Welcome Elinor Teague
A note from Elinor Teague to the readers: After writing gardening columns for the Fresno Bee for 18 years, it is a pleasure to be able to continue to offer readers gardening advice and tips here on the Fresno County Master Gardeners’ website.
Catch her on KYNO for the "Master Gardener Minute" on Friday, Saturday, and Sunday at 7:40am, 1:40pm, and 5:40pm.
Readers’ questions and comments are always welcome.
Our Garden Helpline is working remotely by e-mail only.
Questions? Send an email to mgfresno@ucanr.edu
Including photos is helpful. We are looking forward to hearing from you!
Feeding tomatoes during the hot valley summer
By Elinor Teague
Fertilizing plants in July and August is always a tricky experiment here in the Central Valley. During the hottest months of the summer growing season root and foliage growth slows as temperatures rise. Flower bud production also slows and eventually stops. Flowers on plants especially cucumbers, beans and tomatoes drop when temperatures are above 90 degrees. Some flowering species of plants like roses will continue producing flowers during our extremely hot summers but the petals are paper thin and the flowers have no fragrance.
Feeding plants in order to promote new growth when they are in a state of semi-dormancy can actually stress the plants. Fertilization during July and into mid-August when Central Valley temperatures are consistently above 100 degrees should be intended to keep non-productive vegetables, perennials and flowering annuals in overall good health.
The most important principal of summertime fertilization in hot weather is to avoid the application of fertilizers with higher nitrogen levels (above 10 percent N) that promote rapid new green growth or to apply them at half or less the recommended rate listed on the label. Experiment with applying lower-number fertilizers with NPK ratios around 4-6-2. The higher percentage of phosphorus encourages flower production on vegetables and flowering plants; the low nitrogen level will maintain consistent but slower foliage growth. Some heat-loving vegetables like peppers and eggplants continue to set fruit in hot weather. Feed them lightly in July and August. Stop feeding all plants when extended heat spikes with temperatures above 100 degrees for several days are predicted.
Slow-release fertilizers like Osmocote have higher NPK percentages. Osmocote Classic had an NPK of 19-6-12, which is very high, but because the nutrients are released over a 3- to 4-month period of time the effect of the higher nutrient percentages is somewhat mitigated. As an experiment, try to time an application in April of high-nitrogen slow-release fertilizers so that the 3- to 4-month effective period ends in July and then apply again in August.
Monthly side dressing of compost are great all through both the summer and winter growing seasons. Average compost NPK percentages are 1-1-1 and compost is a true slow-release fertilizer as well as a source of beneficial micro-organisms and beneficial fungi. Adding compost also restructures the soil, improving water retention and drainage. The beneficials in fresh, moist home-made compost will still be alive in our summer heat. Scratch a cup or two of compost monthly into the top of the soil around all plants.
It’s also very important to practice crop rotation and avoid planting highly nitrogen-sensitive plants like tomatoes in places where beans and peas have been growing. Beans and peas fix nitrogen into the soil. See the photo below of one 8-foot-tall Black Cherry tomato vine, which continues to grow vigorously up my garage wall. It was all vine with no flower clusters and few leaves at first but luckily a single feeding in early June of a ‘Bloom Buster’ high-phosphorus fertilizer (NPK 10-10-10) improved flower and fruit set, and the addition of fresh homemade compost improved leaf production. A step ladder will help with harvesting.
Research project documents plants' level of drought tolerance
By Elinor Teague
How can gardeners be certain that plants labeled as drought-tolerant are truly drought-tolerant? Many nurseries and garden centers have a section set aside for drought-tolerant plants species and there are many online sources of information on planting drought-tolerant gardens that include plant lists, but are all those plants equally able to survive and thrive on less water than other more thirsty species? And how much water does each species or the many cultivars of drought-tolerant plants need to remain healthy and disease- and pest-free in their climate zones? For many gardeners planting a drought-tolerant garden is a bit chancy.
UC Master Gardeners now have an excellent source of research-based, very specific and helpful evaluations of newly and recently introduced drought-tolerant plants suitable for the Fresno/Madera climate zone with the revamped and expanded website of the UC Landscape Plant Irrigation Trials.
The website includes a plant index with irrigation recommendations and aesthetic ratings for all the plants evaluated at the UC Davis field site since 2005 and at the South Coast Research and Extension Center in Irvine since 2018. Both sites evaluate landscape plants, grasses, small trees and bushes considered suitable for growing in the WUCOLS* Central Valley region (Sunset climate zones 8, 9 and14 and CIMIS* ETo* zones 12, 14,15 and 16) and the Southern Coastal region (Sunset climate zones 22, 23 and 24 and CIMIS ETo zones 1, 2, 4 and 6).
For those who are not familiar with UCLPIT, it is a research program begun at UC Davis in 2004 by graduate student Karrie Reed and her advisor Loren Oki, both of whom are still very much involved with the project. The original field trial site at UC Davis was expanded with the second site in Irvine.
Members of the plant/nursery industry, including growers and hybridizers, submit plants for evaluation. The plants to be evaluated were all planted two years previously so that root systems have become established. Evaluations are performed in spring, summer and fall in the field by volunteer UC Master Gardeners, horticulturists, landscape experts, educators, garden writers and others who are invited to participate. The field trails are not open to the general public. Three samples of each plant type receive either high, moderate or low amounts of water during the field trials. The field at UC Davis is in full sun. There is also a 50% shade structure where shade plants are grown.
The goal of the project is to match the water supply to the plants needs. Measurements of the plants’ evapotranspiration or ETo is weather-based using CIMIS weather stations at UC Davis and the South Coast REC - much the same process as smart weather-based irrigation systems. In this research project the amount of water given to each plant does not change; it remains a fixed amount. The frequency of irrigation changes. The goal is to determine the lowest amount of irrigation that will keep each plant species healthy and vigorous in drought-conditions.
The spring field trials for this year will be held on June 11 at UC Davis and on June 17 in Irvine. Master Gardeners interested in participating in the field trial evaluations can register online at the website listed above. Check under the heading “Open Houses."
*WUCOL (Water Use Classification of Landscape Species)
*ETo is the evapotranspiration of a reference plant
*CIMIS (California Irrigation Management Station)
Keep potted plants beautiful and healthy by repotting every year
By Elinor Teague
The best time to repot container plants is in early spring, just as new growth begins.Instructions on repotting are basically the same for houseplants and for outdoor potted plants.
Because the soil in container pot subsides or settles over time, many people mistakenly add more soil on top of the existing soil to bring up the soil level. Roots won't grow into the new top soil; roots grow downward. All container plants especially those in smaller 4-, 6- or 8-inch pots should have the potting soil replaced annually even if there are no roots showing through the drain hole and the plant is thriving. Our water here in the Central Valley is highly alkaline with high salts levels. The salts build up quickly in small pots creating whitish crusts on the soil surface and hard ridges of salts around the inner rim of the pot. A thorough flushing of the potting soil will remove some but not all of the salts. Dump the old soil into the green waste bin or the kitchen compost pile and trim off any dead or long winding roots on the plant. Use a wire brush to scrape off the salt residue inside the pot then cover the drain hole with a coffee filter or mesh window screen fabric before replanting. Add a few tablespoons of fresh nutrient-rich compost to the new potting soil if you have some.
Annual soil replacement is not always practical for plants in really large pots. Removing a large plant, emptying the pot and lifting large bags of potting soil to refill the pot requires a couple of strong people with strong backs. Root pruning or root shaving every two or three years will recreate room in the pot for root growth. Use a two-pronged barbecue fork to pry apart the roots then cut back long roots with sharp pruners or shave compacted rootballs with a serrated bread knife or a bonsai root shaving tool until the rootball is one or two inches smaller on all sides and on the bottom.
There are many formulations of potting soils for container plants on the market. Do use sand-based mixes for succulents and cacti, African violet mixes (which often contain peat moss) for African violets, cape primroses and other gesneriad species and orchid barks or moss formulations for orchids. Water retention properties vary considerably among brands of all-purpose potting soils. Experiment (and keep notes) of which brands of potting soil hold water longer.
Many national brands of potting soils add fertilizers to their products but few of those brands list the types and amounts of nutrients on their labels. Some also add water-retaining materials to the mix. It's best to add your own fertilizers keeping mind that, as the water flows out of the drain holes, so do the nutrients. Feed potted plants every two weeks with half the recommended application rate. For flowering plants in small pots, liquid fertilizers including African violet foods with a higher phosphorus content are great. Granular low-number fertilizers are fine for most foliage potted plants. Most Mediterranean herbs need little or no fertilization.
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