Webinar Title: Preparing Cut Flowers for Drought and Heat: Tips and Tricks from the Desert
Webinar Date: July 23, 2026
Speaker: Melanie Stock, Associate Professor and Extension Specialist, Utah State University; Director, Small Farms Lab
Moderator: Gabrielle LaTora, University of Georgia
Recorded introduction: Bethany Harris
Duration: 29:23.7
Series: Cut Flower Symposium
Segment: 06 of 08
CEU Categories: [PENDING]
NARRATIVE SUMMARY
Melanie Stock directs the Small Farms Lab at Utah State University, where she works as a soil scientist on high-value crops and water use efficiency. She opened by putting Logan, Utah beside Georgia and arguing the two places share more than they differ. The forecast that week ran in the high 80s and 90s at both ends of the country. What separates them is humidity and elevation: Utah State sits near the Idaho border at roughly five thousand feet, the state spans USDA hardiness zone 4 up to a zone 8 or 9 in St. George, and the thin dry air lets solar radiation drive surface temperature hard.
Soil carried the first half. Organic matter coats individual soil grains and glues them into larger aggregates, opening the big pores Stock likens to a freeway for water. Clay soils then infiltrate and drain faster, and sandy soils, which she says have no attraction to water, begin holding on to it. Building that organic matter is a marathon rather than a sprint: several sources rather than one, and restraint with compost and manure, since most plant nutrients count as salts in the soil and salts accumulate under high tunnel plastic. Her fact sheet table of lab-analyzed materials sets a salinity target of two. The readings of 16 and 11 both came from bird sources, where the white on the manure is urine and the urine holds the salt. Because the NPK runs close to equal parts, she applies these materials to meet the phosphorus need and supplements nitrogen separately. Cover crops add organic matter without the salt, and she offered three ways to slip them into a full planting schedule.
Research filled the second half. A wool mulch trial across six warm season annuals under simulated drought held at least 5 percent more soil moisture and kept the root zone five to seven degrees cooler; every crop performed better in wool except statice. A perennial trial saved 30 percent of the water used during establishment, against about 10 percent for landscape fabric. Three years of sprinkler work in turfgrass and zinnia found afternoon irrigation outyielded pre-dawn irrigation, and a nearby farm cut its irrigation in half with shade cloth.
Word count: 371
YOUTUBE TIMESTAMPS
0:00 Welcome and speaker introduction
0:53 Tips and tricks from the desert: the agenda
2:46 Utah and Georgia compared: zones and elevation
4:22 Organic matter and soil structure
7:04 Holding water in sandy soils
8:45 Adding organic matter without overdoing it
10:22 Reading a compost and manure analysis
12:03 Cover crops and how to fit them in
14:04 Crop residue and residue management
15:03 Tillage: moderation and intention
16:13 Plastic mulch and root zone temperature
17:01 Natural mulches: wood chips and straw
17:48 The wool mulch trial in warm season annuals
19:47 Wool in perennials: growth and water saved
21:00 Choosing crops that take heat and drought
21:52 Day versus night sprinkler irrigation
23:22 Water at establishment, bloom, and dahlia
24:39 High tunnels and a DIY design
25:44 Shade cloth, wind, and stem length
26:30 Summary, closing, and USU survey
27:34 Q&A: wool mulch after harvest
QUESTIONS & ANSWERS
Q: What actually makes a soil hold up to heat and drought?
A: Organic matter and the structure it builds. Stock described organic matter as the remains of plants and animals coating individual soil grains and gluing them into larger aggregates. Those aggregates open big pores, which she compared to getting on a freeway instead of taking back roads from city to city. Water then infiltrates and drains faster.
Q: I have heavy clay. Does the same advice apply to sandy ground?
A: It works in both directions. In clay, organic matter lets water infiltrate and drain. In sand, where infiltration and drainage are already fine, the problem is that the soil will not hang on to water. Stock said sand sees water like a stranger down the street, with no attraction there, and organic matter coating those particles starts to create one.
Q: What should I watch on a compost or manure analysis if I grow under a high tunnel?
A: Salinity. Stock said the magic number is two, and that going a little above it will not shoot the soil up immediately. She used readings of 16 and 11 as reference points for what is genuinely high. Georgia rainfall flushes salts through the soil, but plastic over a high tunnel keeps them in.
Q: Should I size a manure application to my nitrogen need or my phosphorus need?
A: Phosphorus. The NPK in these materials runs about equal parts nitrogen, phosphorus, and potassium, so Stock uses them to hit the phosphorus need and supplements nitrogen separately. Applying enough to meet the nitrogen need overloads the soil with everything else.
Q: Every bed is in production. How do I fit cover crops in?
A: Stock offered three approaches: use an edge of the season when you are not growing as much, especially if you rotate crops; seed cover crops between established crops so they are not competing with the main crop, which the Midwest has been researching; or run them as an agritourism option, which she has seen cut flower farms do. She showed crimson clover and buckwheat, and noted that millet can serve as a cut flower and for wreath making.
Q: Is tillage always the wrong answer?
A: No. Stock said moderation and intention are key, and declined to give a one size fits all approach. Tillage incorporates organic matter deeper into the root zone and can give a fast boost when breaking ground. The drawback is that it destroys soil structure and breaks up aggregates, and soil microbes are sensitive to physical disturbance and to changes in pH. She raised conservation tillage, working the ground every couple of years rather than every year.
Q: What did wool mulch do in the annual trial?
A: The trial ran six warm season annuals under a simulated drought, matching the water restrictions Utah imposes in dry years, with wool mulch against bare soil. Stock reported at least 5 percent more moisture in the soil at any given time, which she put at hundreds of gallons, and a root zone five to seven degrees cooler. The difference narrowed once the plants got big and the canopy closed, so the help came early, while plants were establishing and growing actively. Every crop performed better in wool except statice, which did not care where it was.
Q: How much water did wool save in the perennial study?
A: About 30 percent during establishment last year, against roughly 10 percent for plastic landscape fabric compared with bare soil. Soil temperature under wool stayed moderate while bare soil and fabric swung widely, and growth was greater in wool across all three crops. Stock also noted that nutrient release from wool varies but that there is a great deal of it, released slowly.
Q: Is it better to run sprinklers at night or during the day?
A: The three-year study in turfgrass and zinnia cut flowers found the opposite of what everyone assumed. Night irrigation ran between 3 and 5 a.m., daytime irrigation between 3 and 5 p.m., and yield measured in stems per square yard was much better under daytime irrigation. Watering in the afternoon cooled the air and the soil, which the zinnias liked, and the night-irrigated soils were the drier of the two through the summer.
Q: If I cannot water everything, when does water matter most?
A: Two phases. Establishment is the first, and bud through harvest is the second. The vegetative stage between them is more tolerant, though Stock cautioned that too much stress there can delay bloom. She also suggested planting by water demand, grouping the heavy drinkers together so that a drought response can target the areas that need it rather than the whole farm. Dahlia is the exception she called out by name: she looked for ways to save water on them and found none.
Q: What does shade cloth do that a high tunnel does not?
A: Shade does not change the air temperature, but it reduces the sun load on the crop, which lowers stress in heat and drought. It also blocks wind, which has a drying effect and makes plants hunker down, so stem length increases on both counts. A farm near Stock that paired shade with irrigation cut its irrigation by 50 percent.
Q: Do I till wool mulch in after harvest, or save it for the next planting?
A: This was the one question taken live, combined by the moderator from two chat questions. Stock said wool does not lend itself to tillage and that incorporating whatever is left after a season would be problematic, so she places it in perennial or no-till situations. Growers who want to till can pull off what remains. The perennial study underway is testing fresh wool laid down annually against a single application left for the duration, and she expects wool to break down faster in Georgia than in Utah, where there is less water to break it down.
ADDITIONAL RESOURCES
- Fact sheets on production for the six cut flowers in the wool trial, plus the compost and manure analysis table:
smallfarmslab.com, under the fact sheets tab - High tunnel design plans for the DIY structure built at Utah State:
tunnel.usu.edu - Cover crop research and the blog by Andrew McGuire, Washington State University, cited for the crop residue literature review
- SARE cover crop resources, and UGA Extension cover crop resources, both recommended by the speaker
- A five-question USU survey was offered by QR code and in the chat at 27:16. It is a program evaluation, not a contact address.
Processed for UGA Center for Urban Agriculture / GTBOP Archives
Source: Corrected SRT (Stage 1) – GTBOP_Transcript_2026-07-23_StockDroughtAndHeat.srt (438 blocks)