Young grapevines in the San Joaquin Valley often experience delayed spring growth (DSG), characterized by poor budbreak and stunted shoot elongation. DSG is more common in cane-pruned vines and certain varieties like Thompson Seedless. Factors that increase the likelihood of DSG include young vine age, rootstocks like Freedom, overcropping, warm fall temperatures without frost, and dry soil conditions over winter. DSG results from vines having insufficient reserves or weak vascular connections to support normal growth from dormant buds after winter. Proper pruning and crop load management as well as effective disease and irrigation practices can help prevent DSG.

1. Delayed spring growth in the San
Joaquin Valley
Matthew Fidelibus
Viticulture & Enology
UC Davis & KARE

2. Appearance of DSG
• Usually observed on young vines
• Poor budbreak & delayed shoot elongation
• Especially common on canes, and particularly
the middle of canes

3. DSG on young, cane-pruned vines,
Freedom rootstock

4. Factors that increase likelihood of DSG
• Young vines
• Certain varieties and rootstocks
• Cane pruning
• Overcropping
• Late harvest
• Excessive late-season growth
• Warm fall temperatures
• Dry soil in fall and winter

5. DSG of Sunpreme on Freedom;
Own-rooted vines in background

6. Fall 2020 temperatures warmer than average;
no hard freezes over winter
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Average min temp
2021 min temp
Avg max temp
2021 max air temp

7. Rainy season starting later, and
lately having fewer big storms
Month 2021 Precip Average
October 0 0.67
November 0.24 1.42
December 0.63 2.05

8. Some susceptible varieties
• Thompson Seedless, Crimson Seedless,
Redglobe, Selma Pete, Fiesta, Sunpreme,
Chardonnay, Merlot, Grenache, Cabernet
Sauvignon, and Sauvignon blanc are all
particularly susceptible
• Freedom and Harmony are especially
susceptible rootstocks

9. Normal growth from dormant buds
requires rehydration & vascularization
• Dormant buds are dehydrated and have relatively
weak vascular connections with the vine
• In spring, sap flow (bleeding) helps resolve any
embolisms and rehydrate the buds
• Bleeding depends on root pressure that develops
after carbohydrates & other organic compounds are
deposited in the xylem, increasing osmotic pressure
and water uptake from soil
• Rehydrated buds must develop new vascular
connections with vine to support growth

10. Irregular budbreak and stunted shoots suggest
insufficient reserves or vascularization
• Carbohydrates, water, and minerals are
needed to resolve embolisms and rehydrate
and feed developing shoots as they emerge
from dormancy
• Vine age, cultural practices, and weather can
affect the vine’s ability to meet these needs

11. Preventing DSG
• Pruning severity and crop load consistent with
vine capacity
• Effective disease management, particularly
powdery mildew
• Irrigation and nutrition management that
maintains the canopy without promoting late
season growth

12. Prognosis
• Young vines with poor budbreak or greatly delayed
growth may need retraining or, in severe cases,
replacement
• If sufficient shoots resume growth without too much
delay, no action may be needed
• Fruit yield & quality reduced on stunted shoots, but
severely affected vines might become overcropped
• Overcropping may reduce fruitfulness and
predispose the vine to DSG again, the following
season

13. In spring, microscopic shoots form within the basal node of
lateral shoots and the preformed shoots also initiate cluster
primordia, a process strongly affected by carbohydrate supply

14. Current
Crop
Next Year’s
Crop

15. Primary Dormant Node (Bud)
Dormant nodes contain preformed shoots
complete with the clusters each could bear

16. Secondary
Primary
Tertiary
Flower Cluster

17. From: Li-Mallet, A, A. Rabot, and L. Geny. 2016.
Botany 94:147-163 https://cdnsciencepub.com/doi/10.1139/cjb-2015-0108