probability that many of these roots will swell into tubers, making an easier plant to divide in the fall.

Transplanted from 3 1/2" pot to a 6" pot

By the time this dahlia is ready for the garden, it will be quite tall, approximately 12-18". After hardening these cuttings off, we will strip off another 1-2 sets of leaves, and plant them deep in the garden.

We've still got some growing to do before transplanting outside

There are downsides to this method; this requires a fair amount of indoor plant maintenance, and shipping costs are higher due to the extra weight of the plant. On the other hand you will get a significant head start on blooms by transplanting a well-established dahlia. You've also lessened the chance of loss due to rot, because you've planted a rooted cutting in lieu of a dormant tuber. In the end, we are trying to give the rooted cutting a greater opportunity to produce viable tubers in the fall. I hope that you've enjoyed this blog, feel free to email with any questions (or suggestions) that you may have!