I planted seedlings from a reputable source just before May 24 in my 6 x3 foot planters on my terrace. Once in, they began grow, and then the rain came. We had loads of it, and everything seems trapped in time. The little tomatoes that had started just stopped growing . They are not rotten, or shriveled… the just seem to have paused? The beds were built last year, and good quality triple mix was used. The beds we built “self watering “ using a coil of corrugated sleeved perforated pipe in the base. The planter were great last year, bumper veggie crop.
Now, everything is in perpetual adolescence? The only thing I can think is the roots stayed too wet for too long? It’s something about these big containers, as the smaller pots are fine.
I face east, but as I’m on the roof of the house, I have full Sun all day.
Thank you for contacting Toronto Master Gardeners. You are growing vegetables in a self-watering container in full sun on a rooftop. The soil is a triple mix, you had a good crop of vegetables last year, but this year growing is slow. I will address several issues that might be causing slow growth.
All containers must allow for drainage; self-watering containers usually have an overflow tube. The perforated pipe at the bottom holds the moisture below the soil. Once the soil is saturated the extra water must drain away from the soil, otherwise vegetable plants and seedlings are in danger of root rot. The recommendation would be to add an overflow above the perforated pipe if the tank fills up.
Triple mix is not recommended for containers. Potting media have a coarser texture than garden soil. It is the preferred soil for seeding trays and containers. Larger pores in the potting soil are created by adding mineral aggregates like perlite and vermiculite. Potting mix also needs ingredients that retain moisture such as peat moss or coir. However, if your crop last year was good, the soil type is less likely to be the main issue.
There is no evidence that biotic pathogens have caused slow growth however, next year you might consider solidarization before planting. Thus, soil in containers can be used again without pathogens to harm the next crop. This is important when the same crops will be grown. At the end of this season, remove all plant matter and cover the soil with black plastic for four to six weeks to kill off unwelcome elements and prepare the soil for new plants.
Fertilizing is also recommended for container vegetables in reused soil. Much of the nutritional value of reused potting soil is leached away after one season. Replenish these lost nutrients by adding new potting soil and manure or compost. Because compost/manure is dense, it can lead to compaction and should be used judiciously in containers (a ratio of one part compost to three or four parts new potting soil is good). I would use a 50:50 ratio of reused potting soil to amendments. Reusing potting soil is a money-saver, but nutrition loss can be a concern even when revitalized.
Is it very windy on the roof? Windbreaks would keep your plants from drying out or getting damaged in harsh weather. Trellises or other latticed windbreaks are best because they have holes that will disrupt the wind flow, rather than stop it completely. Solid windbreaks are more likely to be knocked down by high winds. You don’t want to eliminate wind flow but rather to decrease it. The trellis should be on the north or west side of the planter to act as a windbreak, but any orientation will help to reduce wind damage.
What to do now with the current crop? Address the drainage issue first. Carefully remove and repot some of the seedlings to the left of the tomato, and the nasturtiums. Place them temporarily in other pots. Dig down through the soil to check for very wet soil (if you squeeze a handful a lot of water comes out). If the soil is okay, and the roots of the removed plants seem healthy, amend the soil to improve drainage by adding extra perlite. Then fertilize. Use a mix of new potting soil and the compost of your choice, either vegetable or animal. You might consider purchasing some new plants while they are still available, or starting seeds of quick-growing crops like herbs and lettuce. All the best on revitalizing your garden!