Rick cornered Helpful Husband on the 19th hole at the golf course. Rick keeps trying to grow a perfect spring tomato but once again his tomatoes are tall, thin and floppy. He hoped asking Helpful Husband would get the message across to me and it did.
I get this question annually and gardeners with Greenhouse Gardens who thought they bought their way out of this problem are not immune to leggy tomatoes and floppy stems.
Why your plants aren't producing earlier in the greenhouse
Plants grow fast
Unless you are a commercial grower there is no point in starting plants indoors before early March. Many growers wait until late March or early April to start seeds indoors. Plants growing for months and months before planting out will be taller than they need to be.
Plants always reach for the light
I suspect this may be Rick’s problem. He says he covers his plants with fabric to get them growing. Fleece fabric cuts out 10- 50% of the light available to plants. I start my seeds under a clear plastic cover and as soon as the seeds sprout the cover comes off. I never block the light of sun-loving crops when they are trying to grow. Rick needs to remove his cover sooner. He also needs to make sure his growing tips are within 15 cm of his LED or fluorescent lights or else they will stretch for it.
Plants grow faster and taller in warm conditions
Under grow-lights indoors, the heat is higher than in natural conditions outside. That is why we are growing them inside! On clear sunny spring days even our greenhouse is very hot. The secret if you can’t adjust the temperature is to add another stress: wind. A small fan will move the air around the plant and that strengthens the stems and keeps them shorter. Add a fan right away to your indoor grow-op or your greenhouse growing area.
Plants shoot up if fertilized
Rick has been babying his plants and fertilizing since day one. This is overkill. Start fertilizing only after small seedlings have been moved into the greenhouse soil or into pots for moving into the greenhouse once the outdoor weather settles. I mix compost and soil-less mix only after I move seedlings up from their original seeding flats. Any fertilizing when they are small just makes them sprout tall and weak.
Move plants deeper into the greenhouse soil or pots
If your tomato plants are longer than you want them to be, just remove the lower leaves on the stem and lay the plants in a trench in your greenhouse soil with the growing tip popping out of the soil. Or set the plant deeper in a pot so that it will root along the stems as it grows.
5 Tips Recapped
- Wait to start tomatoes until your conditions are right. If your planting out date isn’t until May, start plants in mid to late March.
- Never cover growing plants and keep plants close to the light or high on a greenhouse shelf as soon as they sprout.
- Keep the temperature as cool as possible without dipping below plus 5 C
- Place a fan near plants so they experience stress
- If all else fails bury tall plants deeper when you transplant them
P.S. to Rick. You can pop over and grab one of my sturdy tomatoes if you are stuck. They are the ones that have been stressed and kept short on purpose. I promise they will zoom along as soon as they hit your warm moist greenhouse soil. LOL
