Is setting up Wall O' Water's still worth it?

Newly set up Wall O' Waters

I've written before about the Wall O' Water product for season extension in Colorado's high and dry continental climate. This is the one with tubes in the side of the plastic cone that you fill with water to absorb the sun's heat and keep the plant growing within them warm.

What about setting them up now in late May when the growing season is supposedly on and the danger of a spring freeze low?

My answer is it is still a good idea for tomatoes, peppers, eggplant and warm season vegetables. Why? Now they can be used not so much to extend the season and protect from a spring freeze but to warm plants at night.

Have you noticed that nights are still in the forties F?  As I mentioned in the April 22 post on "Choosing tomato varieties", the minimum nighttime temperature for growing tomatoes is 55 degrees F. In our high elevation climate with low humidity, there isn't anything to hold in heat on clear nights so radiational cooling is extreme.

If you look at historical average low temperatures for Denver, we don't exceed 55 degrees F until June 22nd. Even so, we often have nights over the summer below 55 degrees in June, July and August - 16 nights in 2016!

Go ahead and set up a Wall O' Water when planting your tomatoes out over Memorial Day to take the chill off the night temperatures. Your plants will get up and growing faster for your effort.

Photo Credit: Newly set up Wall O' Water - Carl Wilson

Click here for manufacturer's website Wall O' Water

Still Useful to Plant in Wall O' Waters

Denver is receiving more sun and temperatures have warmed this week. That doesn't mean that it is ideal weather for planting tomatoes and other warm season vegetable transplants. Nighttime temperatures are still falling into the forties, far below the 50 F (and better yet 55 F) degrees nighttime temperature requirement for tomatoes. Note that the vine crops (squash, melons, pumpkins, etc. require 60 F degree nights).

A week after water channels filled at 
setup of Wall O' Water, sun has warmed water
sufficiently for planting within WOW cone. 
Plant deep for rooting along stem of this leggy 
tomato transplant.

So what's a gardener to do? You may have raised tomatoes from seed on your windowsill or purchased at a plant sale and the transplants are getting leggy. This is where Wall O' Waters come to the rescue. Even though often thought of for use in planting in the garden in April, they are still useful now.

Unlike mid-May when cloudy skies provided little solar radiation for heating the water in the tube walls of the Wall O' Waters, we are now receiving more sunlight. This provides warmth at night offsetting still cold night temperatures. Planting in Wall O' Waters also provides protection from wind and a sheltered environment for recovery from transplant shock.

Another benefit is protection from hail until plants grow above the walls. Even then plants pruned to the top of the Wall O' Waters by hail will retain enough undamaged plant within the Wall O' Waters to regrow.

If warm season transplants are planted in the open now without protection, they recover from transplant shock slowly and become stunted. We are assuming that night temperatures remain above freezing. They will require a week or more to recover from cold night stunting even when night temperatures warm above 50 to 55 degrees F in June. Although plants are leggy, you may be better off keeping them in pots and bringing them indoors at night until night temperatures warm if you aren't using Wall O' Waters.

See the manufacturer's website for more information on Wall O' Waters. Look to purchase them at your favorite local garden center.

Photo credit: Leggy tomato transplant for planting in Wall O' Water - Carl Wilson

Warm Season Vegetable Transplanting and Plant Sale Recommendation

This past week we saw a week of rain ending with snow that dropped 3.3 inches of precipitation in my Denver garden. The wet week ended May 10th with an overnight low of 31 degrees F.

Two years in a row! Tomatoes in Wall
O'Waters on May 12, 2014.

Any early-transplanted warm season vegetables required protection with Walls O'Water or second best the use of frost blankets. Even so warm season vegetables will likely be set back and take time to resume growth. Cloudy weather during the week didn't allow much solar gain for Walls O'Water.

Planting thoughts this week should take into account wet soils. Give them time to dry to a medium moisture content before transplanting or seeding. Don't walk in or work soil when wet; you will only destroy soil structure if you do. Meanwhile, consider what warm season vegetable varieties you want to plant this year.

Vegetable transplants being grown
by Denver Master Gardeners for their
May 16 and 17, 2015 sale.

I'm impressed with the wide selection of vegetable varieties offered by CSU Extension Denver Master Gardeners at their spring plant sale this coming weekend. The sale is Saturday, May 16 from 8am to 3pm and Sunday the 17th from 10am to 3pm.

Location is the Denver CSU Extension office in Harvard Gulch Park, 888 E. Iliff Ave, Denver, CO. This plant sale promises to be worth a visit and proceeds benefit CSU Denver's education programs.

Click to download and then open this file for more information and a list of varieties offered at the sale: Denver CMG Spring Plant Sale.

Switch to warm season crops

It looks like the time to plant warm season vegetables without temperature modifiers (water walls, etc.) is finally here. Starting June 1, the forecast is for nights to consistently attain 50 degrees F and days to be in the 80's and even 90 degrees F. With the warm nights, tomatoes, peppers, eggplant and the rest of the vegetables mentioned last post will now prosper when planted.

This also means the end of cool season vegetables like the lettuce and bolting rapini (broccoli raab) pictured above. It's time for these to go into the compost as they are now most likely bitter or fibrous. Rapini in bloom does make a good bee plant if you want to encourage bees or are keeping bees. In tnat case you can wait until after flowering to pull plants.

Direct seed plants from a different plant family such as squash, beets and carrots or plant warm season transplants in place of the rapini.

Photo credit: Cool season vegetables gone by, Rapini blossoms - both Carl Wilson

When will the cold nights end?

Although this title seems like a song lyric, for the warmest of the warm season vegetables it's true. Tomatoes, peppers, eggplant, winter squash, pumpkins, watermelon and cantaloupe have more requirements to think about than not being able to take frost.

This group of vegetables grows well when daytime temperatures are over 60 degrees AND nights are over 50 degrees F.  It's this night temperature part that's problematic in high altitude climates like the Front Range.  The May 20 low was 38 degrees F and nights are predicted to remain in the forties for at least the next week. It likely will be June until they warm sufficiently for planting outdoors without additional temperature support.

That nighttime temperature support can come from water walls or perhaps a warm microclimate location with lots of stone or masonry to absorb and radiate heat. Otherwise the best approach may be to get on the shuttle - moving transplants out by day and indoors at night. This helps harden off plants for eventual transplanting anyway. Hardening off is toughening them up to lower outdoor humidity, wind and higher light intensities especially UV light not present indoors.

For what seems to be everybodys' favorite vegetable, tomatoes, it may be tempting to plant outdoors in a year like this when the apparent last frost was April 16. Stunted growth and susceptibility to pests such as flea beetle results. Plants can normally outgrow this pest when they are established quickly and get up and growing but are severely set back when stunted by cold nights and eaten by pests.

Waiting to transplant can often result in better growth and a harvest that arrives just as early as plants transplanted before the arrival of warm nights.

Photo Credit: Tomato that was transplanted when night temperatures were warm easily outgrows early flea beetle injury (see pin holes on lower leaves) Carl Wilson