Thursday, May 26, 2011

Holding transplants

  • With forty degree nights, growers are in a balancing act between how long transplants of very tender vegetables can be held versus planting and knowing they will be set back by the cold.

    Many transplants may be running out of nitrogen as seen on the tomatoes in the top of this photo. These plants are starting to come back with addition of a soluble nitrogen fertilizer when watering. A product that also contains phosphorous is useful to avoid the purple backs of leaves seen with phosphorous deficiency. The tray of plants at the bottom of the photo received regular fertilization.

    Don't apply too much fertilizer or you will end up with lanky growth. Of course these plants could be bumped up to pots larger than the 4 inch ones they are in but that is hardly desireable considering planting can hopefully be done in a week or so once nights are at least above 50, preferably 55 degrees F.

    What can be done in the meantime while waiting for warmer nights?

  • Harden off plants by moving them outdoors on suitably warm days and back in at night.

  • If tramsplants are very tender cover them with floating row cover fabric while outside. This should prevent sunscalding until they've adjusted to higher light intensity and have hardened off.

  • Maintain enough fertility to keep transplants growing and leaves from turning yellow.

  • Remeber that transplants set out too early or transplants running out of fertilizer require recovery time which adds to the days to harvest time.

  • Keep blossoms pinched from plants. Now is not the time to set fruit as you want to keep them in vegetative growth, not flowering/fruiting growth.

  • Watch the weather forecasts for when night temperatures are predicted to be 50 degrees F or higher.

  • Transplant tender (not the very tender) transplants such as cucumber and summer squash that tolerate cool nights as long they are above freezing. Remaining cool season vegetable transplants such as chard, beets, romaine lettuce that will hold up better in summer heat, cauliflower, etc. can be put out (photo).

  • Finish any soil prep such as compost additions and build new beds while weather is cool to work.

Photo credit: Held tomato transplants, Planting cabbage, romaine lettuce, Swiss chard - Both Carl Wilson


  1. Is it too late to try to kill off grass, to create a new garden plot?

    I know I can try to dig it up, but I'm worried about the roots bringing it back....

  2. You can use glyphosate herbicide to kill weeds and then prepare the soil. You may not be able to plant everything you want this first year but you can seed appropriate day to maturity (50 day for example) crops depending on your location and length of growing season.

  3. How long should I wait between herbicide application and vegetable seed/transplant planting? I'm in the Denver metro area, so I know I don't have long....

    1. Follow the directions on the herbicide label. The main waiting period after spraying is for the weeds to die before you do your soil prep.

  4. Mr. Wilson,
    While you were busy writing this article it appears that I jumped the gun and transplanted my tomatoes in the garden. I was lured out by the sunshine! Do you recommend that I try to pull them back out of the garden or just prepare to make a run to the nursery in a week or two if they can't make it through the cooler temperatures?

    1. No use pulling them out. They will just be set back and take longer to start active growth thus delaying fruit set and harvest until later in the summer. Hope for a late frost and extended warm weather into the fall so you can realize a larger crop.

  5. In the post above you recommend pinching of blossoms. At what point should I stop pinching blossoms off of my tomato plants and let flowers form?

    1. Quit pinching blossoms after you transplant into the garden.