Leaves: Keep an eye on the plant and note if any leaves start to lose the normal vigorous green colour, curl or droop.If they are starting to go round and round the edge of the pot then the plant is in danger of becoming ‘pot-bound’ and needs more space. Roots: Holding the plant upside down with the stem between your fingers you can remove the plant pot and examine the roots.Soil: After about 8 weeks the plant will have used most of the nutrients in the small pot and growth may slow down.You may notice that the soil is drying out more quickly because the plant is taking up the water faster and more moisture will be lost through the larger leaves, particularly if it’s under grow lights. Size: Once the plant has grown wider and about twice as tall as the pot it will be struggling to get enough water.That’s why it’s important to watch for these signs to determine when plants are ready to move: Light often needs to be supplemented to prevent ‘leggy’ growth, watering needs to be daily and even good quality seed-starting potting soil will only have limited supplies of nutrients that eventually need replenishing. Intensive care is necessary to ensure that things that are usually available naturally in the garden (light, water, nutrients) are supplied in the correct quantities. Raising plants in pots or seed trays is a bit like giving them life support.

Tomatoes in a pot vs tomatoes in soil Signs That it's Time to Plant Out Getting plants out into the main vegetable bed is essential for good growth! However, transfer them too early and you risk them being damaged by late frosts or setting their progress back with adverse weather conditions. The plant on the right was transferred to the greenhouse vegetable bed at an optimal time whereas the one on the left was kept in a pot too long (I often end up raising more plants than I have room for!) In just over three weeks the difference in growth and plant health is clear. Both were started at the same time, raised in identical conditions from the same seed packet using the same potting compost.

To illustrate the problem take a look at the picture below which shows two tomato plants from my own greenhouse this year. With this in mind here’s my guide to deciding when pot-raised plants should leave home and settle down in your vegetable beds. It’s a pity because a little good advice can save a lot of disappointment and significantly increase the levels of success in the garden. In the first year some of their plants will be a success while others will keel over and die for no apparent reason and it can take several seasons with all their weather variations before it becomes apparent why they failed. Most gardeners have to learn the hard way about the best time to plant out seedlings they have raised indoors or in a greenhouse.

When to plant seedlings outside