Central Valley gardeners need to develop plans for dealing with extreme weather conditions, including summer heat spikes, continuing drought and winter storms with high winds and heavy rainfall carried by bigger, stronger atmospheric rivers. Planning for the extreme weather conditions that are becoming increasingly common begins with asking lots of questions, such as:
- What to plant?
- When to plant?
- How to minimize heat stress?
- How to keep existing plants and trees alive?
- When and how to fertilize?
Experimentation, observation and, most importantly, sharing successes and failures can help us find answers and make hard decisions.
Switching out less heat- and drought-tolerant plants for even hardier varieties will be a first priority and will be based on observation. If a plant, bush or tree wilts easily or loses its leaves and drops flowers easily for more than two summer growing seasons, replacement is the best option.
Changing the planting schedule to get the roots of seedlings and transplants established before the first heat spike will entail planting at least two weeks earlier in the season than in years past, in mid-March and no later than the first week of April. We'll need to wait until mid-October to plant seeds and transplants of cool-season annuals and vegetables and to transplant perennial landscape plants and trees.
Regular, consistent fertilization is always recommended to encourage slow steady growth and flower production, but how does consistent fertilization work with unpredictable heat spikes? High temperatures (above 95 degrees) and shorter, hotter nights like those we usually experience in July and most of August cause plants to enter a state of semi-dormancy during which growth and flower production slow down, but what happens to the growth rate of plants when there are multiple heat spikes earlier in the growing season? This year's heat spikes stunted growth, scorched foliage and caused premature flower drop. Some transplants and seedlings of warm-season annuals and vegetables did not survive into summer. The October heat wave killed many established landscape plants that had struggled to regain vigor after a brutally hot summer. Reduce fertilizer amounts, apply low-nitrogen, longer-lasting granular formulations and avoid feeding heat-damaged plants immediately after a heat wave. Let plants recover very slowly, if possible, then feed them lightly at 1/4 the recommended rate.
Soil must be heavily amended to increase water retention. Mulch levels must be maintained at a depth of three- to four-inches year-round. All plants should receive deep, slow irrigation two or three days before a heat spike is predicted and leaf canopies should be kept as full as possible to provide much-needed shade.
Source: 2024 heat spikes, June 6/7, 2024 to October 3/7, 2024, Climate.gov