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

Anxious to Plant

Like everyone else, we are wondering when temperatures are going to thoroughly warm in order to transplant warm season vegetables to the garden. The five day forecast consistently shows "lows in the lower to mid 40's." For tomatoes and peppers, nighttime lows should be no lower than 55 degrees F.

The problem everyone is having is tomatoes stuck in the greenhouse getting leggy. Getting them out of a humid greenhouse where they can be put out on warm days and brought indoors into a non-greenhouse (drier) environment for night protection is ideal for hardening off. This should slow growth and curb leggy tendencies.

The outdoor part of this daily plant shuttle should have them located in a protected, short sun exposure location. Plants exposed to intense Colorado sun often sunscald because they have not developed the chlorophyll-protective plant pigments to shield them from UV and intense light.

One tomato plant brought to me this week for diagnosis showed the typical bleached, thin tan tissue typical of high light exposure. Transplants grown indoors during the cloudy spring weather we've had don't have the ability to stand up to the occasional clear day of intense Colorado sunlight.

Meanwhile, cool season vegetables such as this pak choy are happy growing in the cool, moist weather. The warm season transplants are just going to have to wait until Memorial Day weekend or later for the warm nights they require.

Photo credit: Greenhouse tomatoes and Pak Choy - Carl Wilson

Unique tomatoes and chiles featured at plant sale

Vegetable gardeners looking for better plants can find them at the CSU Extension Plant-A-Palooza plant sale May 14. The sale features tomato plants from around the world and better chiles for chile lovers.

Tomatoes available include Azoychka, a Russian heirloom that produces yellow, 3-inch tomatoes in 70 days. It has a good acid content to balance its sweet, citrusy flavor. Zhefan Short is from the Zhengjiang province of China. This 68 day tomato produces pink 3 inch fruits with good sweet/acid balance in the juice. Stupice from Czechoslovakia is a prolific, early bearing red type with great taste. Other heirlooms will be available too.

The chiles featured are grown from seed acquired from the New Mexico Chile Pepper Institute. The Institute returned fifty year old seed lines to what they used to be before they wandered off-type in the last few decades. The bonus for gardeners is traditional heritage chiles that yield 10 percent more and have 20 percent more flavor.

Two chile types will be sold. ‘Nu-Mex Heritage 6-4’ provides consistent medium heat with good yield. ‘New Mex Big Jim’ produces a high heat level for those who like their chiles hot.

The Plant-A-Palooza plant sale fundraiser has long been known for heritage tomato transplants in addition to modern tomatoes, peppers, basil, perennials and annuals. The sale takes place on Saturday, May 14 from 8 am to 3 pm or sold out in Denver’s Harvard Gulch Park, 888 E. Iliff Avenue (at Emerson Street). More information at 720-913-5270.

Photo credit: Tomato transplants, Carl Wilson

Rain at last - more needed

The official Denver precipitation total is now up to 0.84 inches for April (still 0.45 below normal for the month though). People closer the foothills received more rain during the upslope weather late in the week. Seedlings are coming up below the poly germination blanket (photo left) even without added sprinkling. See how to use this germination aid in previous post.

The name of the game now is to keep moisture on and through your soil. This is particularly true if you have added compost or turned under a winter cover crop for soil improvement.

Remember that the melding of the organic matter into the soil relies on microorganisms and they aren't active unless there is sufficient moisture. Turned under winter cover crops like rye and Austrian winter pea need a month to break down before planting vegetables IF the soil is moist enough for the microorgaisms to work over the buried plants.

Compost will release nitrogen during the growing season in addition to improving the structure of the soil. Again, soil moisture is needed for this to happen.

Check not only surface moisture, but also subsurface moisture content. After a dry winter, initial rains may have only moistened the top few inches. You may have to add supplemental moisture to wet the soil throughout the soil "profile." How does your soil moisture look down 6 to 10 inches?

Photo credit: Germinated seedlings under blanket - Carl Wilson

Dry spring weather

Both low precipitation and frequent drying winds have dogged Front Range gardeners trying to germinate vegetable seeds this spring.

Many of the cool season vegetable seeds planted at the beginning of the season are small and can't be planted deep. These include broccoli, onions, lettuce, kale and radish. Being near the surface leaves them vulnerable to drying out during the days-to-germination period. If seeds start germination and then dry before emergence, they often perish.

What to do? In addition to frequent, light watering, the use of straw mulch or germination blankets can help. A useful germination blanket is spun polyester floating row cover fabric tacked down with wire U-pins. These fabrics gerenally allow 85% light transmission as well as passage of moisture through to the soil.

Blanket removal immediately upon seedling emergence is not mandatory and can be delayed until several true leaves have formed and seedlings are well established - that is if fabric is anchored loose enough to "float".

Photo credit: Floating row cover seed germination blanket, Carl Wilson

Vegetables 101 class

Learn the keys to successful vegetable growing on the Front Range including tips and tricks to make your gardening life easier. Colorado’s climate realities include a short growing season, cool summer nights, dry air, erratic late spring and early fall frosts. Soil conditions add another gardening challenge.

The guiding hand of you, the grower, makes all the difference in adjusting growing conditions to achieve results. Come learn when and how to intervene to produce the vegetables you want for fresh eating and preserving.

Instructor: Carl Wilson, writer of Front Range Food Gardener

and CSU Extension horticulturist in Denver

For: Beginning to intermediate gardeners

Dates: Saturday, March 19, 2:30 to 4:30 p.m.

repeated Saturday, April 16 2:30 to 4"30 p.m.

Location: 200 Santa Fe Dr., Denver

Click to Register: Denver Urban Homesteading

Cost: $25

Photo credit: Seedlings in spring garden before thinning, Carl Wilson