Successful tomato starts

Propagating seeds can be so frustrating. We’ve struggled over the years, sometimes getting off to a flying start but often lamenting the slow and stunted growth of our seedlings that really makes the cheaper price of a packet of seeds over a punnet seem a false economy.

You too? Well, this post is designed to give you some pointers on how you might be able to hit your stride as a propagating champion and get those babies off to their best start possible.

We started off this year by buying a new seedling tray made from hard plastic. The flimsy plastic numbers we were getting from local shops were just too fiddly to be useful and often led to damaged plants during the seed raising process. It took quite some finding but eventually we happened across the perfect tray – durable plastic to last for years, the perfect size to fit in our heated propagation tray (more on that in a minute), deep with lots of room for roots to grow, and with a large single hole in the base to push out the seedling without damaging the roots, stem or leaves.

We used a mix of sieved potting mix and a little worm casting mixed through. There was nothing particularly special about the potting mix but we did look for the Australian standard ticks on the side of the packet.

Each cell in the tray was filled with the potting mix and pressed fairly firmly into place with fingers before filling again. At this stage, we gave the tray a really good water with the hose to make sure the potting mix was wet. It’s best to do this step before adding your seeds to minimise the risk that they will be dislodged by the watering.

Making a shallow dent in each cell, a tomato seed or two was placed on top then a small amount of potting mix was sieved over the top to cover the seed. Finally the tray was watered again on the mist setting of the hose. This is enough to wet down the surface potting mix, again without disturbing the seeds.

The final step on sowing day was to place the finished tray into our mini heated propagator. These are fairly easy to come by and to our minds they are absolutely essential to get your seeds off to a super quick start. Particularly for your warmth loving summer vegetables – things like tomatoes, chillies, capsicum and eggplant really need some heat for their seeds to wake up and do their thing.

Now we’ve had two of these propagators for years and have learned some lessons the hard way.

First, keep the air vents at the top closed. This allows seeds to be in a perfect starting temperature and a good amount of humidity that prevents the potting mix from trying out too quickly. Ideally you won’t water these again until the seedlings have emerged which is why you watered really well before sowing your seeds.

Second, we’ve placed this near a window but, despite everything you will read about how easy it is to start seeds by putting them ‘on a window sill’, seeds want light as soon as they emerge. So…

Three, once you see their little seedling leaves emerge (also known as the cotyledons), you’ve gotta get these guys and girls outside into the light. ASAP.

You can see how some of the super eager seedlings have shot up really tall and are leaning over to the left. This has been a bane of our seed start attempts throughout eternity and finally we’ve worked out the solution. As we mentioned above, getting these babies out into the sunlight is key to avoiding this straining towards the light, or ‘legginess’.

But there’s a second trick that you can use which both rescues already leggy seedlings AND makes for stronger plants. AMAZING, right?

Tiny seedlings like these are at once super fragile and also really resilient. Which means, if you are careful, you can actually lift them out of the cells with a pencil or narrow dibber and replant them deeper than they were before. You will need to focus on lifting the soil under and around the seedling, not lifting the seedling itself, and eventually you will feel the seedling give way. Try to hold it by one of the cotyledon (leaves) not the stem. The seedling can regrow leaves but if you break the stem you are done for.

Once the seedling is free, firm down the soil in the cell with your finger and create a deep hole with the pencil/dibber into which you can re-plant the seedling. It should go nice and deep, giving the little one lots of new root growing opportunity along the buried stem, leaving only a shorter strong stem above the soil level.

This year, COVID-19 has given us a golden opportunity to really focus on optimising growing conditions for our seedlings. For us this meant bringing the trays of seedlings outside during the day, still with the cover on, but the air holes open if it was at all sunny, and then returning to the propagator each night until all the seeds had popped up.

One final tip. Now this might sound a bit weird, but it has been scientifically proven that seedlings develop better when they have some movement. All that’s needed is a little wobble of the container or a hand lightly brushing their leaves each day, probably to mimic natural wind conditions that make their root development stronger. If they don’t move at all, they are also prone to grow really tall and leggy.

By mid August, just three weeks from sowing, our seedlings had outgrown their little propagator and it was time to move to the ‘greenhouse’. Now, we do own a little structure that serves as a mini outdoor greenhouse but it was already pretty full so we improvised with a clear plastic tub instead. This allowed our seedlings to soak up the slightly filtered light during the day, be protected from cold winds and be brought back inside overnight. They no longer needed the heat from the propagator but the warmer indoor temperatures overnight kept their growth powering along. Note though that our house is not heated overnight so we are still talking about overnight temps in the low teens (celsius).

Before we knew it, indeed, just five short weeks since the seeds were sown, these beauties were ready for more room to grow.

Being short on 10cm pots, and having 39 extremely healthy seedlings, we decided to pot on every second seedling leaving ample growing room for those remaining and allowing those potted on to spread their leaves and roots even further. Here’s where having the hole in the bottom of the tray comes in handy. You can just tilt the tray towards vertical and push a finger into the hole and the seedling should pop right out.

As a side note, if you find that the potting mix is breaking apart it may be that the roots haven’t developed enough and you’re not ready to pot on. But we’ve also found that moisture levels of the plants has an effect – both too wet and too dry can cause issues when removing seedlings from the trays. Try watering the day before transplant to optimise your chances of a good clean exit from the cell.

From here, it was a matter of keeping the seedlings watered and continuing to bring them inside overnight until they started to outgrow the plastic tub while we waited for the weather to warm up through early spring. Before long, we had moved the seedlings to overnights in the garden shed instead of indoors to prep them for planting out.

The garden all around us seemed to be bursting into life far sooner than usual and the days were so warm that in mid September, we took the plunge and planted out our first 7 plants during a flush of warm weather.

The seedlings were certainly larger than any we’ve every planted out from homegrown before at around 20-30cm tall. It was almost unbelievable how well they had grown and how healthy they looked. The proof though came when we popped each seedling from the pot to reveal a super healthy root system, not yet pushed for space but certainly ready to do everything it could to sprint away once it hit our garden beds.

We’ve never planted tomatoes this early before and had to jam these guys in amongst carrots, silverbeet and pak choi but our thinking is that the density of surrounding plantings will give them a little extra protection from cold and winds as they establish and when their roots need more room, we will have harvested the remaining plants.

With some colder nights descending, we’ve also covered the bush tomatoes with horticultural fleece. If it looks like we’ll get frost, we’ll cover the rest too but fingers crossed we are past the point of frost in Melbourne.

As an experiment, we will be planting a second lot of the exact same tomatoes from the same batch in about a month’s time and we will see which tomatoes do better. Will keep you posted with our results!